Effect of pH on Metribuzin Activity in the Soil

Abstract
Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] applied preemergence resulted in increased phytotoxicity with increasing soil pH. In the field, fall panicum (Panicum dichotomiflorumMichx.) control, number of dead corn (Zea maysL.) and soybean [Glycine max(L.) Merr.] plants, and crop injury ratings increased, and plant height and grain yield decreased as the soil pH increased. In the greenhouse, corn and soybean grown in soil showed decreased dry weights due to metribuzin as pH increased. By contrast, the pH response to metribuzin was not evident in nutrient-sand culture, indicating that, in soil, pH affected the availability of metribuzin for plant absorption.