Avoid deep tillage after sterilization to prevent reintroduction of weed seed and disease organisms from below the sterilization or fumigation zone. A soil test should be taken before planting to determine the amount of fertilizer to apply for each crop. All phosphorous and potassium fertilizers should be applied before planting and incorporated directly into the soil.
Nitrogen fertilizers should be applied in split applications, part before planting and the rest as needed during the growing season. Nitrogen fertilizers can be applied as sidedressings or through a drip irrigation system. Secondary and minor fertilizer elements should be applied as needed.
Hydroponic culture of greenhouse vegetables involves producing crops in sand, gravel, or artificial soil-less mixes in bags, tubes, tubs, tanks, or troughs designed to allow the circulation of nutrient solution needed for crop growth. Unlike conventional soil culture, hydroponic culture of greenhouse vegetables is less forgiving and requires intense management.
Although current automation systems can minimize fertilization and irrigation labor inputs, continuous monitoring of the system is important.
Growers must be highly knowledgeable about plant growth, nutrient balances, cultural media characteristics, and plant physiology. Nevertheless, hydroponics allows the culture of greenhouse vegetables in areas where soils are not suitable for vegetable production. Tomatoes are the most common vegetables grown in greenhouses, followed by cucumbers. Both are grown in the off-season fall, winter, and spring to take advantage of premium prices.
Leaf and Bibb lettuces often are grown in the winter in cooler areas of the state. Other popular crops include bell peppers, eggplant, and herbs like basil. Introducing supplementary carbon dioxide into the greenhouse has been found to significantly increase the yields of greenhouse tomatoes and other vegetables. Supplementary carbon dioxide is most effective on days when the greenhouse has been shut up for several days with no ventilation. Maximum results can be achieved by injecting 1,—1, ppm CO 2 into the greenhouse using propane burners or other CO 2 generators.
Integrated pest management IPM is a holistic approach to the management of pests. IPM does not exclude the use of pesticides in the greenhouse.
Rather, pesticides are used in combination with cultural, mechanical, and biological control as well as insect monitoring to maximize the effectiveness of control methods. Reduced use of pesticides under more effective timing schedules reduces not only the adverse effects of these chemicals on the environment and people but also the chance of pests developing resistance.
One or two tomato crops can be planted in the greenhouse during the year. Planting, transplanting, and harvest dates will vary depending on location. Because most tomato varieties will begin to ripen days after planting, seed should be planted so the fruit begin to ripen soon after first frost for fall crops. In cooler areas of New Mexico, tomato crops are generally planted in early July and transplanted to greenhouse beds in mid-August. Harvest will begin in October and may continue until early March. Harvesting may be terminated at an earlier date if heating costs become extreme.
Late spring harvest can be accomplished by delaying planting until late fall or early winter. Planting dates in southern New Mexico should be delayed until mid-August or later due to hot weather in mid-summer.
Plants are best started in individual containers plastic pots, peat pots, or cubes to reduce labor costs and reduce transplanting shock. Using commercial sterile potting mixes will decrease the incidence of seedling disease problems. Custom soil mixes can be used, but must be pasteurized to eliminate insects, diseases, and weed seed.
After emergence, remove the plastic and move the pots into full sun.
Thin the seedlings to one plant per pot. This initial cold treatment should help seedlings develop larger cotyledons and thicker stems. Plants should also set more early fruit, increasing both early and total yields. Temperatures can be reduced slightly during cloudy days. Irrigation water may have to be heated in the winter before use. As plants become larger, feeding can be increased to twice a week.
Transplants should be established in the greenhouse beds approximately four to six weeks after seeding. Set transplants in the soil 1 inch deeper than they were in the pots. Space plants 15—18 inches apart in rows 3—3. Water immediately after transplanting. Plants should be trained as single main stems by removing all side shoots or suckers that develop between leaf petioles and the stems.
Remove shoots by snapping them off, not cutting, because diseases can be transmitted on the knife blade. Vines can be supported by plastic or binder twine loosely anchored around the base of the plants with a non-slip loop, and to overhead support wires to gauge running the length of the row. Overhead wires should be at least 7 feet above the surface of the bed and be firmly anchored to support structures. Twine should be wrapped clockwise around the vine as it develops, with one complete swirl every three leaves. The vine should be supported by the twine under the leaves, not the stems of the fruit clusters.
Also wrap twine in the same direction, using clips or tape to keep vines from slipping down the twine. Do not try to wrap the twine around the growing tip because the tip may break. When plants reach overhead supporting wires, untie the twine and lower vines and twine at least 3 feet. After lowering, vines should all lean in one direction in one row. Vines in adjacent rows should lean in the opposite direction.
Retie twine with the vines to the support wire. Be sure to leave at least 4—5 feet of extra twine for this purpose when initially tying vines. Remove any leaves that lie on the soil. Keep two leaves above the top flower cluster. Topping vines will force remaining food reserves into maturing fruit already present on the vines. Continue to remove any suckers that develop. As fruit mature on the lower part of the vine, pinch off older leaves below the fruit. This will provide better air circulation, which helps to reduce the incidence of disease and opens vines up for spraying and harvesting.
Growers should remove any deformed, immature fruit that will ultimately become culls. Removing excess fruit will also result in larger tomatoes at harvest that can be sold at a premium price. Mechanical pollination of tomato flowers is generally needed in the greenhouse due to limited air movement and high humidity.
An electric or battery-powered vibrator can be used to vibrate flower clusters just above the area where they originate from the stem. The vibration will release pollen necessary for pollination.
This can be done twice a day around am and pm. Because all flowers on a cluster do not open at the same time, the same cluster will have to be vibrated again as new flowers open. Air from a mist blower also has been found effective in pollinating tomatoes. A number of factors can result in poor fruit set.