Predicting soil water, tile drainage, and runoff in a mole-tile drained soil

Abstract There has been considerable intensification of agriculture on mole‐tile drained soils in New Zealand. Management techniques and tools are needed for predicting and understanding water and nutrient transport. While simple water balance models have been effective in estimating soil water deficit, such models cannot differentiate between the different water loss mechanisms. More complex water‐transport models include the ability to predict the flow of water and nutrients through mole‐tile drainage systems but none have yet been applied, or tested, under New Zealand conditions. Here we test such a model against existing data. The simulation model APSIM was used to estimate soil water extraction by pasture, slow drainage through the fragipan, mole‐tile drainage, surface runoff, and evaporation from the soil surface of the Tokomaru silt loam. Soil hydraulic properties were derived from the literature. Comparison was made against previously published data on soil water deficit, tile drainage, and surfac...