Nitrogenous Fertilizer Application Rates and Plucking Intervals in East Africa Tea: Effects on Soil Micro-Nutrients (Al, Fe, Cu, Zn)

Abstract

Depletion of nutrients are high in Eastern Africa tea soil due to high rainfall causing surface run-off and leaching, together with removal with crop. Nutrients Replenishment of nutrients by applying fertilizer is therefore necessary. However, nitrogen fertilizers may cause micro nutrients imbalance. Varying plucking intervals lead to changes in tea yields and quality. Despite varying tea growing conditions in Eastern Africa, recommended nitrogen fertilizer rates and plucking intervals are similar. Nitrogen fertilizer and plucking intervals may influence soil micro nutrients levels in different locations to varying degrees. This study determined effects of plucking intervals and NPKS 25:5:5:5 fertilizer rates on soil micro nutrients (Al, Fe, Cu, Zn) levels in different locations within Eastern Africa. Soil samples were collected from fertilizer trials on clone TRFK 6/8 at Timbilil, Changoi, Arroket (Kenya), Maruku, Katoke (Tanzania), Kitabi and Mulindi (Rwanda), from a 5x3 factorial with five nitrogen fertilizer rates (0, 75, 150, 225 and 300KgN/ha/year) and three plucking intervals (7, 14 and 21 days) as treatments at each site. Plucking intervals had no influence on the soil micro nutrients. Application of higher rates of nitrogen increased (p≤0.05) soil Al, Fe, and Cu levels but reduced (p≤0.05) soil Zn. The levels of soil micro-nutrients changed (p≤0.05) from location to location. However, the levels were adequate and did not constrain tea productivity.