Response of eucalypt species to fertiliser applied soon after planting at several sites

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Abstract
Forestry organisations in several Australian States co-operated to establish a series of field trials in 1971–72 designed to improve current knowledge on eucalypt nutrition. Six fertiliser treatments and a single seedlot of E. globulus were used in all trials and other species, selected for local suitability, were included in some of the trials. A response in growth was recorded to nitrogen, phosphorus or a combination of the two at all sites. No additional response was obtained to potassium with or without trace elements. The nature of the response was determined by site factors rather than species. Whilst the effect of fertiliser on the concentration of nitrogen and phosphorus in the foliage was not great, the effect on the ratio of nitrogen to phosphorus was often substantial. It is postulated that there is an optimum ratio of nitrogen to phosphorus in the foliage of eucalypts for maximum growth. The data in this paper indicate that this ratio is about IS for E. globulus and E. sieberi. Trees which had higher ratios than this responded to phosphorus and those which had lower ratios responded to nitrogen. Data for other species were not conclusive. The absolute concentration of nutrients required in the foliage for maximum growth has not been determined.