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George Hochmuth

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.

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George Hochmuth and Ed Hanlon

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.

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George J. Hochmuth

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.

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George J. Hochmuth

Vegetable producers are under increasing pressure to minimize production inputs such as water and fertilizers. Research on fertilizer placement and scheduling, soil testing, and drip irrigation fertigation has provided technologies to enable vegetable growers to produce profitable yields of high-quality vegetables while reducing nutrient inputs. Plant tissue testing has been an integral part of nutrient management on the farm. Although plant sap testing has been evaluated for more than 70 years, only recently has testing technology been developed to the point where farm use is facilitated. Researchers in several states, including Florida, have evaluated various methods for determining nitrate-N and K concentrations in petiole sap. Researchers in Florida have developed petiole sap sufficiency ranges for the major vegetable crops and strawberries, and these guidelines are widely used by vegetable growers and crop consultants as an aid for making informed fertilization decisions. In this workshop, research results and field experiences with fresh sap testing for N and K will be discussed, including field test equipment, testing methods, and current test applications.

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Robert C. Hochmuth and George J. Hochmuth

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.

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Charles S. Vavrina and George Hochmuth

`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.

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Osmar Alves Carrijo and George Hochmuth

Experiments were conducted to evaluate the yield response of tomato (Lycopersicon esculentum Mill.) to P, either preplant-incorporated or injected through the drip irrigation system, on soils with low, high, or very high soil P content. Fertilization through the drip irrigation system (fertigation) was more efficient than preplant incorporation of P for soil that tested low in P (9 mg·kg–1 Mehlich-1 P). On soil testing low in P, marketable yield response to preplant soil P application rates (0 to 100 kg·ha–1) was maximum at 61 kg·ha–1 P according to the linear-plateau model, but 37 kg·ha–1 P according to the quadratic-plateau model. The lower value is about one-half the P recommended by Univ. of Florida for low-P soils. On soil testing high in P (48 mg·kg–1 Mehlich-1 P) the linear-plateau model predicted a maximum yield of 72.8 t·ha–1 with 25 kg·ha–1 P. The Univ. of Florida recommended no P for that soil. On soil testing very high in P (85 mg·kg–1 Mehlich-1 P), there was no yield improvement with P fertilization.

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Stephen M. Olson, George J. Hochmuth and Robert C. Hochmuth

Studies were conducted at the NFREC, Quincy, and AREC, Live Oak, Fla., to compare watermelon {Citrullus lanatus [(Thumb.) Matsum & Nakai]} plant establishment by transplanting and direct-seeding. Cultivars used were `Charleston Gray' in 1984, 1985, 1986, and 1989; `Jubilee' in 1988 and 1989; and `Crimson Sweet' in 1987 to 1990. Early yields were greater with transplants for all three cultivars in all years. With `Charleston Gray', total yields with transplants were higher in 1985 and 1989, but not in 1984 or 1986. The average fruit weights with transplants were also greater in 1985 and 1989 than in 1984 or 1986. With `Jubilee', total yield with transplants was higher in 1989, but not in 1988. Average fruit weight with transplants was greater in 1989 than in 1988. With `Crimson Sweet', total yields were higher with transplants in 1989 and 1990, but not in 1987 or 1988, but fruits were larger with transplanting compared to direct-seeding only in 1990. In all experiments, yields with transplants were never less than those with direct-seeded plants.

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George J. Hochmuth and Donald N. Maynard

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.