Manure Application Increases Soil Bacterial and Fungal Network Complexity and Alters Keystone Taxa

Purpose Soil bacteria and fungi play critical roles in mediating soil nutrient cycling. Exploring the effect of fertilization on soil microbial communities is of great importance to comprehend the sustainability of agricultural ecosystem. Methods In this study, responses of the bacterial and fungal communities in the wheat rhizosphere and bulk soils to four fertilization regimes: no fertilizer (CK), 100% chemical NPK fertilizers (NPK), 50% chemical NPK fertilizers + 50% manure (NPKM), and 100% manure (OM) were investigated. Results Chemical fertilization significantly decreased the bacterial alpha-diversity, while manure fertilization maintained the bacterial diversity in both rhizosphere and bulk soils. Fertilization increased the relative abundance of the bacterial orders Flavobacteriales and Xanthomonadales by 46.0-61.6% and 36.3-59.4% compared with CK in the rhizosphere soils. Application of both chemical fertilizers and manure enhanced the bacterial network complexity and stability. Chemical fertilizer addition significantly weakened the fungal network complexity, while manure fertilization maintained the fungal network complexity and connectivity. Proteobacteria and Bacteroidetes were the two prominent keystone taxa of bacterial networks in CK and NPK, while Actinobacteria was the prominent keystone taxa in NPKM and OM. In addition, Myrothecium became the keystone taxa of fungal networks induced by manure addition. Conclusions Our results suggest that soil bacteria were more sensitive than fungi to fertilization, and manure amendment was beneficial to increase soil microbial network complexity and stability. These findings provide a comprehensive understanding of how fertilization affects the productivity and sustainability of agricultural ecosystems via soil microbial communities.

Automated summary

The study found that chemical fertilizers significantly decreased bacterial diversity, while manure maintained it. Fertilization increased the relative abundance of specific bacterial orders. Additionally, manure had different effects on bacterial and fungal networks, but was beneficial in increasing soil microbial network complexity and stability.