Runoff and Drainage Losses of Atrazine, Metribuzin, and Metolachlor in Three Water Management Systems

Abstract

Rainfall can transport herbicides from agricultural land to surface waters, where they become an environmental concern. Tile drainage can benefit crop production by removing excess soil water but tile drainage may also aggravate herbicide and nutrient movement into surface waters. Water management of tile drains after planting may reduce tile drainage and thereby reduce herbicide losses to surface water. To test this hypothesis we calculated the loss of three herbicides from a field with three water management systems: free drainage (D), controlled drainage (CD), and controlled drainage with subsurface irrigation (CDS). The effect of water management systems on the dissipation of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one), and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] in soil was also monitored. Less herbicide was lost by surface runoff from the D and CD treatments than from CDS. The CDS treatment increased surface runoff, which transported more herbicide than that from D or CD treatments. In one year, the time for metribuzin residue to dissipate to half its initial value was shorter for CDS (33 d) than for D (43 d) and CD (46 d). The half-life of atrazine and metolachlor were not affected by water management. Controlled drainage with subsurface irrigation may increase herbicide loss through increased surface runoff when excessive rain is received soon after herbicide application. However, increasing soil water content in CDS may decrease herbicide persistence, resulting in less residual herbicide available for aqueous transport.

Controlled Drainage as a Targeted Mitigation Measure for Nitrogen and Phosphorus

“…The drain flow reduction of 6 to 54% found in this study is in agreement with the findings of 8 to 64% reductions in other field studies conducted on silt and clay loam (Tan et al, 1999;Gaynor et al, 2002;Drury et al, 2009;Fang et al, 2012;Sunohara et al, 2014;Williams et al, 2015). The effect of CD was clearly strongest at the highest regulation level (70 cm), which agrees with earlier studies (Evans et al, 1995;Wesström and Messing, 2007).…”

Effects of environmentally relevant concentrations of atrazine on gonadal development of snapping turtles (Chelydra serpentina)

“…James et al [26] (http:// www.hortnet.co.nz/publications/nzpps/proceedings/old/ 94nzpps.htm) measured 0.88 mg/kg of atrazine in soil following application at the same rate as that used to simulate our low exposure (1.5 kg/ha); this is an order of magnitude lower than for soil measured in our high-dose group (8.1 mg/kg) but similar to that for our low-dose group (0.64 mg/kg). Similarly, an application rate of 1.1 kg/ha yielded peak soil concentrations of 0.97 mg/kg of atrazine [27]. Thus, our low exposure resulted in soil concentrations similar to those found in soil following actual spray applications.…”

Long-Term Monitoring of Waterborne Pathogens and Microbial Source Tracking Markers in Paired Agricultural Watersheds under Controlled and Conventional Tile Drainage Management

“…Notwithstanding these benefits, controlled tile drainage is currently not a practice that is ubiquitous in tile-drained regions throughout the world, and little is known about how this practice, when imposed en masse at a watershed scale, impacts the sources and degree of fecal pollution in surface water. A majority of experimental research on CTD is set at the field/plot scale and has focused primarily on other pollution targets (18)(19)(20). However, recently Schmidt et al (21) found that CTD could potentially increase instantaneous loads and concentrations of fecal indicator bacteria and Campylobacter spp.…”