Chapter 9 Transplant Production
Cultural Practices
See Cornell Report: Brushing for height control in transplants
Many crops are transplanted in New York because of the late spring, relatively short growing season, and desire to obtain maturity as early as possible. Transplants can be grown in greenhouses, plant beds, or field nurseries operated by vegetable growers or commercial plant growers. A good transplant is healthy, stocky, and relatively young with four to six true leaves. Such plants require uniformly fertile soil or mix, good light, even spacing, and proper temperature and water. Exposure to full sun outdoors or reduced temperature and watering near the end of the growing period toughen the plant and allow it to accumulate food reserves for starting the new root system after transplanting. Tender, very young, or weak plants often die. Overmature or hardened plants usually resume growth slowly and often have reduced yield and smaller fruit. Cabbage, broccoli, cauliflower, celery, and onion plants used for early spring planting may go to seed prematurely or "button" if subjected to cool temperatures during the growing period. Desirable daytime and minimum nighttime temperatures for growing plants and the approximate time required at these temperatures are listed in Table 9.1.
The greater the difference between daytime and nighttime temperatures, the more plants appear to "stretch" (stems elongate). For some crops, a stockier, thicker-stemmed plant might be obtained when day and night temperatures are reversed (e.g., 60°F day, 70°F night). We do not have enough data to recommend this approach, but growers may wish to experiment on a small scale.
Excellent plants can be grown in flats or cell or plug trays either by direct seeding or the conventional seed-plant flat combination. Direct seeding often reduces growing time and labor costs and can produce 25 percent more plants per flat. Seed can be planted by hand in rows or spots or broadcast and later thinned to the desired spacing. Reasonably good seed spacing can be obtained using a vacuum-operated seed-spotting tank built to the dimensions of the flats or cell trays. For tomatoes, peppers, and eggplant, wider spacing of 16 plants per square foot in the flat can lead to stocky plants that produce high early yields. Close spacing of 48 to 72 plants per square foot leads to more slender, wiry, less expensive plants. Although their early production is light, these plants usually give high total yields, which are desirable for processing and for late-market crops.
Growing Media
Soil
A good soil is characterized by at least four percent organic matter to give it good structure; medium texture (fine sandy loam or silt loam); medium to good fertility level; low soluble salts; pH of 6.0 to 6.8; and freedom from diseases and pests. Sufficient phosphorus (about two pounds of 0-20-0 per cubic yard) must be mixed thoroughly and uniformly with the soil. A soil test should be run well before use of any soil or compost, so necessary corrections in soluble salts, pH, and fertility levels can be made. Soluble salts should be kept below a K x 105 reading of 100 to 125, although muck soils can tolerate a somewhat higher amount without injury. Leaching and keeping the soil in the flat moist are partial solutions for high soluble salt problems. Refer to Disease Management section for information on soil sterilization and control of diseases.
Artificial Mixtures
The artificial mix formula listed in Table 9.2 has proved practical for all vegetable plants. This mix is lightweight, does not crust, holds water well, and does not require sterilization.
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| Material | Amount for 1 cubic yard of mix |
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Shredded Sphagnum peat moss |
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| Horticultural vermiculite |
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| Ground limestone |
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| 20% superphosphate (powdered) |
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| Calcium or potassium nitrate |
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| Fritted trace elements |
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| Iron (chelated such as 138, 330) | |
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Fertilizers should be spread evenly over the peat and vermiculite. Two ounces of nonionic water wetter, such as Aquagro, in ten to 20 gallons of water per cubic yard help to wet the mix. Mix the ingredients thoroughly on a clean floor or in a concrete mixer. Fill the flats, packs, or pots, and water thoroughly; wait approximately 15 to 30 minutes and water again. Transplant seedlings or sow seed in mixture. Do not plant too early because plants grow rapidly in the mix. For information on planting dates, see section on Planting Dates. In flats with transplants, apply a soluble fertilizer (one pound per 100 gallons of water) approximately three weeks after thinning or transplanting, and repeat once or twice a week. Calcium nitrate works well for this purpose.
Plant Containers
Old flats should be steamed before reuse because they may be contaminated with fungi capable of causing damping-off in seedlings. See Section 9.6 for details. Seeds are planted in wooden flats and plastic or styrofoam containers. The roots of vine crops (melons, cucumbers, and squash) need to be surrounded by a good mass of soil, so seeds should be planted in plastic trays with individual cells filled with artificial mix or thin-walled peat pots filled with mix or soil. Peat pots must be soaked thoroughly before planting and set deep enough in the field for the soil to cover them completely. If few roots have penetrated the pots at time of setting, it may help to break out the bottoms. If conditions are dry after transplanting, extra water or irrigation may be needed to keep the soil moist inside the pot until the roots become established outside. In the trays, the mix will hold together well in pulling and setting if the root system is fairly well developed and the mix is moderately moist. These containers sometimes are used for early tomatoes, peppers, eggplant, and other transplanted vegetables.
Transplanting
Set plants in the field as soon as possible after pulling. Protect the roots from sun and wind between pulling and setting. Freshen roots of southern plants by running fresh water over them. To transplant, set plants one to two inches deeper than they were in the plant bed and firm the soil around the roots. Apply water using the transplanter or by irrigating immediately after transplanting, especially if the soil is somewhat dry. High temperatures or strong drying winds at the time of transplanting increase mortality and delay recovery. If possible, avoid planting under such conditions or be prepared to irrigate immediately.
Planting Dates
Table 9.3 includes approximate minimum and optimal temperatures for seed germination, the usual method of establishing the crop (use of transplants or crowns, root division, or direct seeding), and the range of dates on which each crop normally can be planted in New York State. See also Planting Method sections in individual crop chapters. Dates are given for planting the commercial field with either transplants or seeds as indicated. Plants to be grown in field nursery or plant beds should be started four to eight weeks earlier. Certain crops that are usually transplanted can also be seeded directly in the field under some conditions. Seeding should be done two to four weeks ahead of the usual transplanting date. Long Island and other moderated districts are considered to be in the planting range for fresh market. Therefore, the range for many crops will be somewhat narrower for much of upstate New York. Usual frost dates and other local weather or soil conditions must be considered in making final determinations of planting dates in each district. Most growers start planting when the first, favorable weather break occurs in or near the planting range indicated. Earlier plantings are possible with the use of row covers, hot caps, and other crop protection systems. See Chapter 7.
Disease Management
Minimizing disease problems in the greenhouse starts long before planting. Maintain a one-month crop-free, weed-free period to break pest cycles. Disinfect walls, walkways, benches, and pipes in production houses, and seal for three to four days prior to planting. Routinely disinfect walkways and tools. Continuously remove and destroy any old or diseased crops and all weeds, from inside and bordering outside of greenhouse, as these may harbor insects and diseases. Avoid piling plant residues near the greenhouse to minimize potential disease reintroduction. Finally, clean hands, tools, and boots or shoes prior to entering a clean greenhouse to minimize disease spread.
Growing transplants successfully involves control of damping-off fungi often present in the soil. Seed treatments alone are not enough. Unfortunately, few chemicals are registered for vegetable bedding plants; any chemical usage must go hand in hand with good cultural practices. Ridomil Gold EC may be used on broccoli, cabbage, Chinese cabbage, cauliflower, cucurbit vegetables, head lettuce, spinach, legume vegetables, onions, and tomatoes for the control of Pythium damping-off. Consult the label for the appropriate rates and method of application. Note that this is for seedlings planted in beds and not transplants grown in flats in an enclosed environment, such as greenhouses or glasshouses.
Rely on the use of light, well-drained soils or soilless mixtures free of pathogens; careful control of moisture, light, and relative humidity; and soil drenches (on certain crops) to reduce disease.
Damping-off becomes more troublesome when plants and soils are overwatered, excessively shaded, and permitted to remain wet for long periods. Water only in the bed or flat. Keep humidity as low as possible by ventilating properly. Automatic fan ventilation is ideal for plant-growing houses.Soil Sterilization
Soil to be used for growing transplants in flats can be sterilized by steam or chemicals. With steam, the entire soil mass should be brought to a temperature of 180°F for 30 minutes. Add organic matter, superphosphate, and other fertilizers before sterilization. Leach the soil after sterilization to reduce soluble salt accumulation. Store the soil for two weeks before use to avoid plant damage from toxic materials released during steaming. Use a plastic seal with chemicals; be sure the soil temperature is 55°F or above, and provide waiting periods of four to 14 days. With adequate ventilation, the following chemical is suitable for this purpose: one quart of Vapam HL in five gallons of water over 1/2 cubic yard. For outdoor plant beds or seedbeds in fields, the following chemical can be used after preparing the soil as for seeding: one pint of Vapam HL per 50 square feet, applied as a drench and sealed with water. Follow label directions for timing, crop safety, and method of application. In general, soils must be at least 55°F at the six inch depth, and a lapse of 14 days between treatment and seeding must be allowed; 21 days is better.*Methyl bromide requires only two to three days after uncovering. Do not use *Methyl bromide for soils in which onions will be grown. Artificial soils do not require sterilization.
Flat Sanitation
All flats should be steamed before reuse. They can be stacked on a bench or the floor and covered with a tarpaulin beneath which steam is released. Minimum treatment should be 180°F for 30 minutes. Flats should be separated horizontally by 3/4 inch strips or stacked in a staggered manner with vertical spaces of about one inch. Flats can be used immediately.
If steam is not available and chemicals must be used, chlorine solutions (one part laundry bleach to nine parts water) are probably the most effective sanitizers. Apply by dipping the flats and draining the solution back into the tank. Stack the flats under a tarpaulin for 24 hours; then uncover, but keep them wet by spraying with water until the odor is gone. This usually takes four to six days. To be sure flats are safe for use, put a wet one in a plastic bag for 24 hours, and check the closed bag for odor.
Cornell Vegetable Team
http://www.hort.cornell.edu/extension/commercial/vegetables/vegeteam/index.html
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Maintained by Curtis
Petzoldt, New York State IPM Program. Address comments or questions to
vegrec@nysaes.cornell.edu
Last modified March 4, 2008.