Effect of two organic amendments on atrazine degradation and microorganisms in soil

Silkworm excrement and silkworm excrement derived biochar were added to both sterilized and unsterilized soil at rates of 0 and 0.5% (w/w). The effects of the two organic amendments on atrazine degradation and the microbial community in soils with an atrazine content of 5 mg.kg(-1) were studied. In unsterilized soils, the residual fraction of atrazine at 56 d was increased in the silkworm excrement- and biochar-amended soils, by 2.18 mg.kg(-1) and 0.72 mg.kg(-1), respectively. Furthermore, both organic amendments increased the accumulation of desethylatrazine (DEA). However, unlike DEA, deisopropylatrazine (DIA) accumulation increased in silkworm excrement-amended soil and decreased in biochar-amended soil. There was a negative relationship between the depletion rate of DOC and the degradation rate of atrazine. With respect to microorganisms, the Biolog Ecoplate test revealed that biochar and silkworm excrement improved microbial activity and community diversity in atrazine-contaminated soil. Additionally, Illumina-MiSeq analyses showed that both organic amendments increased the proportions of Proteobacteria, Actinobacteria, Aspergillus and Cephalothecaceae in soil but decreased that of Bacteroidetes and Talaromyces.