Effects of exogenous sulfadiazine on microbial community diversity in vegetable soil applied with manure

Objective  To determine the effect of sulfadimidine (SM₂) applied with manure in soil on microbial community, and provide a basis for reasonably conducting environment quality evaluation and fertilization management of soil around the farm.

Method  Manure and soil around the farm that were not contaminated by antibiotics were collected to construct the manure-soil model. Different SM₂ adding dosages were setted, including the control group (0), low dosage group (5 μg·kg^–1), medium dosage group (500 μg·kg^–1) and high dosage group (5 000 μg·kg^–1), and the soil samples were collected on 1, 7, 14 and 50 days respectively after SM₂ application. Biolog technology and phospholipid fatty acid (PLFA) labelling were used to compare and analyze the capacities of carbon source utilization, and the structural and functional diversities of soil microbial communities in different treatments.

Result  The application of SM₂ improved the overall carbon source utilization capacity of soil microbial community. After applying SM₂ for 50 days, the utilization capacities of medium and high dodage groups to all carbon sources except esters were significantly stronger than those of the control group. The capacities of low dodage group utilizing all carbon sources after applying SM₂ for 7 days were obviously enhanced. The applications of medium and high SM₂ dosages might affect the propagation and quantity distribution of some dominant flora in soil community. With the extension of SM₂ application time, the responses of soil microbial community to SM₂ at different dosages was different. The quantity changes of Gram-positive bacterium, Gram-negative bacterium and fungi were significant, while the change of actinomycetes number was not obvious.

Conclusion  The application of SM₂ will affect the structural and functional diversities of soil microbial communities for a long time. The farm should dispose animal excrements in time to eliminate antibiotic residues, and reduce the ecological damages to soil environment.