| Abstract: | The adsorption of glyphosate in a slurry system by 9 soils was correlated with an arbitrary single point inorganic phosphate sorption index which gave a measure of unoccupied phosphate sorption capacity, but not with total phosphate sorption capacity at pH 2.6, the level of iron and aluminium soluble in Tamm's acid oxalate or with clay content, organic matter content or pH. It is concluded that inorganic phosphate excludes glyphosate from sorption sites. The extent of adsorption was higher than, though of the same order as, that of diuron though the two are not related. From consideration of the results of previous experiments with plants grown in culture solution it is suggested that the low phytotoxicity of glyphosate applied to the soil is not due simply to high adsorption. Rather it is the result of a combination of moderate adsorption and the low intrinsic activity of this compound when made available to the root system. |
