Compound microbial agents improve the soil properties, fertilizer utilization and bacterial community structure in a continuous cropping soil

Abstract To determine the effects of compound microbial agents on soil nutrient and fertilizer utilization, the diversity and metabolic pathways of continuous cropping soil bacterial communities, and the key driving factors, a pot experiment was established with six treatments: no fertilizer application (T1), conventional fertilizer application (T2), T2 + microbial agents (T3), T2 + biochar + microbial agents (T4), T2 + attapulgite clay + microbial agents (T5), and T2 + organic fertilizer + microbial agents (T6). We used high‐throughput sequencing technology to determine changes in wheat growth, soil nutrients, and bacterial community structure composition and diversity in different treatments. The results showed that (1) microbial agents alone and combination treatments significantly increased spikelet number, grain number per spikelet, and seed weight of wheat as compared with T2 and T1 ( p < .05). (2) The application of microbial agents significantly improved soil nutrient content and fertilizer utilization, in that T4 significantly improved soil organic matter and total nutrients, T6 significantly improved soil effective nutrient content, T3, T4, T5, and T6 significantly increased agronomic efficiency of nitrogen fertilizers (AE N ) by 22.6%, 41.5%, 24.7%, and 30.8% compared with T2, T4, and T5 significantly improved nitrogen fertilizer utilization (RE N ) by 33.0% and 24.0%, 49.6% and 39.5% compared with T3 and T2 ( p < .05). (3) The compound microbial agents significantly affected the composition of soil bacterial communities, for example, it significantly decreased the relative abundance of Actinobacteriota and Proteobacteria , and significantly increased the relative abundance of Firmicutes . (4) The diversity and richness of soil bacterial communities were mainly influenced by TP, TN, AN, TC, and OM content in the soil. The combined application of microbial agents with organic fertilizers, biochar, and attapulgite changed the balance of the original soil microbial system, provided more nutrients to the soil environment, and supplemented the microbial species required by the crop, thus increasing the soil nutrient content. In addition, PICRUSt analysis showed that the metabolic pathways were generally similar across different treatments. These results improve the understanding of soil microecological environment in arid areas and support sustainable agriculture by establishing soil improvement strategies with a single and combined application of microbial agents to improve soil fertility.