Effects of atrazine application on soil aggregates, soil organic carbon and glomalin-related soil protein

Atrazine is still widely used in China. Atrazine residue (1.86-1 100 mg/kg) in the soil has exceeded the allowable limit (1.0 mg/kg), affecting soil structure and soil aggregate composition. To understand the long-term application of atrazine on soil aggregates and the binding agent, four treatments were established in cornfield planted since 1998, including without atrazine applied (AT(0)), atrazine applied (28% atrazine, 1 200-1 350 mL/ha/year) once a year from 2012 to 2018 (AT(6), 167 mg/kg), from 2008 to 2018 (AT(10), 127.64 mg/kg) as well as from 2002 to 2018 (AT(16), 102 mg/kg) with three replications. Along with the increase of atrazine application time, the mass fraction of soil aggregates > 5 mm and 2-5 mm decreased significantly while the mass fraction of soil aggregates 0.5-2 mm and < 0.5 mm increased gradually, and the change of aggregate binding agents contents were the same as that of aggregates. The contents of soil organic carbon (SOC) and glomalin-related soil protein (GRSP) in the aggregates > 5 mm and 2-5 mm were significantly negatively correlated with the years of atrazine application. Our results show that although atrazine residue in the soil does not increase with the increased yearly application, its concentration is still markedly higher than the permitted limit value and seriously affected the content of SOC and GRSP of aggregates > 2 mm, which can lead to a decrease of soil aggregate stability and soil quality.