Relationship between Growth Rate and Foliar Concentrations of Nitrogen, Phosphorus and Potassium for Eucalyptus grandis

Abstract

The growth responses to applications of N, P, K and lime are described briefly for four comprehensive fertiliser experiments with Eucalyptus grandis. Foliar concentrations of N, P and K were determined for these experiments, and their relationship to growth rate and fertiliser application investigated. Highly significant correlations between these factors were established. The combined influence of fertiliser applications and foliar nutrient levels on height growth-rate were studied by multiple regression techniques. Nitrogen and phosphorus were found to be the most important foliar concentrations in these analyses, together with applications of phosphate and lime. In three experiments very close relationships were determined which explained between 42 and 74 % of the variation in height growth-rate. These percentages decrease with increasing age of sampling. It is concluded that foliar N should be 2.0 %. foliar P 0.17 % and foliar K 0,70 % for satisfactory growth of E. grandis. Likewise the foliar NIP ratio should be between 10 and 16, that for P/K between 0,21 and 0,26, and that for N/K about 3.