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item Delgado, Jorge

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 2/7/2001
Publication Date: 11/7/2001
Citation: Delgado, J.A. 2001. Use of simulations for evaluation of best management practices on irrigated cropping systems. Book Chapter. In Modeling Carbon and Nitrogen Dynamics for Soil Management. p. 355-381. M.J. Shaffer, L. Ma, and S. hansen (eds). Lewis Publishers, Boca Raton, FL.

Interpretive Summary: Our objective was to study and conduct a baseline evaluation of the variability at center-pivot irrigated systems, and how this variability is correlated with production and the potential to use this data for the development of management zones and for precision agriculture. There was a correlation between fine soil organic particles, organic matter, soil NO3- -N, potassium and electrical conductivity. Nitrate, phosphorous, potassium, and soil organic matter were also correlated with soil texture.The center pivot was divided into areas according to the distribution of fine particles. The finer textured areas had the greatest concentration of nutrients, higher yield for potato and higher SPAD readings for malting barley. These results show that there is potential to use soil chemical and physical characteristics to manage nutrients by zones. Interaction with factors that may reduce yields such as Na, the SAR Rand the extremely low and high soil pH also need to be accounted for. New emerging technologies can be used to reclaim these areas that are being affected by acid soil pH. If such improvement in reclamation is achieved, then management zones are and will be dynamic since changes in pH will affect productivity. Reclassification of a previous management zone into a new management zone as pH levels are corrected, may be needed.

Technical Abstract: Nitrogen fertilizer is susceptible to losses due to NO3- -N leaching from irrigated cropping systems with shallow root zones that are grown under center-pivot irrigation in coarse sandy soils. Although farmers are implementing best management practices (BMPs) there is still field variability in some of these center pivot irrigated circles that can contribute to lower N use efficiency. We are conducting studies to evaluat the potential to use precision farming for improvement of nutrient management under irrigated potato (Solanum tuberosum L.) followed by malting barley (Hordeum vulgare L.). Residual soil NO3- -N and concentrations of other macro and micro nutrients were spatially correlated with soil electrical conductivity (P<0.05). Soil pH was correlated spatially, with malting barley SPAD readings (P<0.05). Management and years of N fertilizer application and application of concentrated sulfuric acid as a desiccant for potato vines may have contributed to lowering the pH of these soils. Barley grown in the acidic areas of the field showed a lower chlorophyll SPAD reading. Soil texture was spatially correlated with soil organic matter, EC, and macro and micro nutrients and residual soil NO3- -N (P<0.05). Texture should be considered as a driving variable when establishing management zones, however, pH, sodium absorption ratios and the interaction with other variables such as soil chemical and physical characteristics, yield and others should also be considered. These initial results show that there is potential to use precision farming to improve nutrient management on a potato-malting barley rotation and protect water quality.