Abstract
Agricultural and soil management practices have been reported to affect alachlor sorption–desorption and degradation rates. Though alachlor has been banned in the E.U. since 2006, it is still used in U.S. corn and soybean production. The objectives of this study were to: (a) assess differences in alachlor sorption due to tillage treatments (chisel plow and ridge tillage) on soils from three midwestern U.S. locations; and (b) determine the effect of various soil amendments on the sorption–desorption and mineralization of alachlor. Soils were amended at a rate of 10% (w/w) with biochars derived from soybean stover, sugarcane bagasse, and wood chips, as well as the uncharred feedstock materials. Sorption–desorption studies were performed using the batch equilibration method, and alachlor mineralization was evaluated in a 30-day incubation. Tillage management did not affect alachlor sorption to soil across the three sites, despite the fact that the tillage operations were imposed for 4 years (p > 0.05). While the sorption coefficient (Kd) values for alachlor were relatively low in the three unamended soils (Kd = 1.76, 1.73, and 1.15 L·kg−1 for IL, MN, and PA soils, respectively), biochar amendments increased alachlor sorption between 4× and 33× compared to the unamended soil. The amendments also affected alachlor mineralization such that degradation was slower in both biochar- and raw feedstock-amended soils. Based on these results, biochar additions are expected to affect the availability of alachlor for transport and degradation. Furthermore, this study highlights the larger impact of biochar addition than tillage practices on altering immediate alachlor sorption capacities.
Highlights
Agricultural management practices are continually evolving to optimize crop yields and improve soil quality
There were no significant differences in the soil organic carbon (SOC) content of the soils as a consequence of the tillage management (Table 1)
This study examined the overall impact of tillage and amendment addition as means to improve alachlor sorption in the soil system across three soil types
Summary
Agricultural management practices are continually evolving to optimize crop yields and improve soil quality. Over the past few decades, there has been a shift toward conservation tillage and a growing interest in the application of soil amendments (e.g., compost, biochar). Such changes in management alter the soil environment, which in turn may influence the efficacy, leaching risk, and persistence of herbicides in agricultural soils [1,2,3,4,5]. Alachlor can be applied to soil alone or as a mixture (e.g., with atrazine) for pre-emergent weed control at rates up to 4 lb ai/acre [6] Degradation of this herbicide in soils occurs predominantly through
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