Effects of hexaconazole application on soil microbes community and nitrogen transformations in paddy soils

The ecological risks of widely used hexaconazole on soil microbes remain obscure. Thus, a 3-month-long experiment using two typical paddy soils in China (red soil and black soil) was conducted to assess the effects of hexaconazole (0.6 (T1) and 6 (T10) mg kg(-1) soil) on the overall microbial biomass, respiratory activity, bacterial abundance and community structure, and nitrogen transformations. Soil was sampled after 7, 15, 30, 60, and 90 days of incubation. The half-lives of the two doses of hexaconazole varied from 122 to 135 d in the black soil and from 270 to 845 d in the red soil. Both dosages of hexaconazole did not affect NH4+-N content, N-2-fixing bacterial populations, total bacterial diversity, and community structure, but transitorily decreased the populations of total bacteria in both soil types. In the black soil, T10 negatively affected microbial biomass carbon (MBC) and soil basal respiration (R-B), but transitorily increased NO3--N concentration and ammonia-oxidizing bacteria populations, while T1 had almost no effect on most of the indicators. As for red soil, both concentrations of fungicide significantly, but transitorily, inhibited MBC and R-B, while only T10 had a relatively long stimulatory effect on NO3--N concentration and ammonia-oxidizing archaea populations. This study showed that over application of hexaconazole is indeed harmful to soil microorganisms and may reduce soil quality and increase the risk of nitrogen loss in paddy soils. (C) 2017 Elsevier B.V. All rights reserved.