ISHS Acta Horticulturae 175: Symposium on Physiology of Productivity of Subtropical and Tropical Tree Fruits
GROWTH MANAGEMENT OF MATURE CITRUS WITH APPLIED NITROGEN |
| Author: | J.C. Chapman |
| Abstract:
A single annual vegetative flush is adequate for the continued growth and fruiting of a mature evergreen fruit tree. To provide the wood for flowering, fruit set and development of the following crop, a vigorous flush should be encouraged. In citrus, nitrogen application is made in late winter to stimulate the spring growth flush which provides both leafy growth and flowers. Nitrogen applied at other times of the year is wasteful and detrimental to fruit quality. Nitrogen can be applied in a single application at low rates. Of five common sources of nitrogen considered, urea is the least toxic while sodium nitrate is the most toxic. However, most forms of nitrogen are suitable for use on citrus provided soil amendments are made to counteract any deleterious changes in soil condition. Optimum rates of nitrogen per annum for citrus vary widely throughout the world depending on rainfall, soil type, sod management and in some cases, cultivar. Excessive nitrogen affects fruit quality adversely but usually does not reduce yields unless the source of nitrogen has a high potential for toxicity. Research in Queensland has produced evidence that the required nitrogen rate does not vary greatly with planting distance. Nitrogen is best applied over two thirds or greater of the ground surface in an orchard than over restricted areas. | |
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