Cotton:Guidelines

GUIDELINES: COTTON PRODUCTION

STATISTICS

OUTLINE OF MANAGEMENT ACTIVITIES

Cultural Practices

_____ Test soil for nutrient status and pH every year. Maintain records of test results and fertilizer applications. _____ Plant early to maximize the growing season. _____ Taking tissue test early in the season can help in scheduling nitrogen applications during the current year. _____ Nitrogen can be applied as a preplant fertilizer or through the irrigation water. _____ Good water management provides enough water for the plants to fruit but not enough to trap the oxygen supply underground. _____ Incorporate a prompt, thorough plowdown at the end of harvest to help in insect pest control and proper decay of existing debris.

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 and Cabbage Loopers .. Beet Armyworm .. Cotton Aphid .. Cotton Bollworm .. Cotton Leaf Perforator .. Cutworms .. Darkling Beetles .. False Chinch Bug .. Field Crickets .. Grasshoppers .. Leafhoppers .. Lygus Bugs .. Omnivorous Leafroller and False Celery Leaftier .. Pink Bollworm .. Saltmarsh Caterpillar .. Seedcorn Maggot .. Silverleaf Whitefly .. Stink Bugs .. Thrips .. Tobacco Budworm .. Webspinning Spider Mites .. Western Yellowstriped Armyworm .. Wireworms

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

Disease Pest Management

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

Weed Pest Management

_____ Scout "SUSPECT INSECTS" .. barley, hare (Hordeum murinum ssp. leporinum) .. barnyardgrass (Echinochloa crus-galli) .. bermudagrass (Cynodon dactylon) .. bindweed, field (Convolvulus arvensis) .. bluegrass, annual (Poa annua) .. bromegrasses (Bromus spp.) .. canarygrasses (Phalaris spp.) .. chickweeds (Stellaria spp.) .. clovers (Trifolium spp.) .. cockleburs (Xanthium spp.) .. crabgrass, large (Digitaria sanguinalis) .. cudweeds (Gnaphalium spp.) .. cupgrasses (Eriochloa spp.) .. datura, sacred (Datura wrightii) .. fescues (Festuca spp.) .. fiddlenecks (Amsinckia spp.) .. filarees (Erodium spp.) .. fingergrasses (Chloris spp.) .. fleabane, hairy (Conyza bonariensis) .. foxtails (Setaria spp.) .. goosefoot, nettleleaf (Chenopodium murale) .. groundcherries (Physalis spp.) .. groundsel (Senecio spp.) .. henbit (Lamium amplexicaule) .. horseweed (Conyza spp.) .. johnsongrass (Sorghum halepense) .. junglerice (Echinochloa colona) .. knapweed, Russian (Acroptilon repens) .. knotweed, common (Polygonum arenastrum) .. lambsquarters, common (Chenopodium album) .. lettuce, prickly (Lactuca serriola) .. lovegrasses (Eragrostis spp.) .. mallow, little; cheeseweed (Malva parviflora) .. lettuce, miner's (Claytonia perfoliata) .. morningglories (Ipomoea spp.) .. mustards (Brassica spp.) .. nettles (Urtica spp.) .. nightshade, silverleaf (Solanum elaeagnifolium) .. nightshades (Solanum spp.) .. nutsedges (Cyperus spp.) .. oat, wild (Avena fatua) .. pigweeds (Amaranthus spp.) .. pineapple-weed (Chamomilla suaveolens) .. polypogon, rabbitfoot (Polypogon monspeliensis) .. puncturevine (Tribulus terrestris) .. purslane, common (Portulaca oleracea) .. radish, wild (Raphanus raphanistrum) .. redmaids; desert rockpurslane (Calandrinia ciliata) .. rocket, London (Sisymbrium irio) .. ryegrasses (Lolium spp.) .. sandburs (Cenchrus spp.) .. shepherd's-purse (Capsella bursa-pastoris) .. sida, alkali (Malva leprosa) .. sowthistles (Sonchus spp.) .. speedwells (Veronica spp.) .. sprangletops (Leptochloa spp.) .. spurges (Chamaesyce spp.) .. thistle, Russian (Salsola tragus) .. velvetleaf (Abutilon theophrasti) .. 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):

COTTON DEVELOPMENT

Germination

Cotton seedlings germinate like most plants with the primary root forcing its way into the soil to anchor the plant. The hypocotyl elongates and pushes through the soil surface with cotyledons that have already developed for early growth. Most cotton varieties have cotyledons that produce a poisonous substance to humans and animals called gossypol. This is a defense mechanism to protect the plant against rabbits and rodents.

Roots

The root system rapidly develops and can penetrate six feet deep or more into the soil. The taproot will have penetrated about ten inches and begun to form lateral roots by the time the seedling emerges. Most lateral roots are in the upper two feet of soil.

Branches

There are several different types of branches that form on cotton plants. Branches develop from buds in the axils at the bases of mainstem leaves. Fruiting branches grow as a series of segments that each develop from an axillary bud on the previous segment. Vegetative branches, which may give rise to secondary fruiting branches, mainly bear leaves and grow from a terminal bud.

Fruiting Structures

The cotton fruiting structure begins as a flower bud which is a series of concentric whorls. Just inside of the bracts is the calyx which is a small green ring around the base of the five petals. At the center of the square of flower is the upright, cylindrical pistil that is surrounded by pollen producing anthers. The enlarged ovary is found at the base of the pistil for easy pollination. Cotton plants are unusual because they can have nectaries to attract insects located in several places: inside the calyx, at the base of the bracts, on the lower sides of the main leaf veins, and tiny nectaries on petioles and flower stalks.

Boll, Seed, and Lint Development

Each fruit must be pollinated and fertilized. Cotton is self pollinated and once the pollen reaches the stigma, fertilization is relatively fast. The pollen travels down a tube between the pistil and ovary to fertilize the ovules. After fertilization, the bolls and their seeds grow quickly and are fully formed at about five weeks after fertilization. The cotton fibers develop on the outer layer of the seed coat and take about 18-21 days to reach their full length.

REQUIREMENTS

Temperature is the main factor that determines how fast a cotton plant will grow. However, the range of temperatures is abstract that determine when certain growth should occur. Seeds may take longer to germinate if temperatures are too cool. As the temperature increases, the plant grows to reach its maximum size until temperatures become too hot and the growth ceases. Each growing phase also has optimum temperature requirements so it is difficult to define optimum growing temperatures. Temperatures can also affect pest management because certain temperatures may encourage infestations more than other temperatures.

Nutrients Requirements

Cotton has a vigorous root system which is important in the necessary nutrient uptake. Cotton plants should always have access to nutrients for optimal production. A preplant application of fertilizer is important in the early growth phases. Initially the nutrient uptake is slow, but rapidly increases.

The nutrients should be placed where the plant can use them, which is close to the roots. Both phosphorus and potassium must be incorporated into the soil because of their immobile behavior. Nitrogen can be applied either broadcast or through irrigation. In areas where the soils may leach or denitrification causes losses, nitrogen should be applied in split applications. One half of the nitrogen can be applied as a preplant fertilizer and when the plants are 8-12 inches high, the remaining half should be a side dress application. If leaching or denitrification does not occur, the entire amount of nitrogen fertilizer can be applied before planting.

Water

A careful water management program should be used to maintain a moist condition around the root system. This allows the root system to grow and take in necessary nutrients for the plant.

Carbohydrate Stress

Carbohydrate stress is when the vegetative growth in the plant has significantly slowed because the energy is being used for boll development. Plants must grow enough so that their leaves can supply energy for as many bolls as possible and have time for them to mature within the season to reach maximum yields. If carbohydrate stress stops too early, the plants will not produce as many bolls as was possible. If carbohydrate stress is delayed too long, too much vegetative growth and many bolls are produced, but there is not enough time in the season for them to mature. Plant spacing and water and nutrient supply are important cultural practices that may influence the overall success of the crop.

Shedding of Fruiting Structures

Plants may shed both squares and bolls in response to carbohydrate stress. Cotton plants produce more fruiting bodies than the plant can support to maturity and so the excess structures are shed. Approximately 40-50% of all bolls produced will be shed due to carbohydrate stress with the older or infected bolls being shed first. Water stress can also initiate shedding.

Effect of Pest Injury on Energy Balance

Most pests damage the plant by destroying the energy resources necessary to carry out normal plant development. For example, Verticillium wilt reduces the plant's ability to distribute the products of photosynthesis though the vascular system. Lycus bugs destroy small squares early in the season which effects how many bolls are produced. If the number of bolls is small, the plant continues to produce vegetative growth making it tall and rank. Root-knot nematodes stimulate excess photosynthesis that is distributed into root galls and interfere with the flow of water and nutrients through the roots.

CULTURAL PRACTICES

HIGH YIELD MANAGEMENT It is impossible to control all the factors that contribute to high cotton yields, but there are some manageable factors that should be taken into consideration. These include planting early to utilize the entire growing season, planting populations of approximately 40,000-60,000 plants per acre where growing conditions allow, water should always be available to the plant but not in excess amounts, all weeds, insects, and diseases should be properly controlled, and harvesting should be done to eliminate large losses.

MAXIMUM ECONOMIC YIELDS Fertilizer programs are probably the single factor that affects high yields the most. The amount of fertilizer to apply is based upon the needs of each individual field, thus requiring a soil test.

SUMMARY Maximum yields will vary from region to region but general cultural practices will have a significant impact on management of pests or other problem areas. Some things to consider when planting cotton include seedbed preparation, planting, irrigation, field sanitation, water management, weed, insect and disease control, fertilization, and harvest. Timing the fruit set when the plants are strong enough to support the fruit load is important in minimizing losses.

FERTILIZATION

Nitrogen is the nutrient that is most in demand since the plants require a large amount and it can be lost due to leaching and denitrification. For nitrogen to be most efficient it must be available when it is most needed, with not too much excess nitrogen remaining and the end of the season. Cotton uses little nitrogen during seedling growth but needs the majority during fruiting. Excessive nitrogen or nitrogen applied too late in the season can delay maturity and may stimulate growth of unnecessary stems and leaves that end up as trash at harvest. Nitrogen application may be either done as preplant, side-dressing, or through irrigation. Preplant can always be incorporated into the soil so the new seedlings will have access to it. Side-dressing is a good way to resupply nitrogen in soils that leach and may lose much of the preplant application. Applying fertilizer through irrigation water is another option but is difficult to determine if the fertilizer is distributed evenly. Phosphorus, potassium, and zinc are the other nutrients that are most in demand and can be applied as preplant fertilizers. The most efficient way of application is to incorporate them into the soil as preplant fertilizers. A soil test will determine how much of all nutrients that needs to be applied.

FERTILIZER ECONOMICS-COTTON

Information on fertilizer economics is available in all cotton growing areas and provides an excellent basis for developing economic evaluations. Based on this information, growers can substitute local production costs and market prices to determine the optimum fertilizer programs for producing maximum economic yields. Also, a prompt thorough plowdown immediately after harvest sheds and buries all cotton stalks and other crop debris preparing the field for the next season of crops. This helps in the decomposition of the leftover debris and also prevents the field from being a source where insect and weed populations grow.

IRRIGATION

A soil probe and test are extremely helpful in determining the soil type, which indicates how much water to apply at irrigation. This amount will change according to the soil type, stage of crop growth, the amount of water already available, and weather. Applying too little water slows the growth and development of the plant, but too much water encourages unwanted diseases and pests.

Preirrigation and "Irrigating Up"

Preirrigation is applying water to the soil before planting to fill the soil reservoir early in the season. The preferred way is to irrigate the soil before planting rather than applying water shortly after planting, which could disturb the seed set. Preirrigation fills the soil profile without cooling the soil in most cases. The amount of water to apply depends on the soil type, for example in sandy soils that do not hold a lot of water, preirrigation has little advantages.

Postplant Irrigations

Postplant irrigations are to bring the soil profile back to field capacity where the roots have used their moisture supply. It is important that the plant's roots do not go dry because the plant will not draw in the necessary nutrients. The amount of water applied should be closely monitored to avoid soil waterlog or rapid drying. It is critical to avoid water stress during flowering or the bolls may shed. The final irrigation should allow only the final bolls to mature. If too much water is applied late in the season the bolls may not open, rotting may develop, and late growth may occur.

Irrigation Scheduling

Developing a schedule for applying water is often a practical guide to follow to avoid insufficient or excessive irrigation. The following are some ideas that may be considered when developing a schedule. Before applying any water, it is important to check the soil moisture levels and estimate how much water is available in the crop's rooting depth. The condition of the plant may be a good indication that water needs to be applied. In vigorously growing cotton plants, the upper portion of the main stem remains green, while the lower stem is reddish. When the level of water stress increases, the reddish color moves to the growing tip. Many plants will wilt around noon and some plants will wilt during the mornings or hot afternoons which means that water is needed. However, it is important to schedule irrigations according to the need shown by most of the crop rather than the condition of a small number of plants. Several techniques of measuring water stress are used which include leaf water potential that is measured in units of bars, pressure bombs that use the difference between atmospheric pressure and the pressure inside the leaf, thermal infrared energy that measures the canopy temperature, and tensiometers that measure the moisture content in the soil.

Managing Salinity

The irrigation water should be checked every 2-3 years for salts and more frequent if salt has been a problem in the past. The soil should also be tested for salinity since high salts can inhibit or delay germination and injure seedlings. If salt is high or accumulated in the soil from previous irrigations extra water may occasionally be needed to leach salts from the root zone.

PLANTING

A successful cotton crop begins with high quality seed that has been through a "cold test", which will ensure a higher germination rate. Fungicide seed treatments should be used to decrease losses from seedling diseases however, insecticidal seed treatments are not recommended because so few incidents occur in the seedling stage. When planting, the soil temperature should reach 60° F (15.5° C) for 3 days in a row at a depth of 8 inches. This increases the chances of high germination rates and fewer problems with seedling pests and diseases. In soils that have been preirrigated, make sure that the soil has drained adequately before planting, to avoid seedling diseases and compacted soil that causes poor root systems. The seeds should be planted 1 to 1 1/2 inches below the soil. This keeps enough moisture around the seed to germinate and the temperature of the soil is not too cool. Finally, fields should be planted at a rate of 20,000 to 60,000 plants per acre or 1 1/2 to 4 1/2 plants per foot.

SEED VARIETIES

Planting resistant cultivars is the most economical method of control against diseases or other conditions that may cause losses. Resistant cultivars should always be planted if there has been any indication of disease in the past. In some cases, certain varieties, although not resistant, can be planted to make them less susceptible to insect damage.