Fertilization effects on the long-term stability of crop yields

Sustainable crop production requires adequate nutrient management. However, at longer time scales, effects of nutrient supply on the stability of crop yields are largely unknown and suitable quantification methods are a controversial topic. We here quantify and analyse the long-term impact of fertilization on yield stability of winter wheat, winter rye, potato and sugar beet using a set of different stability metrics. From 1955 to 2008, crops were grown on a fertile loess soil in a crop rotation at a Long Term Fertilization Experiment located in Germany. Yield data were obtained in eight unreplicated fertilization treatments, representing a gradient of nutrient supply using synthetic fertilizers, organic fertilizers, or a combination of both. The yield stability of winter wheat and potato was positively related to nutrient supply. Organic amendments reduced the probability of low yield events and improved the stability for winter wheat and sugar beet yields, however, only at low levels of nutrient supply. Effects were modulated by the interaction between nutrient supply and weather conditions. Contrasting with the results reported in other studies the yield stability remained almost constant or even slightly increased between 1955 and 2008. We suggest that observations from long-term fertilization experiments on crop yield anomalies are of great value for supporting the development of sustainable cropping systems.