Short-Term Application of Magnesium Fertilizer Affected Soil Microbial Biomass, Activity, and Community Structure

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.