|Lerch, Robert - Bob|
Submitted to: North American Agroforestry Conference
Publication Type: Proceedings
Publication Acceptance Date: 5/31/2007
Publication Date: 6/10/2007
Citation: Lin, C.H., Lerch, R.N., Garrett, H.E., Gantzer, C.J., Anderson, S.H. 2007. Utilizing Vegetative Buffer Strips to Remove Dissolved and Sediment-Bound Atrazine, Metolachlor and Glyphosate from Surface Water Runoff. North American Agroforestry Conference, June 10-13, Quebec City, Quebec. p. 113-121. Interpretive Summary: Multiple species vegetative buffer strips (VBS) have been recommended as a cost-effective approach to mitigate herbicide transport in surface runoff derived from agronomic operations. However, the effect of buffer designs and species composition on reducing herbicide transport has not been well documented. Three VBS designs were evaluated in this study: 1) tall fescue; (2) tall fescue with a switchgrass barrier; and (3) native warm-season vegetation (largely eastern gamagrass and switchgrass). These VBS were then compared to a control treatment of continuous cultivated fallow. The study was conducted using 50’ long X 5’ wide plots, with the upper half of the plots cultivated and sprayed with three herbicides: atrazine, metolachlor (Bicep), and glyphosate (Roundup). The lower half of the plots consisted of the VBS designs mentioned above. A rainfall simulator was used to generate runoff. Water and sediment samples were collected throughout the runoff events. The results showed a much higher proportion (40-60%) of glyphosate transported with suspended sediment in surface runoff compared to atrazine and metolachlor (less than 3% was sediment-bound). All VBS significantly reduced the transport of both dissolved and sediment-bound atrazine, metolachlor, and glyphosate in surface runoff. The VBS reduced dissolved-phase herbicide transport by increasing infiltration of water into the soil. This resulted from plant evapotranspiration which decreased soil moisture and increased the water holding capacity of the soil. VBS with native vegetation were most consistently effective at reducing transport of the herbicides. The native VBS removed about 75-80% of the atrazine, metolachlor and glyphosate in runoff. Tall fescue was less effective, removing about 55-75% of the herbicides in surface runoff. The tall fescue with a switchgrass barrier was overall the least effective, removing about 30-60% of the herbicides from runoff. This research will benefit conservation agencies in designing VBS that will maximize their effectiveness at reducing herbicide transport from cropland. It will benefit farmers because well designed VBS will require the least amount of land be taken out of production to achieve conservation goals.
Technical Abstract: Multiple species vegetative buffer strips (VBS) have been recommended as a cost-effective approach to mitigate herbicide transport in surface runoff derived from agronomic operations. However, the effect of buffer designs and species composition on reducing herbicide transport has not been well documented. An experiment consisting of three VBS designs and one cultivated fallow control replicated in triplicate was conducted to assess effectiveness in reducing herbicide transport for claypan soils. The four VBS treatments include: (1) continuous cultivated fallow (control), (2) perennial fescue, (3) fescue with a switchgrass barrier, and (4) native vegetation (largely eastern gamagrass). Rainfall simulation was used to create uniform antecedent soil moisture content in the plots and to generate runoff. Runoff collection equipment is installed across the plots at 1 m above (upslope) the filter strips and at 1, 4, and 8 m into the VBS treatments. The results show a much higher proportion (40-60%) of glyphosate transported with suspended sediments in surface runoff as compared to that of atrazine and metolachlor (less than 3%). All VBS significantly reduced the transport of both dissolved and sediment-bound atrazine, metolachlor and glyphosate in surface runoff. VBS with native species were most consistently effective at reducing transport of these herbicides. Four meters of native VBS removed about 75-80% of the atrazine, metolachlor and glyphosate in surface runoff. The additional length of native VBS had little effect on removal rates. Additionally, four meters of native species VBS resulted in much greater reductions in transport of these herbicides than eight meters of the other tall fescue VBS designs. Thus, the implementation of native species buffers could provide desired reductions in herbicide transport with less land taken out of production.