Although fumigants can effectively control soil-borne diseases they are typically harmful to beneficial microorganisms unless methods are developed to encourage their survival after fumigation. The soil fumigant 1,3-dichloropropene (1,3-D) is widely used because of its effective management of pathogenic nematodes and weeds. After fumigation with 1,3-D, Bacillus subtilis and Trichoderma harzianum fertilizer (either singularly or together) or humic acid were added to soil that had been used to produce tomatoes under continuous production for >20 years. We evaluated changes to the soil's physicochemical properties and enzyme activity in response to these fertilizer treatments, and the effects of these changes on beneficial bacteria. Fertilizer applied after fumigation increased the content of ammonium nitrogen, nitrate nitrogen, available phosphorus, available potassium and organic matter, and it promoted an increase in pH and electrical conductivity. The activity of urease, sucrase and catalase enzymes in the soil increased after fumigation. Taxonomic identification of bacteria using genetic analysis techniques showed that fertilizer applied after fumigation increased the abundance of Actinobacteria and the relative abundance of the biological control genera Sphingomona, Pseudomonas, Bacillus and Lysobacter. The abundance of these beneficial bacteria increased significantly when B. subtilis and T. harzianum were applied together. These results showed that fertilizer applied after fumigation can increase the abundance of beneficial microorganisms in the soil within a short period of time, which improved the soil's fertility, ecological balance and potentially crop quality and yield.
Keywords: Bacterial community structure; Humic acid; Microbial fertilizer; Soil enzymes; Soil physical and chemical properties.
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