Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2006
Publication Date: 11/7/2006
Citation: Delgado, J.A., Khosla, R., Bausch, W.C., Westfll, D., Inman, D. 2006. Nitrogen fertilizer management based on site-specific management zones reduce potential for NO3-n leaching. Journal of Soil and Water Conservation Society. 60:402-410 Interpretive Summary: This study shows that model can be used with SSMZ to evaluate the effect of this practice on residual soil NO3-N and NO3-N leaching. NLEAP could be use with GPS and GIS systems to simulate residual soil NO3-N and potential NO3-N leaching across SSMZ. This is a powerful tool to evaluate the potential use of N fertilizer recommendations based on SSMZ to reduce NO3-N leaching potential. We found that the use of N fertilizer recommendations based on SSMZ reduced simulated NO3-N leaching potential by thirty six percent average. This study shows that the use of SSMZ can reduce the N losses from intensively managed agricultural irrigated systems. The potential exists to use these new field techniques for precision conservation across irrigated fields for the reduction of off-site transport of NO3-N out of the system. We suggest that models can be used with SSMZ to evaluate them and their potential to conserve underground water quality. We propose that there is potential to use models to evaluate SSMZ and to improve their design for precision conservation. This technique will help quantify the potential for site-specific management to improve groundwater quality. We propose that for sensitive areas these technologies can contribute to delineation of more efficient SSMZ that consider hydrological factors to decrease NO3-N leaching losses.
Technical Abstract: Although N is an essential nutrient that is a key component of intensive irrigated agricultural systems, its management to maximize yields and reduce losses to the environment is difficult. One reason is due to the spatial and temporal variability that affect residual soil nitrate-N (NO3-N) and NO3-N leaching potential. It is possible to use site-specific management zones (SSMZ) based on yield history, soil color from aerial photographs, topography, and the producer’s past management experiences to map and manage this spatial soil variability. The objective of this study was to evaluate the potential of N fertilization prescriptions based on SSMZ to reduce NO3-N leaching losses. We used the Nitrate Leaching and Economical Analysis Package (NLEAP) model to assess the benefits of N management based on SSMZ. Simulated residual soil NO3-N was correlated with observed soil NO3-N (r2=0.99, P<0.0001). We found that N management based on SSMZ significantly reduced simulated NO3-N leaching potential by thirty six percent when compared to farmer traditional practices (P<0.01). This study shows that there is potential to use SSMZ to reduce the N losses from intensively managed agricultural irrigated systems without reducing yields.