Spatial heterogeneity of soil properties to predict pesticide movement

Abstract

Agricultural pesticides affect the water quality of surface water runoff and need to be carefully managed. Soil properties have a strong effect on off-site migration of agricultural pesticides. Among the different factors that dictate the off-site migration of pesticides, soil organic carbon content plays a crucial role. Although soil conditions are known to vary strongly within the landscape, little systematic research exists on how heterogeneity might affect the sensitivity of the ecosystem to pesticide application. Critical zones with low soil organic carbon may release an over proportional amount of pesticides into the waterways and hence may require different management rules. In order to understand topographic attributes and its relationship to various soil properties, most importantly, soil organic carbon, we conducted a study into the spatial heterogeneity of some soil physical and chemical properties in a small catchment in the Adelaide Hills, South Australia. Around 200 soil samples were taken and various topographic variables such as gradient, slope and curvature were analysed for their predictive capability of soil conditions. Implications for managing pesticide applications will be discussed.