Clomazone improves the interactions between soil microbes and affects C and N cycling functions.

Clomazone, a widely used herbicide, is mainly used in soybean fields. We previously found that clomazone alters Proteobacteria and Nitrospirae abundances and also alters urease activity, which result in changes in NH and NO contents in soil nitrogen cycling. It remains unknown, however, how the co-occurrence patterns of species and functions of soil ecosystems change in response to clomazone applications in soil. We designed a 3-month greenhouse experiment to investigate soil microorganism dynamics in response to clomazone. Clomazone was applied at three doses (e.g., T1, T10, T100), which significantly increased bacterial abundance at days 15 and 60. Fungal abundance was stimulated at day 30 in T10-treated soils, whereas fungal abundances decreased in T100-treated soils at day 15. Clomazone altered bacterial and fungal community structures. Network analyses showed more complex and highly connected microbial communities in clomazone-treated soils. Moreover, an Acidobacteria-dominated cluster was identified within each network of clomazone-treated soils. Clomazone applied at the recommended rate decreased the functional groups that were associated with denitrification and hydrogen oxidation at days 15 and 60, and enhanced photoheterotrophy from days 30 to 60. High clomazone inputs increased trophic types (e.g., chemoheterotrophy, phototrophy, photoautotrophy and cyanobacteria) and C cycling functional groups (e.g., fermentation and cellulolysis). The half-life of clomazone ranged from 40.1 to 93.5 days in three cases. Our results provide important information for use of this herbicide.