RUNOFF LOSSES OF SURFACE-APPLIED METRIBUZIN AS INFLUENCED BY YARD WASTE COMPOST AMENDMENTS, NO-TILLAGE, AND CONVENTIONAL-TILLAGE

Soil erosion has been shown to result in decreased crop yields and red uced agricultural sustainability (Mississippi Agriculture and Forestry Experiment Station Technical Bulletin, 1989; Littleboy et al., 1992; and Craft et al., 1992). To address the problems associated with soil erosion, Congress passed the Food Security Act in 1985. To comply with this law, farmers must implement conservation plans on highly erodibl e land to ''significantly reduce'' erosion rates. One widely used meth od of soil conservation is no-tillage agriculture. But water runoff is reduced under conservation tillage and infiltration increases, possib ly resulting in more pesticide movement through the unsaturated zone i nto the groundwater (Gish et al., 1991 and Donigian and Carsel, 1987). Most research suggests that pesticide sorption to soil is primarily a function of pesticide partitioning into the soil organic matter rathe r than adsorption into the total soil mass (Karickoff et al., 1979). T he addition of commercially composted yard waste when mixed with soil to increase the organic carbon content and adding to soil surface to r educe erosion and water runoff may reduce pesticide loading to groundw ater compared to no-till. Surface applied organic mulches in general h ave been shown to reduce soil erosion (Adams, 1966; Kramer and Meyer, 1969; and Vleeschauwer et al., 1978). Yard waste compost in particular has been shown to reduce erosion when surface applied (Ettlin and Ste wart, 1993). Since beneficial uses are needed for yard waste compost ( BioCycle Guide to Yard Waste Composting, 1989a and 1989b), adding comp ost to high value horticultural fields should provide a beneficial use for an ever increasing waste product. Research comparing pesticide ru noff in no-till versus conventional-till have been mixed. Kenimer et a l. (1987) concluded that no-till may reduce pesticide loading to surfa ce water while Sauer and Daniel (1987) reported no significant differe nces. Both reported that any reduction in pesticide runoff is due to r educed water runoff (pesticide runoff concentration was found to be la rger in no-till). A compost amended soil should also show the benefit of reduced runoff compared to conventional-till and may show reduced p esticide runoff concentration compared to no-till due to pesticide sor ption to organic carbon. Metribuzin thylethyl)-3-(methylthio)-1,2,4-tr iazin-5(4H)-one] has the potential to be transported into the environm ent(USEPA, 1992, exhibit 4-1 and USEPA, 1985) and it is used to contro l broadleaf weeds in tomato production (University of Kentucky Coopera tive Extension Service, 1992). The use of yard waste compost to reduce erosion will be beneficial in horticulture due to the value and scale of production. The objectives of this research were to study the infl uence of three soil treatments: 1) yard waste compost amended soil wit h compost added to soil surface after rototilling, CA; 2) no-till, NT and; 3) conventional-till, CT on metribuzin concentration and loading to surface water via runoff and in sediment