The effects of fertilizers on early growth and foliar nutrient concentrations of three plantation eucalypts on high quality sites in Gippsland, southeastern Australia

Fertilizer trials of a standard design were established in experimental plantations of Eucalyptus regnans, Eucalyptus nitens and Eucalyptus globulus on sites of high potential productivity in Gippsland, southeastern Australia. The design involved 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)) with four additional treatments including K and trace elements. Treatments were complete after up to four applications at 2, 9, 14 and 26 months post-planting. P additions significantly increased foliar P concentrations and growth of E. regnans to 45 months but poor survival and competition from woody weeds limited growth responses to treatments. Foliar concentrations of N and P in E. nitens and E. globulus at age 1 year were significantly increased by N and P additions and were positively correlated with both early and later growth. Added P significantly decreased the foliar N to P ratios of all species at age 1 year, indicating that P additions, in particular, were required for good early growth. Combined additions of N and P significantly increased growth of E. nitens in the first year but growth responses to further additions of fertilizer were minimal. In contrast, growth of E. globulus increased in response to all fertilizer additions, leading to the greatest mean volumes at the highest combined rates of N and P. Relative gains in productivity were therefore greater in E. globulus (m.a.i. range at 71 months: 10-24 m(3) ha(-1) year(-1)) than E. nitens (16-33 m(3) ha(-1) year(-1)). There were no additional growth responses of any species to added K or trace elements. However, concentrations of K in E. regnans foliage at age 1 year were increased by K additions and were correlated with later growth. Low concentrations of Mg in E. nitens foliage suggest a probable response to Mg additions. General fertilizer prescriptions for the establishment phase of eucalypt plantations on sites of high quality are presented. Refinement of these prescriptions will rely on a better understanding of the nutritional requirements of individual species.