GROWTH AND WATER-USE OF EUCALYPT TREES IRRIGATED WITH SALINE DRAINAGEWATER

Leaf chemical composition, growth and water use of Eucalyptus camaldul ensis (Lake Albacutya provenance) were measured in the 4th year of a s plit-plot salinity by nutrition trial. The main plot consisted of irri gating with five different water salinities: 0.5 dS/m(S0.5), 2 dS/m (S 2), 5 dS/m (S5), 7.5 dS/m(S7.5) and 10 dS/m (S10). The subplot treatme nts consisted either of annual additions of 200 kg N and 100 kg P per hectare (+N+ P) or no addition of nutrients (-N-P). Irrigation with wa ter from a drainage system (treatments S2, S5, S7.5 and S10) added abo ut a further 100 kg N/ha annually. Leaf concentrations of N and P were higher in the +N +P treatments. In S0.5, nutrient addition stimulated growth. In +N +P treatments, raising the irrigation salinity from 0.5 to 2.0 dS/m increased leaf Na and decreased the growth rate, however, further increases in salinity affected neither leaf Na nor growth. In -N-P, growth rate depression due to inadequate nutrition was overcome in S2 and S5 by the 100 kg/ha of N in the drainage water. At higher s alinities, the N added by drainage water did not overcome the effect o f inadequate nutrition. On days when the reference crop evapotranspira tion (ETo) was less than 3 mm/day. the correlations between water use of trees in litres per day and ETo and between water use of trees in l itres per day and the basal area of the tree butt were highly signific ant. On days when the ETo was 3 mm/day or greater, the correlation bet ween tree water use and basal area was highly significant, but that be tween tree water use and ETo was not significant.