Rice:Guidelines
GUIDELINES: RICE PRODUCTION
Contents
STATISTICS
OUTLINE OF MANAGEMENT ACTIVITIES
_____ Scout "SUSPECT INSECTS" .. Armyworms .. Aster Leafhopper .. Crayfish .. Rice Leafminer .. Rice Seed Midges .. Rice Water Weevil .. Tadpole Shrimp
_____ Scout "SUSPECT WEEDS" .. arrowhead, California (Sagittaria montevidensis) .. arrowhead, Gregg (Sagittaria longiloba) .. barnyardgrass (Echinochloa crus-galli) .. bulrush, ricefield (Scirpus mucronatus) .. bulrush, river (Scirpus fluviatilis) .. burhead (Echinodorus cordifolius) .. cattails (Typha spp.) .. ducksalad (Heteranthera limosa) .. naiads (Najas spp.) .. pondweed, American (Potamogeton nodosus) .. redstems (Ammannia spp.) .. sedge, smallflower umbrella (Cyperus difformis) .. spikerushes (Eleocharis spp.) .. sprangletop, bearded (Leptochloa fascicularis) .. watergrasses (Echinochloa spp.) .. waterhyssop (Bacopa spp.) .. waterplantain, common (Alisma plantago-aquatica)
General Checks to be made:
_____ growth stage of rice
_____ density of seedlings (plants/ft2)
_____ tadpole shrimp
_____ midges
_____ population and growth stage of watergrass and barnyardgrass
_____ population and growth stage of sedge and broadleaf weeds
_____ population and growth stage of other weeds
_____ continue checking weed growth every 3 days or until weeds are controlled
_____ other pests or disorders
8 to 14 days after flooding is initiated
_____ growth stage of rice
_____ density of seedlings (plants/ft^2)
_____ leafminer eggs and larvae
_____ newest unfurled leaf for adult weevil damage
_____ population and growth stage of broadleaf, sedge, grass, and other weeds
(continue checking once a week for 5 weeks or until weeds are controlled)
_____ survey weed species present _____ other pests or disorders
2 to 4 weeks after flooding is initiated or soon after rice leaves emerge above water surface _____ first nitrogen analysis on leaf tissue _____ population and growth stage of weeds, especially perennial sedge and broadleaf weeds _____ roots of stunted plants with yellow leaves for weevil larvae root pruning _____ other pests or disorders
Sometime at midtillering _____ weekly for damage by leafhoppers and armyworms
(if armyworms present, special twice-weekly samples)
_____ survey weed species present _____ leaf tissue analysis for nutrients at maximum tillering _____ leaf tissue analysis for nutrients at panicle initiation _____ leaf tissue analysis for nutrients at flag leaf stage _____ check roots for gas toxicity _____ other pests or disorders
Last visit before harvest
_____ survey of weed species just before harvest
_____ survey of disease damage
CHECKLIST OF MANAGEMENT ACTIVITIES
Seed Soaking and Draining Stage _____ overheating, oxygen deprivation _____ seed quality _____ disposal of soak water _____ delay of planting by bad weather _____ prepare for mosquito management
Seedling Stage 1 (germination to 3 leaf stage) _____ seed rot and seedling diseases _____ tadpole shrimp _____ midge larvae _____ crayfish _____ waterfowl, blackbirds, and rats _____ water too cold or too deep _____ seed burial or drift, bunched plants _____ zinc or iron deficiency _____ weed seedlings _____ water-holding requirements _____ herbicide injury
Seedling Stage 2 (4 to 5 leaf stage) _____ tadpole shrimp _____ rice leafminer _____ crayfish damage to irrigation system _____ rats and waterfowl _____ plant nutrient deficiencies _____ weeds and algae _____ crayfish _____ monitoring rice water weevils _____ water-holding requirements _____ herbicide injury
Tillering _____ reduced tillering from nitrogen, phosphorus, and zinc deficiencies _____ rice water weevil damage _____ weeds _____ herbicide injury _____ stem rot and aggregate sheath spot _____ rice leafminer _____ gas and organic acid toxicity (CO<->2</-> or methane)
Maximum Tillers _____ nitrogen and phosphorus deficiency _____ late weed growth _____ herbicide injury _____ stem rot and aggregate sheath spot _____ rice water weevil damage
Panicle Initiation _____ nitrogen deficiency _____ pollen damaged by cool weather; raising water depth _____ armyworm damage _____ rice water weevil damage _____ leafhoppers _____ stem rot and aggregate sheath spot _____ hydrogen sulfide toxicity
Jointing _____ excessive vegetative growth from overfertilization _____ armyworms _____ leafhoppers _____ pollen damaged by cool weather; raising water depth _____ crayfish damage to irrigation system _____ muskrat damage to irrigation system _____ late weeds _____ intermittent drought from inadequate water supply _____ hydrogen sulfide toxicity
Heading _____ blanking and lodging from excessive nitrogen _____ blanking caused by overly cool or hot weather _____ waterfowl _____ armyworms _____ panicles damaged by heat or wind _____ hydrogen sulfide toxicity
Grain Formation _____ lodging due to excessive nitrogen or stem rot _____ stem rot _____ blackbirds _____ rats, muskrats _____ waterfowl _____ draining too early _____ discolored grain due to secondary fungus
Maturity to Harvest _____ maturation slowed by overly cool weather _____ harvester damage _____ preparation of on farm drying and storage facilities _____ premature or late field drainage _____ waterfowl, rats
Postharvest to Preplant _____ stored grain pests _____ crop residue management _____ precision leveling _____ seed bed preparation for next year _____ rat and muskrat control
CROP DEVELOPMENT
Rice develops to maturity through three different phases: the vegetative phase, the reproductive phase, and the ripening phase. The vegetative phase is the period from seed germination to panicle initiation, the reproductive phase is from panicle initiation to flowering and the ripening phase is the final period when the grain reaches full maturity. Each cultivar enters into these phases in a different time frame and has individual needs, such as each requires a different amount of air and water, and the day length may differ among cultivars as well as the environmental conditions.
Vegetative Phase
Rice seed is soaked in water for 18-24 hours before planting because this pregermination creates a faster and more uniform stand of rice. The seed should be planted within 24-48 hours after the pregermination. Then within two weeks the plant enters the first seedling stage when the coleoptile and primary root emerge. Shortly after, the first foliage leaves appear with a sheath and no blade. When the plant has four leaves, it enters into the second seedling stage and the seedling begins to carry out photosynthesis and produce its own food. When the fifth leaf appears, the plant will begin to make tillers and this is a period of rapid vegetative growth. Most tillers that are formed after 7-8 weeks of growth will develop panicles by harvest. Finally, when the tiller number is greatest is right before the end of the vegetative stage and the crown roots are completely developed and adventitious roots begin to develop. As the plants are preparing to enter into the reproductive stage, the growth rate slows and the plant may appear yellow.
Reproductive Phase
As the plant enters into the reproductive stage, panicles begin to form within the culm and leaf sheath at the base of the tiller. About five days after panicle initiation, the internodes on the top part of the plant begin to elongate and the lengths between internodes will be longer at the top of the plant and shorter at the base. Pollen also begins to form in the spikelets, but cold weather can prevent this from happening. Flowering occurs about 35 days after panicle initiation and the flowers are usually sterile and it takes about 7 days for the complete panicle to flower. Rice variety, water depth, temperature, plant spacing, and soil nutrients all influence the time it will take for the plant to flower.
Ripening Phase
The ripening phase may take 30-60 days depending on the variety and the environmental conditions. The grains ripen faster in warmer weather, but may also be lighter and weigh less than rice grown in cooler weather. When the rice grains reach their maximum dry weight their maturity is reached and harvest can begin. Overall rice yield is largely dependent upon the number of panicles that form per unit area, the number of spikelets per panicle, the percent of filled spikelets, and the weight of the single grains.
GROWTH REQUIREMENTS
Sunlight
Too little sunlight because of cloudy or rainy weather during tillering and panicle initiation can reduce the number of panicles, spikelets, or filled grains.
Oxygen
It is important that rice seed does not get buried in the soil because it depletes the oxygen supply. Even though rice is grown in standing water, it needs oxygen to convert starch to plant tissue. Rice growing in unflooded fields have larger root systems and shorter top growth.
Temperature
Successful rice crops require somewhat higher temperatures with water being between 77° and 84° F (25° to 29° C) and air temperatures between from 77° to 90° F (25° to 33° C). If plants are grown when the temperatures are too low they are subject to pests, are shorter in stature, have dark green leaves, and take longer to mature. High temperatures above 95° F (35° C) can affect pollination, seed set, kernel formation, and premature ripening.
Water
It is essential that the field remains flooded for higher yields. Flooding suppresses weed growth, minimizes soil temperature, and allows the nutrients to be available to the plant. Flooded fields yield more kernels per panicle and reach maturity earlier than unflooded rice.
Nutrients
Rice plants that are nutrient deficient are smaller, have weak photosynthetic and growth capabilities, compete poorly with weeds and pests, and are susceptible to disease damage. Plants that are over fertilized have excessive vegetative growth, increased stem rot, blanking, lodging, and weed growth.
Precision Leveling
The most common ways of leveling the field are either land or laser leveling to achieve uniform slopes and elimination basins. Problems with fields that are not level include: poorly leveled basins make it difficult to maintain a reasonably uniform water depth, levees offer sites for weeds to grow and produce seed, and large fields tend to flood slowly and cause management problems. This can usually be corrected by splitting the field into two smaller fields when leveling, or by modifying the irrigation system to flood faster.
Seedling Rates
Seeding rates vary according to the method of seeding, variety of seed used, seed quality, soil fertility, and location. Rice should not be too densely planted because the plants tiller less and lodge more. In most cases, optimal plant populations are around 8-30 plants per square foot.
Maximizing Yields
By properly preparing the soil, rice yields will increase significantly. The best types of soil to use are loams, silt loams or clay loams because water can not easily penetrate through these soils. The seedbed should be level to maintain the flooding level and the topsoil should be low in salts. Water depth can be regulated by careful land leveling.
Tillage and Seed Bed Preparation
Proper seedbed preparation includes reducing soil clod size and other irregularities on the soil surface, tilling the soil in the fall to encourage weed germination before rice is planted, and planing the soil so that water levels will be able to maintain uniform levels throughout the field. In addition, its important to keep weeds in adjacent fields under control.
PLANTING
The ideal time for planting depends on cultivar, field conditions, and weather. For proper seed growth, water temperatures should not fall below 70° F (21.1° C), fungicides should be used to treat the seeds against disease, and certified seed should be used. Planting immediately after flooding will optimize the soil oxygen and minimize losses. The seeding rate will vary among cultivars, but generally 12-20 seedlings per square foot achieves a good stand that will not cause lodging at harvest. If not using certified seed, it may be necessary to use a higher seeding rate to account for a lower germination rate. The crop should be closely monitored to help keep weeds, insects, and diseases under control. The plants may need additional fertilizer, which can be applied aerially through the end of the tillering stage.
CULTIVAR SELECTION
When selecting seeds to plant, the most important consideration is to pick a cultivar that is adaptable to the local area and growing conditions. These seeds will grow more vigorously, are less susceptible to damage, and have fewer pest problems. Cultivars may differ in type of grain, yield, stature, developmental time (maturity), tolerance to herbicides, blanking resistance, and other characteristics. Short cultivars are more resistant to lodging, more responsive to nitrogen fertilizers, less susceptible to cold temperature-induced floret sterility (blanking), produce less straw, and have a higher yield potential than tall cultivars.
Brown rice seeds (H. F. Schwartz; Colorado State University)
Rice seeds (H. F. Schwartz; Colorado State University)
White rice seeds (H. F. Schwartz; Colorado State University)
Wild rice seeds (H. F. Schwartz; Colorado State University)
FERTILIZING
A soil analysis should be taken before planting season to determine the proper amounts of fertilizer to use. Phosphorus, potassium, and one half of the total nitrogen can be applied at planting and then about 50-60 days later the remaining nitrogen can be applied aerially. The first fertilizer application can be preplant, at planting or within 2-3 weeks after planting and can be done either by injecting, drilling, or broadcast and then disced. By closely observing the crop, nutrient deficiencies can be detected and corrected with the appropriate nutrient.
IRRIGATION
The most effective way of irrigation is to flood the fields. Fields should be flooded as soon as possible after seedbed preparations and then planted immediately. This maximizes oxygen levels and minimized problems with insects and pests. Uniform flooding prevents rapid weed growth and helps the plants to grow evenly and promptly. Water levels can be adjusted as situations change to discourage pests and promote the development of rice. When applying pesticides to fields, be sure that the irrigation system is in good order, that drain outlets are boarded and blocked up with plastic and soil, and that tailwater is held for the time required on the label or permit. In most cases fields should remain continuously flooded from just before planting until they are drained for harvest. Draining fields prematurely before harvest causes symptoms of moisture stress including shriveled kernels, delayed maturity, unevenly maturing plants, and results in poor milling yields.
HARVESTING
Rice should be harvested when the moisture content is between 20-25%. When rice is drier, fewer rice kernels can be harvested and when the moisture is greater, storage is difficult. Combine operations must be closely monitored to reduce grain loss during harvest.
POSTHARVEST MANAGEMENT
It is important to manage crop residues after harvest to avoid stem rot diseases, weeds, and various other problems. Some alternatives for removal include burning, complete removal, or incorporating the residues into the soil. Burning is the easiest method of removal, but can only be used with a burning permit if approval is received through local authorities. For burning to be an effective option, the straw must be dry and if it is spread out, it will burn faster. Completely removing the residue is difficult and after it has been taken from the field it is expensive to dispose of since there is no commercial markets for rice straw. However, by cutting straw at ground level, most diseased plant tissue will be removed. Any diseased tissue remaining can cause significant problems for future crops. Incorporating the residues is not expensive or time consuming, but should not be done if the residues have been exposed to stem rot and aggregate sheath spot because they will spread within the remaining residues. The best way to incorporate is to chop the residues and spread them evenly over the field before plowing, which should be done as soon as possible after harvest. By chopping the straw into small pieces, it will decompose more rapidly and completely. If choosing to store rice, take extra precautions that the facilities are clean from weeds or other trash and will not encourage infestations of storage pests. The moisture levels must remain constant (at or below 14% moisture) for proper storage. It is also important to keep all equipment and areas around the field free from weeds and other infestations of insects and diseases.
CROP ROTATION
Crop rotations or fallow periods are often a good option to control weeds because herbicides can be applied when rice is not in the fields. Some diseases and invertebrate pests can also be significantly reduced by rotation. If a field has been fallow, it should be flooded at least two weeks prior to planting to germinate as many weed seeds as possible and then the weeds can be plowed under before planting.
BIOLOGICAL CONTROL
Presently, using natural enemies as a method of pest control is not important in pest management control, but research is being performed to utilize them more in the future.
PESTICIDES
Pesticides are the only feasible means of control in many situations. It is important that pesticides are used properly, because excessive use results in poor control, crop damage, and environmental hazards. It is always necessary to check with a local farm advisor before choosing a pesticide to ensure that it is the proper pesticide to treat the problem. In some cases problems can occur by using pesticides. These problems include: pesticide-resistant strains that are able to withstand the application of a pesticide at a rate which formerly killed most individuals of that species, pest resurgence and secondary pest outbreaks which occur when pesticides kill or otherwise disrupt the activities of natural enemies or competitors of pests, plants being exposed to toxic substances which may be herbicides, pesticides or fertilizers, drift which when aerially applied can expose neighboring crops to a problem, pesticide residues remaining in the water, soil, or on the crop for some time after an application, and hazards to human health, wildlife, domestic animals, and bees.
