PERSISTENCE OF 2,4,5-T IN A HEAVY CLAY SOIL

The persistence of the herbicide 2,4,5‐T was studied at different controlled temperatures and moisture levels in Regina heavy clay. Degradation approximated to first‐order kinetics and the half‐life varied from about 4 days at 35°C and 34% soil moisture to about 60 days at 10°C and 20% soil moisture. The laboratory data were used in conjunction with the appropriate measurements of surface soil temperature and moisture content in the field to simulate the degradation pattern for the herbicide in five separate micro‐plot experiments. Satisfactory agreement with the observed patterns of loss was obtained in two of the experiments but in the other three, the model over‐estimated rates of loss. It is suggested that the reason for this was the difficulty of obtaining a correct measure of soil moisture content to use in the simulation program. Copyright © 1979 John Wiley & Sons, Ltd