Deficit irrigation of cereals and horticultural crops: simulation of strategies to cope with droughts (this issue

Different water management alternatives have been evaluated considering three crops grown in Tunisia under semi-arid conditions: potato, tomato and winter wheat. Irrigation simulations performed with the ISAREG model have demonstrated the interest of using this kind of tool in irrigation management. The economic optimization of different water supply strategies was performed with the help of a linear programming model. Results indicate that, when there is no water restriction, the optimal irrigation strategy is achieved by fulfilling the crop water demand in order to reach the potential yields, whatever the climate conditions are, and considering fixed water prices. When there is limited water availability, each crop reacts differently to the water restriction imposed. Every water supply reduction produces for every crop a decrease in the gross margin per unit surface. Under high and very high demand conditions, the gross margin per unit of water applied decreases for the potato and the tomato crops but increases for the wheat crop. So, considering an average year, the adoption of a deficit irrigation scheme is feasible for the tomato and the potato crops