10 • Chapter 1 techniques for greenhouse production of tomatoes. The cost of producing a crop in a controlled environment is high, and it is essential that the resulting product be of superior quality.
Production of Processing Tomatoes In California, all tomatoes grown for processing are produced in open fields on raised beds, where water is commonly applied via furrow irrigation. In the Midwest, water requirements are generally met by ambient rainfall, with little or no supplemental irrigation. Sprinkler irrigation may be used to promote stand establishment and during early plant growth but can promote certain foliar diseases. Drip irrigation is sometimes used where irrigation water is limited. Water-use efficiency can be at least 200% higher with drip than with furrow irrigation. Seeding rates vary but can be as low as 3.5 ounces (0.1 kg), or about 28,000 seeds, per acre with higher-priced hybrid seed. To obtain an adequate stand, cultural practices during germination must be optimized. At the third to fourth true- leaf stage, the plants are mechanically thinned to a spacing of about 8 inches (20 cm), or about 14,000 plants per acre. Cultivars with small, compact vines may be planted in double rows on a bed. As long as plants are less than approximately 24 inches (60 cm) apart, final yield is not affected. However, wider plant spacing may reduce fruit ripening, which is a disadvantage for mechanical harvesting. The use of transplants to establish a stand of processing tomatoes has increased dramatically in the past decade, despite the greater cost involved compared with direct seeding. In 2008, more than 70% of processing tomatoes in California were produced by using transplants. Stand establishment is usually more assured when transplants are used and certain other costs, such as weed control, are lower. Growers often use fewer than 7,000 transplants per acre. Yields are generally similar to direct-seeded tomatoes that have at least twice as many plants per acre.
The use of transplants to establish a stand of processing tomatoes has increased dramatically in the past decade, despite the greater cost involved compared with direct seeding. Field Fresh-Market Tomato Production Stands of fresh- market tomatoes are almost all transplanted, and a wide range of growing practices are used. Raised beds with plastic mulch and drip irrigation are common. In some production areas, determinate cultivars are used without the need to train the plants on staked trellises. This practice is more common in areas that are well suited to tomato production and when production costs must be minimized. The use of indeterminate cultivars and, in some cases, large determinate cultivars that require staking or trellising is more common for out-of-season production—for example, in winter production in Florida and Mexico, which are major
sources of fresh tomatoes for the United States at that time of the year.
Nutrition Tomatoes are tolerant of a wide range of nutrient regimes, but high yields of high-quality fruit require good nutritional management. Generally, yields are highest at moderate nitrogen levels. Excessive nitrogen causes plants to become vegetative at the expense of flower production. An adequate phosphorus level is particularly crucial to early plant growth, when root systems are small. In some soils, phosphorus fertilization is not needed but is still commonly used. Excessive phosphorus may increase certain physiological disorders, such as uneven ripening and puffiness. High yields can be obtained with moderate levels of potassium. However, optimal levels of potassium are needed to reduce fruit puffiness, uneven ripening, and off flavors caused by low acid levels. Optimal levels of calcium reduce the incidence of blossom-end rot and increase fruit firmness.
Irrigation Four major types of irrigation are practiced in open-field production: furrow, sprinkler, seepage, and drip. Furrow irrigation is popular where ample irrigation water is available, but it is the least efficient of the irrigation methods. Uniform water application is more easily accomplished with sprinklers than with furrows. Sprinklers are used most often only for stand establishment, since their continued use increases the possibility of the development of certain diseases later in the season. Seepage irrigation is based on manipulation of the water table. A series of canals and ditches allows growers to raise or lower subsurface water to maintain proper watering of crops. This method is particularly common in Florida. Drip irrigation is the most efficient method, and uniformity of application is more easily achieved. The highest tomato yields have generally been achieved by using drip irrigation; however, the costs of establishing a drip irrigation system are high.
Ripening Hormones The use of ethylene and ethylene-releasing compounds (e.g., ethephon) is common in tomato production and marketing. Growers of processing tomatoes sometimes apply ethephon to a tomato field to speed ripening. If fresh-market tomatoes are picked before they start to ripen, ripening may be initiated by gassing them with ethylene after field harvesting. Storage life after picking can be managed to some extent with timing of ethylene application. Cooling and refrigeration of fresh-market tomatoes to extend shelf life and reduce losses must be carefully managed. Temperatures below 50°F (10°C) adversely affect ripening and flavor development. Selected References Adams, P. 1986. Mineral nutrition. Pages 281-334 in: The Tomato Crop. J. G. Atherton and J. Rudich, eds. Chapman and Hall, New York. Besford, R. T., and Maw, G. A. 1975. Effect of potassium nutrition on tomato plant growth and fruit development. Plant Soil 42:395-412.