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Rachel Mack, James S. Owen Jr., Alex X. Niemiera and David J. Sample

surface waters with agrichemicals ( Bilderback et al., 2013 ). The purpose of implementing BMPs is to address water quality or water-management issues from specific sites or problems, increase plant production efficiency, and promote environmental

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James S. Owen Jr and James E. Altland

trade 1-gal container. This predicted moisture gradient within a container could greatly affect water management practices for ornamental plant growth throughout the production process. Direct measurement of the moisture gradient would be ideal to more

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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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Mark Freeman and Dale Handley

Much technology concerning efficient use of agricultural energy and water is available. However, this technology is underutilized by many growers because of inadequate training. This Extension program educates growers about evaluating irrigation systems, soil and water problems, irrigation scheduling, and energy use (of pumps). The program uses different communication tools to create awareness in growers, and then encourage adoption. These tools include in-depth surveys, condensed written material, small group discussions, and videotapes. The program also coordinates efforts among various governmental and private agencies.

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Jesús Valencia and Donald M. May

An irrigation water study was conducted in the West side of Fresno County to evaluate the impact of recycled drainage water nitrogen and salinity content in the growth of direct seeded processing tomatoes to reduce nitrate-ground water pollution. Four canal water treatments (0.4 dS/m) received 0, 67.5, 101.2, and 168.7 kg of nitrogen per hectare and four saline water treatments (7.01 dS/m) received 0, 33.7, 67.5 and 135.0 kg nitrogen per hectare. All treatments were established with fresh canal water, and at first flower half of treatments were switched to saline water. The nitrogen content of water had an average of 283 ppm N-NO3 for the canal water and the drainage water contained 4489 ppm N-NO3. There was no significant yield differences between the irrigation methods and the two N-fertilizer sources applied to the tomatoes. However, drainage water produced a significant increase in fruit soluble solids (5.05 Av.) in comparison to canal water and synthetic fertilizer (4.3 Av.). The overall fruit quality and maturity was better in the drainage water treatments than it was in the fresh canal water with synthetic N-applied treatments.

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D.A. Martens and D.L. Suarez

The discovery in 1983 of deformities, reproductive failures, and high waterfowl mortality rates at Kesterson National Wildlife Refuge, western San Joaquin Valley, Calif., due to selenium (Se) -contaminated drainage water, raised concerns that these problems may be occurring in the >600 wetlands and National Wildlife Refuges being utilized to collect irrigation drainage waste water in 17 western states. The waterfowl problems were traced to ingestion of organic Se present as Se-amino acids. Plants assimilate soluble Se into Se-amino acids and release them upon decomposition. Aerobic plant residue decomposition studies showed that 50% of the assimilated Se was mineralized to soluble Se, while the remaining organic Se persisted. This means that each growth cycle results in a steady decrease of soluble Se and an increase in organic Se levels. To test the effect of plant growth on Se accumulation, two types of evaporation ponds were evaluated, one with prolific plant growth, and the second relatively devoid of plant growth. Soil Se analysis showed that plant growth dramatically increased Se accumulation in the surface layers. Evaluation of additional Se-contaminated sites showed that Se accumulation followed an exponential function and accumulated rapidly above a 2% soil organic C content. Without plant growth, the Se remains mobile and diffuses to low concentrations in the underlying soil, suggesting that plant residue cycling is an important factor in Se accumulation and toxicity.

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L.L. Lockett, C.B. McKenney and D.L. Auld

Many segments of private industry use data gathered from public attitude and opinion research as an integral part of the planning, program development, and evaluation process. These basic techniques were used to determine public perception of five species of Texas native plants grown at three irrigation rates under xeriscape conditions. Nearly half of the average annual residential water costs go to lawns and gardens. Minimizing the amount of water used in irrigation could provide significant savings of money and a precious natural resource. The complexities of measuring social attitudes, how to develop a valid survey instrument, methods of analyzing survey data, and appropriate interpretation will be discussed. Use of public perception could be a powerful tool in developing water conserving technologies.

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Dean A. Martens and Donald L. Suarez

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John S. Selker

Avoiding groundwater contamination from agricultural activities is possible only if the processes that control deep percolation are understood. The source of contaminant movement to groundwater is typically through preferential flow, processes by which the bulk soil is bypassed by some part of the infiltrating water. Three mechanisms give rise to preferential flow: fingered flow, funnel flow, and macropore flow. Fingered flow occurs in coarse-textured soils and can be minimized by starting with an initially well-wetted profile. Funnel flow is likely in layered soil profiles of silt or coarser-textured soil, in which avoiding slow overirrigation is critical. Macropore flow is observed in all structured soils in which maintaining irrigation rates well below the saturated conductivity of the soil is essential. These prescriptions are quite different than conventional recommendations, which fail to consider groundwater protection.

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Lenny Wells

Pecan [Carya illinoinensis (Wangenh.) K. Koch] tree stem water potential (ψ), shoot length, nut yield, and nut quality for the following treatments were evaluated in a commercial pecan orchard in Berrien County, GA; 1) current recommended irrigation schedule, 2) a reduced early season irrigation schedule, and 3) non-irrigated control. Water Stress on pecan occurred at ≈−0.78 MPa using the pressure chamber to measure stem water potential. Regression analysis suggests that irrigation scheduling for mature pecan trees may be needed when volumetric water content reaches 10% on Tifton loamy sand soil. Water stress in pecan is correlated with soil moisture from budbreak through the end of nut sizing. Pecan trees bearing a moderate to heavy crop load may undergo water stress during the kernel-filling stage regardless of soil moisture level. Therefore, it is suggested that water stress during the kernel-filling period is a function of nut development, crop load, or both in addition to soil moisture. The reduced early season irrigation schedule provided a 38% reduction in irrigation water use with no significant effect on pecan tree water stress, yield, or quality, suggesting that pecan trees can tolerate moderate early season water stress with no effect on pecan yield or quality under southeastern U.S. environmental conditions.