Abstract
The impact of the aeration status of soils on the environmental fate of the soil-applied pre-emergent herbicide metolachlor is of significance to sustainable agriculture practices and has not been investigated thoroughly by existing research works. To address this knowledge gap, we examined the adsorption, desorption, degradation, and mineralization of radioactively labeled [14C] metolachlor in Catlin, Flanagan, and Drummer soils under aerobic and anaerobic conditions. Based on our findings, anaerobic conditions in the soil significantly reduced the adsorption of 14C-metolachlor while also promoting its desorption, thereby potentially releasing a greater amount of herbicide from the soil after a field application. The first-order degradation and mineralization kinetics of 14C-metolachlor were distinctively enhanced by anaerobic conditions in all the soils tested. Furthermore, the degradation and mineralization rates of 14C-metolachlor in non-sterilized versus sterilized soil microcosms clearly indicated microbial activity in the degradation of metolachlor in soil. The results from this study suggest that soil redox conditions could impact the bioavailability and environmental fate of herbicide metolachlor and should be taken into consideration as part of sustainable weed management programs.
Highlights
Metolachlor [2-chloro-N-(2-ethyl 6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] (Figure 1) is a soil-applied herbicide widely used for pre-emergent weed control in a variety of crops like corn, soybean, peanuts, potatoes, tobacco, and vegetables [1]
Agricultural practices such as soil aeration can end up having a great impact on the microbial bioavailability of soil-applied herbicides such as metolachlor, and the findings of this study provided clear evidence for enhanced bioavailability and microbial biodegradation of metolachlor in the anaerobic soil systems
The respective Freundlich adsorption coefficients for anaerobic and aerobic soil conditions indicate that the adsorption of metolachlor in the soils was noticeably reduced under anaerobic conditions
Summary
Metolachlor [2-chloro-N-(2-ethyl 6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] (Figure 1) is a soil-applied herbicide widely used for pre-emergent weed control in a variety of crops like corn, soybean, peanuts, potatoes, tobacco, and vegetables [1]. Fernandez-Cornejo et al [2] reported metolachlor as one of the top five most-used herbicides, based on the amount of active ingredient applied.
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