Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/1/2004
Publication Date: 11/1/2004
Citation: Potter, T.L., Truman, C.C., Bosch, D.D., Bednarz, C.W. 2004. Fluometuron and pendimethalin runoff from strip and conventionally tilled cotton in the southern Atlantic Coastal Plain. Journal of Environmental Quality. J. Environ. Qual. 33:2122-2131. Interpretive Summary: Surface water contamination by pesticides and their breakdown products is a problem with national and international dimensions. In the USA surveys conducted over the past decade found residues of one or more these compounds in almost every sample tested. Levels detected were generally low; however, negative ecological impacts were indicated in many cases. Increasingly growers and natural resource managers need performance on the data on the most effective runoff control measures. Our research has focused on documenting the value of reduced tillage (RT) management in cotton production in the Atlantic Coastal Plain. We found that a widely used RT practice, strip-tillage (ST), reduced runoff of the herbicide, pendimethalin, by 3 to 4 times when compared to a conventionally tilled field. ST also reduced total runoff and erosion by factors of 2 to 3. This has clearly demonstrated the value of ST as a conservation practice for local growers. Our studies with a second herbicide, fluometuron, indicated little potential for runoff in part due to relatively rapid leaching. Given this it appears that ground water resources may be impacted through use of this compound. On-going research is addressing this concern.
Technical Abstract: In many agricultural settings, runoff is the main source of pesticide contamination of surface water. Reduced tillage can be a means of control; however, performance data are lacking for many crop, climate, and geographic settings. This is the case in the southern portion of the Atlantic Coastal Plain where cotton acreage increased three fold in the past decade. This has resulted in substantial increases in pesticide use. To more effectively protect water quality in the region and improve the accuracy of pesticide risk assessments, data are needed on tillage impacts on pesticide runoff from cotton fields. We report on the behavior of two widely used herbicides, fluometuron and pendimethalin on 0.15-ha plots in strip-tillage (ST) and conventional tillage (CT) management at a site near Tifton, GA. Runoff due to natural rainfall was monitored for two years. In addition, rainfall simulations were conducted on 0.0006-ha micro-plots. In all studies, pendimethalin runoff rates were significantly greater from CT versus ST plots. This was related to its strong soil sorption and higher CT erosion and runoff rates. No significant differences were observed for fluometuron runoff as a function of tillage, simulated or natural rainfall, or application timing. Runoff rates were uniformly low. Soil chemical analysis indicated that this was due to its relatively rapid leaching and removal from the zone at the soil surface where the compound is available for runoff. Fluometuron soil sorption is weak. Results also demonstrated the value of rainfall simulation in runoff risk assessment. Simulations allowed investigation of storm events relative to herbicide application with return intervals of 5-10 years. Capturing events of this type in natural rainfall investigations is logistically difficult and may not be feasible.