Abstract
Adsorption of chlorotoluron by straw ash is related to its carbon content. The ash has a high adsorptive capacity immediately after straw burning but this rapidly declines. The decline is probably due to leaching of an acid organic fraction from the ash. However, the reduced adsorption capacity is still sufficient to account for increases in chlorotoluron adsorption on sites where zero or minimum tillage leaves the ash at or near the surface of the soil.