Multifunctional effects of nitrification and urease inhibitors: Decreasing soil herbicide residues and reducing nitrous oxide emissions simultaneously

Abstract

Glyphosate pollution and greenhouse gas emissions are major problem in achieving sustainable soil management. It is necessary to develop effective strategies to simultaneously reduce herbicide residues and nitrous oxide (N₂O) emissions in soil. This study aimed to: (1) quantitative analyze the effects of nitrogen (N) cycle inhibitors (nitrification inhibitors 3,4 dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD) and urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT)) on glyphosate degradation and reduction of N₂O under different soil moistures; (2) identify the functional microbes and genes associated with glyphosate degradation and N₂O emissions; and (3) decipher the main mechanisms of N cycle inhibitors affecting glyphosate degradation at different soil water contents. Compared to the control, the application of DMPP, DCD and NBPT reduced glyphosate residues in soil by 33.0 %, 60.3 % and 35.7 %, respectively, under 90 % water holding capacity (WHC). The application of DCD stimulated Acidobacteria and the phnX gene to degrade soil glyphosate. Further, soil glyphosate residues were significantly and negatively related to soil N₂O emissions at both 60 % and 90 % WHC. Compared to the control, NBPT application decreased cumulative N₂O emissions by 91.4 % at 90 % WHC by decreasing soil nitrate N (NO₃^--N) and inhibiting amoC and narG genes at 90 %. The application of N cycle inhibitors could be a potential strategy to simultaneously reduce glyphosate residues and soil N₂O emissions. Our study could provide technical support to reduce the risks of herbicide exposure and reduce greenhouse gas emissions.

Keywords: Functional genes; Glyphosate degradation; Nitrogen cycle inhibitors; Nitrous oxide emissions; Soil moisture.