Mulching rain-fed farmland ecosystems changes the soil physicochemical properties, especially soil organic carbon (SOC), but the metabolic limitations of soil microorganisms after these changes are unclear. We established a long-term experiment in 2012 with three treatments: no mulch (CK), straw mulch (SM), and plastic film mulch (FM). In 2019 the soil enzyme activities were measured in five maize growing periods: planting time, six-leaf period, silking period, milk period, and physiological maturity. Extracellular enzymatic stoichiometry models were used to examine microbial metabolic limitations. The vector length and angle were employed to determine the C and N/P limitations of soil microorganisms. Compared with CK, the average SOC and total nitrogen (TN) contents were 9.7% and 7.8% higher under SM, respectively, in each period. The SOC, TN, and total phosphorus (TP) contents were 5.6%, 4.8%, and 2.8% lower under FM, respectively. Compared with CK, the C- and N-acquiring enzyme activities were 20.5% and 5.2% lower under FM, respectively. The alkaline phosphatase enzyme activities were 2.7% and 13.5% higher under SM and FM, respectively, than CK. Soil nutrients, pH, and temperature influenced the C and P limitations of soil microorganisms. The different P limitation responses under SM and FM were mainly due to SOM. The decomposition of SOC was a key source of soil available P. The soil hydrothermal conditions under FM accelerated the decomposition of SOC in the early years, thereby increasing the P limitation. However, long-term SM increased the SOC due to the annual input of straw and its decomposition released available P to alleviate the P limitation for microorganisms. Thus, the temperature, water, pH, and SOC affect the P limitation for microbes under mulching conditions, but the SOC content of alkaline soil in arid farmland is the main factor that leads to microbial P limitation.

覆盖雨养农田生态系统改变了土壤的理化特性，尤其是土壤有机碳（SOC），但这些变化后土壤微生物的代谢限制尚不清楚。我们在2012年建立了一项长期实验，采用了三种处理方法：不覆盖（CK），秸秆覆盖（SM）和塑料膜覆盖（FM）。在2019年，在五个玉米生育期测量了土壤酶活性：种植时间，六叶期，蚕丝期，牛奶期和生理成熟度。细胞外酶化学计量模型用于检查微生物的代谢限制。使用载体长度和角度确定土壤微生物的碳和氮/磷极限。与CK相比，SM下每个时期的平均SOC和总氮（TN）含量分别高出9.7％和7.8％。SOC，TN，在FM下，总磷（TP）含量分别降低了5.6％，4.8％和2.8％。与CK相比，调频条件下获得C和N的酶活性分别降低了20.5％和5.2％。在SM和FM下，碱性磷酸酶的活性分别比CK高2.7％和13.5％。土壤养分，pH和温度影响土壤微生物的碳和磷限制。SM和FM下不同的P限制响应主要归因于SOM。SOC的分解是土壤有效磷的关键来源。FM下的土壤热液条件在早期加速了SOC的分解，从而增加了P的限量。然而，由于秸秆的年输入量，长期SM增加了SOC，并且其分解释放了可用的P以减轻微生物对P的限制。从而，