Gross water requirement (IRg) for each plot was controlled by the special valve set for that plot, and the exact amounts used were read on a flow meter. The net irrigation requirement (IRn) must replenish the actual crop evapotranspiration water (ETa), as rainfall and other components of the water balance. The gross irrigation requirements (IRg) must increase the (IRn), in order to compensate the irrigation efficiency and to leach salts: