ISHS Acta Horticulturae 175: Symposium on Physiology of Productivity of Subtropical and Tropical Tree Fruits
ASSESSMENT OF NUTRITIONAL STATUS OF PERENNIAL FRUIT TREES |
| Authors: | R.A. Stephenson, A.W. Whiley, B.W. Cull |
| Abstract:
A holistic approach to the assessment of the nutritional status of, and the rapid development of nutritional management programmes for tropical and subtropical fruit trees has been successfully adopted at the Maroochy Horticultural Research Station. It involves a field monitoring approach whereby the periodic analysis of soil and the measurement of vegetative flushing and flowering activity and leaf nutrient levels, together with meteorological records and cultural practices is used. This is an alternative to traditional randomised, factorial trials. Soil analysis is useful in assessing the suitability of the root environment and identifying nutrient deficiencies and imbalances, but is unreliable, when used in isolation, in determining the nutritional status of trees and developing nutritional management programmes. The monitoring of vegetative flushing, which is influenced by meteorological conditions, cultural practices and general tree health, is essential for accurate interpretation of leaf nutrient levels. Vegetative growth, flowering and fruit development all influence leaf nutrient levels, particularly N, P and K, either directly by drawing on leaf nutrient reserves or indirectly by determining the age of leaves available for sampling. These growth patterns vary with species, cultivar, location and season and therefore need to be monitored to allow meaningful interpretation of leaf nutrient levels and potential yield. Monthly leaf analysis indicates seasonal nutrient patterns which reflect those of vegetative growth and fruiting. The best time to sample leaves can be determined in part by the stability of nutrient levels over a period of time. Leaf analysis is the most reliable indicator of tree nutritional status when used in combination with flushing activity and phenological development. By analysing leaves and recording yields from individual trees of good performance in different locations over a period of years, tentative standard leaf nutrient levels can be determined. Those nutrients associated with the highest yields can be identified. Where monthly leaf analysis is carried out, the times at which these nutrients have the largest influence on yield can be determined. This will influence the selection of leaf sampling time. Tentative standard leaf levels may be adjusted on this basis and fertilizer practice managed accordingly. | |
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