Dryland soils that have ECe values greater than ~8 dS/m can be described as being highly salt affected and such soils are generally too saline for major crops to produce commercial yields. The growth of plants for commercial use in these landscapes necessitates the use of halophytes. The case for this is made more compelling by the fact that many halophytes have an increase in growth with some salinity (50-200 mM NaCl) in the root zone (Greenway and Munns, 1980). Current databases list more than 1800 halo-phytes that have potential uses for man (USDA, 2009). However, in practice few of these plants have had widespread commercial adoption. One exception has been the use of saltbushes (Atriplex species) in
Australia to provide fodder for sheep (Barrett-Lennard et al., 2003). Although these plants will withstand salt concentrations of more than seawater salinity in the root zone (Aslam et al., 1986), their optimal growth in the field occurs more in the 'moderately saline' to 'highly saline' range (ECe values 4-16 dS/m; E.G. Barrett-Lennard and M. Altman, unpublished results, 2008). Recent surveys suggest that more than 245,000 ha of salinized agricultural land are now managed in farming systems based around the use of these plants (Trewin, 2002).
From the point of view of cropping, we cannot ignore the pioneering work of the late Dr Nicholas Yensen, who made a number of selections within the halophytic genus Distichlis to produce accessions suited to the production of grain, forage and turf (Yensen and Bedell, 1993). In an assessment of six lines of Distichlis grown for 18 weeks over the North American summer, three lines had growth optima at ~90 mM NaCl, but two of the lines assessed had growth optima at ~290 mM NaCl (Yensen et al., 1985). Despite the promise of this work, Yensen's Distichlis lines are still only planted on a relatively limited scale.
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