Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2014
Publication Date: 5/15/2014
Citation: Potter, T.L., Bosch, D.D., Strickland, T.C. 2014. Comparative assessment of herbicide and fungicide runoff risk: a case study for peanut production in the Southern Atlantic Coastal Plain (USA). Science of the Total Environment. 490:1-10.
Interpretive Summary: Compelling arguments can be made that pesticide use substantially increases economic returns to farmers while lowering consumer food costs and increasing food security. However pesticides also have well documented potential for adverse impact on human health and the environment. A primary concern is water quality impairment when residues are transported from farm fields to streams and rivers in surface runoff. Our study was designed to evaluate relative runoff risks of an herbicide, metolachlor, and fungicide, tebuconazole, commonly used for peanut production and to determine the potential for a widely used conservation tillage practice, strip-tillage (ST), to reduce runoff losses of both products. We found that runoff risk of the fungicide was more than 10 times greater than the herbicide. This was in spite the fact more herbicide was applied to our peanut fields. Data showed that tebuconazole risks were higher due to fact that it was applied more frequently and at times within the growing season when risks of runoff were high. Only single applications of the herbicide were made at planting in May. Because May is one the driest months of the year in the region potential for runoff is low. Our studies emphasize the need to focus on the fungicides in future studies of pesticide runoff from peanut and other crops. The current investigation was one of the first to do this. The study also showed that peanut farmers should be encouraged to use conservation tillage practices like ST which can substantially reduce pesticide runoff.
Technical Abstract: Peanut (Arachis hypogaea) is produced intensively in the southern Atlantic Coastal Plain of the eastern USA. To effectively protect the region’s water quality data are needed which quantify runoff of pesticides used to protect these crops. Fungicides are used intensively yet there is little published data which describe their potential for loss in surface runoff. This study compared runoff of a fungicide, tebuconazole (a-[2-(4-chlorophenyl)ethyl]-a-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol), and an herbicide, metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide) from 0.2 ha fields in strip (ST), a commonly used conservation-tillage practice, and conventional tillage (CT) near Tifton, GA(USA). Following their first application, metolachlor and tebuconazole were detected at high frequency in runoff. Concentrations and their annual losses increased with application frequency and runoff event timing and frequency with respect to applications, and when fields were positioned at the top of the slope and CT was practiced. Runoff one day after treatment (DAT) contributed to high tebuconazole runoff loss, up to 9.8% of applied on an annual basis. In all cases, metolachlor loss was more than 10 times less even though total application was 45% higher. This was linked to the fact that the one metolachlor application to each crop was in May, one of the region’s driest months. In sum, studies showed that fungicide runoff rates may be relatively high and emphasize the need to focus on these products in future studies on peanut and other crops. Our investigation was one of the first to do this. The study also showed that peanut farmers should be encouraged to use conservation tillage practices like ST which can substantially reduce pesticide runoff.