Cole Crops:Guidelines
GUIDELINES: COLE CROP PRODUCTION
Contents
STATISTICS
OUTLINE OF MANAGEMENT ACTIVITIES
Crop Rotation
_____ If field has not been planted with crucifers for two to three previous years, field should be evaluated with an appropriate soil test for nutrient status and pH. _____ Test for organic matter status every three years. _____ Fertilizer should be applied in accordance with soil test results and expected uptake of nutrients. _____ Account for additional nitrogen supplied by organic matter, compost, manure and cover crops. _____ Determine from Cooperative Extension or seed supplier the expected nutrient uptake. _____ Nitrogen fertilizer should be applied by split application (some applied at planting and some applied as a sidedress). _____ Apply compost or manure (calculate nitrogen contribution) and adjust fertilizer application accordingly. _____ Use in-state grown transplants (preferred). _____ Use disease-free or hotwater-treated seed. _____ Winter cover crops are preferred and should be a legume or legume/grass mix. _____ Calculate the nitrogen contribution of the cover crop and adjust fertilizer application appropriately. _____ Keep an experimental plot to test reduced rates of fertilizer. Record the results.
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. _____ Calibrate all sprayers 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 and 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" Aphids Beet Armyworm Cabbage Aphid Cabbage Looper Cabbage Maggot Cutworms Darkling Beetles Diamondback Moth Flea Beetles Garden Symphylans Imported Cabbageworm Leafminers Seedcorn Maggot Silverleaf Whitefly Wireworms
_____ Sample 25 to 40 plants weekly during periods when flies are active to determine presence of cabbage maggot eggs. _____ Use an insecticide for cabbage maggot only when eggs reach threshold present. _____ Use an insecticide for cabbage maggot as a banded application. Use either as a soil drench directed at the base of the plant, or as a banded preplant incorporated granular. _____ Use non-chemical controls like floating row covers to exclude or control cabbage root maggot. _____ Monitor (where present) diamondback moth (DBM) adults using pheromone traps. _____ Monitor (where present) cabbage looper (CL) moth adults using pheromone traps. _____ Monitor foliar pests (i.e. imported cabbageworm) weekly by sampling 25-40 plants. _____ Make sure treatments for caterpillar pests (DMB, ICW, CL) conform to Cooperative Extension IPM program thresholds. _____ Use microbial insecticide, such as Bt, in the management of DBM, CL and ICW infestations. _____ Monitor "occasional pests" such as onion thrips by weekly scouting of foliage. _____ Use resistant cultivars if thrips are historically a problem. _____ Alternate classes of insecticides, Bt/synthetics and/or strains of Bt to reduce resistance (especially where multiple applications of foliar insecticide are used).
Disease Pest Management
_____ Monitor fields weekly for disease symptoms. _____ Keep weekly records of scouting results. _____ Accurately identify diseases. _____ Apply fungicides and bactericides only when disease symptoms occur (i.e. note weather conditions which are particularly favorable for a specific disease). _____ Use only those pesticides which suppress the targeted disease.
Weed Pest Management
_____ Scout "SUSPECT WEEDS" barley, foxtail (Hordeum jubatum) barnyardgrass (Echinochloa crus-galli) bindweed, field (Convolvulus arvensis) bluegrass, annual (Poa annua) canarygrass, littleseed (Phalaris minor) chickweed, common (Stellaria media) goosefoot, nettleleaf (Chenopodium murale) groundcherries (Physalis spp.) groundsel, common (Senecio vulgaris) knotweed, common; prostrate knotweed (Polygonum arenastrum) lambsquarters, common (Chenopodium album) lettuce, prickly (Lactuca serriola) little mallow; cheeseweed (Malva parviflora) mustards (Brassica spp.) nettle, burning (Urtica urens) nightshade, black (Solanum nigrum) nightshade, hairy (Solanum sarrachoides) nutsedges (Cyperus spp.) oat, wild (Avena fatua) pigweeds (Amaranthus spp.) pineapple-weed (Chamomilla suaveolens) polypogon, rabbitfoot (Polypogon monspeliensis) purslane, common (Portulaca oleracea) radish, wild (Raphanus raphanistrum) rocket, London (Sisymbrium irio) shepherd's-purse (Capsella bursa-pastoris) sowthistles (Sonchus spp.)
_____ Use last years scouting records to begin this years scouting. _____ Scout field(s) for weeds in prior year mid-to-late season. _____ Record all weeds by identity and field location. _____ Use banding of herbicides & cultivation to reduce herbicide use rates or control weeds through cultivation (no herbicide use). _____ Don't use herbicides of the same class on the same field in succeeding years. (Use crop rotation and corresponding herbicide selection). _____ Prevent weeds in field alleys and roadways from going to seed. _____ Use an experimental plot to test a different weed management technique 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):
CROP DEVELOPMENT
All cole crops pass through a seedling development phase, a rosette period, and heading phase. During seedling development the seeds germinate and must be thinned or transplanted. During the rosette phase, the ultimate size of the plant will be determined and the crop reaches its marketable shape in the final heading phase.
Seedling Development
Seedling development requires water, oxygen, and temperatures that range from 68°to 77°F (20°to 25°C). Once the taproot has emerged and anchored the seedling, it can tolerate higher temperatures, but warmer temperatures increase germination problems. Seedlings are extremely susceptible to insect and disease problems so planting under optimum temperatures and soil conditions will speed seedling growth and reduce damage. Seedlings can either be thinned or transplanted but direct seeded plants will have a stronger taproot.
Thinning or Transplanting to Heading
During the rosette period, the stems of the plant thickens and grows in length. The lengthening of the stem will grow and the first leaves will begin to unfold signaling the heading stage. The growing point will continue to produce leaves but these leaves have very short stalks.
Heading: Cabbage and Lettuce
Heading in lettuce and cabbage begins when the rosette leaves begin to grow more upright and then roll outward to form wrapper leaves. The wrapper leaves form around entrapped leaves in the center that develops as the head. Mature heads are firm, but the shape may vary according to variety.
Sprout Formation: Brussels Sprouts
Brussel sprouts form as the auxillary buds above each leaf begin to enlarge into small heads and can be harvested after about one month of enlargements. Pre-mature heading of cauliflower and broccoli can occur when plants are exposed to several days of cold temperature during the juvenile growth sages. Pre-mature heading can also be a result of inefficient water, nitrogen deficiency, excessive salt, or weed competition. Broccoli develops in many short clusters with beaded heads. These beads are actual flower buds that will bloom with maturity. Cauliflower is made of excessively branched flower stalks that are initially hidden by leaves until it is about two inches in diameter. Cauliflower must be harvested before the curds become loose and the true flower stems beneath the head elongate and form flowering stalks. Broccoli is harvested while the bud clusters are still compact and the buds are tightly closed and green.
Brussels sprouts(H. F. Schwartz; Colorado State University)
GROWTH REQUIREMENTS
Nutrients
Most of the nutrients that the plants take in are in the upper foot of soil since this is where the majority of the roots are found. Plants that are deficient in nutrients do not compete well and look as though they have been exposed to disease. Nutrient deficiencies limit yields, delay or advance maturity and decrease market and storage quality. Lack of nutrients may even change flavors and other plant quality characteristics, and cause plants to not tolerate stress well. Most plants will only need to have nitrogen and phosphorus added on a yearly basis.
Water
Cole crops do not retain much water as most of it evaporates out through the leaves. This evaporation acts as a coolant for the plant when the temperature becomes too high. Monitoring the amount of water is particularly important when the temperatures are high, the humidity is low, or unusual winds occur because the plant will require more water as water is lost due to transpiration.
Temperature
When the requirements for light, water and nutrients are met, temperature controls the rate of plant growth. Temperatures for proper growth range from about 59°to 68°F (15°to 20°C). It is important that plants are grown under optimum temperature requirements because temperatures that are too high or too low may hinder growth development. Changes in the temperature can initiate reproductive growth, vegetative growth, or inhibit plant growth completely. When plants are exposed to freezing temperature, the leaves may be thick or the plant may be more susceptible to secondary infections making them less marketable.
CULTURAL PRACTICES
Field Selection
When selecting a field for cole crops, choose a field with deep, uniform soil, if possible. When the soil consistency is not uniform, other irregularities will occur in the field such as uneven irrigation and herbicide applications. It is advised to have the soil and irrigation water tested in a laboratory for salinity, nutrient deficiencies, and soil pH. Residues left in the soil from previous crops or tailwater from other crops can contain herbicides that are particularly detrimental to seedling growth.
Land Preparation
Fields that are well prepared produce crops more efficiently and control weeds are better. Some good field preparation techniques include properly grading the land, providing good drainage, avoid working in the soil when it is wet, avoid soil crusting, and making the final bed tops flat and uniform. Deep plowing may help control deep rooted weeds.
CULTIVAR SELECTION
There are several factors that should be taken into consideration when selecting cultivars. High quality seeds should be used that are adapted well to the local growing conditions. Uniform maturity is also a trait that should be looked for when selecting a cultivar. This is especially important because growers want to limit the number of trips made through the field, so having a relatively uniform maturing field will decrease the amount of field travel that will need to be made. Another important factor is to select cultivars that are resistant to pathogens or other pests that may infest the crop.
PLANTING METHODS
Cole crops and lettuce can be transplanted or directly seeded. Most broccoli, cabbage, and lettuce are directly seeded and brussel sprouts are almost always transplanted. Direct seeded crops may be planted to a stand or thinned 4 to 5 weeks after emergence, which provides an opportunity to weed the surrounding areas that are planted. For crops that are direct seeded, they should not be planted to a depth greater than an inch, and in most cases, such as lettuce, they should not be deeper than one centimeter. Raised beds of 6-9 inches make cultivating and irrigating easier and are recommended for all crops. The proper time to plant varies with region, crop and cultivar, and available markets but it is important that the soil and air temperatures are warm enough that the seeds will quickly emerge.
FERTILIZING
It is important to have the soil and plant tissues analyzed for nutrient levels because a properly fertilized crop will produce higher yields. The soil should be tested before planting occurs to apply the proper amounts of fertilizer. Soil analysis can help determine the proper rate of fertilizer to apply in specific areas. All the nutrients except nitrogen can be applied preplant and usually will not need further applications during the growing season. Plant tissue analysis can be helpful in determining growth problems and charting nitrogen levels. Nitrogen applications are usually made several times during the growing season.
IRRIGATION
A good method of irrigating is to sprinkler irrigate from planting to thinning and furrow irrigate thereafter. Sprinkler irrigation will leach excess salts from the top of the soil bed to below the rooting zone, which makes this form of irrigation good for seedlings. Furrow irrigation is best for the developing plants because it is important that the plants remain as dry as possible to avoid disease problems. Sprinklers can splash rots found in the soil onto the leaves of the plants increasing the chances of more disease problems. Making sure the field is properly grated, the clods are uniform size, and there are no compacted areas will increase uniform water distribution and good drainage.
Sprinklers
Sprinklers are a good method to irrigate seedlings, but should not permit runoff or puddling. Linear sprinkler systems provide good uniformity of water and herbicides, but should be used when there is no wind to provide a uniform distribution.
Scheduling Irrigations
It is often difficult to determine a good irrigating system so the plants receive the proper amount of water and fertilization. Determining how much water is needed to bring the soil to field capacity is important to avoid too little or too much water being applied. This amount will vary greatly depending upon the soil texture and root depth of the plants. Cole crops and lettuce receive most of their water in the top foot of the soil and should be irrigated when this soil moisture has been depleted by 40-50%. Using evapotranspiration data, it can be determined how much water is being lost through the leaves. This information combined with the amount of water needed to reach field capacity can help estimate the amount of water needed on a daily basis. Crops do not compete well when stressed for moisture so it is important to avoid skipping irrigations to produce a healthy crop. In all crops, a final irrigation is necessary a few days to a week before harvest to assure turgidity of the harvested crop.
CROP ROTATION
Rotating crops is an effort to control certain pest populations by introducing new crops in which the pest does not thrive. Rotating crops may also allow the use of certain herbicides to fight against weeds, which may not be used with cole crops. Rotation also discourages corky root of lettuce, black rot and black leg of cole crops and cyst nematodes making them easier to control.
SANITATION
It is important to keep the equipment and fields as clean as possible to avoid contaminating fields with pathogens, insects, nematodes, and weeds. Contaminated surface and irrigation water can also introduce pest organisms. When transporting equipment from one field to another always wash off dirt and any debris from the frame and wheels of tractor and equipment.
VARIETY
MISC. PHOTOS
Broccoli (H. F. Schwartz; Colorado State University)
Broccoli + yellows (Mike E. Bartolo; Colorado State University)
Cabbage (H. F. Schwartz; Colorado State University)
Cauliflower (H. F. Schwartz; Colorado State University)
