Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Early growth responses to Acacia melanoxylon to superphosphate, lime and boron.

Abstract

Three replicated trials were established on a silt loam soil in Canterbury, New Zealand, to evaluate the effect of post-establishment fertilizing of Tasmanian blackwood (Acacia melanoxylon). The site was relatively poor in N, P, S and B and had a low soil pH as indicated by plant leaf analysis, soil analysis and published soil type data. The location has a substantial water deficit over the summer. The environment was a relatively harsh one for blackwood growth with height increments averaging between 0.5 and 0.7 m per year. For these trials, blackwood was planted in August 1988 as container grown stock, with a nurse crop (established 1 yr previously) of Eucalyptus camaldulensis in rows on either side of the blackwood rows. Weeds were controlled by spraying 1 m2 round each tree with terbuthylazine in the spring of 1988-90. Grass cover was reduced thereafter by grazing with sheep from October 1991, and with cattle beginning in August 1992, until July 1993. Pruning was done to 1.5 m for blackwood and 2 m for eucalypts before cattle grazing. Blackwood seedlings were fertilized in spring 1989 with 200 g superphosphate. The 3 subsequent treatments were (1) boron in combination with other nutrients (including superphosphate) in June 1990, (2) superphosphate with or without lime in August 1990, and (3) superphosphate and lime interactions at different dosages in April 1992. Growth measurements were made to April 1994. Superphosphate fertilizing led to a reduction in stem diameter increment of up to 30%. Height growth was relatively unaffected. Lime and boron had no consistent effect. It is suggested that superphosphate fertilizing may have stimulated growth of surrounding vegetation, thus leading to increased competition for other limiting resources, particularly water.