Evaluation and application of the OILCROP-SUN model for sunflower in southern Italy

Crop simulation models are potentially useful tools in agricultural decision-making. In Italy, few applications have been recorded, and those implemented have been mainly restricted to the estimation of crop water requirements in irrigated basins or the estimation of potential crop yields. In general, a model must be evaluated in a variety of conditions as a prerequisite for its use. The OILCROP-SUN model was first parameterised and then validated, using independent data sets coming from three southern Italian environments in which sunflower was subjected to different irrigation schedules. The validation showed the model to be effective in simulating phenology, seed yield and seasonal evapotranspiration, whereas seed weight was rather poorly simulated. The model simulated the temporal changes in soil water content, leaf area index and total dry matter reasonably well. The model application consisted in comparing spring vs. summer sowing of sunflower in the three environments and in selecting the optimal threshold value of available soil water at which to start automatic irrigation. As for the sowing dates, the spring sowing showed a higher seed yield and net return than the summer sowing. With regard to the irrigation regimes, the highest seed yield was obtained with a soil water content within the 80–100% range of available soil water, while the highest economic return was reached using a threshold value of 40% of total soil water.