Losses of Atrazine in Runoff Water and Soil Sediment

Atrazine losses in runoff water and soil sediment were determined in 1967 and 1968 after seven rates (0, 0.6, 1.1, 2.2, 4.5, 6.7, and 9.0 kg/ha) of atrazine were applied pre‐emergent to corn (Zea mays L.) seeded on field plots of Hagerstown silty clay loam (14% slope). Average losses for all rates in 1967 in runoff water and soil sediment equaled 2.4% and 0.16% of the total applied, respectively. In 1967, at the recommended rate (2.2 kg/ha) for pre‐emergence applications to Pennsylvania soils, composite losses were 2.5% of the applied or approximately 0.05 kg/ha. In 1968, one year after atrazine application, the average loss over all rates for the combined substrates was 0.01%. Analyses of soil core samples taken from all plots in 1967 revealed that 1 month after atrazine application an average of 67.9% remained in the soil, and 3 months later recoveries had decreased to 21.4% of that applied. The following year atrazine remaining in the soil had decreased to 15.9% in April and to 5.4% in September. At the recommended rate of application, recoveries decreased from 39% of that applied to 9% for the same time period in 1967. In 1969, typical atrazine toxicity symptoms were found in oats growing on plots which had received 6.7 and 9.0 kg/ha of atrazine in 1967. Damage was confined to the uppermost parts of the slope on these treatments.