LONG TERM FERTILIZER USE ON HIGH YIELDING CLONE S 15/10 TEA: YIELDS

Abstract

High production of young tender shoots of Camellia sinensis L. O. Kuntze to make tea beverages leads to soil nutrients depletion through harvested crop and leaching. The production can be sustained by replenishing the lost nutrients through regular addition of fertilizers and/or organic manures. In Kenya, NPKS 25:5:5:5 or NPK 20:10:10 are the recommended fertilizers for tea. Clone S15/10 is a high yielding tea and has yielded of over 10000 kg made tea (mt) per hectare per year in a year with good cropping weather. Long term(18 years) experimentation on the amounts of fertilizers needed to sustain the yields demonstrated that application of nitrogenous fertilizer resulted in significant (P less than 0.05) yield responses. The application of high rates of fertilizer produced quadratic yield response with a maximumat about 300 kg N ha-1 year-1. Quantities between 200 and 250 kg N ha-1 year-1 were considered optimal. There were no significant (P less than 0.05) differences in the yields responses due to use of NPKS 25:5:5:5 and NPK 20:10:10. The NPK formulation to use on tea in Kenya should therefore be decided based on other factors like availability, cost, ease of handling, etc. Despite the control plot not receiving fertilizer for the 18 years, it continued to produce yields higher than most seedling tea receiving adequate nutrition. In a subsequent trial to assess if splitting annual fertilizer application could improve yields, applying fertilizer at half rate annual rate every six months or one third rate at four months intervals did not cause any significant changes in yields at all rates tested for six years.The splitting annual fertilizer applicationsmay therefore be practised for other reasons like uniform distribution of the fertilizer in the tea plantations, cash flow and storage considerations, ease of handling, etc. In a trial to establish the effect of plucking rounds on yields, therewere significantly (P less than 0.05) higher yields when harvesting interval was 7 days compared to 14 or 21 days intervals in the eight out of ten years of experimentation. Inmost years the 14 day plucking interval produced the lowest yields. These results demonstrate that shorter plucking intervals are beneficial to high tea production in theKenya highlands. Keywords: Long term nitrogen, high yielding clone, NPK formulations, splitting annual fertilizer application, plucking rounds, yields.