Soil net nitrogen mineralisation across global grasslands

Soil nitrogen mineralisation (N(min)), the conversion of organic into inorganic N, is important for productivity and nutrient cycling. The balance between mineralisation and immobilisation (net N(min)) varies with soil properties and climate. However, because most global-scale assessments of net N(min) are laboratory-based, its regulation under field-conditions and implications for real-world soil functioning remain uncertain. Here, we explore the drivers of realised (field) and potential (laboratory) soil net N(min) across 30 grasslands worldwide. We find that realised N(min) is largely explained by temperature of the wettest quarter, microbial biomass, clay content and bulk density. Potential N(min) only weakly correlates with realised N(min), but contributes to explain realised net N(min) when combined with soil and climatic variables. We provide novel insights of global realised soil net N(min) and show that potential soil net N(min) data available in the literature could be parameterised with soil and climate data to better predict realised N(min).