By John Wallace, Ph.D. and Dwight Lingenfelter
Weed regrowth and new seedlings in small grain stubble or fields harvested for corn silage should be controlled prior to cover crop seeding to start clean and give cover crops a competitive advantage. Early September seeding windows allow for the use of diverse cover crop mixtures as well as winter-killed species. Whether you plan to use grass cover crops or diverse mixtures, make sure to consider the following issues related to herbicide program approaches.
Burndown programs prior to cover crop establishment?
It is important to understand the potential for burndown products to impact cover crop establishment due to soil residual activity. The simplest and most risk-free approach is to use only glyphosate or paraquat to start clean prior to cover crop seedings. These broad-spectrum products have no soil residual activity. However, additional products are often needed to control glyphosate-resistant species (horseweed, Palmer amaranth, waterhemp) as well as some other no-till weeds.