FIELD-SCALE VARIABILITY OF SOIL-STRUCTURE AND ITS IMPACT ON CROP GROWTH AND NITRATE LEACHING IN THE ANALYSIS OF FERTILIZING SCENARIOS

Soil structure variability was inventoried on a field scale, and translated to basic input data for a solute transport and crop production simulation model. After validation of the model, it was used to simulate the spatially varying effect of slurry application and N-fertilizing scenarios by multiple point-simulations. Feasibility of scenarios was determined by comparing nitrate leaching concentrations with current and pursued threshold levels. Disjunctive kriging was used to estimate and map the probability that these threshold levels were exceeded. Emphasis was given to the effect of soil-specific slurry application rates and N-fertilizer levels on leaching probabilities and crop yields. Soil-specific N-treatments increased field yields, because crop response to N, both in slurry and in fertilizer, was soil dependent. The leaching response to N-treatment was also soil dependent.