DECOMPOSITION AND MOVEMENT OF HERBICIDES IN SOILS, AND EFFECTS ON SOIL MICROBIOLOGICAL ACTIVITY AND SUBSEQUENT CROP GROWTH

Abstract

Experiments were conducted to determine the residual effect of sulphuric acid, copper sulphate, sodium chlorate, barium chlorate and sodium dichromate on three typical Alberta soils. No problem of residual effect was found with the two leaf sprays, sulphuric acid and copper sulphate. Sodium chlorate will remain toxic over a period of about two years, depending mainly on the organic matter content of the soil and the amount of leaching that takes place. The distance that the chlorate will leach down into the subsoil will depend on the amount of rainfall and the character of the soil. As soon as the chlorate is leached out or is reduced the soil returns to its normal productive power. Sodium dichromate decomposes very rapidly in the soil. It has a depressing effect on nitrification and on the activity of the soil micro-organisms. However, there is practically no residual effect from the use of sodium dichromate on soils of medium to high organic matter content.