SITE-SPECIFIC FERTILIZER APPLICATION FOR POTATO PRODUCTION AND EFFECTS ON N-LEACHING USING DYNAMIC SIMULATION MODELING

The effects of site-specific N fertiliser recommendations on potato yi eld and leaching of nitrate were studied for a farm field in the Nethe rlands. A validated process based dynamic simulation model was used to calculate potato yields and leaching of nitrate for seven fertiliser doses on 65 locations during 1994. Results of the simulations are disc ussed using the distribution function and interpolated spatial pattern s. The leaching risk was analysed by comparing cumulative nitrate leac hing concentrations with a pre-set threshold value based on government regulations for drinking water. The current recommended fertiliser ra te was 250 kg N ha(-1) (R-scenario). Two site-specific fertiliser scen arios were defined: one scenario based on seven fertiliser doses (S-sc enario) and the other scenario based on 7 years of simulated water lim ited yield (B-scenario). The R-scenario resulted in an average yield o f 11.57 t dry matter ha(-1) and a nitrate leaching quantity of 95.9 kg NO3 ha(-1) for 1994. Both site-specific fertiliser scenarios resulted in a lower average yield. Calculated average yield was 11.13 t dry ma tter ha(-1) for the S-scenario and 11.29 t dry matter ha(-1) for the B -scenario. Nitrate leaching was reduced by 2.4 to 39.3 kg NO3 ha(-1) f or the S-scenario and 39.7 kg NO3 ha(-1) for the B-scenario. (C) 1997 Elsevier Science B.V.