A closer look at fertilizer legislations for silage maize across selected European countries: part I—insufficient consideration of net nitrogen mineralization

Abstract Optimizing nitrogen (N) efficiency in European silage maize cultivation requires better quantification of N savings beyond existing regulations and identifying further opportunities to enhance efficiency. This study focuses on understanding how site and management factors influence net N mineralization. A comprehensive dataset from silage maize field trials across five Central European countries was analyzed using a multistage framework to develop a linear regression equation for estimating net N mineralization during the growing season based on key parameters known before the growing season. The final regression model, with a R adj 2 of 0.38, identified ten significant variables affecting net N mineralization. Evaluation of German and French fertilization frameworks, using representative regional use cases, indicated that national guidelines may underestimate or insufficiently capture net N mineralization. Major factors influencing soil net N mineralization included management practices impacting biomass quantity and the carbon-to-N ratio of plant residues, with N fertilization showing a negative effect on net N mineralization. Weather conditions and soil clay contributed to the observed variability to a lesser extent. For silage maize following grain cereals, a predominant cropping sequence within the investigated regions, the highest net N mineralization was achieved by combining straw removal with a frost-killed non-legume cover crop, suggesting potential for reduced N fertilization without yield loss.