An investigation of localised soil heterogeneities on solute transport using a multisegment percolation system

A multisegment percolation system (MSPS) consisting of 25 individual collec tion wells was constructed to study the effects of localised soil heterogen eities on the transport of solutes in the vadose zone. In particular, this paper discusses the transport of water and nutrients (NO3-, Cl-, PO43-) thr ough structurally stable, free-draining agricultural soil from Victoria, Au stralia. A solution of nutrients was irrigated onto the surface of a large undisturbed soil core over a 12-h period. This was followed by a continuous irrigation of distilled water at a fate which did not cause pending for a further 18 days. During this time, the volume of leachate and the concentra tion of nutrients in the leachate of each well were measured. Very signific ant variation in drainage patterns across a small spatial scale was observe d. Leaching of nitrate-nitrogen and chloride from the core occurred two day s after initial application. However, less than 1% of the total applied pho sphate-phosphorus leached from the soil during the 18-day experiment, indic ating strong adsorption. Our experiments indicate considerable heterogeneit y in water flow patterns and solute leaching on a small spatial scale. Thes e results have significant ramifications for modelling solute transport and predicting nutrient loadings on a larger scale.