Bioactivity of Atrazine in Nine Saskatchewan Soils

Bioactivity of atrazine was determined for nine Saskatchewan soils. The amount of the herbicide required to reduce the growth of shoots by 50%, GR 50 , was estimated from dose-response data, using logistic regression curves. GR 50 values varied from 0.09 μg/g for Asquith sandy loam to 1.73 μg/g for Melfort silty clay loam. Using rank correlation coefficients, it was shown that there was a significant correlation of GR 50 with soil organic matter content. In addition, when the amorphous oxides of Al and Fe were extracted with pyrophosphate, each also showed a high correlation with GR 50 .