A Water Stress Index for Tea (Camellia sinensis)

Abstract

A simple Stress Time Index (STI) for predicting yield loss in the tea crop due to drought is proposed, based on the daily summation of the difference between the potential soil water deficit and a specified limiting value. Validation of the technique with results from a line-source irrigation experiment with a single clone in the Southern Highlands of Tanzania suggests that there is a linear relationship between STI and relative yield loss during the warm dry season. As a result of changes in the composition of the shoot population at each harvest the apparent critical deficit at which shoot growth is restricted increases from below 20 to 300 mm as the dry season progresses. The rate of yield loss with increasing STI also varies through the dry season for the same reason.