Residual herbicide concentrations in on‐farm water storage–tailwater recovery systems: Preliminary assessment

Abstract

AbstractOn‐farm water storage–tailwater recovery systems reduce groundwater usage and intercept agrochemical loads, but pesticide residue dynamics in these systems are not well understood. This study monitored concentrations of seven herbicides in seven northeast Arkansas tailwater recovery systems (April 2017–March 2018). Clomazone, glyphosate, metolachlor, and quinclorac were frequently detected, with minimal detections of 2,4‐D, dicamba, and propanil. Concentrations peaked during the growing season (1 Apr.–15 Sept.), reflecting an interaction of application and precipitation. Clomazone, glyphosate, and quinclorac concentrations were greater in ditches (<0.80–67, <0.50–6.2, and <0.40–62 μg L−1, respectively) than in the associated reservoir (<0.80–6.0, <0.50–4.1, and <0.40–6.0 μg L−1, respectively), but metolachlor concentrations were not different between structure types (maximum 22–32 μg L−1). Off‐season concentrations were mostly below detection, except for quinclorac. Cycling recovered tailwater through the system and irrigating from reservoirs may minimize risk of cross‐crop contaminations with residual herbicides. Managed groundwater recharge should use reservoir water during winter to protect groundwater quality.