INCREASING SALINITY TOLERANCE OF GRAIN CROPS - IS IT WORTHWHILE

The productivity of wheat and barley was compared in soils of different salt concentrations with a limited water supply. Productivity was assessed as total dry weight or dry weight per unit of water used (water use efficiency, WUE). Barley achieved the highest productivity because it used more of the available water and it had a greater WUE for above-ground dry weight. However, when WUE for total organic weight of roots and shoots was determined, or WUE was corrected for grain production, wheat and barley had the same productivity. In two experiments in drying soils with different salt concentrations but the same amount of soil water, wheat and barley had a higher dry weight than salt-tolerant grasses and they were more productive than C4 halophytes and non-halophytes when adjusted for water use. In one experiment, sown at a low plant density, barley and wheat used less water than some halophytes and they completed their life cycle leaving some water behind in the soil. Their higher WUE did not compensate for their lower water use. However, when all species were sown at a high density, wheat and barley were either as productive or more productive than the most salt-tolerant species, including a C4 halophyte, as they used all the available water and had the highest WUE. A sunflower cultivar was similarly more productive than a salt-tolerant relative. The contribution that salt-tolerant relatives of wheat, barley and sunflower can make to genetically improving the productivity of these species in dry saline soils is questioned.