Split application of nitrogen fertilizer rates in two tea cultivars grown in the Eastern and Western highlands of Kenya: I. Confirmatory results on yield effects.

Abstract

Two experiments were conducted in Kericho and Kangaita, Kenya during 19991-98 to investigate the effects of nitrogen fertilizer rates (50, 100, 200, 400 and 800 kg/ha) and frequencies of application (1, 2 and 4 split applications per year) on tea (clone 11/4) yields. The application rates resulted in quadratic yield responses with agronomic peaks occurring at 200 kg N ha-1 year-1 in both sites. Mean annual peak yields over the eight year period were 2625 and 1886 kg mt/ha at Kericho and Kangaita, respectively. Although splitting fertilizer application appeared to give slightly higher yields especially for the Kangaita site, the differences obtained were not significant (P≤0.05%) in both experiments throughout the experimental period; showing that the split application of nitrogen does not give annual yield benefits. The analysis of the monthly yield distribution for the 100 and 200 kg N/ha rates in the experiments showed that the split application of the fertilizers did not alter the distribution, but appeared to be influenced by the weather patterns. These results confirm that splitting of nitrogen fertilizers in tea in Kenya should be done for other reasons but not for better annual yields or crop distribution.