Pruning of Acacia salicina trees irrigated with runoff water in arid zones

In arid and semi arid lands, forest and agricultural productions are declining due to water scarcity and drought. The objective of this study was to determine the effects of shoot pruning at different heights of acacia salicina lindl, grown in the Israeli Negev Desert and irrigated with runoff water. The specific objectives of this study were to examine the most appropriate pruning height, growth rate and biomass production, water use efficiency of A. salicina shrubs irrigated with floodwater and the water uptake rate and soil water content change at the different pruning height treatments. The trees were planted in 1993 in a 0.5 ha plot at a design of 1m between trees within the rows and 4 m between rows (1,250 trees ha-1). The trees were pruned at a height of 0.5m, 1.0m and 2.0m above soil surface and were compared to non-pruned trees (NP treatment, served as control treatment). Measurements of trunk diameter at a height of 0,3 m above soil surface, re-growth of new branches and soil water uptake by trees, using a neutron moisture gauge that has been previously calibrated in the field), were take every two weeks. Three pruning were carried out during the two years of the experiment. The first pruning was at the beginning of the experiment in March 2003, the second one in December 2003 and the third one in October 2004. Biomass measurements were taken after the second and the third pruning. A non-destructive biomass evaluation was carried out to the NP treatment by using a linear regression of cross Sectional Area (CSA) of trunk versus biomass yield developed from an adjacent plot of A. salicina of the same age. The results of the experiment indicate that more biomass was obtained from the 2,0 m pruning treatment followed by the 1,0 m. Water Use Efficiency had the same pattern. Under the condition of this experiment, the most appropriate pruning height for A salicina trees irrigated with floodwater is 2, 0 m