Intensive slurry management and climate change promote nitrogen mining from organic matter-rich montane grassland soils
Marcus Schlingmann, Ursina Tobler, Bernd J. Berauer, Noelia García-Franco, Peter A. Wilfahrt, Martin Wiesmeier, Anke Jentsch, Benjamin Wolf, Ralf Kiese, Michael Dannenmann
Abstract
Abstract Aims Consequences of climate change and land use intensification on the nitrogen (N) cycle of organic-matter rich grassland soils in the alpine region remain poorly understood. We aimed to identify fates of fertilizer N and to determine the overall N balance of an organic-matter rich grassland in the European alpine region as influenced by intensified management and warming. Methods We combined 15 N cattle slurry labelling with a space for time climate change experiment, which was based on translocation of intact plant-soil mesocosms down an elevational gradient to induce warming of +1 °C and + 3 °C. Mesocosms were subject to either extensive or intensive management. The fate of slurry-N was traced in the plant-soil system. Results Grassland productivity was very high (8.2 t - 19.4 t dm ha −1 yr −1 ), recovery of slurry 15 N in mowed plant biomass was, however, low (9.6–14.7%), illustrating low fertilizer N use efficiency and high supply of plant available N via mineralization of soil organic matter (SOM). Higher 15 N recovery rates (20.2–31.8%) were found in the soil N pool, dominated by recovery in unextractable N. Total 15 N recovery was approximately half of the applied tracer, indicating substantial loss to the environment. Overall, high N export by harvest (107–360 kg N ha −1 yr −1 ) markedly exceeded N inputs, leading to a negative grassland N balance. Conclusions Here provided results suggests a risk of soil N mining in montane grasslands, which increases both under climate change and land use intensification.