Glyphosate is widely used for weed control in greenhouse vegetable production. However, its extensive use has raised increasing concern regarding its potential impacts on soil nitrogen (N) cycling and nitrous oxide (N 2 O) emissions. Current findings on how glyphosate influences soil N transformations and N 2 O emissions remain inconsistent, likely due to variability in application intensity and soil cultivation duration. In this study, a 15 N tracing experiment was conducted to evaluate the effects of glyphosate at different application rates (50, 150, and 450 mg kg − 1 ) on soil N transformation rates and N 2 O emissions in greenhouse vegetable soils with short-term (V1, 1-year) and long-term (V10, 10-year) cultivation histories. In V1 soils, glyphosate significantly reduced the rates of organic N mineralization ( M Norg ), organic N oxidation to NO 3 − ( O Norg ), NH 4 + oxidation to NO 3 − ( O NH4 ), NH 4 + immobilization to organic N ( I NH4 ), and NO 3 − immobilization to organic N ( I NO3 ), but increased the mean residence times of NH 4 + and NO 3 − , indicating slower N turnover. In V10 soils, glyphosate significantly stimulated M Norg and accelerated NH 4 + turnover but had negligible effects on other N transformation processes. Glyphosate application also reduced the I NH4 / O NH4 ratio in both soils, indicating weakened inorganic N retention and increased risk of NO 3 − accumulation. While low doses of glyphosate did not alter N 2 O emissions, higher concentrations (≥ 150 mg kg − 1 ) significantly reduced emissions in V10 soil. however, no such effects were observed in V1 soil. These findings highlight that glyphosate-induced changes in soil N cycling and N 2 O emissions are influenced by application dosage and vegetable cultivated years.
Xie et al. (Fri,) studied this question.