COPPER DEFICIENCY A PROBABLE CAUSE OF STEM DEFORMITY IN FERTILIZED EUCALYPTUS-NITENS

Serious malformation of tree stems and branches was first observed 17 months after planting Eucalyptus nitens (Deane & Maiden) Maiden trees on an improved pasture site in southern Tasmania. The trees were planted in a 5(2) factorial fertiliser trial with application of nitrogen at 0, 60, 120, 240, and 480 kg/ha and phosphorus at 0, 30, 60, 120, and 240 kg/ha. The phosphorus was semibroadcast as a single dose just after planting in September 1990 and the nitrogen was applied over a 2-year period from planting. At 21 months of age, the degree of malformation increased significantly with increasing levels of nitrogen or phosphorus fertilisers and was most severe at the highest levels of application. There was a significant linear trend of decreasing diameter growth with increasing levels of phosphorus fertiliser. The concentration of Cu in the foliage was significantly lower in malformed than unaffected trees whilst other macro- and micro-nutrient foliar levels were within the normal range for healthy individuals. Whilst the symptoms appear similar to those of ''Toorour syndrome'' previously reported for Pinus radiata D. Don on improved pasture sites in Australia, we believe the present symptoms may result from Cu deficiency induced at high fertiliser levels. The deformations substantially reduce the merchantability of trees from the plantation.