|Lerch, Robert - Bob|
|LIN, CHUNG - University Of Missouri|
|GOYNE, KEITH - University Of Missouri|
|KREMER, ROBERT - Retired ARS Employee|
|ANDERSON, STEPHEN - University Of Missouri|
Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2017
Publication Date: 6/1/2017
Citation: Lerch, R.N., Lin, C.H., Goyne, K.W., Kremer, R.J., Anderson, S.H. 2017. Vegetative buffer strips for reducing herbicide transport in runoff: effects of buffer width, vegetation, and season. Journal of the American Water Resources Association. 53(3):667-683. doi: 10.1111/1752-1688.12526.
Interpretive Summary: Vegetative buffer strips (VBS) are areas of grasses, trees, and/or shrubs planted adjacent to cropped fields to trap contaminants present in surface runoff. VBS have been shown to be effective for reducing sediment and nutrient transport from fields, but they have not been tested for reducing herbicides from high runoff potential soils. Claypan soils represent one type of high runoff soil and streams in watersheds dominated by these soils have been shown to have the highest herbicide concentrations of any area within the U. S. Corn Belt. Therefore, a multi-year study was initiated to test the effectiveness of VBS for reducing herbicides in runoff from an eroded claypan soil. The study evaluated the effects of different vegetation cover (three different grasses and a bare ground control), buffer width, and season on the movement of three commonly used herbicides - atrazine (Aatrex), metolachlor (Dual), and glyphosate (Roundup). Atrazine and metolachlor move by dissolving in the water and glyphosate moves in the water and by binding to soil particles. The grass treatments were tall fescue, tall fescue with a 3 ft wide switchgrass hedge at the upslope end, and a native grass mixture. The grass treatments were similarly effective at reducing herbicide movement by decreasing the volume of runoff water and by depositing eroded soil, with bound glyphosate, within the buffers. Of the main factors studied, vegetation cover and buffer width impacted herbicide losses much more than season. Grass treatments reduced herbicide losses by 19-28% and sediment loss by 67% compared to the bare ground control. Grass treatments modestly improved surface soil quality 8-12 years after establishment, with increases in organic carbon, total nitrogen, and atrazine binding to soil. Equations were developed from the data to predict the reductions in herbicide loss for different buffer widths. These relationships showed that VBS can provide significant reductions under expected field conditions. Overall, the findings indicated that a variety of different grasses will be effective for use in VBS and that sufficient buffer width is crucial for achieving significant reductions in herbicide transport. This research will benefit conservation agencies and landowners by providing simple criteria for effectively implementing VBS to control herbicide losses from cropped fields.
Technical Abstract: The effect of vegetative buffer strip (VBS) width, vegetation, and season of the year on herbicide transport in runoff has not been well documented for runoff prone soils. A multi-year replicated plot-scale study was conducted on an eroded claypan soil with the following objectives: 1) assess the effects of season, vegetation, and buffer width on runoff transport of atrazine, metolachlor, and glyphosate; 2) develop VBS design criteria for herbicides; and 3) compare differences in soil quality among vegetation treatments. Rainfall simulation was used to create uniform antecedent soil water content and to generate runoff. All grass treatments effectively reduced dissolved-phase and sediment-bound herbicide transport via reductions in surface runoff and sediment loads. Of the main factors studied, vegetation treatment and buffer width impacted herbicide loads much more than season. Grass treatments reduced herbicide loads by 19-28% and sediment loads by 67% compared to the control. Grass treatments modestly improved surface soil quality 8-12 years after establishment, with increases in organic C, total N, and atrazine sorption. Herbicide loads as a function of buffer width were well described by 1st-order decay models which indicated that VBS can provide significant load reductions under anticipated field conditions. These models provide conservation agencies and landowners a simple tool for effectively implementing VBS to control herbicide losses from cropped fields.