Importance of soil organic matter fractions in soil-landscape and regional assessments of pesticide sorption and leaching in soil

Agricultural policy frameworks aim to develop scientifically sound measures that can be used to assess the environmental performance and risks associated with agricultural systems. As part of this assessment, pesticide leaching models are applied at large scales to assess the risk of pesticide groundwater contamination across soil series, agricultural fields, watersheds, or regions. Measurements of pesticide sorption by soil are among the most sensitive input parameters in pesticide leaching models. Soil organic matter (SOM) is the single most important soil constituent influencing pesticide sorption in soils. The interaction of pesticides with SOM is often studied in the laboratory using batch-equilibrium experiments in combination with techniques that quantity chemical and structural characteristics of SOM. This paper reviews these laboratory studies and discusses their importance to the development of agricultural policy frameworks. This review paper was written as part of a symposium on "Meaningful pools in determining soil C and N dynamics" which was held by the SSSA and the Canadian Soil Science Society during the 2004 ASA-CSSA-SSSA International Annual Meetings in Seattle., WA.