Testing and Application of the AquaCrop Model for Wheat Production Under Different Field Management Conditions in South-Eastern Australia

A field experiment involving two spring wheat varieties (EGA Gregory and Livingston) was conducted for 2 years (2013 and 2014), late sown in the first year and early sown in the second year, under two soil water regimes (rainfed and supplemental irrigation) at Wagga Wagga, Australia. The FAO’s AquaCrop model version 4.0 was calibrated and validated for crop canopy cover, dry aboveground biomass, soil water content and grain yield. The root-mean-square error (RMSE) for grain yield and dry aboveground biomass was 0.293 and 2.2 t ha−1, respectively. The RMSE for the rootzone soil water content was 25 mm. The validated model was used to analyse the effect of in-season and off-season conditions on grain yield and water productivity. Grain yield and water productivity decreased (50% for Gregory and 43% for Livingston) with the delay in sowing date. Applying four irrigations to the mid-May sown wheat resulted in a higher (6.5, 5.7 and 5.2 t ha−1, respectively, at 80% exceedance probability) yield relative to the mid-April and mid-June sowing dates. Applying supplemental irrigation both in September and October resulted in a better yield (6.7 vs. 6.0 t ha−1) and water productivity than applying irrigation only in October. The effect of off-season managements such as mulch and pre-irrigation on yield is 68% higher in low-rainfall years that that of in the wet years.