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Effect of Soil pH on Microbial Degradation, Adsorption, and Mobility of Metribuzin

Published online by Cambridge University Press:  12 June 2017

James S. Ladlie
Affiliation:
Dep. Crop and Soil Sci., Michigan State Univ., E. Lansing, MI 48824
William F. Meggitt
Affiliation:
Dep. Crop and Soil Sci., Michigan State Univ., E. Lansing, MI 48824
Donald Penner
Affiliation:
Dep. Crop and Soil Sci., Michigan State Univ., E. Lansing, MI 48824

Abstract

Metribuzin [4-amino-6-tert-butyl-3-(methylthio-as-triazin-5(4H)one] degradation by soil microorganisms decreased as the soil pH decreased. Metribuzin and atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] mobility increased with increasing concentration and soil pH. 14C-metribuzin had greater mobility on soil thin-layer plates than 14C-atrazine because of differences in water solubility and basicity. Adsorption increased with decreasing soil pH. The pKa for metribuzin was 0.99 ± 0.08. Adsorption increased gradually as the soil pH decreased toward the pKa of metribuzin. Protonation of the amine group with subsequent adsorption to soil colloids was the postulated reason for the reduction in phytotoxicity, microbial degradation, and mobility of metribuzin at low soil pH levels.

Type
Research Article
Copyright
Copyright © 1976 by the Weed Science Society of America 

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