Identification and mitigation of nitrate leaching hot spots using NLEAP-GIS technology

Leaching of NO3---N from agricultural lands often occurs in well-defined hot spot areas when viewed across geographical regions of hundreds or thousands of kM2 and often appears as areas of high NO3---N concentrations in shallow underlying aquifers. Delineation of high-NO3---N zones can be achieved by combining models such the Nitrate Leaching and Economic Analysis Package (NLEAP) with Geographical Information System (GIS) technology to calculate the long-term potential mass of NO3---N leached from the crop root zone. Once identified, the hot spots can be further analyzed with the model to evaluate and rank appropriate alternative management techniques. A simulation analysis using the NLEAP model showed that long-term NO3---N leaching from corn (Zea mays L.) grown under furrow irrigation on a coarse-textured soil could be reduced by 53% with N management alone, while an 84% reduction in leached NO3---N was achieved for combined N and water management (sprinkler irrigation). This type of modeling analysis can be completed after a few weeks of effort, while comparable field studies would take several years to finish.