EFFECTS OF STOCK PLANT AGE AND FERTILISER APPLICATION AT PLANTING ON GROWTH AND FORM OF CLONAL ACACIA HYBRID

Some Acacia hybrid plantations in Vietnam are prone to heavy branching and poor stem form. The age of the stock plants used to produce cuttings for clonal propagation and/or high rates of fertiliser application at planting have been suggested as causal factors. Their effects on growth, stem form and branch size of three Acacia hybrid clones were examined in south Vietnam. Experimental treatments were: fertiliser: F-0 (no fertiliser) and F-H (high fertiliser, i.e. a mix of superphosphate and NPK (nitrogen-phosphorus-potassium) fertiliser in the planting hole at rates equivalent to 16, 45 and 8 g tree-1 of N, P and K respectively) and planting stock raised from cuttings taken from stock plants aged 1 and 4 years. Stock plant age had no effect on growth and form traits, nor were there differences between clones. Fertiliser increased growth during the first three years, but by age 4 years, had no significant effect on stem diameter or stand volume.