Estimating phosphorus leachability in reconstructed soil columns using HYDRUS-1D model

Modern agricultural production uses phosphorus (P) extensively to meet the challenges of feeding rapidly growing population and changing lifestyles, making P a leading source of impairment for rivers and streams in Canada. Developing effective management strategies to reduce P losses from agro-ecosystems requires improved understanding of P transport pathways in the soil. The purpose of this study was to investigate vertical distribution and transport processes of phosphate (PO4) in reconstructed soil columns using HYDRUS-1D model. Results obtained from field experiments were used to calibrate and validate the HYDRUS-1D model. The results showed that 98% of the total P applied was concentrated in the top 0.2 m of the columns, and decreased progressively with soil depth. The model over-predicted PO4 adsorption, leading to a weak correspondence between the simulated and the measured results for PO4. This is a suggestion that the HYDRUS-1D model could not account accurately for the different soil structures found in the undisturbed soil columns and the preferential flow that occurs in these columns. This may be due to the fact that Freundlich isotherm, which is part of the transport equations, could not adequately describe PO4 adsorption onto the soil particles.