THE USE OF FLORAL ANALYSIS TO DIAGNOSE THE NUTRITIONAL STATUS OF ORANGE TREES

Abstract

A field experiment was conducted in a commercial orange orchard (Citrus sinensis L. cv. ‘Valencia late’), established on a calcareous soil in the south of Portugal, to investigate if flower analysis could be used to diagnose the nutritional status of the trees and predict fruit quality. In April 1996, during full bloom, flowers and leaves were collected from 20 trees. Leaf samples were again collected in June and August from the same trees. In February 1997 the fruits were harvested and their quality evaluated. The concentrations of phosporous (P) and magnesium (Mg) in flowers were correlated with those in leaves, and were also predictive of the chlorophyll content of leaves 60 days later. However, by 120 days after full bloom these effects were masked, possibly by a fertilizer application carried out by the farmer. The iron (Fe) concentration in flowers was correlated with chlorophyll measured either 60 or 120 days after full bloom. These parameters can therefore be used to predict the appearance of iron chlorosis. Fresh weight and diameter of fruit were related to flower P, Mg, and manganese (Mn) concentrations, while the percentage of citric acid in the fruit juice was inversely correlated with Fe flower concentrations.

ACKNOWLEDGMENTS

This work was supported by the European Commission-funded AIR3-CT94-1973 Project to E.A.F. and J.A., and by the Portuguese Praxis XXI program, Project 3/3.2/HORT/2160/95, to A. de V., M. P., and E.A.F. We thank Mr. José Dias Rafael for the use of his orchard and Pedro Ferreira for excellent technical assistance. We thank Drs. Anunciación Abadía, Michael Goss and Manuel Sanz for reading the manuscript and providing helpful comments.