Abstract

                                Persistence of oxyfluorfen in Alfisol and Vertisol was studied at three moisture levels (at saturation, FC and 50 % FC) and at two temperature levels (10+ 2 0 C and 27 + 2 0 C ) for the period of 137 days in the laboratory. Degradation of oxyfluorfen was more rapid at high temperature and moisture levels. The disappearance curve / semi logarithmic plot followed first order kinetics with two distinct pathways, an initial faster rate followed by a slower and more gradual disappearance. The rate of degradation of oxyfluorfen increased with increase in temperature from 10 0 C to 27 0 C. In the present investigation for oxyfluorfen the rate of reentry into labile pool was considered negligible. The rate of entry into bound pool was higher for Vertisol than for Alfisol and was higher at higher temperature. It decreased with soil moisture in the order: saturation > field capacity > 50% field capacity. At high temperature and moisture level, the half values were lower compared to low temperature and moisture level. Persistence of oxyfluorfen was varied by more than 30 per cent between the field studies and laboratory studies.

Key words : Oxyfluorfen, persistence, Half life values, temperature and moisture levels, alfisol, vertisol.