Jessica A. Kelton, Auburn University
Controlling weeds in any agricultural system can be a major challenge and cost, especially without advance preparation. Without a weed management plan in place before planting, weeds can easily emerge and out-compete crops. They can reduce yield, increase labor demands for last-resort weed control such as hand weeding, and hurt profits. Weed control is more challenging in conservation tillage systems than in conventional systems because control strategies common in conventional systems, notably tillage and cultivation, are not options.
The types of weeds change when a conservation tillage system is implemented. In addition to an herbicide program, an effective weed management plan should include appropriate cultural practices, especially the use of high-biomass cover crops and rotations of spring-, summer- and fall-planted crops. Diverse, year-round rotations can interfere with the life cycle of weed species, and they allow for an expanded range of herbicide options, which can help counter herbicide resistance in weeds. There are many practices that will improve a crop’s competitive advantage over weeds. Giving a crop better access to water, light and nutrients than weeds will favor crop growth and can lessen the impact of weeds on yield. Reduced-tillage systems allow for mechanical control options in conjunction with herbicides and cultural practices, whereas mechanical control is not available in no-till .
This chapter begins with an overview of how the weed community changes in a conservation tillage system and is followed by a discussion of primary weed management strategies, including the combination of herbicides and such cultural practices as cover crops and crop rotation. The issue of herbicide resistance is discussed, as are reduced tillage in organic systems, remedial weed control strategies and some crop-by-crop considerations.