Study on the effects of winter irrigation during seasonal freezing-thawing period on soil microbial ecological properties.

The seasonal freeze-thaw period is a critical time for restoring soil fertility. Winter irrigation during this period alters soil moisture in agricultural fields, which in turn affects the soil's temperature, nutrients, and microbial factors within the soil micro-environment. Soil microorganisms play a crucial role in soil nitrogen fixation. Investigating the changes in soil microbial communities during the seasonal freeze-thaw period under winter irrigation conditions can help further understand the regulatory mechanisms of winter irrigation on the soil microenvironment. The experimental micro-areas were selected at the Key Laboratory of Modern Water-Saving Irrigation of Xinjiang Production &Construction Group. Based on soil moisture conditions, winter irrigation quotas of 0, 45, 90, and 135 mm were established. Soil samples were collected according to the seasonal freeze-thaw process in the experimental area, and measurements were taken for soil moisture, temperature, salinity, nutrients, as well as the quantity and diversity indices of soil bacteria and fungi. Using single-factor correlation and principal component analysis, the interactions between soil microbial indicators and their influencing factors under winter irrigation conditions were examined. Under winter irrigation conditions, during the seasonal freeze-thaw period, pH significantly affects the richness of soil bacterial populations and the quantity of bacteria (P < 0.05). Soil organic matter significantly influences the diversity of fungal populations (P < 0.05). The combined effects of soil moisture content, temperature, and pH significantly impact the quantity of soil microorganisms (P < 0.05), with soil moisture content being the determining factor. There is a significant correlation between the diversity and richness of soil microbial communities (P < 0.05). The results indicate that winter irrigation during the seasonal freeze-thaw period not only alters the composition and metabolic capacity of microbial communities but also affects the interrelationships among microbial diversity indices, thereby impacting microbial stability. Furthermore, a winter irrigation quota of 45 mm during the seasonal freeze-thaw period has multiple positive effects on the soil micro-environment, effectively promoting plant growth, improving soil health, and supporting the development of sustainable agriculture.