Soil multifunctionality driven by shift of bacterial rather than fungal community promotes cropland productivity via enhancing nitrogen use efficiency

Soil multifunctionality is the key to maintain soil health and develop sustainable agriculture. Soil microbiomes are crucial for regulating numerous functions, but how soil multifunctionality are driven by the shifts of microbial communities and nutrient supplies in agricultural ecosystems remains unclear. Moreover, the relationships between soil multifunctionality and cropland productivity have not been fully understood. To address these knowledge gaps, we conducted field experiments including different nitrogen (N) application rates in four sites of Northeast China with a gradient of climatic conditions and soil organic carbon (SOC). Soil functions related to SOC, N, phosphorus, and bacterial and fungal diversity, community composition, network complexity, and stability were combined to quantify soil multifunctionality. We found that soil multifunctionality accounted for approximately 20 % of variations in maize production. SOC was the most important predictor of multifunctionality. SOC content and fractions, including readily oxidizable carbon, carbohydrate, and lignin, were primary factors shaping the soil microbial communities. In addition, the larger impact of SOC on bacterial communities resulted in greater roles of bacterial diversity and network complexity in supporting soil multifunctionality compared to fungi. The higher SOC also shifted microbial community composition, increasing the abundances of dominant bacterial phyla Acidobacteriota and Chloroflexi, with Acidobacteriota showing a strong positive correlation with soil multifunctionality. PLS-PM results revealed that soil multifunctionality directly and positively affected N use efficiency (NUE), turn to enhance crop productivity. These findings highlight the contribution of soil multifunctionality to cropland productivity, as well as the importance of SOC and the bacterial community in sustaining ecosystem functions in croplands.