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

Abstract

The need to control glyphosate [N-(phosphonomethyl)glycine]-resistant weed biotypes with tillage and preemergence 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, 1 d after a preemergent 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 (fine-silty, mixed, active, thermic Typic Endoaqualf), simulated rainfall (60 mm h(-1)) was applied to 0.0002-ha microplots for approximately 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 preemergence herbicide losses in the spring to levels equivalent to or better than that of NT, thereby protecting environmental gains provided by GRCs.

Comparative Losses of Glyphosate and Selected Residual Herbicides in Surface Runoff from Conservation-tilled Watersheds Planted with Corn or Soybean

“…Similarly, we noted that average glyphosate loss in the corn years was greater from the no‐till watersheds (0.25%) than from the chiseled (0.08%) and disked watersheds (0.01%). The higher losses of glyphosate from the no‐till watersheds may be a consequence of greater residue cover than in the other tillage treatments, resulting in decreasing contact with the soil and less sorption (Accinelli et al, 2005; Krutz et al, 2009).…”

“…Growing transgenic corn and soybean, and partially or totally replacing these residual herbicides with glyphosate should reduce the impact of the production of these crops on surface water quality. It is critical, however, to maintain a diversity of weed management practices in the face of the evolution of glyphosate‐resistant weeds (Duke and Powles, 2008; Krutz et al, 2009).…”

Integrating Cover Crops and POST Herbicides for Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Control in Corn

“…Winter-annual cover crops have long been used as a conservation tillage practice to prevent soil erosion and water runoff and to improve soil structure, soil quality, organic carbon, and nitrogen (Krutz et al 2009;Teasdale 1996). However, recent interest in cover crops is primarily attributed to the potential for early season weed control (Norsworthy et al 2011;Price et al 2012).…”

Forms of phosphorus transfer in runoff under no-tillage in a soil treated with successive swine effluents applications

“…This increases nutrient levels in the soil (Adeli et al 2008;Scherer et al 2010;Lourenzi et al 2013) and provides the capacity for greater dry matter production by crops (Table 1). As a consequence, water infiltration in the soil profile under a no-till cultivation system is favorable (Ceretta et al 2005;Krutz et al 2009). Solution transfer in surface runoff is directly associated with rainfall volume (Ceretta et al 2010b).…”