Prototype geographic information system for agricultural water quality management using cropsyst

A prototype raster geographic information system (GIS) coupled with a decision support submodel for agricultural nitrogen nonpoint source pollution analysis is presented herein. This analysis is an extension of the one-dimensional approach used to simulate and analyze farm production systems and their impact on the environment. The farm system was rasterized into an aggregation of spatial units with homogeneous physical and management characteristics. A crop model to simulate the farm and the environmental response to management alternatives was integrated with this prototype GIS. The system coordinates the running of the crop model on each homogeneous unit and results are passed to a maximum expected utility decision analysis submodel. Only the crop yield and chemical leaching are considered in the decision model. Based on the utility of these two parameters and the probability of realization, the management alternative that potentially leads to the highest yield and lowest nitrogen leaching will be recommended. This prototype model was evaluated with field data from a controlled lettuce production with intense nitrogen application in Arizona. The results achieved compared well with the actual field data including the best management practice recommended for this farm production system.