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Jonathan Lynch and Kathleen Brown

We have developed solid-phase P buffers capable of maintaining P concentrations in soiless media much lower than conventional fertilizers, in the range of available P levels found in natural soil. In addition to substantially reducing PGH reaching into the environment, these buffers can have a number of useful effects on crop growth. Using various floriculture and ornamental species, plants grown in media buffered at low P levels have stimulated root branching and growth, increased drought resistance, better transplant establishment, better shoot form, better vegetative growth, increased flowering, and continued development of buds in the postharvest environment. Phosphorus availability regulates many aspects of root architecture including adventitious rooting, lateral branch density, root gravitropism, and root hair formation. It appears that many of the effects of P on root growth may be mediated by ethylene. We hypothesize that the high P concentrations used in many horticultural systems are detrimental to optimal plant growth, and that buffered media represent an opportunity to improve production systems while also reducing environmental pollution from nutrient effluents.

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George Hochmuth, Osmar Carrijo, and Ken Shuler

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.

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Michael A. Schnelle, Sharon L. von Broembsen, and Michael D. Smolen

A comprehensive educational program focusing on water quality protection was developed for the Oklahoma nursery industry. The program focused on best management practices to limit pesticides and nutrients in irrigation runoff and on capture and recycle technology as a pollution prevention strategy. Key professionals from the departments of entomology and plant pathology, biosystems and agricultural engineering, and horticulture formed a multidisciplinary team within the Oklahoma Cooperative Extension Service (OCES). During 1998, water quality workshops were conducted on-site throughout Oklahoma at leading nursery operations. These workshops were designed to highlight best management practices (BMPs) that were already in place as a foundation on which to implement additional BMPs with the assistance of the OCES team. Training workshops were augmented by written publications, by web-based information, and by videotape instruction. These provided for ongoing education beyond the formal grant period. The written materials included a water quality handbook for nurseries and a fact sheet on capturing and recycling irrigation runoff. The water quality handbook was also made available on the web and a website on disease management for nurseries using recycling irrigation was provided. The water quality video, highlighting successful growers, was designed to show aspects of both best management practices and capture and recycle technology. Results of these 3-year extension efforts will be discussed.

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Leslie K. Lake, Warren E. Shafer, Sheryl K. Reilly, and Russell S. Jones

Plant growth regulators (PGRs) are often used in crop production for specific niche market needs. PGRs are frequently viewed as secondary business opportunities by the private sector, especially when compared to herbicide, insecticide, and/or fungicide markets. Nonetheless, PGRs are regulated by the U.S. Environmental Protection Agency (USEPA), and the additional cost of regulatory compliance as part of commercial development is significant. Of the two broad classes of pesticides regulated by the USEPA, conventional chemicals and biological pesticides (or biopesticides), many PGRs belong to the biopesticide class, specifically the biochemical category. Because of USEPA's responsibility to assure that any pesticide used in commerce will not result in unreasonable adverse effects to humans or the environment, specific data requirements have been established for product registration. Registrants must address each requirement, either by submitting relevant data or a request to waive the requirement, prior to receiving a federal registration. For biochemical PGRs, the acceptability of data or waiver requests, as well as any proposed label uses, are reviewed by the Biopesticides and Pollution Prevention Division (BPPD). The BPPD was formed in 1994 to facilitate the development of biopesticide products. Given the time and expense associated with PGR product development and commercialization, registrants should work closely with the USEPA and other stakeholders to help ensure successful product development.

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Hagai Yasuor, Alon Ben-Gal, Uri Yermiyahu, Elie Beit-Yannai, and Shabtai Cohen

Producers of horticultural products face new and growing standards regarding food quality and safety as well as environmental responsibility and sustainability. The objective of this research was to reduce environmental pollution by increasing nitrogen use efficiency (NUE) in vegetables without negatively affecting fruit yield or quality. Bell pepper was used as a case study for intensive vegetable cropping. Pepper cultivars with different vegetative vigor were drip-irrigated with solutions containing 9.2, 56.2, 102.3, and 158.5 mg·L−1 nitrogen (N). Fruit yield, quality, and nutritional value were measured. Nitrogen balance was determined by quantifying N in soil and in plant tissues. Maximum yields were found when peppers were irrigated with 56.2 mg·L−1 N. Nitrogen concentrations of 102.3 and 158.5 mg·L−1 N loaded 400 and 800 kg·ha−1 N into the environment, respectively, whereas for the 56.2 mg·L−1 N concentration, N was almost completely taken up and used by the plants. Nitrogen treatments had no significant negative effect on pepper fruit physical or chemical quality parameters including sugar content and acidity. Reduced N application did not affect nutritional quality components of the pepper fruit such as β-carotene and lycopene content or total antioxidant activity. The vigorous cultivar used N more efficiently. The results demonstrate how the environmental impact of intensive agriculture can be minimized without harming fruit yield or quality by reducing N application level and adopting cultivars with improved N use efficiency.

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Heidi J. Johnson, Jed B. Colquhoun, and Alvin J. Bussan

There is significant interest from vegetable processors, growers, and consumers in organic sweet corn (Zea mays) production. Organic nitrogen (N) management is particularly challenging in high N consuming crops such as sweet corn because of the low N content and low N to phosphorus (P) ratios of organic soil amendments. Various management programs were compared to determine the optimal combination of soil amendments and green manure crops for organic sweet corn production. Alfalfa (Medicago sativa), rye (Secale cereale), and field pea (Pisum sativum) were used as green manure crops. Composted poultry manure and a high N content organic fertilizer were used as organic amendments. Ammonium nitrate was used in a conventional management program for comparison. Treatments were designed to deliver a full rate of N (150 lb/acre), a half rate of N (75 lb/acre), and to limit the amount of P applied. Phosphorus can become a source of pollution when applied to erodible soils, particularly when soils already contain excessive P. Sweet corn yield in many of the organic programs was highly variable among years while the yield was more consistent in the conventional program. This was attributed to differences in organic N mineralization in both the green manure crops and the amendments. The most stable yield from an organic treatment, among years, was achieved using the commercially available organic N fertilizer. Commercially available amendments were costly, and although organic sweet corn received a premium price in years when organic yields were lower, profit was reduced by the high cost of N management.

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Olya Rysin, Amanda McWhirt, Gina Fernandez, Frank J. Louws, and Michelle Schroeder-Moreno

In this study, we investigate the economic viability and environmental impact of three different soil management systems used for strawberry (Fragaria ×ananassa) production in the southeastern United States: 1) a conventional production system that is based on the current production practices implemented by growers, 2) a nonfumigated compost system with summer cover crop rotations and beneficial soil inoculants, and 3) an organic production system that includes practices approved for use under the National Organic Program (NOP). Under our assumptions, all three systems resulted in positive net returns estimated at $14,979, $11,100, and $19,394 per acre, respectively. The nonfumigated compost system and organic system also both resulted in considerable reductions in negative environmental and human health impacts measured by a set of selected indicators. For example, the total number of lethal doses (LD50) applied per acre from all chemicals used in each system and measuring acute human risk associated with each system declined from 118,000 doses/acre in the conventional system to 6649 doses/acre in the compost system and to 0 doses/acre in the organic system. Chronic human health risk, groundwater pollution risk, and fertilizer use declined as well in the compost and organic systems as compared with the conventional system.

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R. Scott Johnson, Rich Rosecrance, Steve Weinbaum, Harry Andris, and Jinzheng Wang

The suspected contributory role of soil fertilization to nitrate pollution of groundwater has encouraged exploration of novel fertilizer management strategies. Foliar-applied urea has long been used to supplement soil N applications, but there have been no apparent attempts to replace soil N applications completely in deciduous orchard culture. Two experiments were conducted to study the effect of foliar-applied low biuret urea on productivity and fruit growth of the early maturing peach [Prunus persica L. Batsch (Peach Group)] cultivar, Early Maycrest. In a 3-year experiment, a total foliar urea regime was compared to an equivalent amount of N applied to the soil. The foliar treatment supplied adequate amounts of N to the various organs of the tree including the roots, shoots, and fruit buds, but mean fruit weights were lower than in the soil-fertilized treatment. In a 2-year experiment, a 50%-50% combination treatment of soil-applied N in late summer with foliar-applied N in October, maintained yields and fruit weight equal to the soil-fertilized control. Some soil-applied N appears necessary for optimum fruit growth. Soil N application may be needed to support root proliferation and associated processes, but we did not determine a threshold amount of soil-applied N needed. The combination treatment also reduced excessive vegetative growth which is characteristic of early maturing peach cultivars. Therefore, this combination treatment offers promise as a viable commercial practice for maintaining tree productivity and controlling excessive vegetative growth in peach trees.

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Tiangen Wang and Stephen K. O'Hair

Concerns relating to pollution from nitrogen fertilizers leaching into ground water are increasing. This is especially important in southern Florida because the pollution threatens fragile ecosystems in Biscayne Bay, and the two National Parks that abut agricultural areas. The current research is focused on the development of an automatic system which can monitor \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} leaching from plant nursery pots. \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} electrodes and a load cell were used for real-time measurements of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document}, and leachate volume. The leachate was directed to pass the sensing areas of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}, reference, pH, and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} electrodes. It was collected and weighed in a container placed on a load cell. The analog signals from the electrodes and load cell were digitized through data acquisition technology using a 16-bit A/D converter and a self-developed software program. With this system the volume of the leachate and concentrations of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} in the leachate were determined in situ. Based on this design, the dynamics of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} leaching from pots can be observed. This system can be used to 1) determine soil (or media) holding capacity of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document}, 2) evaluate the effects of nitrogen fertilizer formulations on water quality, 3) develop best management practices of nitrogen application in containerized plant production, and 4) determine the soil-holding capacity to optimize the use of water. The advantages of the developed system are 1) low labor cost for sample collection and analysis and 2) high measurement resolution resulting from a minimization errors that occur during sampling and other manual operations.

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Erin C. James and Marc W. van Iersel

Nitrate pollution and water conservation are two of the most important environmental concerns for greenhouse growers. Closed irrigation systems, such as ebb and flow, can minimize these problems. The objective of this study was to determine optimal fertilizer concentrations for petunia (Petunia×hybrida Hort. Vilm-Andr.) and begonia (Begoni××emperflorens-cultorum Hort.) grown with ebb-and-flow irrigation. `Ambassador Scarlet' begonia and `Dreams Mix' petunia were grown as bedding plants in three soilless media. Plants were fertilized with solutions of a 20N-4.4P-16.6K water-soluble fertilizer with electrical conductivities (EC) of 0.15, 0.6, 1.2, 1.8, 2.4, or 3.0 dS·m-1. Maximum growth occurred with a fertilizer EC of 2.2 dS·m-1 for petunia and 1.6 dS·m-1 for begonia. Petunia growth was best in the medium with the highest porosity (Metro-Mix 220), but choice of medium had little effect on begonia growth. Leachate EC and pH were determined throughout the experiment, using the pour-through method. Leachate EC rose with increasing fertilizer concentration, and increased over time. The pH of the leachate decreased with increasing fertilizer concentration and dropped 0.5 to 1 unit over the course of the experiment with the higher fertilizer concentrations (≥0.6 dS·m-1). Plant growth was not very sensitive to leachate EC. Begonia and petunia grew well when the EC at the end of the production cycle was between 1.7 to 6.1 and 2.1 and 5.4 dS·m-1, respectively.