Nutrient dynamic in cocoa leaves under different nitrogen sources: a reference tool for foliar analysis

Abstract

Cocoa is a crop in increasing demand and cultivated worldwide. However, basic information concerning the movement of nutrients in leaves over time is still unknown, and methods to find an optimal time to collect a sample are still ambigu-ous. The present work focused on describing the movement of foliar nutrients (N, P, K, Ca and Mg) in productive 5-year-old cocoa clone CCN51 plants at the same dose of 114.8 kg ha-1 under different sources of nitrogen fertilization (Urea, calcium ni-trate, ammonium sulfate and a control without application). Samples were taken from the time the leaf reached 70% of its total expansion until 10 months of age. The results indicated that the contents of N, Ca and Mg increased as the leaf grew, remained stable between 116 and 158 days of shoot emergence (DSE) and then decreased at the beginning of the leaf senescence period. While the K and P con-tents decrease from the beginning of the trial until 158 DSE where they are stable until the final stage of leaf life. Around 110 to 120 DSE, the leaves of cocoa CCN51 show a more stable nutritional content, a period in which samples can be collected for leaf analysis.