Responses of Tea (Camellia sinensis) to Irrigation and Fertilizer. I. Yield

Summary The yield responses of clonal tea (Clone 6/8) to irrigation and fertilizer were studied in a field experiment (based on the line-source technique) at a high altitude site (1840 m) in the Southern Highlands of Tanzania over a three-year period. In this area (latitude 8°33′S) the annual dry season can last up to six months with potential soil water deficits reaching 600 to 700 mm. In the third year of the experiments yields for the fully irrigated, well fertilized (375 kg N ha−1) treatments had reached 4.9 t ha−1 of made tea. These were reduced by about 2.9 kg ha−1 for each mm increase in the potential soil water deficit. For tea with little or no fertilizer applied the loss of yield was about 1.4 kg ha−1 mm−1. These figures provide a basis for assessing the potential benefits from irrigation where other factors, such as large saturation deficits of the air, do not restrict shoot extension and yield. Yield responses to nitrogen (applied as N:P:K 20:10:10) were essentially linear up to a maximum of about 375 kg N ha−1 in the fully irrigated plots, and 300 kg N ha−1 for the unirrigated plots. Irrigation increased the proportion of crop harvested during the dry season, up to 45% in the fully irrigated treatments. The commercial implications of these results for ‘high’ and ‘low’ input producers are discussed.