use of Soil Property Data and Computer Models to Minimize Agricultural Impacts on Water Quality
As described by its most vocal proponents, Soil Specific Crop Management (SSCM), is a technology for optimizing net returns to the grower. By applying farm chemicals in a spatially varying manner according to localized needs and yield potentials, the grower can place these materials in the portions of the field that need them most. It is now widely assumed that such an approach will carry environmental benefits as well, although this has yet to be demonstrated in any scientifically valid way. Conceptually, it would seem that making chemical applications more efficiently in tune with localized crop and soil needs would reduce waste and therefore the net outflows of chemicals from the field. However, there is no guarantee that this will always be the case, and if it is desired to derive environmental benefits from this technology then there will have to be an environmental component built in to the SSCM application strategies. A prescription for accomplishing this is proposed in this chapter. Following a brief historical perspective on the issues surrounding pesticide impacts on water quality, the important environmental impacts that are to be avoided are enumerated. This is proceeded by a listing of the soil properties that would need to be monitored for SSCM reduction of such impacts. A discussion is then presented of the modeling techniques available for describing pesticide movement through soil, including a list of the key pesticide properties that would need to be part of any computerized system for prescribing application strategies. The final section of the chapter is devoted to an implementation strategy based on the introduced soil, pesticide, and modeling concepts. The recommended tactic is to use the USDA-SCS screening/modeling method that is now being developed for field-averaged soil properties. With only a few modifications, this SCS procedure could be adapted to the SSCM paradigm with presumed beneficial effects on the environment.