Imazapyr in one of the herbicide which very effective towards alang-alang. The influence of soil constituents and soil moisture towards soil absorption of imazapyr were studied at Long Ashton research Station using 14c_imazapyr. Twelve soils with clay content from 8 to 40%, organic matter content range fro. 0.238 to 8%, pH from 4 to 8, and Fe content from 0.005 to 0,147% were used in this study. Results showed thet the higher the organic content, and Fe content and the lower the pH the greater the soil adsorption of imazapyr. In the trials using batch slurry methods with excess water, it was found that there were no soil adsorption of imazapyr and several soils showed negative adsorption phenomenon. It shows that the high soil moisture, soil adsorption of imazapyr will be negligible and the herbicide will be very mobile. It was found also that Al content could increase imazapyr adsorption in soil from Sembawa. With careful considerations of those factor involved, the adsorption of imazapyr in the soil surface can be> predicted. *Tantono Subagyo; Pusat Penelitian Perkebunan Sembawa
