Calibration and Validation of Daisy Model for Sunflower under Partial Root-Zone Drying

Due to the increased water consumption and the depletion of water resources, deficit irrigation is an optimal strategy for cultivation, which is usually applied by utilizing the methods of Deficit Irrigation (DI), Regulated Deficit Irrigation (PRD), and Partial Root-zone Drying Irrigation (PRD). In the PRD method, just one side of the plant is irrigated in each irrigation interval. Under these conditions, in the part of the irrigated plant, the roots absorb enough water and grow, so that there is no change in the amount of the plan’s photosynthesis. There are some models, including WOFOST (Van Diepen et al., 1989; Boogaard et al., 1998), EPIC (Jones et al., 1991), AquoCrop (Steduto et al., 2009), and STICS (Brisson et al., 2003), that can simulate crop yield under different soil conditions, Climates, irrigation schedule, and agricultural managements (Hashemi et al., 2018). These models simulate PRD irrigation, such as the DI method. Daisy is the first model, differentiating the gained results between the two methods (Hansen et al., 1990; Hansen et al., 1991); a semi-experimental model that considers the Richards equation (Richards, 1931) to simulate the soil water content and the experimental equations to simulate crop yield parameters. The PRD sub-model in the Daisy was developed and upgraded based on the data gained from potato cultivation under PRD irrigation (Liu et al., 2008; Plauborg et al., 2010). Since this sub-model was developed only for the potato, the aim of the present study was calibration and validation of two parameters; stomatal slop factor (m) and specific leaf weight modifier (LeafAIMod) in the PRD sub-model, to run the Daisy model to simulate sunflower under the PRD irrigation.