Effects of exponential nutrient-loading on morphological and nitrogen characteristics and on after-planting performance of Eucalyptus globulus seedlings

Exponential nutrient-loading (50 mg N seedling−1) and conventional (25 mg nitrogen [N] seedling−1) fertilizer application regimes at Jayfields nursery (New South Wales, Australia) were investigated as potential ways of attaining a specified foliar nitrogen (N) concentration of 15-20 g kg−1 in Eucalyptus globulus seedlings at planting. Foliar N concentration, specific leaf area (SLA) and % dry matter (DM) were assessed during the nursery production phase. Foliar N, SLA and % DM were similar at 6, 8, 10 and 12 weeks after germination in the nursery. However, at age 16 weeks after germination (immediately prior to planting), foliar N and SLA were higher, and % DM lower, in exponential nutrient-loaded seedlings than conventionally fertilized seedlings. After-planting height and biomass accumulation of seedlings raised under exponential nutrient-loading and conventional fertilization regimes were investigated at three trials typical of the range of sites established with E. globulus plantations, in the 'Green Triangle' region (northwest Vic., Australia). Although seedling heights were not significantly different between nursery treatments at all sites, biomass was 1.5- to 2-fold greater in exponential nutrient-loaded seedlings than conventionally fertilized seedlings. Application of N greater than the conventional 25 mg seedling−1 is required to attain the specification of 15-20 g kg−1 foliar N concentration at Jayfields nursery, thereby maximising after-planting performance in the Green Triangle.