Evaluation of water movement and nitrate dynamics in a lysimeter planted with an orange tree

Adoption of high input irrigation management systems for South Australian horticultural crops seeks to provide greater control over timing of irrigation and fertilizer applications. The HYDRUS 2D/3D model was used to simulate water movement in the soil under an orange tree planted in a field lysimeter supplied with 68.6 mm of irrigation water over 29 days. Simulated volumetric water contents statistically matched those measured using a capacitance soil water probe. Statistical measures (MAE, RMSE, tcal) indicating the correspondence between measured and simulated moisture content were within the acceptable range. The modelling efficiency (E) and the relative efficiency (RE) were in the satisfactory range, except RE at day 19. Simulated daily and cumulative drainage fluxes also matched measured values well. Cumulative drainage flux was 48.9% of applied water, indicating large water losses even under controlled water applications. High drainage losses were due to light texture of the soil and high rainfall (70 mm) during the experimental period. Simulated root water uptake was 40% of applied water.