| dc.description | Once pesticides reach the soil, there are several factors that affect their soil behavior. To identify
the principal soil and herbicide properties that control their adsorption and leaching, a study
of five Chilean agricultural and forest soils was performed. Simazine, diuron, terbuthylazine
and MCPA were applied to the top of 45-cm tall by 12-cm diameter disturbed soil columns,
filled with either an Andisol, Ultisol, Entisol or one of two Inceptisol soils. After herbicide
applications, each lysimeter received 24 mm of simulated rain every 24 hours for five days.
Once water percolation stopped, the lysimeters were divided into five sections and herbicide
concentrations were quantified using High Pressure Liquid Chromatography. Relationships
between soil physicochemical properties, herbicide sorption (adsorption and desorption) and
herbicide leaching were determined. All herbicides exhibited the least depth reached from the
Andisol soil (10 cm) and the highest from the Ultisol soil (45 cm). The principal soil property
that affected herbicide adsorption was the soil organic carbon content, specifically the fulvic
acid-humins fraction. Soil leaching was related to the inverse of soil adsorption (1/Kd), cation
exchange capacity, humic substances content and herbicide pKa. These results suggest that
it is possible to develop simple quantitative models to predict the soil-leaching properties of
pesticides. | |
