Cyclic irrigation with salt water and desalinated water

Several strategies have been adopted to allow the use of salt water with a minimum of damage. In the Tunisian south and to produce cherry tomatoes mainly for export, salt water is mixed with desalinated water by the reverse osmosis technique using electrical energy. In the irrigated perimeter of Tunisian Cap Bon, an expensive transfer of surface water over a distance of about 100 km is made to save this perimeter threatened by marine intrusion. The simultaneous use of abundant salt water and scarce fresh water in irrigation requires special strategies of type (i) Mixing between fresh water and salt water but in well determined proportions. Mixing tanks are required, which is an additional cost to the farmer (i) Alternating fresh and salt water inputs (or cyclic irrigation) but it is necessary to maintain an acceptable salinity in the soil. Cyclic irrigation is well suited to the case where fresh water is produced by solar desalination. The longer the irrigation period, the higher the salinity thresholds observed in the soil.