Impact of Temperature and Sustainable Agricultural Practices on the Degradation of Herbicides

Abstract

The objective of this work was to evaluate, through a laboratory experiment, the impact of the use of wheat straw as mulch or as an organic soil amendment on the degradation kinetics of the herbicides S-metolachlor (SMOC) and foramsulfuron (FORAM), and in the formation of their major metabolites at two incubation temperatures. The treatments assayed corresponded to milled wheat straw (P), two agricultural soils non-amended (S1 and S2) and amended with 10% (w/w) of P (S1+P and S2+P). The samples treated with both herbicides were incubated at 14ºC or 24ºC and 40% of their corresponding maximum field capacity in the dark. FORAM always showed a faster degradation than SMOC in the unamended soils, and viceversa in P, S1+P and S2+P treatments. The application of straw to soil increased the half-lives (DT₅₀) for both herbicides at the two incubation temperatures due to their higher adsorption and lower bioavailability of the herbicides to be degraded. The degradation of SMOC on straw was much faster than that observed for FORAM. The herbicides showed a faster degradation at 24°C (1.1-3.1 times) than that observed at 14°C. The formation of the three metabolites was observed in all the treatments.