Soil-Water:Management-A

SOIL, WATER, AND FERTILIZER MANAGEMENT

© Copyright 2001, 2002 Hamilton-Locke. Reproduction and distribution are permissible for educational purposes only. No changes are to be made to this document without the consent of Hamilton-Locke and/or the author.

A

Access Road

‘‘Access Road, USDA/NRCS, Conservation Practice Standard’‘

DEFINITION

A travelway constructed as part of a conservation plan.

SCOPE

This standard applies to vehicular and equipment roads constructed to provide access to farms, ranches, fields, conservation systems, structures, woodlands, and recreation areas.

PURPOSE

To provide a fixed route for travel for moving livestock, produce, equipment, and supplies; and to provide access for proper operation, maintenance, and management of conservation enterprises while controlling runoff to prevent erosion and maintain or improve water quality.

CONDITIONS WHERE PRACTICE APPLIES

Where access is needed from a private or public road or highway to a conservation enterprise or measure, or where travel ways are needed in a planned land use area.

DESIGN CRITERIA

Access roads shall be designed to serve the enterprise or planned use with the expected vehicular or equipment traffic. The type of vehicle or equipment, speed, loads, climatic, and other conditions under which vehicles and equipment are expected to operate need to be considered.

Visual resources and environmental values shall be considered in planning and designing the road system.

Access roads range from seldom used trails to all-weather roads heavily used by the public and built to very high standards. Some trails facilitate control of forest fires are used for logging, serve as access to remote areas for recreation, or are used for maintenance of facilities.

Where general public use is anticipated, roads should be designed to meet applicable federal, state, or local criteria.

Sound engineering practices shall be followed to insure that the road meets the requirements of its intended use and that maintenance requirements are in line with operating budgets.

Location

Roads shall be located to serve the purpose intended, to facilitate the control and disposal of water, to control or reduce erosion, to make the best use of topographic features, and to include scenic vistas where possible. The roads should generally follow natural contours and slopes to minimize disturbance of drainage patterns. Roads should be located where they can be maintained and so water management problems are not created. To reduce pollution, roads should not be located too near watercourses.

Alinement

The gradient and vertical and horizontal alignment shall be adapted to the intensity of use, mode of travel, and the level of development.

Grades normally should not exceed 10 percent except for short lengths, but maximum grades of 20 percent or more may be used if necessary for special uses.

Width

The minimum width of the roadbed is 14 ft for one-way traffic and 20 ft for two-way traffic. Single-land logging or special-purpose roads have a minimum width of 10 ft, with greater widths at curves and turnouts. The two-way traffic width shall be increased approximately 4 ft for trailer traffic.

The minimum tread width is 10 ft for one-way traffic and 15 ft for two-way traffic. The tread width for two-way traffic shall be increased approximately 4 ft for trailer traffic.

The minimum shoulder width is 2 ft on each side of the tread width.

Where turnouts are used, road width shall be increased to a minimum of 20 ft for a distance of 30 ft.

Side slopes

All cuts and fills shall have side slopes designed to be stable for the particular site conditions.

Areas with geological conditions and soils subject to slides shall be avoided or treated to prevent slides.

Drainage

The type of drainage structure used will depend on the type of enterprise and runoff conditions. Culverts, bridges, or grade dips for water management shall be provided at all natural drainage ways. The capacity and design shall be consistent with sound engineering principles and shall be adequate for the class of vehicle, type of road, development, or use.

Roadside ditches shall be adequate to provide surface drainage for the roadway and deep enough, as needed to serve as outlets for subsurface drainage. Channels shall be designed to be on stable grades or protected with structures or linings for stability.

Water breaks or bars may be used to control surface runoff on low-intensity use forest or similar roads.

Surfacing

Access roads shall be given a wearing course or surface treatment if required by traffic needs, climate, erosion control, or dust control. The type of treatment depends on local conditions, available materials, and the existing road base. If these factors or the volume of traffic is not a problem, no special treatment of the surface is required.

Unsurfaced roads may require controlled access to prevent damage or hazardous conditions during adverse climatic conditions.

Toxic and acid-forming materials shall not be used on roads. This should not be construed to prohibit use of chemicals for dust control and snow and ice removal.

Traffic safety. Passing lanes, turnouts, guardrails, signs, and other facilities as needed for safe traffic flow shall be provided. Traffic safety shall be a prime factor in selecting the angle and grade of the intersection with public highways. Preferably, the angles shall be not less than 85 degrees. The public highway shall be entered either at the top of a hill or far enough from the top or a curve to provide visibility and a safe sight distance. The clear sight distance to each side shall not be less than 300 feet, if site conditions permit.

Erosion control

If soil and climatic conditions are favorable, road-banks and disturbed areas shall be vegetated as soon as possible and skid trails, landings, logging, and similar roads shall be vegetated after harvesting or seasonal use is completed. If the use of vegetation is precluded and protection against erosion is needed, protection shall be provided by non-vegetative materials, such as gravel or other mulches.

Roadside channels, cross drains, and drainage structure inlets and outlets shall be designed to be stable without protection. If protection is needed, riprap or other similar materials shall be used.

GENERAL CRITERIA

Watercourses and water quality shall be protected during and after construction by erosion-control facilities and maintenance. Filter strips, sediment and water control basins, and other conservation practices shall be used and maintained as needed.

Dead end roads shall be provided with a turnaround. In some areas turnarounds may also be desirable for stream, lake, recreation, or other access purposes.

Parking space as needed shall be provided to keep vehicles off the road or from being parked in undesirable locations.

PLANS AND SPECIFICATIONS

Plans and specifications for constructing access roads shall be in keeping with this standard and shall describe the requirements for applying the practice to achieve its intended purpose.

ACCESS ROAD SPECIFICATIONS

Construction operations shall be carried out in such a manner that erosion and air and water pollution are minimized and held within legal limits. The completed job shall present a workmanlike finish. Construction shall be according to the following requirements as specified for the job:

1. Trees, stumps, roots, brush, weeds, and other objectionable material shall be removed from the work area.

2. Unsuitable material shall be removed from the roadbed area.

3. Grading, sub-grade preparation, and compaction shall be done as needed.

4. Surfacing shall be done as needed.

5. Roads shall be planned and laid out according to good landscape management principles.

Quantity

1. Effects on the water budget, especially on volumes and rates of runoff, infiltration, evaporation, transpiration, deep percolation, and ground water recharge.

2. Effects of snowcatch and melt on water budget components.

3. Effects on downstream flows or aquifers that would affect other water uses or users.

4. Effects on the volume of and timing of downstream flow to prohibit undesirable environmental, social, or economic effects.

Quality

1. Short-term and construction-related effects of this practice on the quality of on site downstream water courses.

2. Effects on erosion and the movement of sediment, pathogens, and soluble and sediment-attached substances that would be carried by runoff.

3. Effects on the visual quality of water resources.

4. Effects on the movement of dissolved substances below the root zone toward the ground water.

5. Effects on wetlands and water-related wildlife habitats that would be associated with the practice.

Acidic soils

Soil acidification is a natural process, but some management and environmental situations can accelerate this process. The basic process of soil acidification involves the removal of bases and their replacement with hydrogen ions. High rainfall climates foster low soil pH as water movement through soil leaches basic cations (calcium, magnesium, potassium, and sodium), leaving exchange sites filled with hydrogen ions. Natural rainfall has a pH around 5.6 because it contains carbonic acid formed from reactions of atmospheric CO₂.

Soil microorganisms also contribute to soil acidification through their participation in biochemical reactions that release hydrogen ions. One such reaction is nitrification where ammonium (NH₄⁺) is converted to nitrate (NO₃^-) plus hydrogen ions. Fertilizers, or any other soil amendment, containing ammonium or amine nitrogen accelerate soil acidification through nitrification. Plants also contribute to acidification by selectively removing basic cations from the soil to meet growth requirements and replacing them with H⁺ from root respiration processes.

Pollutants in the atmosphere can also be sources of soil acidification. Atmospheric oxidation of sulfur and nitrogen oxides form soluble sulfuric and nitric acids that enter soils as acid rain. The pH of acid rain may drop below 4.0. Other airborne, acid-forming compounds from industrial activities can reach soils as dry deposits. The effect of these depositions on soil pH varies with each soil=s ability to buffer acid additions.

Plant and Microbial Response to Acid Soils

Each organism has a soil pH range necessary for optimal growth. Some plants thrive in rather acid or alkaline soils, but most prefer a pH near neutrality. Within the optimum pH range, the reactions and processes essential to growth occur at their most ideal rate and toxins in the environment are minimized. Soils too acid for optimum growth of a desired plant type should be limed.

Beneficial organisms tend to dominate soil microbial activities when soil pH is maintained near neutrality. Bacterial activities are most inhibited by acid conditions, while soil fungi are most inhibited by alkaline conditions. Root nodule bacteria responsible for nitrogen fixation in legumes function best near neutrality. Beneficial effects of soil organisms, like organic matter decomposition, a factor in aggregation and associated improvement in soil aeration and drainage, also occur optimally when soil pH is near neutrality.

Environmental Associations to Acid Soils

The behavior of hazardous elements and compounds in the soil environment is sensitive to soil pH. Heavy metals (arsenic, cadmium, lead, mercury, zinc, etc.) Typically increase their desorption and solution concentrations in soil under acid conditions. As liming raises the pH of acid soils, metal absorption onto soil colloids increases, which, in turn, decreases their mobility and redistribution in nature.

The use of pesticides entails some hazards to the environment and their effectiveness is often related to soil pH. Once pesticides enter soil a major factor governing their fate is absorption onto colloids. Absorption decreases their concentration in solution, chemical effectiveness, and mobility in the environment and is related to soil pH in two ways. First, the absorption capacity on several soil colloids increases as pH increases. Secondly, pH regulates the degree of protonation (formation of charged groups) of the pesticide molecule and, hence, its capacity for binding to colloids.

Some mining operations involving sulfur-laden ores generate strongly acid wastes when these deposits oxidize to form sulfuric acid. Runoff and erosion of these deposits pose a threat to neighboring land and water. Stabilization of these sites with vegetation requires liming and, often, fertilizer treatments.

How Limestone Raises Soil pH

Limestone is a naturally-occurring, soft, sedimentary rock composed predominantly of calcium carbonate (CaCO₃), but usually containing some magnesium carbonate (MgCO₃) and/or other impurities. If significant amounts of magnesium carbonate are present, the material is called dolomite. Limestone containing both calcium and magnesium is considered a premium material because, in addition to correcting soil acidity, it supplies two plant nutrients instead of just one.

Acid neutralization begins when limestone slowly dissolves in soils forming calcium (ca²⁺) and carbonate (CO₃^2- ions. The calcium ions are attracted to exchange sites where, by mass action, they displace the hydrogen ions (H⁺) comprising the reserve acidity. This exchange reaction raises the base saturation on the colloids, a necessary step in decreasing soil acidity. The displaced hydrogen ions join the active acidity in the soil solution where they can react with carbonate ions to temporarily form carbonic acid (H₂CO₃). If carbonic acid was a stable compound, liming would actually increase acidity in the soil solution. But, its unstableness leads to a rapid decomposition to water (H₂O) and carbon dioxide (CO₂). The carbon dioxide molecule, being a gas, escapes from the soil and prevents reformation of carbonic acid. The net effect of the liming process repositions hydrogen ions from where they were causing soil acidity, to now reside as part of the neutral water molecule. Also, as the liming reaction raises soil pH, aluminum ions are converted to complex aluminum hydroxyl ions and lose their ability to generate hydrogen ions by hydrolyzing water.

This neutralization reaction happens slowly in soils because limestone is slow to dissolve and has limited mobility due to its rapid attraction to cation exchange sites. Fine limestone particles will react faster than coarse particles. Also, thoroughly mixing limestone within the soil speeds its reaction. Generally, acid neutralization is maximized one growing season after limestone application.

Added costs using Buffer Practices

‘‘Added costs using Buffer Practices, USDA/NRCS, Core 4 Technical Reference’‘

Added costs include those items that increase the cost to the landowner and are primarily made up of the buffer installation cost. Depending on the acreage, spacing, and necessity of tree shelters, forest buffers can be quite expensive to install. In this scenario, the landowner installed the buffer and obtained cost share assistance to help defray installation costs. Maintenance costs will also be incurred over time. CRP offers a flat reimbursement for annual maintenance costs that reduces the cost to the landowner.

Added returns using Buffer Practices

‘‘Added returns using Buffer Practices, USDA/NRCS, Core 4 Technical Reference’‘

Added returns include those items that will increase income to the landowner. For conservation buffers, the landowner receives an annual CRP rental payment from the USDA based on soils information for the buffer acres.

Adsorption in filter strips

‘‘Adsorption in filter strips, USDA/NRCS, Core 4 Technical Reference’‘

Particles and soluble material that move through filter strips can get caught on the stems, leaves, crowns, and soil surface. Some of this is caused by physical filtration as described above. Other binding forces are chemical and biological in nature. Electrostatic charges build up on plant material because of the various ions that are the product of plant metabolism. These forces permit the positive charge of one material to bond with the negative charge of another. Pesticides are attracted to organic material, including soil organic matter, in this way. Another bond is developed when soluble material is held by the soil ion exchange sites and later made available for plant uptake or transformation by the chemical, physical, or biological processes that take place in soils.

Aerobic conditions retain phosphorus

‘‘Aerobic conditions retain phosphorus, USDA/NRCS, AgWaste Management Handbook’‘

Compounds of phosphorus, iron, manganese, and other elements react differently where oxygen is present or absent in the surrounding environment. This is true in the soil environment as well as in impoundments. Under anaerobic conditions iron changes from the ferric to the ferrous form, thus reducing P retention and increasing P solubility.

Table 3-4 Estimated dissolved phosphorus concentrations in runoff from land with and without animal wastes surface applied

Soils receiving frequent applications of wastewater can become saturated and anaerobic. Such soils will not be as effective at removing and retaining phosphorus as well aerated soils.

Aerobic lagoons used in treatement of agricultural waste

‘‘Aerobic lagoons used in treatment of agricultural waste, USDA/NRCS, AgWaste Management Handbook’‘

Aerobic lagoons can be used if minimizing odors is critical (fig. 10-24). These lagoons operate within a depth range of 2 to 5 feet to allow for the oxygen entrainment that is necessary for the aerobic bacteria.

The design of aerobic lagoons is based on the amount of BOD₅ added per day. Figure 10-25 shows the acceptable aerobic loading rates for the United States in lb-BOD₅ /acre/day. The lagoon surface area at the average operating depth is sized so that the acceptable loading rate is not exceeded.

Even though an aerobic lagoon is designed on the basis of surface area, it must have enough capacity to accommodate the waste volume (WV) and sludge volume (SV). In addition, depth must be provided to accommodate the normal precipitation less evaporation on the lagoon surface, the 25-year, 24-hour storm precipitation on the lagoon surface, and freeboard.

Should State regulations not permit an emergency outflow or for some other reason one is not used, the minimum freeboard is 1 foot above the top of the required volume. Figure 10-24 demonstrates these volume depth requirements.

Aerobic lagoons need to be managed similarly to anaerobic lagoons in that they should never be overloaded with oxygen demanding material. The lagoon should be filled to the minimum operating level, generally 2 feet, before being loaded with waste. The maximum liquid level should not exceed 5 feet. The water level must be maintained within the designed operating range. Sludge should be removed when it exceeds the designed sludge storage capacity. Aerobic lagoons should also be enclosed in fences and marked with warning signs.

Figure 10-24 Aerobic lagoon cross section

Figure 10-25

Design example 10-6-Aerobic lagoon

‘‘Design example 10-6-Aerobic lagoon, USDA/NRCS, AgWaste Management Handbook’‘

Mr. John Sims of Greenville, Mississippi, has requested assistance on the development of an agricultural waste management system. He has requested that an alternative be developed that includes an aerobic lagoon to treat the waste from his 50,000 caged layers, which have an average weight of 4 pounds. Completed worksheet 10A-4 shows the calculations to size the lagoon for this design example.

Worksheet 10A-4-Aerobic lagoon design

Affect of pH of kaolinite on the adsorption of herbicides =

Agricultural chemical waste management

‘‘Agricultural chemical waste management, USDA/NRCS, AgWaste Management Handbook’‘

Many agricultural enterprises use large amounts of agricultural chemicals. The use of these chemicals seems to increase as the cost of labor increases. With this increased usage comes the potential for surface and ground water contamination as a result of improper storage of chemical residue, rinse water, and unused chemicals and the improper disposal of empty containers. Considerable research is being conducted in this area; however, to date few easily managed, cost-effective alternatives have been identified. State and local regulations should be considered before planning any chemical handling system.

The chemicals and solids in rinse water should be concentrated. This can be done by collecting the material in an evaporative pond. Once the sludge has dehydrated, it should be placed in a leakproof container.

If possible the container should be disposed of by local or state officials or by private businesses that specialize in this activity. Proper clothing and breathing equipment should be used when handling spent chemicals and sludge from settling/drying basins.

Precaution should be taken to prevent animals and children from gaining access to such facilities.

Rinse water may be collected in below ground pits.

This liquid can then be used as a part of the makeup water when the chemical is needed again. Separate pits are needed for different chemicals.

Purchase and use only the amount of material actually needed. This requires accurate determination of the amount of pesticide solution needed and careful calibration and operation of application equipment.

Once a chemical solution is prepared, all of the material needs to be used for the purpose intended. This reduces the amount of waste material to be processed.

Chemical containers can be disposed of properly in one of two ways. They can be turned over to authorities or businesses that have the responsibility of handling them, or they can be buried. Before the containers are buried, they must first be triple rinsed, opened, and the liquid allowed to evaporate. Burial is practical only in locations where the burial site will always be above the ground water level.

Agricultural impacts on the use of water

(a) Agricultural waste and its impact on water use.

The value of water lies in its usefulness for a wide variety of purposes, and the quality determines its acceptability for a particular use. Therefore, a quality problem occurs when water is contaminated to a level where it is no longer acceptable for a particular use.

Water quality criteria are often used to determine acceptability. Potential water pollutants derived from agricultural waste can be classified as:

(1) nutrients,

(2) oxygen-demanding materials,

(3) bacteria that indicate potential presence of pathogens,

(4) sediment, suspended or dissolved materials, and

(5) agrichemicals and other organic and inorganic materials. For water quality parameters to have meaning, they must be related to one or more beneficial uses of water. The uses include (1) domestic, industrial, and agricultural water supplies; (2) swimming, fishing, boating, and other forms of recreational use; and (3) commercial navigation. Agricultural wastes are not likely to adversely affect commercial navigation.

(b) Impacts on domestic water supplies

Although only a very small amount of the water taken for domestic purposes is used for drinking, it is because of this use that domestic water is of the utmost concern and has the most stringent quality requirements.

Water withdrawn from surface watercourses for domestic or municipal supply is almost always treated to some degree to remove contaminants. In the case of individual home water supplies, this treatment might only involve chlorination to destroy pathogens or other organisms. Municipal water supplies are generally treated more extensively. Water quality concerns for domestic supplies should never be taken lightly.

Failure of supplies to meet standards for even short periods of time can result in serious illness.

Quality requirements for domestic drinking water are determined by the EPA and, in some instances, include modifications and additions from the State health department. Water quality regulations for domestic supplies can be divided into two categories: primary standards related to health concerns and secondary standards pertaining to aesthetic interests.

Health associated regulations often relate to toxic levels of manmade and natural substances. Under the 1986 amendments to the Safe Drinking Water Act, EPA set primary standards for 83 contaminants. Some of the substances that are associated with agriculture include nitrate, bacteria, selenium, lindane, toxaphene, 2-4,D, aldicarb, alachlor, carbofuran, simazine, atrazine, picloram, dalapon, diquat, and dinoseb. Those regulations aimed primarily at aesthetics include such substances as foaming agents, pH, and total dissolved solids.

The primary and secondary standards for drinking water for specific constituents are listed in table 1-4.

Surface water, especially streams, often contains many complex mixes of pollutants that are difficult to remove because levels vary widely over time. Therefore, the 1986 Safe Drinking Water Act Amendments require that all public drinking supplies from surface water undergo filtration and disinfection treatment.

Ground water, however, tends to maintain a quality that remains relatively constant over time, and some substances are not present or occur only at low levels.

Soil filtration removes most turbidity, color, and microorganisms, and some chemicals can be absorbed by the soil. Because of the natural purification of water as it percolates through soil, ground water is often used as a domestic supply with little treatment.

However, ground water monitoring programs have recently increased because of the growing concern that this water supply source may not always be as safe as previously assumed. One of the primary problems of using ground water for domestic purposes is the lack of localized water quality information. Furthermore, localized ground water quality can be radically affected by a local source of contaminant, such as nitrate from confined livestock or other NPS.

Some of the constituents in deep ground water aquifers are associated with agricultural chemicals, but generally not livestock waste. Nitrate is the primary constituent that can pollute ground water and have manure as its source. Water contaminated by nitrate can be treated with an ion exchange process to remove the contaminant, but this can be an expensive process and is not practical for many areas.

Under certain situations livestock waste can be a source of ground water pollution other than nitrate contamination. For example, shallow aquifers that supply dug wells can be contaminated by animal waste. Aquifers overlain by porous materials, such as gravel or some types of limestone, allow pollutants to be easily transported to the ground water. In some cases, poorly designed or constructed wells or earthen manure storage ponds can be the cause of ground water contamination from livestock waste.

Table 1-4 Selected primary and secondary drinking water standards as specified by the EPA

(c) Impacts on industrial water supplies

Industry uses water for a wide variety of purposes, so it is not surprising that water quality requirements for industry also vary widely. Several broad categories of industrial water uses include (1) separation processes, (2) transport of materials, (3) cooling, (4) chemical reactions, and (5) product washing.

Food processing industries are of particular concern because water used to wash food influences the quality of the final product. Water quality of the supply source, however, is less important for most industrial uses than for domestic or other uses because industry possesses the technology to treat water to acceptable levels. Because this treatment can be quite expensive, however, guidelines for upper limits or concentrations of selected constituents in water supplies for some industrial uses are identified. This allows industries to treat only to the acceptable level. Table 1-5 lists the maximum allowable concentrations of constituents in raw water supplies for several industrial operations as determined by the National Academy of Sciences (1974).

(d) Impacts on agricultural uses

Farms require a domestic water supply in addition to water used for a variety of other purposes. Livestock farmers are especially concerned with water quality for health and product quality reasons (especially milk).

A water supply that is both potable (safe to drink) and palatable (nice to drink) is most desirable for livestock consumption, although the water generally does not need to be as pure as that for human consumption.

Livestock farmers must be particularly careful that the farm water supply does not become contaminated by the livestock waste. Surface ponds or tanks to which livestock have ready access are always potential candidates for contamination.

The quality of water needed for livestock consumption varies with the type and age of animals. In general, young animals are less tolerant of water that has high nitrate or fecal coliform levels. Some animals, primarily lactating ones, have a relatively high daily intake of water as compared to their body weight. The daily intake for lactating cows, for instance, may be 25 to 35 gallons of water. High water intake increases the risk of health problems resulting from poor water quality.

Table 1-6 gives recommended limits of concentrations of some potentially toxic substances in drinking water for livestock. Those substances that originate on livestock farms and that often contaminate livestock water supplies include nitrates, bacteria, organic materials, and suspended solids.

Table 1-5 Maximum allowable concentrations of selected constituents in raw water supplies for industrial use (mg/L)

Nitrate-nitrogen standard for human consumption is 10 mg/L. No standards for livestock are established, but it is generally accepted that nitrate-nitrogen levels of over 100 mg/L can adversely affect the growth and health of livestock. Most young animals should be given water in which the nitrate level is much lower than 100 mg/L. The size of the animal generally affects their sensitivity to nitrate-nitrogen. For example, poultry are less tolerant to nitrate-nitrogen than swine, which are less tolerant than cattle.

Fecal coliform count should be essentially zero for calves and less than 10/100 ml for adult animals. A high level of suspended solids and objectionable taste, odor, and color in water can cause animals to drink less than they should. Refer to tables 1-6, 1-7, and 1-8 for specific guidance.

Table 1-6 Recommended limits of concentration of some potentially toxic substances in drinking water for livestock (based on Carson 1981)

Water used to wash food products or food handling equipment at the farmstead, including dairy utensils, must be contaminant free (potable water appropriate for domestic supply).

Irrigation, the largest consumptive use of water nationally, requires a water supply that does not contain substances that adversely affect plant growth. Typically, livestock waste is not the source of any water-borne substances that would harm crop growth unless excessive amounts of wastes are applied. Manure provides nutrients needed for plant growth. Very high levels of nitrate (100 to 500 mg/L) can cause quality problems for certain crops that are irrigated by sprinkler systems. High coliform concentrations in water applied to fruits or vegetables to be marketed without further processing can also be a problem. Livestock can be the source of suspended matter and, indirectly, algae, both of which can interfere with the operation of sprinkler and trickle irrigation systems. In arid regions, soils that are already high in salts can have this condition aggravated by land application of livestock waste.

Table 1-7 Desired and potential problem levels of pollutants in livestock water supplies* 

(e) Impacts on recreation

Kinds of water-based recreation vary, and each has slightly different water quality requirements. For example, swimmers generally prefer crystal clear water, but fishermen prefer that the water have some plant and algae growth, which promotes fish production. Many water quality requirements for recreational uses are highly qualitative and vary from one use to another and even from one user to another. Water-based recreation can be broadly separated into contact and noncontact activities. Obviously, the contact activities present greater health concerns, which relate primarily to disease-causing microbes. Requirements for noncontact recreational activities are similar to those for promotion of aquatic life and aesthetic considerations.

Typically, the acceptability of water for contact recreation is determined by measuring the level of an "indicator organism," such as fecal coliform bacteria, that denotes the likely presence or absence of other potentially harmful organisms. The degree of risk involved is associated with the level at which the organisms are present. Indicator organisms are used because the actual disease-causing organisms are extremely difficult to routinely measure. See table 1-2 for criteria for fecal coliform bacteria.

Table 1-8 Effect of salinity of drinking water on livestock and poultry (Water Quality Criteria 1972)

Surveys for E. coli and enterococci bacteria can be conducted if more rigorously investigated bacterial status of bathing waters is desired. For freshwater bathing, the geometric mean of bacterial densities for E. coli should not exceed 126 per 100 ml, or 33 per 100 ml for enterococci. For marine water bathing, the geometric mean of enterococci bacteria densities should not exceed 35 per 100 ml. Sufficient numbers of samples, generally not less than five spaced equally over a 30-day period, should be gathered and a confidence level applied to the test results according to the intensity of use of the water. This should be accomplished before making a final judgment about the acceptability of the water for bathing purposes.

(f) Impacts on aesthetics

Manure and other waste associated with livestock production can be important sources of aesthetic degradation. For example, they can be the source of objectionable deposits, floating scum, bad odors, and nutrients that promote growth of nuisance aquatic life.

Local regulations are often aimed at maintenance of aesthetic quality of watercourses.

To maintain aesthetic water quality, all water should be free from substances that:

Settle to form objectionable deposits

Float as debris, scum, or other matter to form nuisances

Produce objectionable odor, color, taste, or turbidity

Injure, are toxic, or produce adverse physiological responses in humans, animals, or plants

Produce undesirable or nuisance aquatic life

(USDA/NRCS, AgWaste Management Handbook’‘

Agricultural Safety

‘‘Agricultural Safety, USDA/NRCS, AgWaste Management Handbook’‘

Safety is an important aspect of planning, design, construction, and operation of an agricultural waste management system (AWMS). SCS policy as it pertains to an AWMS includes:

Notification of utility companies when utilities are in the vicinity of engineering investigations or construction activities (National Engineering Manual (NEM), part 503).

Incorporating safety measures into structures (NEM, part 503).

Informing decision maker and contractor of safety requirements at preconstruction conferences (NEM, part 512.13).

Safety requirements for construction activities under formal SCS contracting (Federal Acquisition Regulations, Clause 52.236-13, and Code of Federal Regulations, 29 CFR 1910 & 1926).

Safety requirements for construction contracts under locally awarded contracts (120-V-CGCAM (National Contracts, Grants, and Cooperative Agreements Manual, part 516).

Safety requirements for construction by informal contracting acquired by the decision maker (110-GM (General Manual), part 402.4).

Withdrawing SCS assistance if unsafe construction conditions are not corrected (110- GM, part 402.13).

Policies - USDA and SCS

The policies that guide involvement of USDA agencies in pollution abatement activities are in the following documents:

Agricultural waste and its impact on water use

‘‘Agricultural waste and its impact on water use, USDA/NRCS, AgWaste Management Handbook’‘

The value of water lies in its usefulness for a wide variety of purposes, and the quality determines its acceptability for a particular use. Therefore, a quality problem occurs when water is contaminated to a level where it is no longer acceptable for a particular use.

Water quality criteria are often used to determine acceptability. Potential water pollutants derived from agricultural waste can be classified as (a) nutrients, (b) oxygen-demanding materials, (c) bacteria that indicate potential presence of pathogens, (d) sediment, suspended or dissolved materials, and (e) agrichemicals and other organic and inorganic materials.

For water quality parameters to have meaning, they must be related to one or more beneficial uses of water. The uses include domestic, industrial, and agricultural water supplies; swimming, fishing, boating, and other forms of recreational use; and commercial navigation. Agricultural wastes are not likely to adversely affect commercial navigation.

Agricultural waste as a resource for plant growth

‘‘Agricultural waste as a resource for plant growth, USDA/NRCS, AgWaste Management Handbook’‘

The primary objective of applying agricultural waste to land is to recycle part of the plant nutrients contained in the waste material into harvestable plant forage, fruit, or dry matter. An important consideration is the relationship between the plant's nutrient requirement and the quantity of nutrients applied in the agricultural wastes. A plant does not use all the nutrients available to it in the root zone. The fraction of the total that is assimilated by the roots varies depending on the species of plant, growth stage, depth and distribution of its roots, moisture conditions, soil temperature, and many other factors. The uptake efficiency of plants generally is not high, often less than 50 percent. Perennial grasses tend to be more efficient in nutrient uptake than row crops. They grow during most of the year, and actively grow during the period of waste application, which maximizes the nutrient removal from the applied waste product.

Another major objective in returning wastes to the land is enhancing the receiving soil's organic matter content. As soils are cultivated, the organic matter in the soil decreases. Throughout several years of continuous cultivation in which crop residue returns are low, the organic matter content of most soils decreases dramatically until a new equilibrium is reached. This greatly decreases the soil's ability to hold the key plant nutrients of nitrogen, phosphorus, and sulfur. These nutrients may move out of the root zone, and crop growth will suffer. The amount of crop residue that is produced and returned to the soil is reduced.

Agricultural Waste Characteristics

‘‘Agricultural Waste Characteristics, USDA/NRCS, AgWaste Management Handbook’‘

(a) Purpose and scope

Wastes and residue described in this section are of an organic nature and agricultural origin. Some other wastes of nonagricultural origin that may be managed within the agricultural sector are also included. Information and data presented can be used for planning and designing waste management systems and system components and for selecting waste handling equipment.

(b) Variations and ranges of data values

In most cases a single value is presented for a specific waste characteristic. This value is presented as a reasonable value for facility design and equipment selection for situations where site specific data are not available. Waste characteristics are subject to wide variation; both greater and lesser values than those presented can be expected. Therefore, much attention is given in this section to describing the reasons for data variation and to giving planners and designers a basis for seeking and establishing more appropriate values where justified by the situation.

Onsite waste sampling, testing, and data collection are valuable assets in waste management system planning and design and should be used where possible. Such sampling can result in greater certainty and confidence in the system design and in economic benefit to the owner. However, caution must be exercised to assure that representative data and samples are collected.

Characteristics of "as excreted" manure are greatly influenced by the effects of weather, season, species, diet, degree of confinement, and stage of the production/reproduction cycle. Characteristics of stored and treated wastes are strongly affected by such actions as sedimentation, flotation, and biological degradation in storage and treatment facilities.

Definitions of waste characterization terms

Table 4-1 gives definitions and descriptions of waste characterization terms. It includes abbreviations, definitions, units of measurement, methods of measurement, and other considerations for the physical and chemical properties of manure, waste, and residue.

The first four physical properties-weight (Wt), volume (Vol), total solids (TS), and moisture content (MC)-are important to agricultural producers and facility planners and designers. They describe the amount and consistency of the material to be dealt with by equipment and in treatment and storage facilities.

The first three of the chemical constituents- nitrogen (N), phosphorus (P), and potassium (K)-are also of great value to waste systems planners, producers, and designers. Land application of agricultural waste is the primary waste utilization procedure, and N, P, and K are the principal components considered in development of an agricultural waste management plan.

Total solids and the fractions of the total solids that are volatile solids (VS) and fixed solids (FS) are presented.

Volatile solids and fixed solids are sometimes referred to, respectively, as total volatile solids (TVS) and total fixed solids (TFS). Characterization of these solids gives evidence of the origin of the waste, its age and previous treatment, its compatibility with certain biological treatment procedures, and its possible adaptation to mechanical handling alternatives.

Waste that has a very high water content may be characterized according to the amounts of solids that are dissolved and/or suspended. Dissolved solids (DS) or total dissolved solids (TDS) are in solution. Suspended solids (SS) or total suspended solids (TSS) float or they are kept buoyant by the velocity or turbulence of the wastewater. Table 4-1 Definitions and descriptions of waste characterization terms (% w.b. is percent measured on a wet basis, and % d.b. is percent measured on a dry basis)

Table 4-1 Definitions and descriptions of waste characterization terms - Continued

Wastes are often given descriptive names that reflect their moisture content, such as liquid, slurry, semi-solid and solid. Wastes that have a moisture content of 95 percent or more exhibit qualities very much like water and are called liquid waste or liquid manure.

Wastes that have moisture content of about 75 percent or less exhibit the properties of a solid and can be stacked and hold a definite angle of repose. They are called solid manure or solid waste. Wastes that have between about 75 and 95 percent moisture content- 25 and 5 percent solids-are semi-liquid (slurry) or semi-solid. Because wastes are heterogeneous and inconsistent in their physical properties, the moisture content and range indicated above must be considered generalizations subject to variation and interpretation.

Table 4-1 also lists physical and chemical properties of livestock and other organic agricultural wastes.

Data on biological properties, such as numbers of specific microorganisms, are not presented in this section. Microorganisms are of concern as possible pollutants of ground and surface water, but they are not commonly used as a design factor for no-discharge waste management systems that use wastes on agricultural land.

The terms manure, waste, and residue are sometimes used synonymously. In this section manure refers to combinations of feces and urine only, and waste includes manure plus other material, such as bedding, soil, wasted feed, and water that is wasted or used for sanitary and flushing purposes. Small amounts of wasted feed, water, dust, hair, and feathers are unavoidably added to manure and are undetectable in the production facility. These small additions must be considered to be a part of manure and a part of the "as excreted" characteristics presented. Litter is a specific form of poultry waste that results from "floor" production of birds after an initial layer of a bedding material, such as wood shavings, is placed on the floor at the beginning of and perhaps during the production cycle.

Because of the high moisture content of "as excreted" manure and treated waste, their specific weight is very similar to that of water-62.4 pounds per cubic foot.

Some manure and waste that have considerable solids content can have a specific weight of as much as 105 percent that of water. Some dry wastes, such as litter, that have significant void space can have specific weight of much less than that of water. Assuming that wet and moist wastes weigh 60 to 65 pounds per cubic foot is a convenient and useful estimate for planning waste management systems.

Odors are associated with all livestock production facilities. Animal manure is a common source of significant odors, but other sources, such as poor quality or spoiled feed and dead animals, can also be at fault. Freshly voided manure is seldom a cause of objectionable odor, but manure that accumulates or is stored under anaerobic conditions does develop unpleasant odors. Such wastes can cause complaints at the production facility when the waste is removed from storage or when it is spread on the fields. Manure-covered animals and ventilation air exhausted from production facilities can also be significant sources of odor. The best insurance against undesirable odor emissions is waste management practices that quickly and thoroughly remove wastes from production facilities and place them in treatment or storage facilities or apply them directly to the soil.

Units of measure

Waste production from livestock is expressed in pounds per day per 1,000 pounds of livestock live weight (lb/d/1000#). Volume of waste materials is expressed in cubic feet per day per 1,000 pounds of live weight (ft 3 /d/1000#). Food processing waste is recorded in cubic feet per day (ft 3 /d), or the source is included as in cubic feet per 1,000 pounds of apples processed. In this section English units are used exclusively for weight, volume, and concentration data for manure, waste, and residue.

The concentration of various components in waste is commonly expressed as milligrams per liter (mg/L) or parts per million (ppm). One mg/L is 1 milligram (weight) in 1 million parts (volume); for example, 1 liter. One ppm is 1 part by weight in 1 million parts by weight. Therefore, mg/L equals ppm if a solution has a specific gravity equal to that of water.

Generally, substances in solution up to concentrations of about 7,000 mg/L do not materially change the specific gravity of the liquid, and mg/L and ppm are numerically interchangeable. Concentrations are sometimes expressed as mg/kg or mg/1000g, which are the same as ppm.

Occasionally, the concentration is expressed in percent.

A 1 percent concentration equals 10,000 ppm.

Very low concentrations are sometimes expressed as micrograms per liter (mg/L). A microgram is 1 millionth of a gram.

Various solid fractions of a manure, waste, or residue, when expressed in units of pounds per day or as a concentration, generally are measured on a wet weight basis (% w.b.), a percentage of the "as is" or wet weight of the material. In some cases, however, data are recorded on a dry weight basis (% d.w.), a percentage of the dry weight of the material. The difference in these two values for a specific material is most likely very large. Nutrient and other chemical fractions of a waste material, expressed as a concentration, may be on a wet weight or dry weight basis, or expressed as pounds per 1,000 gallons of waste.

Amounts of the major nutrients, nitrogen (N), phosphorus (P), and potassium (K), are always presented in terms of the nutrient itself. Only the nitrogen quantity in the ammonium compound (NH₄) is considered when expressed as ammonium nitrogen (NH₄ -N).

Commercial fertilizer formulations for nitrogen, phosphorus, and potassium and recommendations are expressed in terms of N, P₂O₅, and K₂O. When comparing the nutrient content of a manure, waste, or residue with commercial fertilizer, the conversion factors listed in table 4-2 should be used and comparisons on the basis of similar elements, ions, and/or compounds, should be made.

Table 4-2 Factors for determining nutrient equivalency

Whenever locally derived values for animal waste characteristics are available, this information should be given preference over the more general data used in this chapter.

Carbon:nitrogen ratios were established using the ash content in percent (dry weight basis) to determine the carbon. The formula used, which estimates carbon in percent (dry weight basis), was: Total dissolved salts values were derived from a paper by R.M. Arrington and C.E. Pachek.

Agricultural Waste Constituents affecting ground water quality

‘‘Agricultural Waste Constituents affecting ground water quality, USDA/NRCS, AgWaste Management Handbook’‘

Nitrates and bacteria are the primary constituents of animal waste that affect ground water quality. Phosphorus and potassium do not constitute a threat to public health through water supplies. In their common forms, phosphorus and potassium are relatively insoluble and are not normally leached below the top several inches of most soils, especially those with a high clay fraction.

Phosphorus readily combines with aluminum and iron in acidic soils and with calcium in basic soils. Because these substances are relatively abundant in most soils, a large fraction of the total phosphorus applied to the land will be quickly immobilized. 0nly a small fraction of the soluble inorganic phosphorus will be available for plants.

In addition to animal waste, other agricultural related wastes and their constituents can impact ground water quality. Salinity has long been recognized as a contaminant of ground water resulting from percolating irrigation application. Two mechanisms influence the amount of salt reaching the ground water. The first is concentration of salt in the irrigation supplies. The process of evapotranspiration concentrates the salt in the root zone, making it available for solution and transport. The more salt in the irrigation supply, the more salt in the leachate. In addition, percolating water dissolves salts from marine shales, increasing the salinity of the aquifers in that manner.

Table 3-7 Typical fecal coliform to fecal streptococcus ratios (as excreted) for several animal species

Agricultural waste management practice standards

‘‘Agricultural waste management practice standards, USDA/NRCS, AgWaste Management Handbook’‘

National standards for agricultural waste management are in the National Handbook of Conservation Practice Standards. The field office standards are in section IV of the Field Office Technical Guide. Conservation practice standards establish the minimum level of quality with which these practices are planned, designed, installed, operated, and maintained. SCS conservation practice standards can be used to address specific waste management needs of producers.

Some examples are:

Waste Management System (Code 312)-The purpose of this system practice is to use the necessary practices in a systems approach such that wastes are properly managed and the degradation of air, animal, water, plant, or soil resources is prevented.

Waste Storage Structure (Code 313)-A fabricated facility for the temporary storage of animal or other agricultural wastes. The purpose of the practice is to store waste until it can be safely and effectively used.

Waste Treatment Lagoon (Code 359)-An impoundment made by excavation or earthfill for biological treatment of animal or other agricultural wastes. The purpose of the practice is to reduce the strength of the waste.

Waste Storage Pond (Code 425)-An impoundment made by excavation or earthfill for temporary storage of animal or other agricultural wastes. The purpose of the practice is to store waste until it can be safely and effectively used.

Waste Utilization (Code 633)-Using animal or other agricultural wastes on land in an environmentally acceptable manner while maintaining or improving soil and plant resources. The purpose of the practice is to safely recycle waste materials back through the soil-plant system.

Filter Strips (Code 393)-A designed area or strip of vegetation for removing sediment, organic matter, and other pollutants from runoff and wastewater. The primary purpose of this practice is to improve or maintain offsite water quality. To meet conservation objectives and offsite water quality goals for lands adjacent to cultivated agricultural land or other land that is periodically disturbed, other practices generally must be installed in the areas contributing runoff to the filter strip. Consequently, a filter strip will not often be a stand-alone practice.

Roof Runoff Management (Code 558)-A facility for collecting, controlling, and disposing of runoff from roofs. The purpose of this practice is to divert noncontaminated runoff away from areas where waste accumulates to areas where clean water can be disposed of safely.

Nutrient Management (Code 590)-Managing the amount, form, placement, and timing of application of plant nutrients. The purpose of this standard is to assure that all sources of plant nutrients, including livestock waste, are included in a fertility program designed to supply plant nutrients for optimum yields, yet minimize nutrient losses to surface and ground water.

Pest Management (Code 595)-Managing agricultural pest infestations (including weeds, insects, and diseases) to reduce adverse effects on plant growth, crop production, and environmental resources. The purpose of this practice in the context of this handbook is to properly manage waste chemicals for environmental protection.

Many other practice standards are used to support those listed, such as those for irrigation and tillage and cropping systems. Others will be developed for constructed wetlands for wastewater treatment, pesticide containment facility, and riparian zone buffer strips.

Until a conservation practice and other technical support documents are available, the technical requirements for constructed wetlands for wastewater treatment issued by SCS should be used.

Agricultural Waste Management System Component Design

‘‘Agricultural Waste Management System Component Design, USDA/NRCS, AgWaste Management Handbook’‘

Alternatives for managing agricultural waste are available for any given agricultural operation. An agricultural waste management system can consist of any one or all of the following functions: production, collection, storage, treatment, transfer, and utilization. These functions are carried out by planning, applying, and operating individual components.

A component can be a piece of equipment, such as a pump; a structure, such as a waste storage tank; or an operation, such as composting. The combination of the components should allow the flexibility needed to efficiently handle all forms of waste generated for a given enterprise. In addition, the components must be compatible and integrated with each other. All components should be designed to be simple, manageable, and durable, and they should require low maintenance. In this section, components are discussed under section headings that describe the function that they are to accomplish.

Agricultural waste management system plans

‘‘Agricultural waste management system plans, USDA/NRCS, AgWaste Management Handbook’‘

The purpose of an AWMS plan is to convey to the decision maker details of the construction and O&M requirements of the system. It is important to remember this in its preparation. As such, the plan should have an easily followed format, use familiar terms, and be concise. It should be neat, invite reading, and be worthy of retention. Presenting the plan to the decision maker in a 3-ring binder encourages retention. An electronic copy could be provided those decision makers having computers. See Planning Considerations, and Agricultural Waste Management Systems, for more information on the AWMS plan(search management explorer).

The preparation of the AWMS plan requires input from all disciplines involved in the planning and design of the system. Information from the AWMS's planning documentation must be extracted for inclusion in the plan. This would include information extracted from inventories, investigation reports, alternatives considered, design reports, installation schedules, and other information that is necessary for explaining the system requirements. However, it is generally not appropriate to include the planning and design documents in their entirety.

An AWMS component design report should be reviewed to ascertain O&M activities that may have been identified as necessary for the component's performance.

These O&M activities should be included in the O&M plan. The plan should include maps, charts, and other illustrative aids that enhance understanding of the system's O&M requirements. Appendix C is an example AWMS plan for a simple agricultural waste management system. A suggested format follows.

Name, address, and location of AWMS

This is self-explanatory.

General statement

Should indicate the purpose of the AWMS and the importance of O&M.

General description of AWMS

Should include the type and size of operation and the basic components of the AWMS. Including a plan view drawing of the component layout would be helpful for describing the AWMS.

Decision maker's responsibilities

It is suggested that this section clearly state that proper and safe system operation and maintenance within the laws and regulations are the responsibility of the decision-maker.

Component installation schedule

Should consider proper sequence of installation so that each component will function as intended in the system.

Operation and Maintenance of production, collection, storage, treatment, transfer, and utilization functions- The specific O&M requirements for each function of the AWMS should follow the component installation schedule section. These requirements should expand on the general O&M considerations described in this section and include the appropriate safety requirements.

Decision maker's acknowledgment

This last section is intended to include a signature line allowing the decision maker to attest to having read and understood the plan.

Agricultural Waste Management System Troubleshooting Guidelines

‘‘Agricultural Waste Management System Troubleshooting Guidelines, USDA/NRCS, AgWaste Management Handbook’‘

Production function

Observed problem

An unusually strong odor is present

Recommended actions

Check for manure covered animals and excess manure. Animals should be where animals are kept cleaned and adjustments made to keep them separate from their manure.

Look for evidence of poor drainage in lot areas. If noted, improve lot drainage and consider such things as installing concrete pavement around feeders and waterers to keep lot drier.

Collection Function

Observed problem

An unusually strong odor is present

Recommended actions

Check for spilled feed that is being allowed to ferment or areas where in animal housing area manure is not being routinely collected and removed. Remove these materials as a measure to reduce odors.

Check the frequency of collection. Suggest consideration be given to more frequent collection to reduce odors.

Check for manure covered animals.

Check for soiled or wet bedding. If found in excessive amounts, a more frequent removal schedule should be considered.

Consider providing additional ventilation.

Storage Function

Observed problem

Waste storage pond

Recommended actions

Pond is filled at or near capacity too Activate the contingency plan for emptying a portion of pond's contents to early allow for future waste storage and storm events.

Undesired material in pond Initiate removal prior to pumping. Take remedial measures to exclude undesired material from pond.

Waste storage structure-Tank

Undesired material in tank Assure that measures, such as sand traps and settling tanks, are in place to prevent mineral material from entering the tank. Install measures to remove undesired material if not in place.

If possible, exclude all foreign material, such as baling wire or twine, plastic bags, wood, and syringes, from the tank. Remove any materials that are found in the tank.

Waste storage structure-Stacking facility

Waste will not stack Suggest ways that the total solids of the waste can be increased, such as using less water or increasing the amount of bedding used.

Treatment Function

Waste treatment lagoon

Observed problem

An unusually strong odor is present

Recommended actions

Check pH of lagoon water (should be between 5.5 and 8.0). The optimum pH is about 6.5. Testing for pH can be done in several ways. A meter with pH electrode provides a means of making a quick and accurate test. Tests should be taken at different locations and depths to assure a pH representative of the lagoon contents. If the pH falls below 6.5, add 1 pound of hydrated lime or lye per 1,000 square feet of lagoon surface daily until the pH reaches 7.0.

Observe color of water. Very black water is indicative of low or no desired biological activity. Other colors, such as purple or various shades of brown, are indicative of water having high suspended solids content, and they normally represent proper operation. Dilution or aeration should be considered as possible ways of reducing odor.

Test composition of water. Concentrations of ammonia should not exceed 600 mg/L, and TVS should not exceed recommended loading rates.

Suggest reducing loading rates, dilution, or aeration as ways to reduce odor.

Undesired material in lagoon Remove undesired material from lagoon if present.

Floating crust formation generally does not effect the treatment function of an anaerobic lagoon; however, it does reduce evaporation from the lagoon surface. If a crust forms and if design assumed a reduction in storage requirements because of normal evaporation, early filling may result. An adjustment, such as reducing the quantity of wastewater inflow, will be required to compensate for less evaporation losses.

Mechanical separation

Plugs with solids Completely wash out the separator. Washing remaining solids from the separator after each use so solids will not dry in place may also reduce potential of plugging.

Vegetative filters

Excessive buildup of solids in Consider solid separation prior to discharge into filter. Regrade and vegetative filter revegetate if buildup of solids is affecting performance of filter.

Vegetation is dying or has died Revegetate as necessary. Consider dilution of the wastewater before discharge. An alternative treatment component to treat wastewater should also be considered.

Composting

Pile temperature, Temperature too low

Check moisture content of pile. Remedy is adding water or wet ingredient if pile is too dry. Add dry material and remix if too wet (moisture content of more than 60%).

Check C:N ratio of pile mix. Remedy is adding high nitrogen ingredient if the C:N ratio is greater than 50:1.

Check pH of pile. Remedy is adding lime or wood ash and remixing if pH is less than 5.5.

Observe pile structure evidenced by pile settling too quickly and few large particles. Remedy is adding bulking agent and remixing.

If weather is cold, remedy is to enlarge or combine piles or to add highly degradable ingredients.

Pile may fail to heat because of improper aeration. Aerate pile and check temperature frequently to see if it increases.

Pile temperature, Temperature prematurely falls consistently over several days

Indicates low oxygen. Remedy is to turn or aerate pile. Check moisture content. If low, the remedy is to add water.

Pile temperature, Temperature is uneven and has accompanying varying odor

Observe differences in pile's moisture content and materials. If observed the remedy is to turn or remix pile.

Pile temperature, Temperature gradually falls, and pile does not reheat after turning or aeration

Observe for completeness of composting as described in the O&M and Safety Inspection Guidelines, finished compost. If complete, no action is required. If composting is not complete, check for low moisture content. If low, add water.

Pile temperature, Pile overheating with temperatures greater than 165 F and rising

Check the height of the composting material. It should never exceed the 5 to 7 feet range. Reducing the height will lessen the probability of spontaneous combustion.

Check for low moisture and a pile interior that looks or smells charred or if temperatures are even exceeding 180 F. If any of these conditions are apparent, then the material should be removed from the composting bin.

Do not add water to the compost as this may promote additional combustion.

Avoid putting materials with dissimilar moisture contents next to each other.

Pile temperature, Pile is extremely overheating with temperatures greater than 170 F

Check for low moisture and a pile interior that looks or smells charred. If these conditions exist, break pile down and re-pile to a reduced size.

Strong ammonia odor is present

Check C:N ratio and add amendment if less than 20:1.

Check pH. Add acidic ingredients and/or avoid alkaline ingredients if pH is greater than 8.0.

If large woody particles are being used as a carbon source and C:N ration is less than 30:1, use another carbon amendment or increase the carbon proportion.

Rotten-egg or putrid odors comes from pile continuously

Check for low pile temperature and too high moisture content. Add dry amendment if these conditions exist.

Check for low pile temperature and poor structure. Adding bulking agent is the remedy for this condition.

Check for low pile temperature and high compaction. The remedy for this condition is to remix the pile and add bulking agent.

Check for low pile temperature and insufficient aeration. Turning pile and increasing air flow are the options for improving this condition.

Check for low pile temperature and too large a pile. The pile size should be decreased to correct this problem.

Check for falling temperature and insufficient aeration. Turning the pile more frequently should improve this condition.

Flies or mosquitoes

Look for fresh manure or food material at pile surface and flies hovering around pile. Files or mosquito problems can be reduced by turning the pile every 4 to 7 days and by covering a static pile with a 6-inch layer of compost.

Look for wet materials stored onsite for more than 4 days. Handling raw materials more promptly should reduce this problem.

Look for nearby standing puddles or nutrient-rich pond. Grade site to drain puddles and maintain pond in an aerobic condition.

Compost contains clumps of materials and larger particles and texture is not uniform

Check for discernible raw materials in compost. Screening compost and, improving initial mixing achieve more complete composting.

Check for wet clumps of compost. Remedy is to screen or shred compost and improve air distribution.

Look for large, often woody particles in compost. Screening, grinding, and sorting of raw materials initially improve composting.

If composted materials heat or develop odors, lengthen composting time or improve composting conditions.

Crops are scum covered following application

Use a clean-water rinse following application to clean plants.

Soil is sealed following application

Reduce potential by lengthening drying cycle between applications, physically disturbing soil surface, or injecting waste.

Applied nutrients are excessive as determined by observed conditions, such as soil and leaf testing.

Change to a crop that uses a greater amount of nutrients. Use double cropping if appropriate.

Increase crop yield with improved management by such things as pretreating with lime, practicing water management, managing pests, splitting waste applications, and making timely harvest.

Take an action that would reduce the amount of nutrients produced.

Treat the waste or a portion of the waste before land application to reduce its nutrient content and to prepare if for refeeding or for use as bedding.

Locate an off-farm use for the waste.

Enlarge area on which waste is applied.

Health hazards

Isolate and treat infected animals to reduce the potential for high levels of pathogenic bacteria in waste material.

Apply waste on sunny days when temperatures are above 40 F, ideally at higher temperatures, when bacterial and virus die-off is maximized.

Apply wastes to crops that will not be eaten raw or directly grazed unless adequate time is allowed for bacterial and virus die-off on the produce.

Apply wastes away from high density population area to reduce the possibility of disease transmittal by such factors as wind, insects, rodents, or flowing water.

Limit amount of waste applied to a single site to reduce the possibility of pathogenic bacterial buildup.

Apply waste when soil is not saturated and when rain is not forecast.

Runoff during or soon after application

Consider reducing rate at which waste is applied, applying waste only when rain is not forecast, not applying waste to snow or frozen ground, installing measures to capture runoff and return to AWMS for storage or treatment, and improving soil internal drainage by installing subsurface drainage.

Agricultural Waste Management Systems

‘‘Agricultural Waste Management Systems, USDA/NRCS, AgWaste Management Handbook’‘

An agricultural waste management system (AWMS) is a planned system in which all necessary components are installed and managed to control and use byproducts of agricultural production in a manner that sustains or enhances the quality of air, water, soil, plant, and animal resources.

Agricultural waste management systems, Collection function

‘‘Agricultural waste management systems, Collection function, USDA/NRCS, AgWaste Management Handbook’‘

Maintenance requirements for the collection function are primarily directed at mechanical equipment. Regularly scheduled lubrication and other preventive maintenance must be performed on electric motors, sprockets, and idle pulleys according to the manufacturer's recommendations.

Flush systems employ pumps, valves, and mechanical equipment involving gear boxes, stems, and guides.

This type equipment also needs regularly scheduled preventive maintenance. Broken sprockets, idle pulleys, drive cables and rods, chains, and scraper blades must be repaired when they are seen to be damaged.

Tractors used in collection must be regularly maintained according to the manufacturer's recommendations.

Equipment used in collection must be under constant surveillance to assure continuous and proper operation. Grates and covers on reception pits must be kept in place and in good condition.

Agricultural waste management systems, Collection function operation

‘‘Agricultural waste management systems, Collection function operation, USDA/NRCS, AgWaste Management Handbook’‘

The collection function involves the initial capture and gathering of waste from the point of origin or deposition to a collection point. The managerial aspects of this function involve frequency and timing, which should be described in the AWMS plan. Frequency of collection is dependent on the type of operation. For a feedlot, the frequency of collection might be only once a year. On the other hand, a dairy with a flush system might collect waste several times a day.

Timing of collection can be an important consideration.

For a feedlot without a storage facility, the timing should coincide with when the waste can be utilized. Timing for a poultry broiler operation may be most appropriate between production cycles when the facility is empty of birds.

Agricultural waste management systems, Complete mix and plug flow digesters

‘‘Agricultural waste management systems, Complete mix and plug flow digesters, USDA/NRCS, AgWaste Management Handbook’‘

These digesters require a constant temperature within a narrow range of variation to produce an optimum amount of biogas. Temperature is maintained by a heating system. The digester operating temperature must be monitored and kept within the temperature range specified by the designer. If the heating system is not functioning properly, waste should be routed around the digester to the storage facility. Both digesters have a cover of some kind. Like the lagoon cover, they must be periodically inspected to assure they are in good condition and are directing the gas to the exit point.

Effluent from anaerobic digesters has essentially the same amount of nutrients as the influent. As such, the O&M plan must address use of the effluent for land application.

Agricultural waste management systems, Composting facilities, recipe

‘‘Agricultural waste management systems, Composting facilities, USDA/NRCS, AgWaste Management Handbook’‘

Composting requires careful management to effectively treat waste. It relies on a proper blend of ingredients, called the recipe, to achieve the microbial activity necessary to stabilize reactive constituents and to attain the temperature necessary to destroy disease-causing organisms. For this reason, the AWMS plan should address careful monitoring of internal temperatures in the compost pile. The plan should give the recipe and recommendations for its adjustment if the temperature levels are either too low or too high.

Caution should be given to the potential for spontaneous combustion. The plan must also address mixing requirements.

Agricultural waste management systems, Composting facilities

‘‘Agricultural waste management systems, Composting facilities, USDA/NRCS, AgWaste Management Handbook’‘

Composting facilities vary widely mainly because there are several methods of composting. However, many facilities use standard construction materials, such as concrete, concrete blocks, lumber, and steel.

Concrete should be inspected regularly for cracks and deterioration, and repaired as necessary. Lumber should be inspected for deterioration and physical damage, and replaced if found to be nonservicable.

Protective coatings for steel structures should be inspected and repaired when damage is found. Manufactured composters should be maintained according to the manufacturer's instructions.

Agricultural waste management systems, Covered anaerobic lagoon

‘‘Agricultural waste management systems, Covered anaerobic lagoon, USDA/NRCS, AgWaste Management Handbook’‘

Operation of a covered lagoon for biogas production is much like that of a lagoon not associated with biogas production. The exceptions are that it is operated to have a constant liquid level, loaded at a higher rate, and has a minimum hydraulic retention time.

The inlet and outlet of the covered lagoon must remain free-flowing to maintain the required liquid level.

The lagoon cover requires special attention to assure that methane produced is captured and directed to where it will be used. The cover should be periodically inspected for accumulation of excessive rainwater, tearing, wear holes, and proper tensioning. Excessive rainwater should be removed in the manner prescribed by the designer, usually by pumping or draining it into the lagoon or storage facility.

Agricultural waste management systems, Maintenance

‘‘Agricultural waste management systems, Maintenance, USDA/NRCS, AgWaste Management Handbook’‘

Maintenance of an AWMS includes actions that are taken to prevent deterioration of the system components, to repair damage, or to replace parts. Maintenance includes routine and recurring actions. The purpose of maintenance is to assure proper functioning and to extend the service life of AWMS components and equipment.

The two types of maintenance required by an AWMS are preventive and reactive. Preventive maintenance involves performing regularly scheduled procedures, such as lubricating equipment and mowing grass.

Reactive maintenance involves performing repairs or rehabilitation of system components and equipment when they have deteriorated or cease to function properly. Examples of reactive maintenance include repair of a leak in a waste storage structure and replacement of a badly corroded piece of pipeline.

Essential to reactive maintenance is the discovery of items requiring attention before there is a serious consequence. Timely discovery can best be accomplished by regularly scheduled inspection of the AWMS components and equipment. The general maintenance and inspection requirements that should be considered for inclusion in the AWMS plan for each function of an AWMS are described in this section.

Proper maintenance of equipment used in an AWMS is essential for continuous operation. A thorough inventory of each function and its related equipment is recommended as a way to organize what must be maintained. The AWMS plan should recommend actions that will assist in the maintenance of equipment.

An action to include would be collecting and filing information on equipment, such as name plate data, shop manuals, catalogs, drawings, and other manufacturer information. Other actions to recommend:

Prepare checklists that give required maintenance and maintenance frequency.

Keep a log book of the hours each piece of equipment is used to assist in determining when maintenance should be performed.

Keep a replacement parts list indicating where the parts can be obtained.

Keep frequently needed replacement parts on hand.

Agricultural waste management systems, Oxidation ditches, channel design

‘‘Agricultural waste management systems, Oxidation ditches, USDA/NRCS, AgWaste Management Handbook’‘

The channel for oxidation ditches is generally constructed of concrete. The concrete should be inspected regularly for cracks and deterioration, and repairs made as needed. The rotor should be lubricated regularly and inspected for proper operation.

Other equipment, such as pumps, agitators, and valves used in its operation, should be maintained as recommended by the manufacturer.

Oxidation ditches require a high level of management to effectively treat the waste in a safe manner. Careful attention must be given to assure that pumps and other equipment are operating properly and that the ditch is not overloaded. Velocities must be maintained that do not permit solids to settle and accumulate.

Input from the designer is essential in developing the operational requirements for oxidation ditches.

Agricultural waste management systems, Production function

‘‘Agricultural waste management systems, Production function, USDA/NRCS, AgWaste Management Handbook’‘

Production is the function of the amount and nature of agricultural waste generated by an agricultural enterprise.

The waste requires management if quantities produced are sufficient enough to become a resource concern. A complete analysis of production includes the kind, consistency, volume, location, and timing of the waste produced.

The waste management system may need to accommodate seasonal variations in the rate of production.

The production of unnecessary waste should be kept to a minimum. For example, a large part of the waste associated with many livestock operations includes contaminated runoff from open holding areas. The runoff can be reduced by restricting the size of open holding areas, roofing part of the holding area, and installing gutters and diversions to direct uncontaminated water away from the waste. A proverb to remember is, "Keep the clean water clean." Leaking watering facilities and spilled feed contribute to the production of waste. These problems can be reduced by careful management and maintenance of feeders, watering facilities, and associated equipment.

A record should be kept of the data, assumptions, and calculations used to determine the kind, consistency, volume, location, and timing of the waste produced. The production estimates should include future expansion.

The majority of the operational actions required for the production function are managerial. Examples of operation actions could include management of the amount of bedding and washwater used. The AWMS plan should document the production rate assumed in the design of the system and give a method for determining the actual rate. An important reason for doing this is to assure that the actual rate does not exceed that assumed in the design of the system. Repercussions can occur if the design rate is exceeded. For example, a storage facility of an AWMS could fill up more quickly than anticipated, requiring that the facility be emptied earlier than intended. A response is needed where a production rate exceeds design assumptions.

For a dairy operation, the response might be reducing the amount of daily washwater used, excluding clean water entering the system, or enlarging the storage facility.

Roof gutters and downspouts

‘‘Roof gutters and downspouts, USDA/NRCS, AgWaste Management Handbook’‘

A good time to inspect roof gutters and downspouts is during storm events when leaks and plugged outlets can easily be discovered. Maintenance items would include cleaning debris from the gutters, unplugging outlets, repair of leaks, repair or replacement of damaged sections of gutters and downspouts, repair of gutter hangers and downspout straps, and repair of protective coatings.

Diversions

‘‘Diversions, USDA/NRCS, AgWaste Management Handbook’‘

Maintenance of diversions includes, as appropriate to the type of construction, mowing vegetation, eliminating weeds, repair of eroded sections, removal of debris and siltation deposits, and repair of concrete. Inspections should be made on a regularly scheduled basis and after major storm events.

Agricultural waste management systems, Production function operation

‘‘Agricultural waste management systems, Production function operation, USDA/NRCS, AgWaste Management Handbook’‘

The majority of the operational actions required for the production function are managerial. Examples of operation actions could include management of the amount of bedding and washwater used. The AWMS plan should document the production rate assumed in the design of the system and give a method for determining the actual rate. An important reason for doing this is to assure that the actual rate does not exceed that assumed in the design of the system. Repercussions can occur if the design rate is exceeded. For example, a storage facility of an AWMS could fill up more quickly than anticipated, requiring that the facility be emptied earlier than intended. A response is needed where a production rate exceeds design assumptions.

For a dairy operation, the response might be reducing the amount of daily washwater used, excluding clean water entering the system, or enlarging the storage facility.

Agricultural waste management systems, Solid/liquid separation

‘‘Agricultural waste management systems, Solid/liquid separation, USDA/NRCS, AgWaste Management Handbook’‘

Solid/liquid separation facilities include settling basins and a variety of stationary and mechanical screening devices. Maximum and minimum allowable flow rates are critical for these type facilities and need to be documented in the AWMS plan. If the flow rate exceeds the rate assumed in design, the residence time in settling basins may not be adequate for efficient settling.

If it exceeds the design capacity of a screening device, its efficiency will diminish. Generally, the screen manufacturer's information provides data on minimum and maximum flow rates. However, the decision maker may need to fine tune the flow rate to fit the consistency of waste produced.

The frequency of cleaning out settling basins needs to be established by the design and documented in the AWMS plan. Solids sometimes adhere to screening devices and, if allowed to dry, can clog the screen.

Rinsing the screen following use should be emphasized in the AWMS plan as a way to help avoid this problem.

Agricultural waste management systems, Solid/liquid separation facilities

‘‘Agricultural waste management systems, Solid/liquid separation facilities, USDA/NRCS, AgWaste Management Handbook’‘

Settling basins are constructed of earth, concrete, or other material. Inspection and maintenance of these facilities are much the same as those for components constructed of similar material.

Screening devices are generally constructed using various kinds of steel. These devices should be inspected regularly for deterioration of protective coatings, and repaired as necessary. Many of these devices also involve the use of electric motors, pumps, and gears. These should be routinely maintained as recommended by the manufacturer.

Agricultural waste management systems, Storage function

‘‘Agricultural waste management systems, Storage function, USDA/NRCS, AgWaste Management Handbook’‘

Storage is the temporary containment of the waste.

The storage facility of a waste management system is the tool that gives the manager control over the scheduling and timing of the system functions. For example, with adequate storage the manager has the flexibility to schedule the land application of the waste when the spreading operations do not interfere with other necessary tasks, when weather and field conditions are suitable, and when the nutrients in the waste can best be used by the crop. The storage period should be determined by the utilization schedule.

Figure 9-2 Waste management functions

The waste management system should identify the storage period; the required storage volume; the type, estimated size, location, and installation cost of the storage facility; the management cost of the storage process; and the impact of the storage on the consistency of the waste.

Waste storage ponds

‘‘Waste storage ponds, USDA/NRCS, AgWaste Management Handbook’‘

Regularly scheduled inspections and timely maintenance are required for waste storage ponds because their failure can result in catastrophic consequences.

The consequences of failure may affect public safety and environmental degradation. Inspections should focus on and result in the repair of leaks, slope failures, excessive embankment settlement, eroded banks, and burrowing animals.

Flow from toe and foundation drains should be inspected for quantity of flow changes and for discoloration.

If flows from these drains suddenly increase, it could mean a leak has developed. If the flow is normally clear and suddenly becomes cloudy with silt, piping of the embankment could be suspected. Appurtenances, such as liners, concrete structures, pipelines, and spillways, need to be inspected and repaired if found to be deficient. Vegetative cover needs to be routinely maintained by mowing, and weeds and woody growth need to be eliminated. Safety features, such as fences, warning signs (fig. 13-4), tractor stop blocks, and rescue equipment, need careful maintenance.

Earthen waste storage ponds should be inspected carefully during and after they are emptied. Generally, these ponds are completely emptied over a short time.

A consequence of this draw-down may be inside bank failures, especially where the pond is constructed in heavier soils or has an imported soil liner constructed of heavier soils. Therefore, it should be recommended that the pond be carefully inspected during and immediately after emptying. Some pond features are best inspected when the pond is filling or is full. For example, inspection for toe drainage and foundation leaks is best done when the pond is filling or full.

Figure 13-4 Waste storage pond warning sign

Waste storage structures-tanks

‘‘Waste storage structures-tanks, USDA/NRCS, AgWaste Management Handbook’‘

Inspection and maintenance of waste storage tanks depend on the type of tank and the material used in construction. However, regardless of the construction they should be inspected regularly for leaks and degradation.

Concrete tanks should be inspected on a regularly scheduled basis for cracks and degradation of the concrete. Any sudden or unexpected drop or rise in the liquid level should be documented, the cause investigated, and the problem corrected.

Inspection or repair of waste storage tanks is a hazardous undertaking because it may involve entry into the tank where toxic, oxygen displacing, or explosive gases may be present. The safety section of this section gives a procedure for safe entry into confined spaces. Because of the caustic nature of wastes, a specialist in the repair of concrete should be consulted if cracks or degradation of concrete are observed.

An important consideration for below ground tanks is maintaining the water table below the elevations assumed in the design of the tank. Drains installed to control the water table must be inspected on a regular basis to assure that they are operating properly. If applicable, a caution should be included in the AWMS plan that liquid waste or water should not be allowed to pond on the ground surface surrounding the tank.

This ponding can result in hydrostatic pressures that exceed the tank's design loadings, which can cause cracking or uplift.

A popular material for aboveground waste storage tanks is fused glass-coated steel. This material is virtually indestructible to the caustic action of the waste if the coating remains intact; however, deterioration of the steel may result if the coating is damaged.

As such, it is important that the surface of these tanks be regularly inspected and repairs made. The area around bolts should be checked for loss of coating and rusting. Repairs should be made according to the manufacturer's recommendations.

Cathodic protection is required for some installations.

When included, the cathodic protection system should be inspected to assure that it is functioning properly.

The cathodic protection inspection requirements are dependent upon the type of system installed. The designer of the cathodic protection should be consulted on what to include in the O&M plan.

Steel tanks generally are not designed to withstand a load against the outside of the tank. Because of this, waste or other material should not be allowed to build up against the outside wall of the tank.

Careful attention needs to be given to the maintenance of safety features associated with waste storage tanks.

These features include warning signs, grates and lids for openings, fences, barriers, and rescue equipment.

Grates, lids, and gates should be secured in place when left unattended.

Waste storage structures-Stacking facilities

‘‘Waste storage structures-Stacking facilities, USDA/NRCS, AgWaste Management Handbook’‘

Concrete and lumber are used in the construction of waste stacking facilities. Concrete should be inspected for cracks and premature degradation. If any problems are found with the concrete, appropriate repairs should be made.

Lumber should be inspected for damage either by natural deterioration or from man, animal, or weather event causes. Damaged lumber should be replaced.

Roofs should be inspected regularly for leaks and damaged trusses, and repairs made promptly.

Treatment function maintenance

‘‘Treatment function maintenance, USDA/NRCS, AgWaste Management Handbook’‘

Agricultural waste management systems, Storage function operation =

‘‘Agricultural waste management systems, Storage function operation, USDA/NRCS, AgWaste Management Handbook’‘

Storage function components include waste storage ponds and structures. Storage structures include tanks and stacking facilities. Monitoring storage levels in relationship to the storage period is of prime importance in the operation of storage components.

The AWMS plan should give target storage levels by date throughout the storage period. To assure that the facilities do not fill prematurely, these levels should not be exceeded. An excellent way to present this in the AWMS plan is to equip an impoundment type storage facility with a staff gauge so that target gauge readings versus dates are given. A stage-storage curve (fig. 13-1) can also assist the decision maker in monitoring the storage's filling. The stage-storage curve relates the pond's water surface at any elevation to the pond's storage at that elevation. For example, if the waste storage pond for figure 13-1 was measured as having a water surface elevation of 304 feet, it can be determined using the stage storage curve that the pond contains 12,500 cubic feet of wastewater at that elevation. This storage can then be compared to anticipated storage if the pond had filled at the design filling rate.

To illustrate comparing actual versus design filling rate using the stage storage curve, say the pond above is in its 50th day of the storage period, and the design filling rate is 200 cubic feet per day. Therefore, the target storage level for that day would be: 200 cubic feet per day times 50 days, or 10,000 cubic feet plus the depth of precipitation less evaporation assumed to occur during this 50-day period.

Using the stage-storage curve, it can be determined that at a storage of 10,000 cubic feet the water surface elevation in the pond would be 303.4. Add the assumed depth of precipitation less evaporation assumed for this 50-day period to this elevation.

Figure 13-1 Stage-storage curve

For this example, if the precipitation less evaporation was assumed in design to be 0.6 feet, the target filling elevation for the 50th day would be 303.4 + 0.6 = 304.0, which would indicate actual filling is at the assumed design rate. However, actual precipitation amounts may vary from that assumed in design. For this reason, actual precipitation less evaporation should also be evaluated. For example, if the actual precipitation is less than that assumed, it would mean the pond above is filling at a rate in excess of the 200 cubic feet per day. On the other hand, if the actual precipitation less evaporation is more, the pond is filling at a rate less than the 200 cubic feet per day.

Keeping a record of the waste accumulation throughout the storage period should be recommended. A record of precipitation and evaporation amounts may also be important in determining the source of filling.

Storage components are generally operated so they are empty at the beginning of the storage period and are filled to or below capacity at the end. The management of storage components may need to be coordinated with the management of the production function if the rate of filling exceeds that assumed in design.

Uncovered impoundment storage components are subject to storm events that prematurely fill them. The AWMS plan should describe a procedure for emptying these facilities to the extent necessary in an environmentally safe manner to provide the capacity needed for future storms.

The design of liquid storage components may require a storage volume reserve for residual solids after the liquids have been removed. The amount reserved for this purpose depends on such things as the agitation before pumping and the care taken in pumping.

Agricultural waste management systems, Transfer function maintenance

‘‘Agricultural waste management systems, Transfer function maintenance, USDA/NRCS, AgWaste Management Handbook’‘

Components and equipment for the transfer function of an AWMS vary widely. Manufactured transfer equipment, such as pumps, conveyors, and tank wagons, should be maintained according to the manufacturer's instructions. Pipelines should be inspected to assure that proper cover is maintained, vents are not plugged, valves are working properly, and inlet and outlet structures are in good condition.

Agricultural waste management systems, Transfer function operation

‘‘Agricultural waste management systems, Transfer function operation, USDA/NRCS, AgWaste Management Handbook’‘

Transfer function components include reception pits, pipelines, picket dams, pumps, and other equipment, such as tank wagons, agitators, chopper-agitation pumps, and elevators. A surveillance type inspection should be recommended to assure that the components are functioning properly.

A clean water flush following use of pipelines, tank wagons, and conveyors is helpful in minimizing the build up of sludge. Methods for unplugging pipelines should be described. Draining of pipelines or other protective freeze protection measures should be addressed.

Struvite, a phosphate mineral that can form a hard-scale deposit in pipelines and other similar waste transfer components, is a potential problem in an AWMS that utilizes recycled lagoon or waste storage pond effluent for flushing. Occasional clean water flushes of the transfer component or addition of struvite formation inhibitors to the wastewater may be effective in reducing struvite buildup. If a struvite buildup occurs, the system may need to be cleaned with an acid solution.

Figure 13-2 Maintenance of minimum treatment volume

Proper agitation prior to transfer needs to be described in the AWMS plan. Agitation should be continued long enough so that the solids in the waste, including those in corners and recesses, are moved into suspension. The plan should address the spacing and duration of agitation. It should also give any precautions needed during agitation to prevent damage to pond liners. The consequences of inadequate agitation can be solids buildup, which can lead to difficult problems.

Agricultural waste management systems, Treatment function operation

‘‘Agricultural waste management systems, Treatment function operation, USDA/NRCS, AgWaste Management Handbook’‘

Treatment components include waste treatment lagoons, composting, oxidation ditches, solid/liquid separation, and drying/dewatering. The treatment function reduces the polluting potential of the waste and facilitates further management of the waste.

Proper operation of this function is essential if the desired treatment is to be achieved.

Agricultural waste management systems, Utilization function maintenance

‘‘Agricultural waste management systems, Utilization function maintenance, USDA/NRCS, AgWaste Management Handbook’‘

Waste utilization equipment includes solid manure spreaders, liquid manure spreaders, injection equipment, and irrigation equipment. The equipment should be maintained according to the manufacturer's recommendation.

If covered lagoons are used for biogas production, maintenance is similar to that needed for uncovered lagoons. The covered lagoons and other covered digesters need routine inspection of the covers or enclosures to check for tears or other opening that would allow gas to escape. Timely repairs must be made. The covered lagoon is generally designed for a constant level that is controlled by a pipe that discharges to either another lagoon or a waste storage pond. This pipe must be kept free of obstructions.

Digesters accumulate sludge that must be periodically removed. Some digesters are heated, and use pumps to circulate heated water. These pumps must lubricated and impellers and seals repaired as necessary.

Agricultural waste management systems, Utilization function operation

‘‘Agricultural waste management systems, Utilization function operation, USDA/NRCS, AgWaste Management Handbook’‘

Utilization is a function in an AWMS for the purpose of taking advantage of the beneficial properties of agricultural wastes, such as its nutrient content. Components of utilization are land application of nutrients and biogas generation. Land application is the most prevalently used method.

The AWMS plan should establish the amount, method, placement, and timing of land application of agricultural wastes. The timing required should consider climate and stage of crop growth to maximize crop uptake and minimize environmental impact. Timing should also consider the potential for premature germination of planted crops if the waste is applied too early. Testing the waste and the soil for nutrient content must be recommended as good practice for use in determining the actual rates of application. See appendix 13A for more information on manure testing.

For liquid waste applied with an irrigation system, the plan should give sprinkler numbers, size and types of sprinklers, length of setting, and flow rates of waste and dilution water, if any. For slurry or solid wastes, the plan should indicate the necessity of calibrating spreading equipment to assure the desired rate of application is achieved (fig. 13-3). Appendix 13A also describes several methods of manure spreader calibration.

Utilization involving biogas/methane production and recovery requires a high level of management to be successful. Complicating the operation of a digester is coordinating use of gas once it is produced. Since compression and storage of biogas is not practical, its use must generally match the energy production. The designer of the biogas system must be involved in developing the specific operational requirements.

Figure 13-3 Manure spreader calibration

Methane production and recovery system options include the covered anaerobic lagoon, complete mix digester, and plug flow digester. Because each operates at a constant level and does not provide for waste storage, they must be operated in conjunction with a storage facility of some type. Operation of biogas components is dependent upon proper loading of waste in terms of volatile solids, total solids, and waste volume. As such, their loading must be carefully monitored. Some manure requires treatment, such as solid/liquid separation and dilution, before it enters a lagoon or digester. The amount of gas produced is a good indication of proper loading. If gas production falls off, the loading should be checked.

Agricultural waste management systems, Waste treatment lagoons

‘‘Agricultural waste management systems, Waste treatment lagoons, USDA/NRCS, AgWaste Management Handbook’‘

Proper operation of waste treatment lagoons includes maintaining proper liquid levels and assuring that the maximum loading rates are not exceeded. Lagoons are designed for an assumed loading rate. The AWMS plan should document the maximum loading rate and suggest that it be monitored to assure that it is not exceeded. This can be done by comparing the sources and amounts of waste entering the lagoon to what was considered in design, such as number of animals.

Laboratory testing may be required if loading becomes a serious question. If the design loading rate is exceeded, the lagoon may not treat the waste as needed and undesirable and offensive odors may result. The rate of filling is important as well. If the rate of filling exceeds the design rate, the storage period is reduced and the lagoon must be pumped more frequently. The AWMS plan should describe a procedure for emptying part of the lagoon contents following a storm event that fills the lagoon prematurely to near its capacity to provide storage for future storms.

The AWMS plan must emphasize the need to maintain the liquid level in anaerobic lagoons at or above the minimum design volume (fig. 13-2). The proper pH must also be maintained if the desired treatment is to be achieved. As such, the pH should be measured periodically. The minimum acceptable pH is about 6.5.

If pH falls below 6.5, a pound of hydrated lime or lye should be added per 1,000 square feet of lagoon surface daily until the pH reaches 7.0.

Aerobic lagoons require a design surface area and a depth within the range of 2 to 5 feet to effectively treat waste. This information must be provided in the AWMS plan. Mechanically aerated lagoons require that a minimum design volume be maintained and the designed amount of aeration be provided for effective treatment and odor reduction. The plan should recommend that these operational aspects be carefully monitored.

Agricultural waste management systems, Waste treatment lagoons, maintenance

‘‘Agricultural waste management systems, Waste treatment lagoons, USDA/NRCS, AgWaste Management Handbook’‘

The inspection and maintenance requirements for a waste treatment lagoon are about the same as those for a waste storage pond. One difference is that ponds generally are completely emptied, whereas lagoons retain a minimum storage pool. Maintenance of aerated lagoons would be complicated by the aeration equipment involved. The AWMS plan should indicate that the maintenance of the aeration equipment is to be according to the manufacturer's recommendations.

Agricultural Waste Management Systems plan (AWMS plan)

‘‘Agricultural Waste Management Systems plan (AWMS plan), USDA/NRCS, AgWaste Management Handbook’‘

An Agricultural Waste Management System plan is prepared as an integral part of and in concert with conservation plans. It is prepared in consultation with the producer and is formulated to expressly guide the producer in the installation, operation, and maintenance of the AWMS. The AWMS plan must account for all management systems operating on the farm that relate to the AWMS operation. For example, manure nutrient management must be a part of the overall nutrient management. The plan must interface with other systems, such as the tillage, irrigation, and cropping systems.

Agronomic practices/treatment, economics of

‘‘Economics of agronomic practices/treatment, USDA/NRCS, Agronomy Manual’‘

To assess the economics of the agronomic practices is often difficult. The traditional method used to assess the economics of various agronomic practices is to compare different methods to achieve a given treatment or purpose. For example, a seedbed must be prepared for planting. One method would be to use mulch-till and compare that cost to using the no-till. It is critical that the costs involved in agronomic practices/treatments be carefully analyzed. For example, in the mulch-till vs. no-till scenario mentioned previously, if the producer owns both mulch-till tools and no-till tools, one can only evaluate operation and maintenance costs of the equipment because the costs of the equipment are already incurred regardless of the system used.

Most agronomic type practices/treatments do not require a direct outlay of cash. Many of the practices and treatments are often more of a change in management techniques rather than a formal installation.

To select the most cost-effective cropland management system, first develop two or more alternative management systems that adequately treat the resources and meet the producer's objectives. Then assess the total costs to implement each system vs. the expected impacts and returns.

Generally speaking, agronomic practices do not cost; they pay. The key is to plan and apply the combination of practices/treatments that address the management style of the producer and will result in use of the land within its capability.

Air, federal laws concerning

‘‘Air, federal laws concerning, USDA/NRCS, AgWaste Management Handbook’‘

The Air Pollution Act of 1955 authorized federally funded air pollution research. Later legislation included the Motor Vehicle Pollution Control Act of 1965, the Air Quality Act of 1967, and the Clean Air Act of 1970. The Clean Air Act provides for uniform air quality standards and control of emissions from existing facilities. It also prohibits construction of new facilities that violate or interfere with Federal or State regulations for air quality standards. Many of the State air quality requirements have been established as a direct result of Federal legislation. Most private citizen complaints and civil suits brought against livestock operators have been because of odor problems.

The Clean Air Act Amendment of 1990 (Public Law 101-549) has provisions of importance to producers of agricultural products. Goals of the law having an agricultural orientation are those for reduction of emissions that cause acid rain and those that target protection of stratospheric ozone. Ammonia volatilization from animal and other agricultural operations will most likely come under increased scrutiny and possible control as a source of soil and water acidification. Some states are starting to request atmospheric ammonia test results on air samples taken at the property lines of the animal operations.

Methane emissions from "rice and livestock production" and from "all forms of waste management including storage, treatment, and disposal" are mentioned in the 1990 law as being of concern with regard to ozone depletion. These sources and others, both nationally and internationally, are to be evaluated by EPA jointly with the Secretaries of Agriculture and Energy, and control options will be developed that can be used to stop or reduce growth of methane concentrations in the atmosphere.

Air as an aspect of planning Agricultural Waste Management Systems

‘‘Air as an aspect of planning Agricultural Waste Management Systems, USDA/NRCS, AgWaste Management Handbook’‘

An AWMS often has an adverse impact on the air resource, so planning must consider ways to minimize degradation of air quality. Objectionable odors from confined livestock, waste storage areas, lagoons, and field application of wastes must be considered in planning an AWMS.

Emissions of ammonia and other gases from farming operations including livestock operations are associated with soil acidification via an acid-rain type phenomenon.

These type emissions are also coming under scrutiny for their contribution to other environmental concerns, such as the greenhouse effect/global warming.

Figure 2-2 Resource considerations

Air movement, humidity, and the odors air may carry from the AWMS must be considered. Windbreaks, screens, or structure modification may be required to create conditions that minimize the movement of air.

Alley Cropping

‘‘Alley Cropping, USDA/NRCS, Conservation Practice Standard’‘

DEFINITION

Trees or shrubs planted in a set or series of single or multiple rows with agronomic, horticultural crops or forages cultivated in the alleys between the rows of woody plants.

PURPOSES

Produce tree or shrub products (wood, nuts, berries, fodder, mulch, etc.) along with crops or forages to improve or optimize the economic viability of the operation. This purpose may be accomplished alone or concurrently with one or more of the following purposes:

• Improve crop or forage quality and quantity by enhancing microclimatic conditions.

• Reduce excess surface water runoff and erosion.

• Improve utilization and recycling of soil nutrients.

• Reduce excess subsurface water or control water table depths.

• Provide food and cover habitat for wildlife.

CONDITIONS WHERE PRACTICE APPLIES

On all lands where crops or forages are grown and improvement of the economic or environmental conditions is desired.

CRITERIA

General Criterguia Applicable To All Purposes

The location, layout, species and density of the trees and shrubs will accomplish the purpose and intended function for both the agronomic or horticultural crop or forage as well as the trees or shrubs. Plant species selection will be based on the following:

• Combinations of crops or forages and woody plants shall be compatible and complementary, and provide the products and crops that meet landowner objectives.

• Crops or forages shall be adapted to the climatic region and the soil resource, marketable and suited to the landowner's equipment and management capabilities.

• Crop or forage sequence and woody species selection shall be determined using an acceptable nutrient balance procedure. Select crops, forages and woody species to maximize the utilization and recycling of soil nutrients, animal wastes and plant residues and to maintain soil organic matter content.

• Crops or forages and woody plants shall be selected for rooting depths and water requirements not to exceed available soil water.

• Select pest resistant crop/forage and tree/shrub varieties.

• Avoid selecting tree or shrub species which provide habitat to animal, bird, or insect species considered to be pests of the accompanying crop or forage.

The distance between the sets of trees or shrubs will be determined by tree or shrub management objectives, light requirements and growth period of the crops or forages in the alleys, erosion control needs, and machinery widths.

Crops (woody and herbaceous) shall be grown in a planned conservation management system.

Tree or shrub rows will be oriented on the contour to control water erosion or perpendicular to troublesome winds to control wind erosion.

Soil erosion by wind or water will be controlled by vegetative or other means until the alley cropping design is fully functional.

Planting dates and care in handling and planting the seed or seedlings will assure acceptable plant survival.

Only viable and high quality planting stock or seed of adapted woody species will be used for establishing the tree or shrub rows.

Site preparation shall be sufficient for establishment and growth of selected species and appropriate for the site.

CONSIDERATIONS

Crop, forage, tree and/or shrub varieties selected should be tolerant to herbicides that will be used in the management of either the crops, forages, trees or shrubs.

Spacing between the rows of trees or shrubs may be adjusted, within the limits listed above, to accommodate equipment widths and turnarounds.

Species diversity including use of native species should be considered to avoid loss of function due to species-specific pests.

High value trees or shrubs should be selected to maximize economic returns.

Anticipate possible offsite effects and modify the practice design accordingly.

PLANS AND SPECIFICATIONS

Specifications for applying this practice shall be prepared for each site and recorded using approved specification sheets, job sheets, narrative statements in the conservation plan, or other acceptable documentation.

OPERATION AND MAINTENANCE

The trees, shrubs, crops, and/or forages will be inspected periodically and protected from adverse impacts including insects, diseases or competing vegetation. The trees or shrubs will also be protected from fire and livestock damage.

All other specified maintenance measures and techniques of tree/shrub establishment will be continued until plant survival and establishment are assured. This includes replacement of dead and dying trees or shrubs and control of undesirable competing vegetation.

Any removals of tree or shrub products and use of fertilizers, pesticides, and other chemicals shall be conducted in a manner that maintains the intended purpose.

The type, use and timing of maintenance equipment will be appropriate to accomplish operation and maintenance tasks while not damaging or degrading the site and soil conditions.

Alley Cropping, definition

‘‘Alley Cropping, definition, USDA/NRCS, Core 4 Technical Reference’‘

Alley cropping is broadly defined as the planting of trees or shrubs in two or more sets of single or multiple rows at wide spacing, creating alleyways within which agricultural, horticultural, or forage crops are cultivated (fig. 3a:1). The trees may include valuable hardwood species, such as nut trees, or trees desirable for wood products. This approach is sometimes called intercropping. The foundation for alley cropping dates back to 17th century (perhaps earlier) Europe where fruit orchards containing intercrops of cereal grains and other crops were grown between the rows of fruit trees. This concept was brought to North America where today most of the emphasis and research focuses on pecan and black walnut alley cropping or intercropping applications. However, there are numerous other potential tree, shrub, and crop combinations.

Alleys for collection in waste system component design

‘‘Alleys for collection in waste system component design, USDA/NRCS, AgWaste Management Handbook’‘

Alleys are paved areas where the animals walk. They generally are arranged in straight lines between animal feeding and bedding areas. On slatted floors, animal hoofs work the manure through the slats into the alleys below, and the manure is collected by flushing or scraping the alleys.

Scrape alleys and open areas

‘‘Scrape alleys and open areas, USDA/NRCS, AgWaste Management Handbook’‘

Two kinds of manure scrapers are used to clean alleys (fig. 10-3). A mechanical scraper is dedicated to a given alley. It is propelled using electrical drives attached by cables or chains. The drive units are often used to power two mechanical scrapers that are traveling in opposite directions in parallel alleys in an oscillating manner. Some mechanical scrapers are in alleys under slatted floors.

Figure 10-2

Figure 10-3

A tractor scraper can be used in irregularly shaped alleys and open areas where mechanical scrapers cannot function properly. It can be a blade attached to either the front or rear of a tractor or a skidsteer tractor that has a front-mounted bucket.

The width of alleys depends on the desires of the producer and the width of available equipment. Scrape alley widths typically vary from 8 to 14 feet for dairy and beef cattle and from 3 to 8 feet for swine and poultry.

Flush alleys

‘‘Flush alleys, USDA/NRCS, AgWaste Management Handbook’‘

Alleys can also be cleaned by flushing. Grade is critical and can vary between 1.25 and 5 percent. It may change for long flush alleys. The alley should be level perpendicular to the centerline. The amount of water used for flushing is also critical. An initial flow depth of 3 inches for underslat gutters and 4 to 6 inches for open alleys is necessary.

The length and width of the flush alley are also factors. Most flush alleys should be less than 200 feet long. The width generally varies from 3 to 10 feet depending on animal type. For underslat gutters and alleys, channel width should not exceed 4 feet. The width of open flush alleys for cattle is frequently 8 to 10 feet.

Flush alleys and gutters should be cleaned at least twice per day. For pump flushing, each flushing event should have a minimum duration of 3 to 5 minutes.

Tables 10-1 and 10-2 indicate general recommendations for the amount of flush volume. Table 10-3 gives the minimum slope required for flush alleys and gutters.

Table 10-1

Table 10-2

Table 10-3

Figures 10-4 and 10-5 illustrate flush alleys.

Figure 10-4

Figure 10-5

Several mechanisms are used for flushing alleys. The most common rapidly empties large tanks of water or use high-volume pumps. Several kinds of flush tanks are used (fig. 10-6). One known as a tipping tank pivots on a shaft as the water level increases. At a certain design volume, the tank tips, emptying the entire amount in a few seconds, which causes a wave that runs the length of the alley.

Figure 10-6

Some flush tanks have manually opened gates. These tanks are emptied by opening either a valve, a standpipe, a pipe plug, or a flush gate. Float switches can be used to control flushing devices. Another kind of flush tank uses the principle of a siphon. In this tank the water level increases to a given point where the head pressure of the liquid overcomes the pressure of the air trapped in the siphon mechanism. At this point the tank rapidly empties, causing the desired flushing effect.

Most flush systems use pumps to recharge the flush tanks or to supply the necessary flow if the pump flush technique is used. Centrifugal pumps typically are used. The pumps should be designed for the work that they will be doing. Low volume pumps (10 to 150 gpm) may be used for flush tanks, but high volume pumps (200 to 1,000 gpm) are needed for alley flushing. Pumps should be the proper size to produce the desired flow rate. Flush systems may rely on recycled lagoon water for the flushing liquid.

In some parts of the country where wastewater is recycled from lagoons for flush water, salt crystals (struvite) may form inside pipes and pumps and cause decreased flow. Use of plastic pipe and fittings and pumps that have plastic impellers can reduce the frequency between cleaning or replacing pipes and pumps. If struvite formation is anticipated, recycle systems should be designed for periodic clean out of pumps and pipe. A mild acid, such as dilute hydrochloric acid (1 part 20 mole hydrochloric acid to 12 parts water), can be used. A separate pipe may be needed to accomplish acid recycling. The acid solution should be circulated throughout the pumping system until normal flow rates are restored. The acid solution should then be removed. Caution should be exercised when disposing of the spent acid solution to prevent ground or surface water pollution.

Amount of limestone to raise pH

Amount of waste applied and amount of phosphorus in soil

‘‘Amount of waste applied and amount of phosphorus in soil, USDA/NRCS, AgWaste Management Handbook’‘

Organic P readily adsorbs to soil particles and tends to depress the adsorption of inorganic P, especially where organic P is applied at high rates. Thus, the concentrations of soluble and labile P increase significantly at high application rates of organic P.

When organic P and commercial superphosphate are applied at the same rates, the superphosphate P will be less effective in raising the concentration of soluble P than the P applied in manure or other organic waste.

This occurs because the organic P competes for adsorption sites, resulting in more P staying in soluble form rather than becoming attached as labile P.

Long-term applications of organic P at rates that exceed the uptake rate of plants will result in saturation of the adsorption sites near the soil surface. This, in turn, results in greatly increased concentrations of both soluble and labile P. The excess soluble P can either leach downward to a zone that has more attachment sites and then be converted to labile P or fixed P, or it can be carried off the land in runoff water.

Figure 3-4 Phosphorus retention and solubility as related to soil pH.

If soils that have high labile P concentrations reach surface water as sediment, they will continuously desorb or release P to the soluble form until equilibrium is attained. Therefore, sediment from land receiving animal waste at high rates or over a long period of time will have a high potential to pollute surface water.

Table 3-4 illustrates typical dissolved phosphorus concentrations reported in surface runoff from fields where animal waste was applied at recommended agronomic rates. Although this table is based on research findings, it is provided for illustration only because it does not necessarily represent concentrations that might occur in different regions of the country where the land slopes, soil types, waste application quantities and rates, or amounts of precipitation could be different than those for which the research was conducted.

Waste that is surface applied can produce total P concentrations in surface runoff higher than those shown in table 3-4,especially if the waste is applied at high rates, not incorporated, applied on snow-covered or frozen ground, or applied on fields with inadequate erosion control practices.

Anaerobic lagoons used in treatement of agricultural waste

‘‘Anaerobic lagoons used in treatment of agricultural waste, USDA/NRCS, AgWaste Management Handbook’‘

Anaerobic lagoons are widely accepted in the United States for the treatment of animal waste. Anaerobic treatment of animal waste helps to protect water quality by reducing much of the organic concentration (BOD, COD) of the waste. Anaerobic lagoons also reduce the nitrogen content of the waste through ammonia volatilization and effectively reduce animal waste odors if the lagoon is managed properly.

Design

‘‘Design, USDA/NRCS, AgWaste Management Handbook’‘

The maximum operating level of an anaerobic lagoon is a volume requirement plus a depth requirement. The volume requirement is the sum of the following volumes:

Minimum treatment volume, ft 3 (MTV)

Manure volume, wastewater volume, and clean water, ft 3 (WV)

Sludge volume, ft 3 (SV) The depth requirement is the normal precipitation less evaporation on the lagoon surface.

Polluted runoff from a watershed must not be included in a lagoon unless a defensible estimate of the volatile solid loading can be made. Runoff from a watershed, such as a feedlot, is not included in a lagoon because loading would only result during storm events and because the magnitude of the loading would be difficult, if not impossible, to estimate. As a result, the lagoon would be shocked with an overload of volatile solids.

If an automatic outflow device, pipe, or spillway is used, it must be placed at a height above the maximum operating level to accommodate the 25-year, 24-hour storm precipitation on the lagoon surface. This depth added to the maximum operating level of the lagoon establishes the level of the required volume or the outflow device, pipe, or spillway. A minimum of 1 foot of freeboard is provided above the outflow and establishes the top of the embankment. Should state regulation preclude the use of an outflow device, pipe, or spillway or if for some other reason the lagoon will not have these, the minimum freeboard is 1 foot above the top of the required volume.

The combination of these volumes and depths is illustrated in figure 10-21. The terms and derivation are explained in the following paragraphs.

Anaerobic waste treatment lagoons are designed on the basis of volatile solids loading rate (VSLR) per 1,000 cubic feet. Volatile solids represent the amount of solid material in wastes that will decompose as opposed to the mineral (inert) fraction. The rate of solids decomposition in anaerobic lagoons is a function of temperature; therefore, the acceptable VSLR varies from one location to another. Figure 10-22 indicates the maximum VSLR's for the United States. If odors need to be minimized, VSLR should be reduced by 25 to 50 percent.

The minimum treatment volume (MTV) represents the volume needed to maintain sustainable biological activity. The minimum treatment volume for VS can be determined using equation 10-4.

If feed spillage exceeds 5 percent, VSP should be increased by 4 percent for each additional 1 percent spillage.

Waste volume (WV) should reflect the actual volume of manure, wastewater, flush water that will not be recycled, and clean dilution water added to the lagoon during the treatment period. The treatment period is either the detention time required to obtain the desired reduction of pollution potential of the waste or the time between land application events, whichever is longer. State regulations may govern the minimum detention time. Generally, the maximum time between land application events determines the treatment period because this time generally exceeds the detention time required.

As the manure is decomposed in the anaerobic lagoon only part of the total solids (TS) is reduced. Some of the TS is mineral material that will not decompose, and some of the VS require a long time to decompose. These materials, referred to as sludge, gradually accumulate in the lagoon. To maintain the minimum treatment volume (MTV), the volume of sludge accumulation over the period of time between sludge removal must be considered. Lagoons are commonly designed for a 15- to 20-year sludge accumulation period. The sludge volume (SV) can be determined using equation 10-6:

Figure 10-21 Anaerobic lagoon cross section

Figure 10- 22 Anaerobic lagoon loading rate

Sludge accumulation ratios should be taken from table 10-4. An SAR is not available for beef, but it can be assumed to be similar to that for dairy cattle.

The lagoon volume requirements are for accommodation of the minimum treatment volume, the sludge volume, and the waste volume for the treatment period. This is expressed in equation 10-7.

Table 10-4 Sludge accumulation ratios (Barth 1985)

Table 10-5 Minimum top width for lagoon embankments (USDA 1984, Waste...)

In addition to the lagoon volume requirement (LV), a provision must be made for depth to accommodate the normal precipitation less evaporation on the lagoon surface; the 25-year, 24-hour storm precipitation; the depth required to operate the emergency outflow; and freeboard. Normal precipitation on the lagoon surface is based on the critical treatment period that produces the maximum depth. This depth can be offset to some degree by evaporation losses on the lagoon surface. This offset varies, according to the climate of the region, from a partial amount of the precipitation to an amount in excess of the precipitation. Precipitation and evaporation can be determined from local climate data.

The minimum acceptable depth for anaerobic lagoons is 6 feet, but in colder climates at least 10 feet is recommended to assure proper operation and odor control.

The design height of an embankment for a lagoon should be increased by the amount needed to ensure that the design elevation is maintained after settlement.

This increase should not be less than 5 percent of the design fill height. The minimum top width of the lagoon should be as shown in table 10-5, although a width of 8 feet and less is difficult to construct.

The combined side slopes of the settled embankment should not be less than 5 to 1 (horizontal to vertical). The inside slopes can vary from 1 to 1 for excavated slopes to 3 to 1 or flatter where embankments are used. Construction technique and soil type must also be considered. In some situations a steep slope may be used below the design liquid level, while a flatter slope is used above the liquid level to facilitate maintenance and bank stabilization. The minimum elevation of the top of the settled embankment should be 1 foot above the maximum design water surface in the lagoon. Table 10-5 Minimum top width for lagoon embankments (USDA 1984, Waste...)

A lagoon should be constructed to avoid seepage and potential ground water pollution. Care in site selection, soils investigation, and design can minimize the potential for these problems. In cases where the lagoon needs to be sealed, the techniques discussed in Appendix 10D, Geotechnical design and construction guidelines for waste impoundment liners, can be used.

Also refer to Geology and Ground Water Considerations for more information on site evaluation, investigations, and testing. Figure 10-23 shows a two lagoon systems.

If overtopping can cause embankment failure, an emergency spillway or overflow pipe should be provided. A lagoon can have an overflow to maintain a constant liquid level if the overflow liquid is stored in a waste storage pond or otherwise properly managed. The inlet to a lagoon should be protected from freezing. This can be accomplished by using an open channel that can be cleaned out or by locating the inlet pipe below the freezing level in the lagoon. Because of possible blockages, access to the inlet pipe is needed. Venting inlet pipes prevents backflow of lagoon gases into the animal production facilities.

Sludge removal is an important consideration in the design. This can be accomplished by agitating the lagoon and pumping out the mixed sludge or by using a dragline for removing floating or settled sludge. Some pumps can remove sludge, but not deposited rocks, sand, or grit. The sludge removal technique should be considered when determining lagoon surface dimensions. Many agitation pumps have an effective radius of 75 to 100 feet. Draglines may only reach 30 to 50 feet into the lagoon.

Figure 10-23 Anaerobic lagoon recycle systems

Management

‘‘Management, USDA/NRCS, AgWaste Management Handbook’‘

Anaerobic lagoons must be managed properly if they are to function as designed. Specific instructions about lagoon operation and maintenance must be included in the overall waste management plan that is supplied to the decision maker. Normally an anaerobic lagoon is managed so that the liquid level is maintained at or below the maximum operating level as shown in figure 10-21. The liquid level is lowered to the minimum treatment level at the end of the treatment period. It is good practice to install markers at the minimum treatment and maximum operating levels. The minimum liquid level in an anaerobic lagoon before wastes are added should coincide with the MTV. If possible a lagoon should be put into service during the summer to allow adequate development of bacterial populations. A lagoon operates more effectively and has fewer problems if loading is by small, frequent (daily) inflow, rather than large, infrequent slug loads.

The pH should be measured frequently. Many problems associated with lagoons are related to pH in some manner. The optimum pH is about 6.5. When pH falls below this level, methane bacteria are inhibited by the free hydrogen ion concentration. The most frequent cause of low pH in anaerobic digestion is the shock loading of organic material that stimulates the facultative acid-producing bacteria. Add hydrated lime or lye if pH is below 6.5. Add 1 pound per 1,000 square feet daily until pH reaches 7.

Lagoons are designed based on a given loading rate. If an increase in the number of animals is anticipated, sufficient capacity to handle all of the expected waste load should be available. The most common problem in using lagoons is overloading, which can lead to odors, malfunctioning, and complaints. When liquid removal is needed, the liquid level should not be dropped below the MTV plus SV levels. If evaporation exceeds rainfall in a series of dry years, the lagoon should be partly drawn down and refilled to dilute excess concentrations of nutrients, minerals, and toxics. Lagoons are typically designed for 15 to 20 years of sludge accumulation. After this time the sludge must be cleaned out before adding additional waste.

Sometimes operators want to use lagoon effluent as flush water. To polish and store water for this purpose, waste storage ponds can be constructed in series with the anaerobic lagoon. The capacity of the waste storage pond should be sized for the desired storage volume. A minimum capacity of the waste storage pond is the volume for rainfall (RFV), runoff (ROV), and emergency storm storage (ESV). By limiting the depth to less than 6 feet, the pond will function more nearly like an aerobic lagoon. Odors and the level of ammonia, ammonium, and nitrate will be more effectively reduced.

Design example 10-5-Anaerobic lagoon

‘‘Design example 10-5-Anaerobic lagoon, USDA/NRCS, AgWaste Management Handbook’‘

Mr. Oscar Smith of Rocky Mount, North Carolina, has requested assistance in developing an agricultural waste management system for his 6,000 pig finishing facility. The alternative selected includes an anaerobic lagoon. The animals average 150 pounds. The 25-year, 24-hour storm for the area is 6 inches (appendix 10B). Mr. Smith needs 180-day intervals between lagoon pumping. During this time the net precipitation should be 2 inches, based on data from appendices 10B and 10C. He wants to use the lagoon for at least 5 years before removing the sludge. Worksheet 10A-3 is used to determine the necessary volume for this lagoon.

Completed worksheet for Design example 10-5

Animal manure application- odors, Impact of Residue Management

‘‘Animal manure application- odors, Impact of Residue Management, USDA/NRCS, Core 4 Technical Reference’‘

With no-till/strip-till and ridge-till practices, odors can present a problem with surface application of animal manure. Consideration should be given to wind direction at the time of application and the nearness of neighbors to help reduce odor concerns. Injecting animal wastes can significantly reduce odors. Injection equipment should be chosen that would not excessively disturb the soil surface and bury too much surface residue. Injecting manure in a no-till/strip-till or ridge-till system should be viewed no differently than knifing-in anhydrous ammonia or other forms of nutrients. Recently developed no-till injectors inject liquid manure with minimal soil and residue disturbance.

The quantity and distribution of manure is important. A large manure application without secondary tillage to mix it with the soil may burn the new crop.

In the case of mulch-till, chisels or disks can be used to incorporate the manure and reduce odor and runoff concerns. Again, care should be taken when incorporating the manure to ensure that sufficient residue is left on the soil surface to meet the erosion reduction goal. For example, a normal tillage trip might be omitted to accommodate the manure incorporation.

Animal Trails And Walkways

‘‘Animal Trails And Walkways, USDA/NRCS, Conservation Practice Standard’‘

DEFINITION

A travel facility for livestock and/or wildlife to provide movement through difficult or ecologically sensitive terrain.

PURPOSES

This practice may be applied as part of a conservation management system to accomplish one or more of the following purposes:

• Provide or improve access to forage, water and/or shelter.

• Improve grazing efficiency and distribution.

• Divert travel away from ecologically sensitive and/or erosive sites.

CONDITIONS WHERE THIS PRACTICE APPLIES

On grazing lands where animal movement is impeded or restricted such as, steep rough terrain,

across rock outcrops, through dense timber or brush, over lava beds, on marsh rangelands, and

grazing lands susceptible to overflow by water.

CRITERIA

General Criteria Applicable For All The Purposes Stated Above.

Trails or walkways shall be constructed wide enough to accommodate movement of livestock and access by operator.

Trails or walkways shall be constructed in such a manner that accelerated erosion will not occur. Where necessary diversions with a safe outlet will be provided.

Trails or walkways seeded or planted to vegetative cover will be protected from grazing until planting material is fully established and capable of withstanding grazing and/or trampling.

Criteria Applicable For Walkways.

Walkways will be constructed to meet minimum height requirements above normal high water.

During the construction process of walkways, borrow pits will be staggered so that access to grazing areas and back to walkway will be available from either side.

When necessary structures will be installed to prevent interference with natural water movement or to control salt water intrusion.

CONSIDERATIONS

Other practices that facilitate grazing distribution and proper intensity such as prescribed grazing should be implemented along with this practice.

PLANS AND SPECIFICATIONS

Each trail or walkway shall have a site specific design based on the criteria in this standard and as supplemented by additional criteria developed by each individual State using this practice.

OPERATION AND MAINTENANCE

Operation will consist of periodic grading or shaping on trails and walkways to maintain designed dimensions. Maintenance will consist of repair that may be needed following major storm events such as high runoff events, high tides or other occurrences that cause damage and interfere in the normal operation of this practice.

Animals as an aspect of planning Agricultural Waste Management Systems

‘‘Animals as an aspect of planning Agricultural Waste Management Systems, USDA/NRCS, AgWaste Management Handbook’‘

Obviously, an AWMS for a livestock enterprise must be planned to be compatible with the type of animals involved. A healthy and safe environment is essential for these animals. Structures need to be planned to both protect the AWMS structure from the animals and the animals from the structure. Planning should also consider hazards from disease, parasites, and insects. Wildlife should also be considered.

Pollution of receiving water can have a significant effect on animals. Organic matter can drastically reduce dissolved oxygen levels in a stream, and high ammonia concentrations can kill fish. In addition, water over-enriched by nutrients, contaminated by agricultural chemicals, or polluted by bacteria can result in an environment that has a very negative effect on animals.

Application of agricultural wastes in Field and forage crops

‘‘Application of agricultural wastes in Field and forage crops, USDA/NRCS, AgWaste Management Handbook’‘

Manure and sewage have been used for centuries as fertilizers and soil amendments to produce food for human and animal consumption. Generally, manure and sludges are applied to crops that are most responsive to nitrogen inputs. Field crops that are responsive include corn, sorghum, cotton, tobacco, sugar beets, and cane.

Sewage sludge should not be used on tobacco. The liming effect of the sludge can enhance the incidence of root diseases of tobacco. It can also elevate cadmium levels in tobacco leaves, rendering it unfit for marketing (USDA 1986).

Cereal grains generally do not receive fertilizer application through manure because spreading to deliver low rates of nitrogen is difficult. Small grains are prone to lodging (tipping over en masse under wet, windy conditions) because of the soft, weak cell walls derived from rapid tissue growth.

Legumes, such as alfalfa, peanuts, soybeans, and clover, benefit less by manure and sludge additions because they fix their own nitrogen. The legumes, however, use the nitrogen in waste products and produce less symbiotically fixed nitrogen. Alfalfa, a heavy user of nitrogen, can cycle large amounts of soil nitrogen from a depth of up to 6 feet. Over 500 pounds per acre of nitrogen uptake by alfalfa has been reported (Schuman & Elliott 1978; Schertz & Miller 1972).

The great danger of using manure and sludges on legume forages is that the added nitrogen may promote the growth of the less desirable grasses that are in the stand. This is caused primarily by introducing another source of nitrogen, but it can also be a result of the physical smothering of legume plants by heavy application cover of manure.

Grass tetany, a serious and often fatal disorder in lactating ruminants, is caused by a low magnesium content in rapidly growing cool season grasses. Cattle grazing on magnesium deficient forage develop health problems. High concentrations of nitrogen and potassium in manure applications to the forages aggravate the situation. Because of the high levels of available nitrogen and potassium in manure, early season applications on mixed grass-legume forages should be avoided until the later-growing legume is flourishing because legumes contain higher concentrations of magnesium than grasses.

Table 6-3 General effects of trace element toxicity on common crops (Kabata & Pendias 1984)

Perennial grasses benefit greatly by the addition of manure and sludges. Many are selected as vegetative filters because of their efficient interception and uptake of nutrients and generally longer active growing season. Others produce large quantities of biomass and thus can remove large amounts of nutrients, especially nitrogen, from the soil-plant system.

Bermudagrass pastures in the South have received annual rates of manure that supply over 400 pounds of nitrogen per acre without experiencing excessive nitrate levels in the forage. However, runoff and leaching potentials are high with these application rates, and they must be considered in the utilization plan.

Grass sods also accumulate nitrogen. An experiment in England carried out for 300 years at Rothamsted showed a steady increase in soil nitrogen for about 125 years before leveling off when an old plowed field was retired to grass (Wild 1988). However, where waste is spread on the soil surface, any ammonia nitrogen in the waste generally is lost to the air as a gas unless immediately incorporated.

Grass fields used for pasture or hay must have waste spread when the leaves of the plants are least likely to be contaminated with manure. If this is done, the grass quality is not lessened when harvested mechanically or grazed by animals (Simpson 1986).

Spreading wastes immediately after harvest and before regrowth is generally the best time for hay fields and pastures in a rotation system. This is especially important where composted sludge is applied on pasture at rates of more than 30 tons per acre. Cattle and sheep ingesting the compost inadvertently can undergo copper deficiency symptoms (USDA 1986).

Some reports show that manure applied to the soil surface has caused ammonium toxicity to growing crops (Klausner and Guest 1981). Young corn plants 8 inches high showed ammonia burn after topdressing with dairy manure during a period of warm, dry weather. The symptom disappeared after a few days with no apparent damage to the crop. This is very similar to corn burn affected during side-dressing by anhydrous ammonia. Liquid manure injected between corn rows is toxic to plant roots and causes temporary reduction in crop growth. Warming soil conditions dissipate the high ammonium levels, converting the ammonium to nitrates, and alleviate the temporary toxic conditions (Sawyer and Hoeft 1990).

Table 6-4 Interaction among elements within plants and adjacent to plant roots

Table 6-5 Summary of joint EPA/FDA/USDA guidelines for sludge application for fruit and vegetable production (USEPA 1983)

Application of agricultural wastes in Horticultural crops

‘‘Application of agricultural wastes in Horticultural crops, USDA/NRCS, AgWaste Management Handbook’‘

Vegetables and fruits benefit from applications of wastes; however, care must be taken because produce can be fouled or disease can be spread. Surface application of wastes to the soil around fruit trees will not cause either problem, but spray applications of liquid waste could.

Manure or sludge applied and plowed under before planting will not cause most vegetables to be unduly contaminated with disease organisms as long as they are washed and prepared according to good food industry standards. However, the scab disease may be promoted on the skin of potatoes with the addition of organic wastes. Well rotted or composted manure can be used to avoid excessive scabbing if it is plowed under before the potatoes are planted (Martin and Leonard 1949). Additional guidelines for the use of municipal sludge are in table 6-5.

Aquifers

‘‘Aquifers, USDA/NRCS, AgWaste Management Handbook’‘

An aquifer is a geologic unit capable of storing and conveying usable amounts of ground water to wells or springs (fig. 7-4). When siting any agricultural waste management component, it is important to know:

What type(s) of aquifers may be present and at what depths.

What the aquifer use classification is, if any.

Aquifers occur in many types of soil or rock material. Productive aquifers include sand and gravel alluvial deposits on flood plains of perennial streams; glacial outwash; coarse-grained, highly porous, or weakly cemented sedimentary rocks (some sandstones and conglomerates); and karst topography. An aquifer need not be highly productive to be an important resource. For example, there are millions of low-yielding (less than 10 gpm) private domestic wells throughout the country. In upland areas, often the only aquifer available for a ground water source is fractured rock occurring near the surface (up to 300 feet deep). An aquifer may be unconfined, confined, or perched. An unconfined aquifer, or water table aquifer, has no upper confining layer (fig. 7-5). Hence, the upper surface of the saturated zone is under only atmospheric pressure. It is, therefore, free to rise and fall with recharge or pumping. Recharge generally occurs locally. The static water level in a well in an unconfined aquifer is the elevation at which water stabilizes after pumping ceases. Unconfined aquifers are the type most commonly experienced in NRCS work. Some unconfined aquifers result in flowing artesian wells. This occurs when the water table locally rises above the ground surface. Topography is the primary control on most flowing wells in major valley bottoms. The valleys serve as ground water discharge areas. Because hydraulic potential increases with depth in valley bottoms, deep wells frequently tap a hydraulic head contour with a head value greater than that of the land surface, and therefore, will flow (fig. 7-6). A confined aquifer is overlain by a confining layer of lower permeability (fig. 7-7). The surface of ground water under confined conditions is often subject to higher than atmospheric pressure because it is confined by impermeable layers bounding the aquifer. A well in a confined aquifer that has higher than atmospheric pressure is called an artesian well. The potentiometric surface is the level to which ground water rises in a tightly cased well penetrating a confined aquifer. Recharge areas are typically remote from any given well location. The classic model of a flowing artesian well (see fig. 7-4) is the case where an aquifer crops out (that is, is exposed at the Earth's surface) and receives recharge in an upland area. Low permeability materials (aquicludes) lying above and confining the aquifer generate hydraulic heads greater than the surface elevation head. The confined aquifer, therefore, produces flowing artesian wells.

Figure 7-4

Figure 7-5 Unconfined aquifer (from AIPG 1984)

Figure 7-6 Cross section through stream valley showing ground water flow lines and flowing (artesian) well from unconfined aquifer (from Fetter 1980)

A perched aquifer is a local zone of unconfined ground water occurring at some level above the regional water table. An unsaturated zone separates the perched aquifer from the regional water table. A perched aquifer generally is of limited lateral extent. It forms in the unsaturated zone where a relatively impermeable layer, called a perching bed (for example, clay), intercepts downward-percolating water and causes it to accumulate above the bed (fig. 7-8). Perched aquifers can be permanent or temporary, depending on frequency and amount of recharge. Perched aquifers can present dewatering problems during construction if not discovered during investigation of the site.

The United States Environmental Protection Agency (EPA), under the provisions of the Safe Drinking Water Act, has the authority to designate sole source aquifers. A sole source aquifer is an aquifer that provides the principal or sole source of drinking water to an area. No Federal funds can be committed to any project that EPA finds would contaminate the aquifer and cause a significant health hazard.

A state may have designated use classifications just as surface water resources have. A state may have designated use classifications to protect aquifers for future use by a municipality, for example. Some aquifers may be regulated against overdraft or ground water mining.

Figure 7-7 Confined (artesian) aquifer (from AIPG 1984)

Figure 7-8 Perched aquifer

Assessment tools

‘‘Assessment tools, USDA/NRCS, Core 4 Technical Reference’‘

A variety of assessment tools is available to nutrient managers. These tools generally fall into one of two categories:

Tools to assess the agronomic needs of a crop.

Tools that assess environmental risk associated with nutrient applications.

Some tools may fall into both categories. Properly using available tools can significantly improve nutrient management decisions.

Agronomic needs assessment tools

‘‘Agronomic needs assessment tools, USDA/NRCS, Core 4 Technical Reference’‘

These tools provide information on the current nutrient status of crops, soils, and soil amendments. They help the nutrient management planner develop a more accurate nutrient budget to determine the amount and type of nutrients actually required by the soil-plant system. Agronomic needs assessment tools include several tests. Sampling techniques for these tests should follow Extension Service or Land Grant University guidelines.

Traditional soil tests

‘‘Traditional soil tests, USDA/NRCS, Core 4 Technical Reference’‘

Traditional soil tests include tests for pH, nitrogen, phosphorus, potassium, soil organic matter, and electrical conductivity (EC). These tests generally are performed on the soil plow layer, but may also be performed on the top few centimeters of the soil if the soil is not regularly tilled. Other soil tests, such as tests for sulfur or zinc, may also be performed in cases where special needs are suspected. Soil tests give the nutrient management planner a sense of the nutrient supply in the soil. If soil test levels of individual nutrients are high, there may be no need to apply these nutrients to the crop. If they are low or medium, fertilization is probably advisable. If soil pH is low, liming may be warranted to allow for adequate uptake of nutrients applied. If it is high, an acidifying amendment may be necessary to optimize crop nutrient uptake. Soil organic matter generally indicates overall soil nutrient status. Electrical conductivity indicates the level of salts in the soil. Salts may be a concern if EC is extremely high. Traditional soil tests provide an important baseline of information and should be performed regularly every 3 to 5 years, or more often if conditions change.

Nitrate testing

‘‘Nitrate testing, USDA/NRCS, Core 4 Technical Reference’‘

Pre-plant nitrate test, pre-sidedress nitrate test and deep nitrate test

In certain parts of the country, the pre-plant nitrate test (PPNT) and pre-sidedress nitrate (PSNT) test are used to determine whether additional nitrogen is necessary. The nitrate concentration in the soil solution of the crop root zone at a given point in the growing season may indicate the amount of nitrogen available in the root zone for crop uptake. If the available nitrogen is sufficient, a sidedress application is not warranted. See appendix E for a procedure to use this information.

The deep nitrate test is another tool sometimes performed to determine how much nitrogen has already leached below the crop root zone. If this test shows significant amounts of nitrate leaching, it may be advisable to include a deep-rooted crop in the rotation and look for other ways (including water management where applicable) to ensure that the appropriate amount of nitrogen is provided to the crop when it is needed.

Traditional plant tests

‘‘Traditional plant tests, USDA/NRCS, Core 4 Technical Reference’‘

A variety of plant tests is available and being developed to provide information on the current nutrient status of the crop. Petiole tests and other plant tissue tests are performed during the growing season to help make decisions about the need to sidedress apply nitrogen or micronutrients. The chlorophyll meter has recently been used to quickly determine the nitrogen status of the crop without destroying any plant tissue. The chlorophyll meter works by analyzing the absorption of light of certain wave lengths characteristic of chlorophyll absorption. The late season chlorophyll meter test and certain tissue tests are also being developed to analyze the nitrogen status of crops just before harvest. These tests can help determine how successful the current nutrient management plan was in supplying the nitrogen needs of the crop so that the nutrient management plan can be refined for the next year. Use of remote sensing, particularly infrared photography, is also increasing as a quick means of assessing crop nitrogen status during the growing season.

Organic material analysis

‘‘Organic material analysis, USDA/NRCS, Core 4 Technical Reference’‘

Organic material, such as manure, municipal wastewater sludge, or other organic products, is often applied to cropland as nutrient sources. Unlike commercial fertilizers, the nutrient content of these amendments varies. The nutrient content of the organic material must be known to develop an accurate nutrient planning budget. Therefore, a series of nutrient tests have been devised for organic material analysis. These tests are chemically similar to soil tests, but generally also include moisture content. Moisture contents of organic material can vary dramatically. The moisture content is needed to calculate the quantity of nutrients in a gallon or ton of organic material applied to the land.

Irrigation water test

‘‘Irrigation water test, USDA/NRCS, Core 4 Technical Reference’‘

Because the salt status and pH of irrigation water can often affect crop uptake of both water and nutrients, water that is to be applied to cropland may be tested for electrical conductivity and pH. Surface irrigation water may also be tested for nitrate, since a high level of nitrate in the water may indicate a reduced need for nitrogen fertilization. Well water may also be tested for boron and chloride. These plant nutrients are beneficial in low concentrations, but toxic at higher concentrations. Irrigation water should be tested at least annually or more often if the water chemistry is expected to change significantly over the growing season.

Environmental risk assessment tools

‘‘Environmental risk assessment tools, USDA/NRCS, Core 4 Technical Reference’‘

These tools provide information on the potential environmental risk associated with nutrient applications. Environmental risk assessments tools may be used to identify sensitive areas in which careful nutrient management is critical to protect a water resource or where nutrient applications should be strictly limited. Risk assessment tools may involve simple analyses or elaborate models. A few of the less complex risk assessment tools available for your use are listed below:

Leaching index

‘‘Leaching index, USDA/NRCS, Core 4 Technical Reference’‘

The leaching index (LI) is a simple index of potential leaching based on average annual percolation and seasonal rainfall distribution. The LI considers the saturated hydraulic conductivity and storage capacity of individual soils, the average annual rainfall, and the seasonal distribution of that rainfall. It does not look at the leaching potential of specific nutrients, but rather the intrinsic probability of leaching occurring if nutrients are present and available to leach. The LI is in section II of the Field Office Technical Guide (FOTG). See appendix B for more information.

Phosphorus index

‘‘Phosphorus index, USDA/NRCS, Core 4 Technical Reference’‘

The phosphorus index (PI) is a simple assessment tool that examines the potential risk of P movement to waterbodies based on various landforms and management practices. The PI identifies sites where the risk of P movement may be relatively higher or lower than other sites. It considers soil erosion rates, runoff, available P soil test levels, fertilizer and organic P application rates, and methods to assess the degree of vulnerability of P movement from the site. A weighting procedure includes the various contributions each site characteristic may have. The PI is in the NRCS FOTG, state supplements to the National Agronomy Manual, or state technical notes.

Water Quality Indicators Guide

‘‘Water Quality Indicators Guide, USDA/NRCS, Core 4 Technical Reference’‘

The Water Quality Indicators Guide (WQIG) is a qualitative tool for assessing surface water quality. It considers five major sources of agriculturally related nonpoint source pollution: sediment, nutrients, animal waste, pesticides, and salts. The WQIG contains a series of field sheets that are completed using onsite observations of physical and biological resources rather than chemical measurements. Two types of field sheets are provided: one for receiving water and the other for agricultural lands draining into the receiving water. The guide can help the user assess the risk of nutrient impairment to waterbodies in a given area. The WQIG is referenced in section I of the FOTG.

Nitrate Leaching and Economic Analysis Package

‘‘Nitrate Leaching and Economic Analysis Package, USDA/NRCS, Core 4 Technical Reference’‘

The Nitrate Leaching and Economic Analysis Package (NLEAP) is a moderately complex, field scale model that assesses the potential for nitrate leaching under agricultural fields. It is one of several water quality models that can be used to assess potential nutrient pollution under different scenarios. NLEAP can be used to compare nitrate leaching potential under different soils and climates, different cropping systems, and different management scenarios. When calibrated to local conditions, this model can be a powerful tool to assess nutrient management planning decisions. NLEAP is referenced in section I of the FOTG.

Revised Universal Soil Loss Equation and the Wind Erosion Equation

‘‘Revised Universal Soil Loss Equation and the Wind Erosion Equation, USDA/NRCS, Core 4 Technical Reference’‘

The Revised Universal Soil Loss Equation (RUSLE) and the Wind Erosion Equation (WEQ) assess the potential for soil loss through water and wind erosion. As nutrient losses are often associated with eroded sediment, these tools can help determine the potential risk of nutrient transport toward waterbodies when combined with estimates of nutrient concentrations in surface soils. RUSLE and WEQ are in section I of the FOTG.

EPA 303(d)

‘‘EPA 303(d), USDA/NRCS, Core 4 Technical Reference’‘

The EPA 303(d) report for your state can often be used to help assess the potential environmental risk associated with a particular land area. This report lists the waterbodies, including stream segments, within each state that have been designated as impaired for one or more uses. A copy of this report may be obtained from your state water quality agency.

Special designations

‘‘Special designations, USDA/NRCS, Core 4 Technical Reference’‘

Certain areas have been designated for special protection: sole source aquifers (aquifers that provide the sole source of drinking water for an area), wellhead protection areas, and hydrologic unit areas. These special designation areas will most likely be at greater risk for environmental contamination.

Sensitive areas

‘‘Sensitive areas, USDA/NRCS, Core 4 Technical Reference’‘

Some areas or regions may have conflicting goals relating to nutrient application. Nutrients are needed for adequate production, but special environmental concerns may also be in these areas. The nutrient management planner must use the results of an agronomic needs assessment and environmental risk assessment to balance these conflicting goals.

Most planning and assessment are done at the field level as opposed to a group of fields or a watershed. This field area is called the agricultural management zone (AMZ) which is defined as the edge of the field, bottom of the root zone, and top of the plant canopy. Sensitive areas for nutrient application can include fields where soils or landscape position would allow nutrients to leach or run off the application site. While the amount of nutrients leaving the AMZ is difficult to predict, methods are available to predict the relative risk that losses will occur.

Sensitive areas may fall into one of three types. The first includes areas that have already been identified or exist by virtue of a state or local designation. A previously identified sensitive area could be listed on the state's 303(d) list of impaired waterbodies, be a designated trout stream, or be listed as a sole source aquifer. These designated sensitive areas are listed because of sensitivity to excess nutrients either in the surface or ground water.

Sensitive areas may also be identified by use of one of the assessment tools mentioned in this section. For example, analysis of the application area with RUSLE may reveal that the field has a high rate of erosion. Erosion and runoff would move nutrients, especially surface applied nutrients, thus making this application site sensitive. Another example would be soils that have high soil test levels of nitrogen or phosphorus.

The leaching potential of the soil may point out a sensitive field.

The third type of sensitive area may be identified by intuitive observation. If the area has high concentrations of livestock or density of feedlot generating large volumes of animal manure, that area could be considered sensitive. Growing continuous potatoes or corn with high application rates of fertilizer or production of specialty crops, such as strawberries or tomatoes, could also be thought of as sensitive.

Sensitive areas should be identified on the conservation plan map, and the reason for the sensitivity noted. Special management practices and conservation measures are required to mitigate sensitive areas.

Analytical water quality monitoring

‘‘Analytical water quality monitoring, USDA/NRCS, Core 4 Technical Reference’‘

Analytical water quality monitoring is another tool that can be used to assess the potential impairment of water-bodies and associated environmental risk. Long-term monitoring, such as monitoring performed by the U.S. Geological Survey and state environmental agencies, can show quantitative trends in water quality over time, although trends are often slow and difficult to predict with short term monitoring.

Soil testing

‘‘Soil testing, USDA/NRCS, Core 4 Technical Reference’‘

Soil testing for environmental risk assessment includes tests for soil nitrates in the root zone and phosphorus in the surface soil. Soil nitrate tests were described previously. The surface soil phosphorus test indicates the buildup of available phosphorus at the soil surface, which can be correlated with risk of phosphorus losses through runoff or erosion.

Others

‘‘Others, USDA/NRCS, Core 4 Technical Reference’‘

The tools described in this document are only a small fraction of the tools that may be available for use by conservationists and nutrient management specialists to help them develop nutrient management plans that are appropriate, needed, and effective. A variety of water quality models, including EPIC, GLEAMS, AGNPS, ANAGNPS, SWRRB, and SWAT, may be used to look at the influence of different management scenarios and environmental conditions on the potential environmental risk of nutrient contamination to waterbodies. A variety of physical, chemical, and biological tests are also available to assess water quality in designated areas. Most states have already designated many environmentally sensitive areas. For further assistance in this area, consult your NRCS state office or state environmental agency .

Available water capacity in soil

‘‘Available water capacity in soil, USDA/NRCS, AgWaste Management Handbook’‘

Available water capacity is a measure of the soil's capacity to hold water in a form available to plants. It is a function of soil porosity, texture, structure, organic matter content, and salinity. Available soil water is estimated as the difference between soil water content at 1/3 or 1/10 bar tension (field capacity) and 15 bar tension (permanent wilting point). The available water capacity is generally expressed as the sum of available water in inches to a specified soil depth.

Generally, this depth is 5 feet or the depth to a root-restricting layer, whichever is less. Available water capacity infers the capacity of a soil to store or retain soil water, liquid agricultural wastes, or mineralized agricultural waste solids in the soil solution. Applying agricultural wastes increases soil organic matter content, helps to stabilize soil structure, and enhances available water capacity.

Limitations for agricultural waste applications are slight if the available water capacity is more than 6.0 inches per 5 foot of soil depth, moderate if it is 3.0 to 6.0 inches, and severe if it is less than 3.0 inches. Soils for which the limitations are moderate have reduced plant growth potential, limited microbial activity, and low potential for retaining liquid and mineralized agricultural waste solids. Lower waste application rates diminish the potential for ground water contamination and help to alleviate agricultural waste overloading.

Soils that have severe limitations because of the available water capacity have low plant growth potential, very low potential for retaining liquid or mineralized agricultural waste solids, low microbial activity, and high potential for agricultural waste contamination of 'Management Explorer'.

Soil suitabilities and limitations for agricultural waste application are based on the most severely rated soil property or properties. A severe suitability rating does not necessarily infer that agricultural wastes cannot be used. It does, however, infer a need for careful planning and design to overcome the severe limitation or hazard associated with one or more soil properties.

Care must be taken in planning and designing agricultural waste management systems that are developed for soils that have a moderate limitation or hazard suitability rating. In general, moderate limitations or suitability ratings require less management or capital cost to mitigate than do the severe ratings.

Slight is the rating given soils that have properties favorable for the use of agricultural wastes. The degree of limitation is minor and can be overcome easily. Good performance and low maintenance can be expected.

Soil suitability for site specific agricultural waste storage or treatment practices, such as a waste storage pond, waste treatment lagoon, or waste storage structure, are not discussed in this section. Soil variability within soil map delineations and mapping scale generally prevent using soil maps for evaluation of these site specific agricultural waste management system components.

Soil investigations conducted by a soil scientist or other qualified person are needed to determine and document site specific soil information, such as soil type, observed and inferred soil properties, and the soil limitations or hazards for the site specific components.

Nonsite specific agricultural waste utilization practices are those that apply agricultural wastes to fields or other land areas by spreading, injection, or irrigation.

The suitability, limitations, or hazards associated with these practices are dependent upon and influenced by the geographical variability of the soil and soil properties within the area of application.

Soil suitability ratings for nonsite specific agricultural waste management system components and practices are determined from soil survey maps and FOTG surface and ground water. Reducing waste application rates, splitting applications, and applying waste only during the growing season diminish potential for ground and surface water contamination and help prevent agricultural waste overloading.

The volume of liquid agricultural waste application should not exceed the available water capacity of the root zone or the soil moisture deficit at the time of application. Low rates and frequent applications of liquid agricultural wastes on soil that has low available water capacity or during periods of high soil moisture deficit can reduce potential for ground water contamination.

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