Marginal Water Productivity of Irrigated Durum Wheat in Semi-Arid Tunisia

This paper aims to estimate water productivity and marginal value of irrigation of durum wheat in central Tunisia. The authors develop a production function, in which the durum wheat irrigation revenue of farmers per hectare is expressed in terms of the used water volume in addition to other production factors. The function was estimated for a sample of durum wheat farms from Central Tunisia. The results show that 31.7% of the farmers were applying water volumes above the economic optimal volume. Applying water above the optimal volume means that the benefit farmers obtain from each supplementary unit of irrigation water is lower than the market price of irrigation water currently applied in the region. Then, water is wasted. The study also shows that most of the farmers in the study area do not apply good practices with respect to irrigation scheduling and irrigation doses. Improving irrigation performance will largely preserve water resources and enhance food security in Tunisia.