Alfalfa:Guidelines

STATISTICS

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OUTLINE OF MANAGEMENT ACTIVITIES

Cultural Practices

_____ Rotate with non-host crops for at least two years if diseases occur. _____ Avoid compacting the soil in land preparation and seeding. _____ Test soil for nutrient status and pH every year. Maintain records of test results and fertilizer applications. _____ Sufficient nitrogen is usually provided by nitrogen-fixing nodules on the roots. _____ Most efficient time to fertilize is before planting. _____ Plant tissue analysis can help to determine nutrient needs.

Pesticide Management

_____ Use approved and registered pesticides according to label. _____ Maintain application records including date, location, applicator, target pest, pesticide name, EPA registration number, formulation, rate and number of acres treated are maintained. _____ All sprayers are calibrated at the start of the season. _____ Minimize pesticide drift. _____ Develop and implement a resistance management plan. _____ Select pesticides which will preserve natural enemies of pests. _____ Use separate sprayers for herbicides and insecticides. _____ Check sprayer(s) calibration at least once during the season. _____ Recalibrate each sprayer as needed. _____ Maintain records of planting dates for treated fields. _____ Keep records of stage of crop of treated field. _____ Use water-sensitive spray cards to test coverage of leaf surfaces.

Insect Pest Management

_____ Scout "SUSPECT INSECTS" .. Alfalfa Caterpillar .. Alfalfa Weevil .. Beet Armyworm .. Blue Aphid and Pea Aphid .. Cowpea Aphid .. Egyptian Alfalfa Weevil .. Grasshoppers .. Leafhoppers .. Sowbugs or Pillbugs, and Crickets .. Spider Mites .. Spotted Alfalfa Aphid .. Variegated and Other Cutworms .. Webworm .. Western Flower Thrips .. Western Yellowstriped Armyworm _____ Keep a scouting record. _____ Identify control measures and implement according to thresholds.

Disease Pest Management

_____ Identify major disease pests. _____ Keep a scouting record. _____ Identify control measures and implement according to thresholds.

Weed Pest Management

_____ Scout "SUSPECT WEEDS" .. barley, foxtail (Hordeum jubatum) .. barley, hare (Hordeum murinum ssp. leporinum) .. barnyardgrass (Echinochloa crus-galli) .. bermudagrass (Cynodon dactylon) .. bindweed, field (Convolvulus arvensis) .. bluegrass, annual (Poa annua) .. bluegrass, bulbous (Poa bulbosa) .. brome, downy (Bromus tectorum) .. canarygrasses (Phalaris spp.) .. chickweed, common (Stellaria media) .. cupgrass, Prairie (Eriochloa contracta) .. dandelion (Taraxacum officinale) .. dodders (Cuscuta spp.) .. fiddlenecks (Amsinckia spp.) .. filarees (Erodium spp.) .. flixweed (Descurainia sophia) .. foxtails, yellow and green (Setaria spp.) .. goosefoot, nettleleaf (Chenopodium murale) .. goosegrass (Eleusine indica) .. groundsel, common (Senecio vulgaris) .. johnsongrass (Sorghum halepense) .. junglerice (Echinochloa colona) .. knotweed, prostrate (Polygonum aviculare) .. lambsquarters, common (Chenopodium album) .. lettuce, prickly (Lactuca serriola) .. mallow, little; cheeseweed (Malva parviflora) .. lettuce, miner's (Claytonia perfoliata) .. mustards (Brassica spp.) .. nettle, burning (Urtica urens) .. nightshades (Solanum spp.) .. nutsedge, yellow (Cyperus esculentus) .. oat, wild (Avena fatua) .. pepperweeds (Lepidium spp.) .. pigweeds (Amaranthus spp.) .. plantain, buckhorn (Plantago lanceolata) .. quackgrass (Elytrigia repens) .. radish, wild (Raphanus raphanistrum) .. redmaids; desert rockpurslane (Calandrinia ciliata) .. rocket, London (Sisymbrium irio) .. ryegrass, Italian (Lolium multiflorum) .. ryegrasses (Lolium spp.) .. shepherd's-purse (Capsella bursa-pastoris) .. sowthistles (Sonchus spp.) .. starthistle, yellow (Centaurea solstitialis) .. stinkgrass (Eragrostis cilianensis) .. thistle, Russian (Salsola tragus) .. witchgrass (Panicum capillare)

_____ Prepare weed maps in mid-to-late season, indicating significant weed species and their location. _____ Use last year's scouting records to begin this year's scouting. _____ Base all herbicide rate, selection and spot or strip sprays on weed survey results. _____ Weeds may be controlled by cultivation, with no herbicide applied. _____ Use reduced rates of herbicide through banding of herbicides and cultivation. _____ Do not use herbicides of the same class on the same field in succeeding years. (Use crop rotation and corresponding herbicide selections.) _____ Prevent weeds within the field, alleys and roadways from going to seed. _____ Use an experimental plot to test different weed management techniques and record the results.

Weather and Crop Monitoring

_____ Monitor weather and crop parameters _____ Keep daily records.

Date: - Min/max temperatures: - Rainfall: - Hours of leaf wetness: - Stage of tree development (by cultivar, weekly):

ALFALFA DEVELOPMENT

Stages of Crop Development

Alfalfa crop development may be divided into three stages which include plant establishment, vegetative growth, and flowering and fruiting.

Establishment

The critical time of plant establishment comes before the first cutting. Up to this time, the plant is using all of its energy to establish roots, crown and canopy, and is trying to compete with weeds and other pests. If the weeds and pests can be controlled during this time, there is a better chance of having an overall good harvest, since they cause less damage after the first cutting. It is important not to harvest too early since regrowth uses such large amounts of carbohydrate to reestablish itself. Most alfalfa plants need three to four months for a well established stand of plants.

Vegetative Growth

A good harvest is dependent upon good vegetative growth which is when the plants resources are aimed to leaf and stem development. This is a rapid growth phase and will lead to seed production quickly. Mature plants will bloom quickly when exposed to conditions such as high temperatures, long days, and reduced water supply. Harvested plants lose all of their reproductive buds and new vegetative growth occurs, leading to the next harvest. Leaves reach their optimum harvesting potential about 5-10 days after unfolding.

CULTURAL PRACTICES

When making the decision about a planting location, several things need to be taken into consideration. The field must be free from heavy weed infestations, especially those that are difficult to control such as dodder and yellow foxtail. The soil must be easily managed and not have problems relating to compaction or drainage. Finally, in order to make the location economically feasible, an alfalfa rotation system needs to be implemented. This helps replenish the soil nitrogen levels and can improve soil quality as well as combat weeds and pests.

PLANTING

Planting times are critical for first year yields as well as the nature of competition with weeds, diseases and pests. Contact a local farm agent to get the specifics of planting times in particular areas. Seeds should be planted 1/4 to 1/2 inch below the soil surface at a rate of 15-20 pounds per acre to produce a strong stand that will compete well.

FERTILIZING

Nutrients removed from an acre of alfalfa in one year by a 10 ton crop (Pounds/acre in 10 tons).

Nitrogen* 550 Potassium 400 Calcium 320 Magnesium 66 Phosphorus 52 Sulfur 40 Iron 4 Chlorine 3 Manganese 2 Boron 0.6 Zinc 0.3 Copper 0.3 Molybdenum 0.02 *There is no net removal of nitrogen since the alfalfa plant adds more to the soil than it removes.

Alfalfa contains nitrogen-fixing bacteria which live in nodules in the plant, making this a valuable rotation crop since nitrogen levels in the soil actually increase. Nitrogen usually does not need to be applied due to the nitrogen-fixing ability of alfalfa; however, it may need to be added to increase the growth rate of seedlings. Potassium, phosphorus, and sulfur frequently need to be added to the soil to avoid deficiencies. The micronutrients, boron and molybdenum, can be toxic to the plants and should not be applied too heavily to the soil. Having a soil test done prior to planting will determine if these nutrients are necessary. The most efficient time to fertilize is before planting so that the fertilizer can be readily available to the plant. After plants are established, closely monitor them and look for plants or areas that may be suffering from any nutrient deficiency. If a problem is suspected, have the plant tissue analyzed before making radical fertilizer adjustments to confirm that a nutrient deficiency is indeed the problem. Pests or other stresses can cause symptoms similar to some deficiencies in plants.

IRRIGATION

Some items to consider for even distribution of water are making sure that the field is level, breaking up any areas of compacted soil, and providing tail ditches. It is also a good idea to preirrigate most soils before planting to ensure that the ground is not too dry and can produce a strong stand of alfalfa that will compete well with weeds or other diseases. Seedling growth will be more uniform if the water and herbicides are evenly distributed and can penetrate well into the soil. As the seedlings begin to emerge, do not irrigate until the plants are a few inches high to avoid seedling diseases. It is important to know the water requirements for alfalfa as too little water reduces growth and too much will encourage root diseases. It is also a good practice to irrigate as late as possible after cutting to avoid weed emergence. Special instruments have been designed to help determine when irrigation is needed by measuring the moisture levels and evapotranspiration. Alfalfa quality can be decreased by poor irrigation water, which contains nutrients at toxic levels and high salt levels. It is a good practice to have the water routinely checked for these and other standard tests to correct any problems that may arise because of poor irrigation water.

HARVESTING

Alfalfa is harvested every 25 to 42 days in the summer and less frequently in the spring and fall due to slower plant growth in cool weather. Decisions involving timing of harvest, cutting height, windrow management, wheel compaction by harvesting equipment and border harvesting can all affect pest problems and must be determined according to the area.

Harvesting Schedules

Knowing the best time to harvest is usually a topic of compromise between the customer's demands and the growers desire to maintain a vigorous stand of alfalfa. The highest quality hay is low in fiber and high in digestible protein and total digestible nutrients and should be cut just before bloom to meet these optimal requirements. However, at this time, the plant becomes very weak from the cutting and harvesting. By delaying harvest until the plant begins to flower, the plant stores carbohydrates in its roots and strengthens the overall stand of the plant. At this time, the fiber and total digestible nutrients are not at their optimal levels. Clearly it is a tradeoff between the health of the plant and the demands of the customer as to when is the most appropriate time to harvest. Regrowth bud development is a good indicator of when the plant has begun to store a substantial amount of food in its roots and is ready for harvest. Alfalfa is at an optimal stage for cutting when a sample of crown shows 60% with regrowth buds averaging 3/4 of an inch (2 cm) tall. Unfortunately some crops are harvested early to reduce insect or pest populations. These early harvests reduce root reserves and may have an economic loss because the plants will be smaller. It is also advised to apply an insecticide treatment for weevils under the windrow of the first harvest to avoid the reproduction of weevil larvae.

SOIL COMPACTION

Harvesting equipment is heavy and easily compacts the soil causing stunted root growth and poor water penetration and drainage. The equipment also crushes or kills plants, which combined with the earlier mentioned items, can significantly reduce the overall yield. In many circumstances, it is possible to make minor modifications to the harvesting equipment so that less damage is done. Adjusting the wheel locations on the swather, rake, baler and bale wagon, and creating permanent traffic lanes are ways of decreasing traffic in the field.

SANITATION

Using disease free seed, clean farm machinery, clean water and uncontaminated manure are the best ways to control unwanted pests or diseases from infecting alfalfa. Cleaning equipment regularly is extremely important since this is how many diseases are transported from one field to the next.

CROP ROTATION

A crop rotation program can reduce problems such as nematode pests, diseases or weeds that are difficult to control without harming the alfalfa. The rotation is usually on a schedule of two or more years with non-host crops. Rotation also benefits other crops because alfalfa improves soil nutrition and helps to reduce soil compaction.

CULTIVAR VARIETY SELECTION

Cultivar selection is critical for producing optimal yields in alfalfa. In most circumstances, choosing resistant cultivars is the best solution since they are tolerant or resistant to many conditions such as insect, disease or nematode pests. They are also able to grow more vigorously under local conditions and consequently production levels increase. Check with a local farm advisor for the most recent listing of varieties available for a particular area.

CONTROL

It is possible to control some pest populations by other organisms in the field. Careful management, including border harvesting and the use of selective pesticides, can increase biological control benefits. Usually biological control agents have been introduced to control insect pests and are often introduced from other regions. At first the quality of alfalfa may be lowered due to gnawed or discolored leaves, but over time the new beneficial species will build up levels to control the pests more effectively.

Common Natural Enemies of Insect Pests

.. lacewings (aphids, alfalfa caterpillar, armyworms) .. lady beetles (aphids) .. syrphid flies (aphids) .. bigeyed bugs (aphids, alfalfa caterpillar, armyworms) .. damsel bugs (aphids, alfalfa caterpillar, armyworms) .. pirate bugs (aphids, alfalfa caterpillar, armyworms) .. spiders (weevils, aphids, alfalfa caterpillar, armyworms)

PARASITES

.. Bathyplectes (weevils) .. Aphidius (aphids) .. Apanteles (alfalfa caterpillar) .. Hyposoter (armyworms) .. Trichogramma (alfalfa caterpillar, armyworms)

INSECT DISEASES

.. Entomophthora (aphids) .. Bacillus thuringiensis (alfalfa caterpillar) .. polyhedrosis viruses (alfalfa caterpillar, armyworms)

Pesticide Use

Pesticides are used primarily to control insects and weeds and occasionally to control rodents or other vertebrates. They include a wide range of chemicals with varying properties. They are most effective against difficult pests by applying several chemicals using only one application of each. Choose a pesticide that has been approved for the area and read the label, as it will outline application procedures and safety precautions. Pesticides are often the most practical way of killing pests to avoid expensive management methods that counter balance the overall profit of the crop.

Pesticide Resistance and Safety

Most alfalfa growers rely on some form of pesticide to reduce pest populations. It is possible for the alfalfa to develop a resistance to a particular pesticide in which it becomes necessary to use another. When applying pesticides, it is important that they do not kill or otherwise disrupt the activities of natural enemies of pests. When a pesticide application kills both a targeted pest and its natural enemies, the pest's population often soon rises above preapplication levels. Secondary pest outbreak is when a pesticide treatment applied to control one pest disrupts the natural control of another and this should also be avoided. The following is a list of other precautions growers need to take when applying herbicides or pesticides. Phytotoxicity is when the plants are poisoned by toxic substances which may be herbicides, fertilizers, or air pollution. It is important that only the proper rates of herbicides be applied at the proper to time to avoid phytotoxicity in the field or neighboring fields if drift occurs. Pesticides can also have an effect on neighboring fields because they often drive out the pests of one field but they drift over to another field, resulting in the same problems. Herbicides and pesticides should be carefully reviewed prior to application to make sure that harmful residues do not remain in the soil for long amounts of time. If label restrictions are not carefully followed, applications may leave illegal residues or cause phytotoxicity in the next crop grown in the field. In areas where honeybees flourish, it must be remembered that some pesticides are toxic to bees and thousands of colonies are lost each year when bees are exposed to treated fields. People applying the herbicides or pesticides can also be at risk. It is possible to avoid problems by following the label directions and state and local regulations. Also, by wearing protective clothing, avoiding drift, and unnecessary use of herbicides or pesticides can prevent other people from becoming exposed. When applying pesticides, consider the impact they could have on wildlife or pets that may pass through the field.