Effect of soil characteristics, farming system and weather on optimum nitrogen application in winter barley and winter wheat

Data from 822 plots were used to test different methods of estimating the optimum nitrogen application in winter barley and winter wheat. No method could estimate with sufficient accuracy the optimum amount as determined with the Nmin-method. Possible explanations are the non-additive effect of the different factors and the almost innumerable combination possibilities of the various factors influencing nitrogen in the soil.