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

  •  Iheb Frija    
  •  Aymen Frija    
  •  Ali Chebil    
  •  Hatem Cheikh M’Hamed    
  •  Stijn Speelman    
  •  Mariem Makhlouf    


Recent studies on agricultural water management in Tunisia report low water productivity for some of the currently widely cultivated crops such as durum wheat. The objective of this study is to estimate water productivity and marginal value of irrigation of durum wheat in central Tunisia. We 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. Results show that 31.7% of the farmers were applying water volumes above the economic optimal volume (more than 2700 m3/ha). Moreover, 50% of the farmers were found to be applying less irrigation water than this 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 (0.110 TND/m3). Then, water is wasted. However, using less water than the optimal volume means that farmers can make further supplementary irrigations and obtain more benefit from it (extra-yield). 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.

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