Calibration and validation of the SWB model for sunflower (<i>Helianthus annuus</i> L.)

Abstract

The Soil Water Balance (SWB) generic crop growth and irrigation scheduling model was used to simulate the crop growth and soil water balance of sunflower (Helianthus annuus L. c v. CAR 1199 and SO 306) grown at Rietrivier. The objectives were to determine crop specific growth parameters for sunflower and to calibrate and validate the SWB model so that irrigation of this crop can be scheduled mechanistically and accurately. A database of growth parameters for sunflower was generated using international literature data or by estimation and included in SWB. Detailed weather, soil and irrigation data from the field trial were then used to calibrate and validate the crop growth and soil water balance subroutines of the model. Simulations of crop growth and soil water deficit to field capacity were inside, or marginally outside the reliability criteria imposed. Deficit irrigation strategies can be simulated reasonably well with the mechanistic SWB crop growth model. The performance of SWB should, however, be tested with independent data sets and for a wider range of yields, cultivars and ecotopes.