Contributions to Weed Suppression from Cover Crops
Sustainable agriculture refers to a strategy of resource management in which the objectives are to satisfy changing human needs while natural resources and the quality of the environment are conserved (Technical Advisory Committee, 1989). Sustainable systems aim to sustain or improve all types of productivity, which may be measured by such diverse indices as crops harvested, soil health, and economic gains. Resources utilized in the process, however, should not be damaged or depleted and should preferably be enhanced. Preferred methods are those that rely on on-farm renewable inputs, although off-farm inputs may be justified if their use results in increased production. Sustainable agriculture should not be considered synonymous with low-input or alternative agriculture (Lal et al., 1991). However, it should be noted that a common strategy shared by all of these cropmanagement choices involves integrating several management practices rather than depending on a few external inputs, such as herbicides, to control weeds. For growers seeking to manage weeds, utilizing practices that may include but are not limited to herbicides, weed management can be a daunting task. Growing cover crops in association with the cash crop might be a useful weed management alternative for some growers and one that is consistent with the goals of sustainable agriculture. Studies indicate that weed suppression can be achieved through the use of cover crops managed judiciously (Lal et al., 1991). In addition to suppressing weeds, other benefits to agroecosystems from growing cover crops include protecting against soil erosion, increasing water infiltration, enhancing soil structure, contributing to soil fertility, sequestering carbon, and improving soil quality (Lal et al., 1991; Sainju and Singh, 1997). Also, potential exists for cover crops to
be utilized in plant disease management and control of crop pests other than weeds (Lal et al., 1991; Grunwald, Hu, and Van Bruggen, 2000b).