Effects of antimony on the soil enzymes, microbial, and rhizobial activity of legumes

Leguminous farmland in China is severely polluted by antimony. Here, to explore the effects of antimony stress on rhizobia and soil microorganisms in leguminous plants, mung beans, kidney beans, and peanuts were grown in soil with different concentrations of Sb3+, Sb5+, and Sb3++Sb5+. Antimony had a promotional effect on soil sucrase and catalase activities and an inhibitory effect on urease activity. The effects of Sb3+ on sucrase, catalase, and urease activities were 3.3–11.1, 1.27–1.29, and 1.24–3.05 times those of Sb5+, respectively. Antimony reduced the rhizobial activity by 20.63–57.84%, with the inhibitory effect positively related to the antimony content. Additionally, the inhibitory effect of Sb3+ was 1.10–2.22 times that of Sb5+. This inhibition decreased the total nitrogen and ammonia nitrogen content in the soil. However, the decrease in Sb3+ was 0.46–1.54 times that of Sb5+. Sb3+ significantly altered the microbial activity.