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ISHS Acta Horticulturae 894: I International Symposium on Tropical Horticulture

CANOPY MANAGEMENT OF SWEET ORANGE, GRAPEFRUIT, LEMON, LIME AND MANDARIN TREES IN THE TROPICS: PRINCIPLES, PRACTICES AND COMMERCIAL EXPERIENCES

Authors:   A.J. Krajewski, S.A. Krajewski
Keywords:   selective pruning, fruit size, light, sap flow, mulching, re-growth, sustainability
DOI:   10.17660/ActaHortic.2011.894.5
Abstract:
Over the past 18 years, citrus canopy management strategies (CMS) were developed improving tree health, productivity, fruit quality and management efficiency of orchards in tropical Southern Africa and Australia. These CMS are based on understanding of knowledge of tree phenology and natural growth habit, recognition of fruiting habits of “strong” and “weak” bearing branch units (SBBU and WBBU respectively), tree physiology, floral biology, environmental physiology, effects of canopy illumination, branch sap flow patterns, and of effects on these of climate, weather, topography, altitude and local pest and disease cycles. Secondly, CMS were derived with an understanding of effects on tree physiology of specific pruning and regrowth management practices. Thirdly, cost-effective methods were developed of optimising growth, form and function of non-bearing trees, trees in full production, and old trees declining due to age and/or shading. The strategy is to create, after planting, strong, balanced tree frameworks, and to maintain these through the orchard’s life by selectively pruning multiple light- and spray “channels” into the trees’ canopies. As new “internal” growth arises and develops, fruiting is displaced to sheltered, well-lit and ventilated canopy interiors. Pruning specifically removes WBBU, and stimulates production of SBBU, directly subtended by scaffold branches in which sap flow is strong. These SBBU bear large, unblemished fruit of uniform high quality. Rejuvenation pruning of old trees is discussed, as is protection of leaf flush from the pests citrus leaf miner, thrips, leafhoppers and pathogens Citrus black spot (CBS), Asiatic citrus canker (ACC) and Huanglongbing (HLB). Also discussed are improvements observed to soil following additions of coarse, organic wood chip mulches derived from triturated prunings, and necessary adjustments in support of CMS to fertiliser practices, irrigation, pest-, disease- and orchard floor management.

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