Pedotransfer functions for isoproturon sorption on soils and vadose zone materials

BACKGROUND: Sorption coefficients (the linear K_D or the non‐linear K_F and N_F) are critical parameters in models of pesticide transport to groundwater or surface water. In this work, a dataset of isoproturon sorption coefficients and corresponding soil properties (264 K_D and 55 K_F) was compiled, and pedotransfer functions were built for predicting isoproturon sorption in soils and vadose zone materials. These were benchmarked against various other prediction methods. RESULTS: The results show that the organic carbon content (OC) and pH are the two main soil properties influencing isoproturon K_D. The pedotransfer function is K_D = 1.7822 + 0.0162 OC^1.5 ? 0.1958 pH (K_D in L kg^?1 and OC in g kg^?1). For low‐OC soils (OC < 6.15 g kg^?1), clay and pH are most influential. The pedotransfer function is then K_D = 0.9980 + 0.0002 clay ? 0.0990 pH (clay in g kg^?1). Benchmarking K_D estimations showed that functions calibrated on more specific subsets of the data perform better on these subsets than functions calibrated on larger subsets. CONCLUSION: Predicting isoproturon sorption in soils in unsampled locations should rely, whenever possible, and by order of preference, on (a) site‐ or soil‐specific pedotransfer functions, (b) pedotransfer functions calibrated on a large dataset, (c) K_OC values calculated on a large dataset or (d) K_OC values taken from existing pesticide properties databases. Copyright © 2011 Society of Chemical Industry