Biomass and mineral nutrient partitioning in a developing tamarillo ( Cyphomandra betacea) crop

Abstract

The accumulation of dry matter (DM) plus macro- and micronutrients by various components of developing tamarillo ( Cyphomandra betacea (Cav.) Sendt. cv. ‘Oratia Red’) plants was recorded over a 3-year period covering growth from seedlings to a mature commercial crop. Five plants were harvested every 2 months and separated into perennial components (tap root, roots, stem wood, stem bark, and wood and bark from year-old branches) and current season’s growth (fruiting laterals, leaves, flowers and fruit) for determination of DM and mineral composition. DM accumulation in the perennial framework conformed to a sigmoidal pattern of increase over the entire trial period. In contrast, DM accumulation by annual components was greatest in the 4–6 months after pruning each season, and reflected the indeterminant pattern of vegetative growth, flowering and fruit set associated with this crop. Nutrient concentrations in dissected components were generally constant. Consequently, accumulation of DM and individual nutrients was strongly correlated. Potassium and nitrogen were the elements acquired in greatest amounts by tamarillo plants in each season. During Year 3, the amount of N, P and K accumulated amounted to 109 kg N ha −1, 11 kg P ha −1 and 145 kg K ha −1 of which 39, 27 and 48% was removed in harvested fruit, respectively. Nutrient accumulation budgets identified the 4–6 months immediately after pruning as the time when exogenous nutrients were acquired in greatest amount, and nutrient reserves in the perennial framework were withdrawn to sustain any shortfall in uptake. Adequate nutrition of commercial crops will depend on application of fertiliser nutrients timed to meet these requirements.