Coating nursery containers with copper carbonate improves root morphology of five native Australian tree species used in agroforestry systems

Seedlings of the native Australian tree species Acacia holosericea, Casuarina cunninghamiana, Eucalyptus argophloia, E. camaldulensis and Melaleuca bracteata, were raised in nursery containers which were coated with CuCO^sub 3^ (50 g l^sup -1^, in a water-based paint solution) or left uncoated for three months. Seedling growth of all species in the nursery was generally less in treated containers, although differences were relatively small. More importantly, CuCO^sub 3^ treatment reduced the occurrence of lateral roots growing down or coiling around container walls for both three- and six-month-old seedlings. Twenty-four months after planting both three- and six-month-old seedlings on a semiarid site in subtropical southeast Queensland, there was no effect of CuCO^sub 3^ treatment on height or basal diameter development of seedlings. However, sample excavations of root systems showed that the poor root morphology exhibited by untreated seedlings when in the nursery had persisted in the field. As such poor root form has the potential to reduce tree growth and wind firmness in the longer term, these results suggest that chemical root-pruning is a helpful nursery practice when raising seedlings for dryland afforestation, and in circumstances where it may be necessary to retain seedlings in the nursery for longer than normal to take advantage of infrequent rainfall events.[PUBLICATION ABSTRACT]