Responses of Tea (Camellia Sinensis) to Irrigation and Fertilizer. III. Shoot Extension and Development

Abstract

SUMMARYRates of shoot extension and development (the unfolding of leaves) were recorded in an irrigation × fertilizer experiment on Clone 6/8 at Ngwazi Tea Research Unit in southern Tanzania. The wide range of mean temperatures (from 15–20°C) meant that the duration of the shoot replacement cycle (the time taken for an axillary bud released from apical dominance to develop three leaves and a terminal bud), in fully irrigated tea receiving 450 kg N ha-l, varied from 65 d in the warm wet season to 95 d in the cool dry season, compared with 75 to 180 d for unirrigated and unfertilized tea. Regression analysis indicated that the base temperature for extension, for Clone 6/8 in high-input plots, was about 10°C, some 2–3°C more than that for development. As a result of these differences in base temperature, the length of shoots with three leaves and a bud varied considerably between treatments and seasons, ranging from 15 mm in the unirrigated plots (at the end of the dry season) to 130 mm in the high-input plots at the start of the rains. Shoots from well fertilized tea were always longer (at a given stage of development) than those from unfertilized tea. The results are discussed in terms of the possible mechanisms responsible for the observed responses (changes in partitioning between roots and shoots), commercial harvesting practices and yield modelling.Extensión y desarrollo de broies en el té