Effects of the long-term application of atrazine on soil enzyme activity and bacterial community structure in farmlands in China.

Atrazine has been used on Chinese farmlands for a long time and over a wide range. The concentration of atrazine (1.86–1100 mg kg⁻¹) has exceeded the allowable limit in the soil (1.0 mg kg⁻¹), and concern is increasing about the potential harm to farmland soil. Four treatments (AT 0 , AT 6 , AT 10 , AT 16) were established to reveal the effects of the long-term application of atrazine on soil health. The results showed a nonlinear regulation of the atrazine residue concentrations in the four treatments. The highest concentration of atrazine residue was in AT 6 , at 167 mg kg⁻¹, and the lowest concentration of atrazine residue was in AT 16 , at 102 mg kg⁻¹, but there was no significant difference between AT 10 and AT 16. The soil urease activity decreased significantly with the increase in the years of atrazine application, the saccharase and cellulase activities in the AT 6 were significantly higher than those observed in the other three treatments, the catalase activity gradually decreased with the increase in atrazine application years, and the activity in AT 6 was significantly higher than that in AT 16. A total of 238 genera were identified by Illumina MiSeq sequencing, and 28 dominant genera were screened. Atrazine significantly increased the relative abundance of Actinobacteria and contributed to the relative abundance of Rubrobacter , Blastococcus , Promicromonospora , Jiangella , Psychroglaciecola and Acetobacteraceae_ uncultured , which exhibited significantly higher abundance in AT 16 than in AT 0. Although there were atrazine-degrading bacteria in the soil, and the atrazine residue decreased with the increase in application years, the concentration of the atrazine residue was still nearly 100 times higher than the allowable limit in the soil, which is a great threat to the soil health. Image 10099 • The results show a non-linear regulation of atrazine residue concentration in the four treatments. • Atrazine can inhibit urease, saccharase and cellulase activities but stimulate catalase activity. • There are twenty-eight genera relevant to atrazine degradation. • Atrazine residue is the main factor affecting the relative abundance of the genera. [ABSTRACT FROM AUTHOR]