Effects of Three Commonly Used Herbicides in Maize on Short-Term Soil Organic Carbon Mineralization

Toxicological effects of herbicides on the non-target microorganisms in the soil that play important roles in degrading organic matter, nutrient cycling, and decomposition should be considered if they were applied at higher concentrations. This study was conducted to reveal the toxicity of three modern herbicides (dicamba + tritosulfuron; DT, isoxinutole + thlencarbuone-methyl + cyprosulfamide; ITC and nicosulfuron; N) on soil carbon mineralization for short term. Recommended concentration (25 g/day for DT1, 30 ml/day for ITC1, and 125 ml/day N1), its 5 (DT5, ITC5, and N5), and 10 (DT10, ITC10, and N10) folds of herbicides were applied on a clay soil with no pesticide application history. Soil + herbicide mixes and soil without herbicide as control were incubated under constant temperature (28 degrees C) and moisture (80% of soil field capacity) for 42 days. In general, all doses of herbicides were significantly decreased soil carbon mineralization in short term (P < 0.05). Cumulative carbon mineralization was declined for 3.4% by DT1, for 15.0% by DT5, for 22.4% by DT10, for 13.7% by ITC1, for 14.2% by ITC5, for 18.6% by ITC10, for 4.7% by N1, for 10.0% by N5, and for 21.0% by N10, respectively, compared to control. Significant decreases were observed in the rates of carbon mineralization except DT1 and N1. Results suggested that higher doses of these herbicides negatively affected on soil microbial respiration.