Effects of Fertilizer Type and Rate on the Quality and Nutrient Content of Four Species of Trees Growing in Sandy South Florida Soils

Abstract

Broadleaf ornamental trees are known to vary widely in their responses to fertilization, depending on the species and soil and other environmental factors. Thus, it is important to study the responses of a wide range of tree species to fertilization, especially on nutrient-poor soils. Four species of temperate to tropical trees, live oak (Quercus virginiana), west indian mahogany (Swietenia mahagoni), black olive (Bucida buceras ‘Shady Lady’), and beautyleaf (Calophyllum brasiliense), planted into a sandy native soil in south Florida were fertilized with a 24N–0P–9.3K turf fertilizer or an 8N–0P–10K–4Mg plus micronutrients palm fertilizer at rates of 10 or 20 g of nitrogen per tree four times per year. Tree height, width, caliper, and nutrient deficiency rating scores for nitrogen, potassium, and magnesium were determined at 1 year after planting (establishment period) and at 3 years after planting (maintenance phase). Data from these measured variables were subjected to principal component analysis to obtain a single measure of overall quality, namely, the scores for each tree on the first principal component. West Indian mahogany showed no response to fertilization during or following establishment. Either fertilizer type or rate improved live oak, black olive, and beautyleaf quality over that of unfertilized controls during both establishment and maintenance phases, but the high rate of the palm fertilizer was superior to either rate of the turf fertilizer for beautyleaf both during establishment and afterward. Leaf nutrient concentrations generally were poorly correlated with overall tree quality, but manganese concentrations differed significantly among treatments for all four species. Based on these results, fertilization of West Indian mahogany is not recommended, but live oak, black olive, and beautyleaf will benefit from fertilizer applied at the time of planting and after establishment.