Irrigation scheduling strategies for horticultural field crops under limited water availability

Horticultural field crops are the main cash crops in most of irrigation projects in Tunisia. They are often cropped in rotation with cereals and fodder crops. However, very irregular precipitation and river runoff occurs, thus variable water availability for irrigation, namely very reduced water supply in drought years. These conditions require the development of irrigation scheduling strategies to minimise the water demand with low impacts on yields. The irrigation scheduling model ISAREG, validated for field crops in two locations in Tunisia, Cherfech in the North acid Hendi-Zitoun in the Center, is used for the simulation of different irrigation scheduling alternatives for tomato and potato crops in Siliana, in the Center. Alternatives are evaluated through the combined use of indicators relative to the reduction in demand for irrigation water, the soil water use, the corresponding yield reduction, and farmers income reduction. The paper presents main results for different probabilities of net irrigation demand in combination with typified water availability limitations during the crop season. A discussion on the applicability of deficit irrigation for horticultural crops is presented.