Downward migration of metalaxyl fungicide in creeping bentgrass sand lysimeters as affected by organic waste, peat and zeolite amendments

Metalaxyl is a fungicide used for control of Pythium spp. diseases in turfgrass. The downward migration of metalaxyl was studied in irrigated lysimeters containing a fine sandy loam soil alone or sand amended with composted brewery waste, composted sewage sludge, peat or zeolite by analysis of the fungicide in leachates collected up to 65 days post application. The Arkport sandy loam soil and sand containing peat, brewery waste or sewage sludge amendments showed somewhat similar patterns of metalaxyl in collected leachates increasing from not detectable initially to peak concentrations between 14 and 21 days after first irrigation and decreasing thereafter. The peak concentrations were in the order: brewery waste > peat > sludge > Arkport sandy loam. In the lysimeter treatments containing sand amended with zeolite, the downward migration of the fungicide with time after application generally increased with the highest attained concentration in the leachate inversely proportional to the total amount of zeolite in the respective lysimeter sand profile. Only small percentages (ranging from 0.21 to 1.22) of the total applied fungicide were accounted for in the leachates. The literature is reviewed and the possible mechanisms of fungicide losses are discussed.