Trade-off strategy for the usage of thiencarbazone-methyl·isoxaflutole on maize fields: Nitrogen-associated microbial response and environmental implications

Due to the lack of knowledge on the mechanism of the effect of new herbicides on nitrogen-functioning microorganisms and nitrogen use efficiency, a balancing strategy for the application of new herbicides in maize fields is rarely proposed. By studying the effects of thiencarbazone-methyl·isoxaflutole (TMI) on nitrogen transformation in soil and nitrogen agronomic efficiency (NAE) of maize, the mechanism of nitrogen functional groups and genes involved was revealed, and controlling factors affecting soil nitrogen transformation were identified. Results showed that on day 18, the nitrate nitrogen (NO3−-N) content increased but ammonium nitrogen (NH4+-N) content decreased with the TMI application. This can be further verified by the positive correlations (p < 0.05) among isoxaflutole residues, “aerobic_ammonia_oxidation” and NO3−-N content. The NH4+-N content increased significantly with TMI application at 10 times the recommended dose (412.5 ml hm−2) on days 30 and 45, which explains the high value of NAE at the high-dose application of TMI. Random forest model and redundancy analysis confirmed the significant impacts of the nifH gene on NH4+-N content and TMI residues on NO3−-N content (p < 0.05). Comprehensively considering the disturbance of nitrogen-related microorganisms and the effects on the NAE of maize, this research proposed a trade-off strategy for the application of new pre-emergence herbicide in maize fields, involving background investigation, experimental design, analytical methods and trade-off indicators. This may be further popularised and achieve a balance between economic and environmental benefits.