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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Production Systems Research » Research » Publications at this Location » Publication #229646
Title: Interactions of Tillage and Cover Crop on Water, Sediment, and Pre-emergence Herbicide Loss in Glyphosate-Resistant Cotton: Implications for the Control of Glyphosate-Resistant Weed Biotypes

Author
item Krutz, Larry
item Locke, Martin
item Steinriede, Robert

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2008
Publication Date: 5/1/2009
Citation: Krutz, L.J., Locke, M.A., Steinriede Jr, R.W. 2009. Interactions of Tillage and Cover Crop on Water, Sediment, and Pre-emergence Herbicide Loss in Glyphosate-Resistant Cotton: Implications for the Control of Glyphosate-Resistant Weed Biotypes. Journal of Environmental Quality 38:1240-1247.

Interpretive Summary: The need to control glyphosate-resistant weeds with tillage and pre-emergence herbicides in glyphosate-resistant cropping systems (GRCs) has caused a reducing in no-tillage acreage, thereby threatening environmental gains made in water quality over the past decade. Consiquently, if enviromnetal gains affored by GRCs are to be maintained, then an in-field best management practice compatible with some form of tillage is required for acreage infested with glyphosate-resistant weeds. The objective of this study was to evaluate the impact of cover crop [rye cover (RC) or no cover (NC] and tillage [no tillage (NT) or reduced tillage (RT)] on water, sediment, and herbicide loss in glyphosate-resistant cotton. Regardless of tillage, RC delayed time-to-runoff, reduced cumulative runoff volume, and decreased cumulative sediment loss. Cumulative loss of the herbicide fluometuron was not affected by tillage or cover crop. Conversely, total loss of the herbicide metolachlor was lower in NT than RT and lower in RC than NC. These data indicate that RC can be established in acreage requiring tillage and potentially curtail water, sediment, and pre-emergence herbicide losses in the spring to levels equivalent to or greater than that of NT, thereby protecting environmental gains provided by GRCs.

Technical Abstract: The need to control glyphosate [N-(phosphonomethyl)glycine]-resistant weed biotypes with tillage and pre-emergence herbicides in glyphosate-resistant crops (GRCs) is causing a reduction in no-tillage hectarage thereby threatening the advances made in water quality over the past decade. Consequently, if environmental gains afforded by GRCs are to be maintained, then an in-field best management practice (BMP) compatible with tillage is required for hectarage infested with glyphosate-resistant weed biotypes. Thus, one day after a pre-emergent application of fluometuron [N,N-dimethyl-N’-(3-(trifluoromethyl)phenyl)urea] (1.02 kg ha-1) and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] (1.18 kg ha-1) to a Dundee silt loam, simulated rainfall (60 mm h-1) was applied to 0.0002 ha micro-plots for 1.25 h to elucidate tillage [no tillage (NT) and reduced tillage (RT)] and cover crop [no cover (NC) and rye cover (RC)] effects on water, sediment and herbicide loss in surface runoff. Regardless of tillage, RC delayed time-to-runoff 1.3-fold, reduced cumulative runoff volume 1.4-fold, and decreased cumulative sediment loss 4.7-fold. Cumulative fluometuron loss was not affected by tillage or cover crop. Conversely, total metolachlor loss was 1.3-fold lower in NT than RT and 1.4-fold lower in RC than NC. These data indicate that RC can be established in hectarage requiring tillage and potentially curtail water, sediment, and pre-emergence herbicide losses in the spring to levels equivalent to or greater than that of NT, thereby protecting environmental gains provided by GRCs.