Influence of soil properties, temperature and pH on adsorption-desorption of imazamox on Indian aridisols

As adsorption-desorption behaviour of herbicide plays an important role in determining leachability, release rate and availability to target species, the present study aims to evaluate the influence of soil properties, temperature and ionic state of imazamox on its adsorption-desorption behaviour. The sorption was significantly influenced by above evaluated parameters and Freundlich adsorption coefficient varied from 0.24 x 10(3) to 7.60 x 10(3) mg(1-1/n) kg(-1) L-1/n. In soils with pH in the range of 6.4-9.5, sorption of imazamox decreased with increase in solution pH while in acidic soil (pH 2.3 to 5.9), adsorption increased with increase in solution pH. At low solution pH adsorption occurs mainly through cationic form while at high solution pH adsorption was predominantly through anionic form. The presence of electrostatic attractive and repulsive forces, Pi ->Pi charge transfer, hydrogen bonding and van der waals forces was key mechanism affecting the adsorption of imazamox. Greater adsorption hysteresis was observed in soils having pH in the range of 6.2-9.5 suggesting relatively less adsorption and difficult desorption of imazamox in these soils. Due to irreversible binding in high pH soil, it can be speculated that it may enhance the chances of crop injury in these soils.