Nitrogen mineralization and nitrogen loss potential following grass-clover termination in fall: insights from incubation experiments and modeling approaches

Accurate prediction of nitrogen (N) mineralization following the termination of grass-clover is essential for improving N efficiency in agricultural systems. In this study, short-term N mineralization after fall termination of grass-clover, followed by a winter rye cover crop, was evaluated over winter in comparison to intact grass-clover (control). Soil samples of a Plaggic Anthrosol were collected after fall termination and in the subsequent spring in two consecutive years (2021–2023) from a field trial with grass-clover in North-West Germany. Nitrogen mineralization was assessed through laboratory incubation experiments and modeling using rate coefficients and pedotransfer functions from the literature. Laboratory results indicated a high short-term N mineralization potential immediately after grass-clover termination in fall and in the following spring. While the potential net N release in the fall-terminated treatment decreased from fall to spring, the control treatment increased. Modeled N mineralization in fall aligned well with the fall-terminated treatment but overestimated the N release for the control. By applying the model under field conditions from fall to spring, grass-clover termination resulted in the mineralization of 61.62 kg N ha−1. This prediction of mineralizable N could be further used to assess the risk of environmentally significant N losses and to optimize N fertilization.