Long-term mineral combined with organic fertilizer supports crop production by increasing microbial community complexity

Soil microbial communities play a critical role in agroecosystem productivity. Most previous studies focused on changes in community composition and diversity, yet the association between microbial community complexity and crop production is poorly understood. In this study, a 26-year fertilization experiment was conducted to analyze effects of soil microbial complexity on maize (Zea mays L.) yield. Compared with no-fertilizer (NF) and mineral fertilizer (MF), the maize yield under the treatment of mineral combined with organic fertilizer (MO) was significantly increased 68.01 % and 27.76 %, respectively. The different fertilization profoundly changed soil chemical properties and microbial community composition. Meanwhile, the bacterial and fungal network of MO have the maximum complexity (edges of network). When 50 % nodes were removed, the network of MO exhibited the strongest robustness. Meanwhile, MO also had the highest degree of functional redundancy. Compared with NF and MF, the relative abundance of bacterial functional groups (carbon, nitrogen, sulfur cycling) was significantly increased by 1.88 %, 0.86 %, and the relative abundance of saprophytic fungi by 13.76 %, 10.54 % in MO, respectively. Most importantly, the results of variance partitioning analysis and RandomForest regression demonstrated that community complexity had the most contribution to maize yield compared to soil chemical properties and microbial community composition. Finally, the results of null model showed that deterministic processes driven bacterial and fungal community assembly processes under all treatments. Overall, our study suggests that microbial community complexity is a key factor in maintaining the sustainability of crop production.