NPK (S) fertilizer use in commercially cultivated clone BBK 35 in different tea growing regions of Kenya: II. Effects of nitrogen rates and plucking intervals on soil chemical …

Abstract

One commercially and widely grown tea cultivar, clone BBK 35 was evaluated for changes in soil chemical properties at different N-fertilizer rates and plucking rounds in five different localities in Kenya. The soils in all the tea areas were strongly acidic with two of the sites at the higher altitude (>2,180 m asl) experiencing cool wet seasons (Karirana and Timbilil) while the other three lower altitude sites (<1,860 masl) having warm-wet seasons (Changoi, Sotik Highlands and Magura-Kipkebe). While a previous paper in this series gives the experimental design and initial soil chemical properties in 1997, the effects of the N-rates (0, 75, 150, 225 and 300 kgN/ha/year) and plucking intervals (7, 14 and 21 days) on some soil chemical parameters down the profile after seven years of annual treatment application in 2004 are discussed herein. Plucking intervals did not have significant effects on the measured soil parameters (pH, extractable Mn, K, Mg, Ca, and P). N-rates caused acidification especially for rates above 150 kgN/ha/year, which was corroborated by the soil extractable Mn. Similarly, there was evidence of leaching of base nutrients, especially extractable Ca and Mg, down the soil profile. The results demonstrate need for prudent use of N-fertilizers at the rates of 150 kgN/ha/year and below, to avoid nutrient imbalances in tea fields.