Salinity tolerance of ornamental grasses adapted to semi-arid environments

The use of poor quality water to irrigate landscapes in arid and semi-arid regions is becoming more common due to increasing demand on water supplies and deteriorating water quality. Four grass species (Muhlenbergia lindheimeri, Helictotrichon sempervirens, Chasmanthium latifolium, and Briza media) and a sedge (Carex tumulicola) were tested for their salinity tolerance. Plants were grown in an aerated hydroponic system using a gravel matrix with a modified Hoagland solution and the addition of calcium chloride and sodium chloride. Treatment solutions had electrical conductivity (EC) of 0.9 (control), 2.5, 5.0, or 10.0 dS m^-1. Plant survival was 100% for C. tumulicola, and C. latifolium, and 94% for M. lindheimeri. Plant survival of B. media was 100, 94, 89 and 6% from lowest to highest EC treatment. Increasing salinity decreased plant height, and visual quality of M. lindheimeri, but had little effect on root length. Shoot growth and visual quality of C. tumulicola were hardly affected by increasing salinity until EC 5.0, but declined sharply at the highest salinity treatment. However, roots were longer at the 2.5 and 5.0 dS m^-1 treatments than the control. Shoot growth of C. latifolium was not affected, but root growth was greater for the two highest salinity treatments compared to the lower ones. Visual plant quality at the highest salinity level was poor. B. media was least tolerant to salinity suffering from reduced growth and unacceptable visual rating even at 2.5 dS m^-1. Plant height and root length decreased with increasing salinity, making this species unsuitable for cultivation under even slightly elevated root zone salinity. Helictotrichon sempervirens plants did not establish during both replicated studies and are possibly not suited to grow in a hydroponic system.