GROWTH, FOLIAR AND NUTRIENT STATUS OF <em>TERMINALIA</em> <em>AMAZONIA</em> PLANTED IN SOUTHWESTERN COSTA RICA

Abstract

A study was conducted to examine the growth of Terminalia amazonia, a promising plantation species native to the humid neotropics, in relation to soil and foliar nutrient levels, its nutrient requirements and suitable management practices, and to suggest further research. Plots of 49 trees were established in 25 three-year-old plantations of Terminalia amazonia, at sites ranging from sea-level to 1200 m above sea-level in tropical wet and premontane life zones in southwestern Costa Rica. Measurements of total tree height, diameter at 10 cm above the ground surface, and crown width at its widest point were taken for all trees in each of the 25 plots. Soil was collected at five points and included three depths: 0 to 5 cm for bulk density and physical and chemical property evaluation, 15-30 cm and below 50cm for chemical and physical property sampling. Sun leaves from seven healthy trees in each plot were also collected. Soil samples were analysed for pH, exchangeable acidity, total C, total N, extractable P, K, Ca, Mg, Na, CEC, base saturation and bulk density. Foliage samples were analysed for concentrations of total N, P, K, C, Ca, Mg and Na. Using the formula d²h to calculate tree volume, the greatest growth measured in each of three different life zones at three years was: tropical wet forest zone, 29.5 m³ ha^-1, tropical moist forest zone, 67.1 m³ ha^-1; and tropical premontane forest zone, 49.6 m³ ha^-1. Surface-soil phosphorous levels were generally below 4 ppm and foliar P levels were 0.16% or less in vigorously growing trees, indicating that T. amazonia is quite efficient in its use of P. The species appeared to be growing better as N levels increased and at lower surface-soil bulk densities.