Turning competition into complementarity: managed clover-based living mulch enhances nitrogen retention, wheat performance, and soil microbial diversity
The planetary boundaries framework highlights the urgent need to reduce agricultural pressures on biogeochemical cycles and biodiversity, particularly those associated with intensive nitrogen fertilization. This study evaluated the use of clover as a permanent living mulch in arable systems to improve nitrogen use efficiency, reduce nitrate leaching, and enhance soil bacterial diversity. A three-year on-farm field experiment in Rhineland-Palatinate, Germany, compared living mulch and conventional cropping systems across different crop rotations and nitrogen fertilization regimes. Living mulch significantly reduced soil nitrate concentrations and the associated risk of leaching, with more than one-third of the main crop's nitrogen demand temporarily immobilized in clover biomass. However, uncontrolled clover growth increased competition for soil nitrogen, thereby reducing wheat biomass and grain yield. The introduction of targeted chemical regulation effectively mitigated this competition, allowing wheat yield and grain protein content to match or exceed those observed in the conventional system, even under reduced nitrogen inputs. In addition, living mulch significantly increased soil bacterial diversity, indicating improved soil ecological functioning. Overall, the results demonstrate that properly regulated clover-based living mulch systems can enhance nitrogen retention, maintain crop productivity and quality, and support soil biodiversity. These findings highlight the potential of living mulch as a viable strategy for reducing environmental impacts while sustaining agronomic performance in arable farming systems.