Biomass, Nutrient Content and Growth Response to Fertilisers of Six-year-old Eucalyptus globulus Plantations at Three Contrasting Sites in Gippsland, Victoria

Abstract

Factorial combinations of three rates of N (up to 400 kg ha^-1 elemental) and four rates of P (up to 200 kg ha^-1) were applied during the establishment phase of Eucalyptus globulus Labill. plantations on three contrasting sites in Gippsland, south-eastern Australia. Mean annual increments of volume at 71 months ranged from 8 m³ ha^-1 year^-1 in control treatments on a duplex sandy loam (annual rainfall 850 mm) and a uniform sand (620 mm rainfall) to 23 m³ ha^-1 year^-1 at the highest combined additions of N and P on a gradational clay loam (1000 mm rainfall). Volumes to 71 months were greatest at the highest combined additions of N and P on the uniform and gradational soils, but significant effects of N and P additions were not sustained on the duplex soil, where the availability of K was limiting after 45 months. Trees were sampled for above-ground biomass and nutrient content at 6 years from four treatments involving the highest additions of N and P and treatment responses were interpreted using vector analysis. The greater magnitude of P vectors than N vectors at all sites indicated that P additions, in particular, were important for good early growth. However, relationships between above-ground biomass and P content indicated accumulation of P in excess of growth requirements and reduced efficiency of P additions at the highest rates. The paper concludes with general recommendations for fertiliser additions during the establishment phase of E. globulus plantations.