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Miguel Urrestarazu, Isidro Morales, Tommaso La Malfa, Ruben Checa, Anderson F. Wamser, and Juan E. Álvaro

( Massa et al., 2010 ; Parry et al., 2005 ) and its efficiency in production ( Patanè et al., 2011 ), the absorption of nutrient ions, such as nitrate and potassium ( Cornillon and Fellahi, 1993 ; Topcu et al., 2007 ), and the pollution of nutrients

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Dennis Decoteau, Jonathan Ferdinand, Jim Savage, Dick Stevenson, and Donald Davis

Penn State's Air Quality Learning and Demonstration Center was completed and open to the public in 2003. The facility houses the State College air monitors for the Department of Environmental Protection and contains self-guided walkways through gardens of air pollution sensitive plants, innovative techniques for demonstrating the effects of air pollutants on plants, displays of recent research findings, industry-supported displays of pollution abatement technologies, and a teaching pavilion. One of our outreach projects, funded by the US EPA and the PA Department of Environmental Protections, is to provide enhanced teacher training on air pollution impacts on the regional and specific vegetation through an in-service training for local science school teachers utilizing on-site and archived data on weather conditions and plant injury symptom development. The picture archive began to be developed during Summer 2005 using video cameras that are permanently mounted for the growing season inside the open-top chambers and focused on a plant (and a specific leaf or set of leaves). Once the teachers are trained to utilize these data sets appropriately, they will be able to access the data during the school year through the Learning Center website and conduct the same analysis with their students in their classroom during the school year. This use of archival information is important because the school year does not coincide with optimum times for observing air pollution symptoms on vigorously growing field-grown plants in Pennsylvania (which is best during the summer).

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Steven A. Weinbaum, R. Scott Johnson, and Theodore M. DeJong

Over-fertilization (i.e., the application of fertilizer nitrogen (N) in excess of the tree or vine capacity to use it for optimum productivity) is associated with high levels of residual nitrate in the soil, which potentially contribute to groundwater and atmospheric pollution as a result of leaching, denitrification, etc. Overfert-ilization also may adversely affect productivity and fruit quality because of both direct (i.e., N) and indirect (i.e., shading) effects on flowering, fruit set, and fruit growth resulting from vegetative vigor. Pathological and physiological disorders as well as susceptibility to disease and insect pests also are influenced by the rate of applied N. Over-fertilization appears to be more serious in orchard crops than in many other crop species. The perennial growth habit of deciduous trees and vines is associated with an increased likelihood of fertilizer N application (and losses) during the dormant period. The large woody biomass increases the difficulty in assessing the kinetics and magnitude of annual N requirement. In mature trees, the N content of the harvested fruit appears to represent a large percentage of annual N uptake. Overfertilization is supported by a) the lack of integration of fertilizer and irrigation management, b) failure to consider nonfertilizer sources of plant-available N in the accounting of fertilizer needs, c) failure to conduct annual diagnosis of the N status, and d) the insensitivity of leaf analysis to over-fertilization. The diversity of orchard sites (with climatic, soil type, and management variables) precludes the general applicability of specific fertilization recommendations. The lack of regulatory and economic penalties encourage excessive application of fertilizer N, and it appears unlikely that the majority of growers will embrace recommended fertilizer management strategies voluntarily.

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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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M.A. Kasrawi, N. Khraishi, and Y. Tabaza

A greenhouse experiment was conducted over two growing seasons to study the physical and mechanical properties of a recycled multilayer plastic cover and its effect on the production of greenhouse-grown tomatoes. Two experimental greenhouses were constructed, one covered with recycled multilayer film and the other with conventional virgin monolayer film. The air temperature under both covers was similar; the soil temperature in the recycled multilayer house was a few degrees lower in the afternoon hours to midnight than in the virgin monolayer house. The recycled multilayer film retained its strength and elasticity over a useful service life of 7 months (one growing season), after which severe degradation occurred as manifested by a 50% loss of elongation at break. During the useful lifetime of the film, haziness, light scattering, and light transmission of the recycled film was similar to the conventional film. The thermal analysis of the recycled film revealed a low stability against thermo-oxidative degradation and the infrared analysis indicated the presence of a measurable amount of degradation products, mainly carbonyl groups, in the recycled film in comparison with conventional film. During the useful lifetime of recycled film, yield components of the tomato crop were identical to the conventional film in both growing seasons. In conclusion, waste plastic recycling offers an attractive solution to nuisance environmental problems. However, the useful lifetime of recycled films needs to be improved.

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Proceedings of the Workshop Fertilizer Management in Horticultural Crops: Implications for Water Pollution

held at the 88th ASHS Annual Meeting The Pennsylvania State University, University Park 24 July 1991

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D.M. Olszyk, G. Kats, C.L. Morrison, P.J. Dawson, I. Gocka, J. Wolf, and C.R. Thompson

Three-year-old `Valencia' orange [Citrus sinensis (L.) Osbeck] trees were exposed to air pollutants for 4. years in open-top field chambers to determine the chronic effects of ambient oxidants (primarily ozone) or sulfur dioxide (SO2) on fruit yield and quality and tree growth. Ozone concentrations averaged 0.012,0.040, and 0.075 ppm for 0800 to 2000 hr during April to October for filtered, half-ambient, and full ambient oxidant chambers. Sulfur dioxide was applied continuously at 0.09 ppm. Oxidant and SO2 effects were only marginally significant, as there was considerable variability in response among individual trees and between years. Across two “on” production years, yields were 31% lower with ambient oxidants, 11% lower with half-ambient oxidants, and 29% lower with sulfur dioxide compared to filtered air. Number of fruit per tree was reduced by ambient oxidants and SO2. Individual fruit weights were reduced by ambient oxidants, but no other fruit quality characteristics showed definite responses to ambient oxidants or SO2. Ambient oxidants had no effect on yield or quality of fruit during one “off' production year. Neither ambient oxidants nor SO, affected tree growth.

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Ed Stover, Chris Wilson, Dominick Scotto, and Masoud Salyani

Parts I and II of this series revealed substantial opportunities for improving spraying of Indian River citrus (Citrus spp.). In this segment of our work we develop guidelines for growers to select the spray parameters providing an optimal balance between efficiency and efficacy while minimizing environmental contamination.

It is proposed that these guidelines could be codified in a simple expert system to make them easier to use. We propose that understanding limiting conditions may be the key to choosing spray options. Wind is a major factor influencing spray deposition and offtarget drift. Based on weather records, wind speeds below 5 mph (8.0 km·h-1) are only routinely observed from 2000 HR until 0800 HR, making night spraying a good choice for low-volume applications. The importance of adjusting sprayer set-up for individual groves is demonstrated, with economic estimates of the cost of failing to make these adjustments. Routine use of careful sprayer adjustments is also likely to reduce off-target drift. Improvements in equipment and spray chemicals are also discussed. Use of non-orchard buffer areas and/or windbreaks appear to offer considerable opportunity for reducing off-site spray movement.

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Ed Stover, Dominick Scotto, Chris Wilson, and Masoud Salyani

Foliar application of spray materials is an integral component of commercial citrus production. An intensive assessment of spray application practices has been stimulated by low fruit value and increased concern about potential surface water contamination in the Indian River citrus region of Florida. Many publications report research results regarding distribution of spray materials within orchards and off-target deposition, but interpretation is challenging because so many factors influence spray results, and integrating this information into practical recommendations is difficult. Canopy geometry and density are prominent factors contributing to variable deposition and spray drift. Environmental factors such as temperature, relative humidity, wind speed, and wind direction also greatly influence spray deposition and drift, and substantial changes can occur within seconds. In addition the physical and/or mechanical set up of the sprayer interact significantly with the other factors. A better understanding of these interactions should help growers optimize spray effectiveness and efficiency while reducing potential off-target effects.

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Bret Sparks, Gregg Munshaw, David Williams, Michael Barrett, Jeffrey Beasley, and Paul Woosley

improperly timed fertilizer applications increase the risk of NPS pollution ( Law et al., 2004 ). Nonpoint source pollution is defined as any nondiscernable source in which pollutants are traveling, such as land runoff, precipitation, or drainage ( USEPA