No-till, Herbicide Resistant Crop Interactions, and Herbicide Resistant Weeds.

Tillage has been an integral to crop production since humans began cultivating crops. However, producers, landowners, scientists, and the general public recognize that there are beneficial and detrimental aspects of tillage. Tillage promotes soil loss and adversely affects surface water quality. Weed management has always been the primary purpose of tillage, and tillage was not an option until the development of effective herbicides for weed control. The ability to reduce or eliminate tillage was enhanced tremendously with the development of herbicide-resistant (HR) crops, particularly glyphosate-resistant (GR) crops. GR crops are planted on the majority of canola, corn, cotton, soybean, and sugarbeet hectares in the United States. However, this has also placed tremendous and unprecedented selection pressure for the development of GR weeds. Several weed species have now evolved resistance to glyphosate; some of which previously had evolved resistance to other herbicide mechanisms of action. This poses a serious threat to soil conservation gains, since in some cases tillage is the only option available to manage these resistant populations. Research is demonstrating, however, that there are situations where the farmer will not have to abandon current conservation tillage practices in order to manage a resistant weed population. Best management practices (BMPs) have been established for either proactive or reactive management of HR populations, still considering support for conservation tillage systems. USDA/NRCS has determined a number of herbicide resistance BMPs that qualify for programs such as the Environmental Quality Incentive Program. For example, Palmer amaranth (Amaranthus palmeri) is the most important weed problem in southeastern U.S. cotton production because of glyphosate resistance. Inversion tillage is an effective tool in helping manage this weed. Programs have been demonstrated that meet conservation compliance, and at the same time carefully use tillage in a highly prescriptive manger as an element for Palmer amaranth management.