SIMPLIFIED LONG-TERM CONCEPT FOR EVALUATING LEACHING OF NITROGEN FROM AGRICULTURAL LAND

A rather simple concept is proposed for predicting the contribution of crop production practices to ground-water N pollution. It is a steady state long term concept. One of the consequences is that the myriad reactions that take place in the soil body itself need not be evaluated. Application of this concept indicates that, in general, the single most important practice under man's control that affects potential pollution is fertilizer use efficiency. As long as yield response is obtained to N fertilizer additions, fertilizer should contribute lesser amounts of N to the ground water providing fertilizer use efficiency is maintained at a high level.