Pesticide dissipation under golf course fairway conditions

The degradation and vertical movement of pendimethalin, chlorpyrifos, isazofos, and metalaxyl were monitored in Kentucky bluegrass (Poa pratensis L.) turf managed as a golf course fairway. Intact turf-soil cores from Mead, NE, on a Sharpsburg soil (fine montmorillonitic, mesic Typic Argiudoll) and Gilbert, IA, on a Nicollet loam (fine-loamy, mixed, mesic Aquic Hapludoll) planted to Kentucky bluegrass were periodically removed to 60-cm depth through 113 d after pesticide application. Cores were sectioned into verdure, thatch, and multiple soil depths. While verdure contained high pesticide concentrations after application, precipitation, and clipping, and degradation reduced the amount in plant tissue with time. Thatch was highly retentive of the pesticides, generally containing the most residue throughout the monitoring period. Pesticide residues tended to be lower in soil at the Iowa site where more thatch was present. Little chlorpyrifos or pendimethalin moved through the thatch to the underlying soil. Isazofos was more mobile and metalaxyl moved through the entire soil column. Soil contained an average of 58% less pesticide than thatch over all sampling times, and concentrations in soil were highest at the 0- to 5- and 5- to 10-cm depths. Average time for 50% dissipation in the turf-soil profile (DT₅₀) was 16, 12, 10, and 7 d for metalaxyl, pendimethalin, chlorpyrifos, and isazofos, respectively. The pesticides appeared to degrade more rapidly in the turfgrass environment than typically reported for other agronomic cropping systems. Variability in pesticide residue concentrations for each soil depth among the turf-soil cores indicated non-uniform dissipation in the field.