Long Term Influence of High Rates of Nitrogenous Fertilizer on Seedling Tea: 1. Effects Young and Mature Leaf Nutrients Contents

Abstract

Nitrogen (N) fertilization is a key agronomic input in tea production. However, the impacts of continuous long-term application of high rates of the nutrient on the dynamics of tea leaf nutrients contents remain insufficiently understood. This study evaluated the effects of continuous application for 40 years, of high nitrogen fertilizer rates (up to 800 kg N ha⁻¹ year⁻¹) on mature and young tea leaves nutrients contents of seedling tea in a field trial at Timbilil Estate, Kenya. Both mature and young leaves exhibited significant (p≤0.05) increases in nitrogen, manganese, aluminium, iron and zinc contents with rising N rates. However, leaf phosphorus, potassium, calcium, magnesium, and barium concentrations declined with increasing rates of nitrogen applications. The changes were more severe than those observed in previous short term low rates of nitrogen fertiliser trials. These results demonstrate that the continuous long term application of high rates of nitrogen could be causing nutrients imbalance in tea plants that may make tea production unsustainable in the long run. The continuous application of high rates of nitrogen should be discouraged in tea production.