LEAF, STOLON AND ROOT-GROWTH OF WHITE CLOVER (TRIFOLIUM-REPENS L) IN RESPONSE TO IRRIGATION WITH SALINE WATER

The effect of irrigation with water at salinity concentrations of 2.6 and 5.2 dS m-1 on the growth of pure swards of six cultivars of white clover (Trifolium repens L.) was examined over three irrigation season s at Tatura, Victoria, Australia. After two irrigation seasons, soil E C(e) levels increased to 6 dS m-1 at 0-60 cm depth in the higher salin ity treatment resulting in highly significant (p<0.001) reductions in shoot dry matter production, flowering densities and petiole and stolo n densities. These saline conditions also increased (p<0.001) concentr ations of Cl and Na in the shoots and reduced (p<0.001) leaf water pot entials and canopy photosynthetic efficiency rates especially at high temperatures. In contrast, root growth increased at shallow depths (0- 15 cm) under both saline irrigation treatments (p<0.001). Cultivars di ffered significantly in salt tolerance (p<0.001), with cultivars Haifa and Irrigation exhibiting superior tolerance in terms of lower reduct ions in herbage yield (p<0.05) and petiole densities (p<0.001) during one irrigation season and lower concentrations of Na and Cl in the sho ots (p<0.05) compared with the other four cultivars (Aran, Kopu, Pitau and Tamar). In addition, canopy photosynthetic efficiency rates (A) in plots irrigated with water at 5.2 dS m-1 were higher in cultivar Ha ifa compared with cultivar Tamar (p<0.05). The salt tolerance ranking obtained for the six cultivars was in broad agreement with earlier gre enhouse studies. Consequently, it appears that, while white clover is an extremely salt-sensitive species, it is possible to grow cultivars which display greater salt tolerance than other cultivars and which pr ovide some scope to increase, or at least to maintain, pasture yields in areas where the soil salinity is low to moderate or where pumped sa line groundwater is re-used for irrigation.