Evaluation of two methods for optimising nitrogen fertilisation of field crops

Two methods are used in Switzerland to optimise the nitrogen fertilisation of field crops: the «corrected norms» method and the Nmin method. Each of the methods suggests a different approach: the «corrected norms» method takes into account field characteristics influencing nitrogen availability, while the Nmin method is based on the measurement of mineral nitrogen present in the soil during periods that are crucial for the plants growth. In this article, both methods are evaluated using nitrogen fertilisation experiments performed by Agroscope for a wide range of arable crops and pedoclimatic conditions. The advantages and limits of each method are presented, and ways for improvement are suggested.