Fertilizers influence soil microbial processes and functions. The use of magnesium (Mg) fertilizer is increasing worldwide, but the effects of mineral Mg application on soil microbial biomass, activity, and diversity remain poorly understood. In this study, a 120-day experiment was conducted to evaluate the effects of magnesium sulfate (MgSO₄) on soil microbial biomass, enzyme activity, and bacterial community composition. Two acidic Mg deficient soils, a high organic matter (S) and a low organic matter soil (X), were treated with MgSO₄ at the dose of 0, 50, 100, and 200 mg kg⁻¹. Results showed that MgSO₄ application significantly increased microbial biomass carbon, and activities of invertase and protease of both soils, but decreased the phosphatase activity in X soil. Mg fertilizer changed the soil bacterial community structure, e.g., the relative abundance of genera Acidobacter, Mizugakiibacter, and Singulisphaera increased while the relative abundance of Acidiphilium, Bradyrhizobium, and Gemmatimonas decreased in S soil. In X soil, the abundance of genera Sphingomonas, Pseudolabrys, and Streptomyces were enhanced and the relative abundance of Anaeromyxobacter, Bradyrhizobium, and Haliangium was reduced by the application of Mg fertilizer. Redundancy analysis showed that soil bacterial community composition was shaped by exchangeable-Mg and sulfate concentrations, pH, and electrical conductivity (EC), and the exchangeable Mg was the strongest factor influencing microbial abundance and composition. Our results suggest that short-term Mg fertilizer application influenced soil microbial biomass, activity, and bacterial community composition.

肥料影响土壤微生物的过程和功能。在世界范围内，镁（Mg）肥料的使用在增加，但是对矿物Mg施用对土壤微生物生物量，活性和多样性的影响知之甚少。在这项研究中，进行了120天的实验，以评估硫酸镁（MgSO ₄）对土壤微生物生物量，酶活性和细菌群落组成的影响。用0、50、100和200 mg kg ^-1的MgSO ₄处理了两种酸性缺镁的土壤，即高有机质（S）和低有机质（X）。结果表明，MgSO ₄施用显着增加了两种土壤的微生物生物量碳，以及转化酶和蛋白酶的活性，但降低了X土壤的磷酸酶活性。镁肥改变了土壤细菌群落结构，例如，属的相对丰度Acidobacter，Mizugakiibacter和Singulisphaera增加，同时的相对丰度Acidiphilium，慢生根瘤菌，和Gemmatimonas S中土壤降低。在X土壤中，鞘氨醇单胞菌属，假单胞菌属和链霉菌属的丰度增加，厌氧杆菌属的相对丰度较高，施用镁肥可减少根瘤菌和Ha。冗余分析表明，土壤细菌群落组成是由可交换的Mg和硫酸盐浓度，pH和电导率（EC）决定的，而可交换的Mg是影响微生物丰度和组成的最强因素。我们的结果表明，短期施用镁肥会影响土壤微生物的生物量，活性和细菌群落组成。