THE ROLE OF PHOTOPERIOD IN DETERMINING SEASONAL YIELD VARIATION IN TEA

Previously published data from two tea experiments in Tanzania and Malawi were re-analysed to identify factors responsible for the marked seasonal peaks and troughs of production observed at the two locations. Simulation modelling indicated that the influence of seasonal variations in temperature or photoperiod on shoot growth rates alone were not able to explain the occurrence of a large peak in September/October followed by smaller and progressively wider peaks in December, February and April in well-irrigated, well-fertilized tea at the two sites. Various mechanisms to explain these seasonal variations in yield are discussed, but it is concluded that the best explanation is the regulation of the numbers of shoots available for harvesting through the effect of photoperiod on shoot activity. The significant production peak normally obtained in September/October at both locations can then be explained by the release of a large number of buds from their resting state around the time of the winter solstice in June. Subsequent peaks are due to successive cohorts of shoots released from apical dominance when the preceding peak is harvested.

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