Tillage Intensity and Cover Cropping Effects on Litter Decomposition and Soil Nitrogen Mineralization During Autumn and Winter

Soil nitrogen mineralization and soil organic matter decomposition are central regulators of nutrient cycling in arable systems, yet their responses to interacting management practices remain insufficiently understood, particularly during autumn and winter. Therefore, this study assessed how tillage intensity and cover cropping jointly shape seasonal nitrogen mineralization and soil organic matter decomposition dynamics. We quantified nitrogen mineralization and evaluated soil organic matter decomposition and microbial biomass at a long‐term field experiment featuring three tillage treatments (regular ploughing, minimal tillage, no‐till) with and without cover cropping, both in autumn and winter. No‐till and minimal tillage systems enhanced nitrogen mineralization across both seasons, likely due to a significantly higher microbial biomass and higher soil moisture. Nitrogen mineralization in autumn was lower under cover cropping, most likely reflecting crop nitrogen uptake; this effect was most pronounced under regular ploughing, highlighting interactive controls of tillage intensity and cover cropping. Under no‐till and minimal tillage, high microbial biomass nitrogen contents—a highly dynamic pool—helped maintain substantial nitrogen mineralization rates in late winter. Unlike nitrogen dynamics, soil organic matter decomposition was highest in autumn. Cover cropping consistently suppressed decomposition rates, likely due to rhizodeposition of labile carbon, while tillage effects on decomposition rates were less distinct and warrant further investigation. Overall, our findings show that agricultural management strongly influences microbial biomass as well as soil moisture and temperature, which in turn govern seasonal soil carbon and nitrogen dynamics. This underscores that management decisions made throughout the entire vegetation period critically regulate nutrient cycling and, consequently, crop productivity.