ABSTRACT
Conservation management systems are more widespread due to environmental regulatory pressure and a desire to reduce input costs. Conservation management systems are defined as those that integrate practices to preserve or enhance soil and water resources. Some examples of conservation management practices include reduced tillage, cover crops, crop rotation, variable row spacing, and timing of crop planting. One objective of conservation management systems is to increase coverage of the soil surface by plant residues to a level of 30 percent or more. Many benefits accrue from plant residue accumulation on the soil surface, such as protection from erosion, conservation of soil moisture, and enhancement of soil tilth. Soil and plant microenvironments are created within these systems and can be manipulated to achieve desired benefits. For example, coverage of soil by plant residues in cover crop systems or minimization of soil disturbance by cultivation may inhibit germination and growth of weeds, in turn reducing the need for herbicides. However, Teasdale (1998) observed that inhibition of weeds by cover crops early in the growing season did not provide adequate control later in the season; thus, herbicides were required. The use of conservation management practices also may alter herbicide dissipation in soil
and plant residues, thereby influencing herbicide efficacy in controlling weeds. Sorption, degradation, movement in leachate or surface water, volatilization, and plant uptake are mechanisms of herbicide dissipation, and these mechanisms can be affected by management-influenced soil characteristics.
