Abstract

The economic feasibility of three different fertilizer management strategies (constant rate, three-rate and multiple-rate technology) in the application of nitrogen fertilizer to corn are compared under different probability distributions for field fertility. A constant rate was more profitable than either variable-rate technology system for homogeneous fields with low fertility. The ap-plication area at which the relative profitability between systems changed was largely determined by the characteristics of the fertility distribution rather than by assumptions regarding costs. Variable-rate technology improves groundwater quality in low-fertility fields by reducing total fertilizer applied and in high-fertility fields by increasing corn yield. Key words: fertility distributions, net returns, precision farming, variable rate. Spatial information technology such as global positioning systems is rapidly being applied in agriculture. Known as precision agricul-ture, site-specific farming, or variable-rate technology, this technology collects and an-alyzes data for alternative locations, thereby permitting management decisions to vary by location. The technology recognizes the spa-tial variability inherent in most agricultural production processes. For example, in crop production, soil fertility can vary significantly within a field so that the typical nutrient man-agement strategy of applying a single rate of fertilizer will result in areas that are either under- or overfertilized. Variable-rate tech-nology allows farmers to apply the optimal rate for each location in the field, thereby im-proving efficiency in fertilizer use and poten-tially significantly decreasing residual nutrient loadings. The question surrounding whether the po-tential increase in gross returns and reduction in fertilizer expenses is sufficient to cover the investment costs of adopting variable-rate technology (VRT) remains unanswered. Pre-