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- Author or Editor: George Hochmuth x
Microirrigation (drip or trickle) is part of intensive vegetable production employed in the humid southeastern part of the U.S. Drip irrigation is increasing in importance for vegetable irrigation because growers can achieve irrigation water savings of about 50% for many vegetables and growers can more efficiently apply fertilizers and labeled agricultural chemicals with drip irrigation. In Florida, more than 10,000 ha of vegetables including tomatoes, peppers, watermelons, eggplants, cucumbers, and squash are irrigated with drip irrigation and this acreage increases every year. With the increasing pressure from urbanization and concern for environmental issues, water quantity and quality are prime considerations in vegetable farming. Drip irrigation will continue to be an important tool for managing water quantity and quality on the vegetable farm. This workshop paper will present the current status of drip irrigation practices used on commercial vegetable crops in the southeastern U.S.
Responses to a 1993 survey showed that drip irrigation was used on 36,400 ha of commercial vegetables in the southeastern and mid-Atlantic United States. Florida led with 44% of total drip-irrigated vegetable area, followed by Georgia, North Carolina, and Pennsylvania, with about 10% each. Drip irrigation was used most commonly on tomato, pepper, and watermelon crops. The most-important benefits of drip irrigation were improved water and fertilizer delivery efficiencies compared to other irrigation systems, such as overhead sprinklers and subirrigation. Challenges with drip irrigation included high installation cost, emitter clogging problems, need for filtration, overirrigation problems, disposal of tubing, and lack of readily available expertise. Most drip irrigation was used with polyethylene mulch and most tubing was thin-wall disposable rather than thick-wall reusable. Eighty-one percent of the drip-irrigated vegetable acreage was fertigated with N and K. Survey responses indicated that drip irrigation use for vegetables is increasing.
Vegetable P fertilization recommendations in Florida are based on a soil test using the Mehlich-I (double-acid) extractant. For several Florida vegetables, including watermelon, there is a lack of crop correlation and extractant calibration data. Phosphorus fertilizer studies were conducted on sites with soils ranging in Mehlich-I P indices from 4 to 30 mg·kg-1. There was a quadratic yield response on soils testing 4 mg·kg-1 P with yield maximizing at about 70 kg·ha-1 fertilizer P. Watermelon did not respond to P additions on soils testing greater than 30 mg·kg-1 of Mehlich-I P.
Efficient N management practices usually involve many potential strategies, but always involve choosing the correct amount of N and the coupling of N management to efficient water management. Nitrogen management strategies are integral parts of improved production practices recommended by land-grant universities such as the Institute of Food and Agricultural Sciences, Univ. of Florida. This paper, which draws heavily on research and experience in Florida, outlines the concepts and technologies for managing vegetable N fertilization to minimize negative impacts on the environment.
The evolution of plastic uses (excluding glazing) in the production of greenhouse vegetables is presented. Plastics are used in almost every aspect of crop production, including providing a barrier to the soil, lining crop production troughs, holding soil and soilless media, and providing a nutrient film channel. Irrigation systems have become very elaborate, with various plastic products used to transport water and nutrients and to provide a means of emitting nutrient solution to the crop. The greenhouse environment is managed from several plastic components, including air distribution tubes, shade materials, and energy curtains. Plastics are now common in greenhouse vegetable crop training, insect monitoring, postharvest handling, storage, and marketing.
Tomato (Lycopersicon esculentum Mill.) was grown in southeastern Florida on sandy soils that tested very high in Mehlich-1 P to evaluate the yield response to P fertilization. One location was used in 1995–96, another in 1996–97. Prefertilization soil samples contained 290 (location 1) and 63 (location 2) mg·kg–1 Mehlich-1 P. Both soil test results were interpreted as very high in P, and P fertilizer was not recommended for the crop. Fertilizer treatments at both sites were 0, 25, 50, 100, 150, and 200 kg·ha–1 P. Neither total marketable yield nor yield in any fruit size category was affected by P fertilization in either season. Amounts of cull (undersized or misshapened) fruits increased quadratically with P fertilization in the second season. Whole-leaf P concentrations increased linearly or quadratically with P application, depending on sample periods, and were always above sufficiency values. Although many tomato growers apply P fertilizer irrespective of soil test recommendations, our results showed that added P was not needed on soils testing very high in P. Furthermore, withholding P applications to soils with high P concentrations will minimize potential P pollution of surface water and groundwater.
Delivery of modern extension programs involves considerable expenses that are becoming scarce from traditional sources. Successful extension educational programs will need to find additional revenue sources to fund educational materials, speaker costs, conferences, and other needs. It is important to become as financially efficient as possible and sometimes this means consolidating some programs and eliminating others. Charging fees to attendees is one means of covering costs of delivering programs. The University of Florida is partnering with the agriculture industry and trade journal publishers to provide resources and publishing for educational programs and materials.
`Allstar” tomatoes raised from seed in Todd™ containerized transplant trays were treated with 1/4 strength Hoagland's solution modified to supply 0, 15, 30, 45, 60, or 75 mg·l-1 N daily. Nutrient application was achieved via ebb and flow irrigation. N was supplied as ammonium nitrate. Tissue sample values for elements tested, excluding N, were essentially adequate for all treatments at transplanting (6 weeks after seeding). Visible transplant differences in the plant house did not translate to significant yield differences in the field when rates of 30 mg·l-1 or greater were used in either spring or fall plantings in FL. A similar trial shipped to PA showed that 75 mg·l-1 in the plant house resulted in the greatest early field yields, but 45 mg·l-1 produced the greatest overall yield.
Carrot production in Florida has been centered in two major organic-soil vegetable production areas. These areas are the Everglades Agricultural Area near Belle Glade, in southern Florida, and the Zellwood vegetable area in central Florida. The state of Florida is currently in the process of purchasing most of the organic soils used for vegetable production near Zellwood, leading to a movement of vegetable production to the surrounding sandy soil or to other vegetable production regions in the state. The move to sandy soils has lead to questions by growers about fertilization of vegetables such as carrot. We conducted a series of fertilization experiments with `Nantes' and `Imperator' carrot to evaluate yields and carrot quality responses to N and K. Carrot yield was maximized with 170 kg·ha–1 N, confirming current extension recommendations for carrot on sandy soils in Florida. The soil used for the K study tested medium (50 mg·kg–1) in K (Mehlich-1 extracted). Carrot yield responded positively to K up to 50 kg·ha–1 K, near the amount predicted for soils testing N medium in K.