The adsorption of atraton and monuron by soils at different water contents

Estimates of adsorption by soil at water contents down to less than wilting point were obtained with a three phase system of soil-water-immiscible organic solvent. The method is restricted to solutes with a water-organic solvent partition ratio of between about 10 and 0.5 if analytical errors are to be acceptable. With the two soils used the results with atraton and monuron were similar. There was little change in adsorption as soil water content was reduced until the level approached that needed to produce a monolayer on the soil surfaces, when it increased sharply. There were no differences at water contents between field capacity and wilting point.