Balanced phosphorus fertilization enhances soil bacterial network complexity to maintain multifunctionality and plant production in dryland agricultural systems

Long-term fertilization significantly affected the function, diversity, and structure of soil microbial communities, which performed an indispensable role in maintaining ecosystem multifunctionality. However, the mechanism of how balanced fertilization affects soil microbial composition, function, and ecosystem multifunctionality is still poorly understood, especially during the whole plant life cycle, which will hinder our understanding the consequences of reducing phosphorus (P) fertilizer inputs as required in sustainable agriculture. Herein, the soil samples from a P fertilization field (with 0, 70, and 120 kg P2O5 ha−1 yr−1) at different stages of wheat (greenup stage (GP: Zadoks stage 26), elongation stage (EP: Zadoks stage 31), and flowering stages (FP: Zadoks stage 64)) were collected to investigate the effects of P fertilizer input on soil bacterial community, assembly, bacterial functionality, and multifunctionality in the Loess plateau. The results showed that soil bacterial diversity and functional groups (microbial P limitation) increased as wheat developed, but the bacterial network complexity and multifunctionality decreased. The highest soil bacterial network complexity, ecosystem multifunctionality, and homogeneous selection (deterministic processes) were observed in the balanced P fertilization treatment (P70), but wheat P uptake, biomass, and grain yield were similar at P rates of 70 and 120 kg P2O5 ha−1. The microbial nutrient limitation was also altered by both P fertilization and wheat growth stages. Moreover, the changes in soil available P and bacterial network complexity were the major determining factors of different microbial C and P limitations and ecosystem multifunctionality. Our results also showed that the core microorganisms with special functions drive the ecosystem multifunctionality by altering the community structure and network complexity of the microbes. Therefore, our result highlights the importance of soil available P and bacterial network complexity in maintaining ecosystem multifunctionality under P fertilizer inputs and provides support for the use of balanced P fertilization in sustainable dryland wheat production from the aspect of ecosystem multifunctionality.