ISHS Acta Horticulturae 707: VII International Symposium on Modelling in Fruit Research and Orchard Management
WATER USE BY YOUNG NAVEL ORANGE TREES (CITRUS SINENSIS (L.) OSBECK) IN ZIMBABWE |
| Authors: | S. Dzikiti, J.R. Milford, K. Steppe, R. Lemeur |
| Keywords: | Leaf transpiration, sap flow, stem diameter fluctuation, internal storage, leaf surface temperature |
| Abstract:
Efficient management of water in any cropping situation requires accurate quantitative information on water use. This is crucial especially for citrus trees grown in the arid and seasonally arid climates where production relies heavily on irrigation. The response of young navel orange trees (Citrus sinensis (L.) Osbeck) to water stress was investigated on 2 clear days during the hot, dry season in Zimbabwe. The dynamics of water flow were measured using sap flow sensors installed at roots, stem and branch level. Cyclical oscillations in sap flow, and consequently in stem diameter, with periodicities ranging from 55 minutes in the morning to 35 minutes in the afternoon were observed. The imbalance between water uptake and water loss by the trees led to fluctuations in stem diameter, which were also measured. Internal water storage contributed significantly to the daily total leaf transpiration of the young trees. For a well-watered tree, approximately 4 % of total transpiration came from internal water storage pools, while about 10 % was withdrawn from the internal water reserves in a water stressed tree between 0800 and 1600 hrs local time. These results show that potentially large errors can occur in models that estimate transpiration of citrus trees without taking into account the contribution of the internal storage especially in water stressed trees. Leaf surface temperature was always in anti-phase to the transpiration oscillations. This suggested that evaporative cooling and transpiration rates of the citrus trees were generally restricted by water supply at least for parts of the day. | |
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