[Response Characteristics of Farmland Soil Enzyme Activity and Microbial Nutrient Restriction Under Long-term Mulching Measures in the Loess Plateau].

To study the response characteristics of long-term mulching measures on soil enzyme activity and the limitation of microbial nutrients in the Loess Plateau Region, the study adopted a random block design and setup based on the long-term field positioning experiment conducted in 2008. Four types of inter-field management measures were established, including conventional no-mulch （NM）, straw mulch （SM）, mulch mulch （PM）, and ridge mulch （RPM）. The changes in soil nutrients and extracellular enzyme activities, their ecological stoichiometry and influencing factors under different cover measures, were investigated using a one-way analysis of variance, a stoichiometric model of soil extracellular enzymes, and redundancy analysis （RDA）. The results showed that mulching significantly affected soil basal nutrients （P <0.05） and that the dissolubility of organic carbon, available nitrogen （AN）, and available phosphorus （AP） showed significant dynamic changes with plant growth. The extracellular enzyme activity of C, N, and P cycles showed a positive response and increased or changed by 21.03%-161.14%, 1.11%-60.68%, and 17.55%-37.66%, respectively, with the effect of SM and RPM being more significant. During long-term tillage, soil microorganisms as a whole faced C and N nutrient limitations. Under the mulching treatment, the vector angle increased significantly by 11.52%-23.17% in the early growth stage of crops, indicating that the microbial nitrogen limitation was alleviated, while the overall vector length showed an increasing trend and increased by 10.38%-84.38%. Additionally, the level of C restriction became stronger over time. The RDA analysis showed that soil water content, AN, and AP content were the key factors affecting the enzyme activity and their measurement relationship in the Loess Plateau. In summary, the implementation of SM and RPM tillage practices in the Loess Plateau Region had a stronger impact on soil nutrient properties and enzyme activities and could be combined to achieve better results. In the meantime, the appropriate application of nitrogen fertilizer should be considered to mitigate nutrient limitations. The research results can help better understand the influence of mulch on soil microbial nutrient utilization strategies in agricultural land and its regulatory mechanisms. Moreover, it provides theoretical foundations for the long-term sustainable development of the Loess Plateau hilly area.