Observations on cocoa flushing in Ghana under different shade regimes, with particular reference to the distribution of natural light.
Adomako, D. | Frimpong, E. B. | Ampofo, S. T. | Brew, K. M.
Unshaded cocoa trees growing on low wet ground, as well as shaded and unshaded cocoa trees growing on dry ground, were studied for the effects of sunlight availability and soil moisture on flushing. The studies covered the period between November 1982 to March 1987, which included the severe dry seasons of 1982/83 and 1983/84. Growth of cocoa seedlings and one-year-old plants in the greenhouse under 35% shade and in the nursery under 50% shade was also studied. In 1983 and 1986 peak flushing occurred as usual in January when there had been little or no rain during the preceding 10 and 4 weeks, respectively. Flushing was earlier, more frequent and more intense in unshaded or 'broken canopy' and roadside (edge) trees than in shaded trees; and there was no relationship between the flushing pattern and soil moisture content. Seedlings growing under 35 or 50% shade in the greenhouse and the nursery flushed at regular 4-weekly intervals without a seasonal peak. One-year-old jorquetted plants also flushed at regular intervals of 4 to 5 weeks each time at a few growing points; but as in the case of mature trees there was peak flushing involving all growing points during the drier part of the year in Oct.-Nov. and Feb.-Mar. There was a highly significant correlation between sunshine hours and flushing (r = 0.999 and 0.949 for 2 different recordings in one plot). These observations are interpreted in the light of the known relationship between sunlight availability, tissue carbohydrate content, bound and free IAA levels in the plant, and flushing.
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