Transformation of organic wastes in soil: effect on bentazone behaviour.

The aim of this study was to evaluate the impact of two organic wastes from olive oil production on the fate of bentazone in soil, and to assess the influence of the transformation of organic matter from these wastes under field conditions. Results on freshly laboratory-amended soils were compared to those with soils amended in the field for nine consecutive years. Two amendments and two doses were studied. Sorption of bentazone increased upon amendment with Kd values from 0.03 to 1.7. The increase was higher for freshly amended soils than for the field amended soils and for the higher dose. Degradation was correlated with sorption in the case of field amended soils, whereas higher persistence in freshly amended soils may be related to the easier microbial availability of DOC molecules than bentazone molecules. The increase in non-conducting pores in amended soils favours sorption and degradation processes reducing leaching. Important differences revealed in herbicide fate between freshly amended soils and aged field amended soils limit further extrapolation of laboratory studies to field studies.