A method to optimize N-application in relation to soil supply of N, and yield of potato

Abstract

Mathematical models of crop growth can provide estimates of the potential yield of potato, and also the minimum, critical N-concentration required, [N_c], to attain that yield. Efficient use of nitrogen requires that the crop incorporates sufficient nitrogen to attain its potential yield and that excess uptake is avoided. Predictions of the rate of supply of nitrogen from the soil are imprecise and so it has been difficult to estimate accurately the required application of fertilizer-N. Our work has shown the feasibility of using the growing crop as a monitor of the rate of supply of N from the soil. Using a low initial application rate of N at planting and monitoring uptake rate, we can estimate the contribution from the soil, and couple that information with estimates of yield and the related [N_c] to give an estimate of the requirement for supplementary applied-N. The method can be seen, therefore, as a means to determine the size of a second or subsequent part of a split application of fertilizer. This approach avoids much of the uncertainty over the fate of applied nitrogen and should offer growers the double benefits of economic use of fertilizer and of minimizing leaching losses. Further, by tailoring applications of N-fertilizer to the crop's requirements the grower will be better able to ensure the quality considerations in his crop.