Effects of water-saving irrigation on microbial community structures, assembly, and metabolic activities in alfalfa rhizosphere soils.

In agricultural areas of arid Xinjiang, China, selecting appropriate irrigation strategies for farmland is essential. Increasing attention is being paid to the ecological effects of different irrigation methods on the soil environment. As a crucial component of soil quality, the microbial community is a key indicator of the impacts of irrigation on the soil environment. To investigate the effects of irrigation treatments on the properties of rhizosphere soil and the underlying microbial community characteristics, this study conducted an alfalfa field experiment applying three water-saving treatments (3750, 4500, and 5250 m³ hm^-2) and regular irrigation (6750 m³ hm^-2, CK). The results showed that the water-saving treatments increased the soil pH, salinity, available nitrogen, and phosphorus levels. The water-saving treatments decreased the richness and diversity of the bacterial community in the rhizosphere but increased those of the fungal community. The influence of stochastic processes on fungal and bacterial communities assembly under water-saving treatments was more noticeable than that under CK. Compared with CK, water-saving treatments reduced the complexity of microbial network and increased the potential negative interaction between bacteria and fungi. Functional prediction analysis showed that species specificity among treatments may result from a specific selection of rhizosphere functional requirements. This study reveals the effect of controlling irrigation quantity on protecting soil microbial diversity and function and improves the understanding of rhizosphere soil community response affected by different irrigation strategies. The results facilitate the development of effective and beneficial agricultural measures.