Application of alternative mineral fertilizer to improve the total phenolic content and antioxidant capacities of tea [Camellia sinensis (L.) O. Kuntze] leaves

Abstract

Introduction - Tea is an important trade commodity for the Eastern Black Sea Region of Turkey. However, repeated, indiscriminate fertilization of tea orchards has caused deterioration of the soil structure and a decrease in yield and quality. Materials and methods - In this study, six fertilization programs were designed based on leaf and soil analyses. In addition to the control (C) and the composite fertilizer (G; 100 kg da(-1) of 25-5-10 (NPK)) commonly applied by regional producers, five different formulations were tested: 70 kg da(-1) of 25-5-10 composite fertilizer (A); A + calcium carbonate (CP); A + magnesium carbonate and calcium carbonate (MP); A + Fe, Zn, Cu, Mn (WT); and A + (Fe, Zn, Cu, Mn, calcium carbonate) (WT + CP). The effects of the tested fertilizer combinations on the total phenolic content and antioxidant capacity of tea leaves (Camellia sinensis (L.) O. Kuntze) harvested at three different times were investigated. Results and discussion - Leaves with the highest phenolic content were from plants that received the WT application. The highest DPPH radical-scavenging capacity (%) was achieved with the WT and WT+CP applications, and the highest FRAP values were obtained from CP, MP, WT, WT + CP applications. The highest phenolic content was obtained from the 2nd harvest period, the highest DPPH values were obtained during the 1st and 2nd harvest periods, and the highest FRAP values were obtained in the 1st harvest period. Conclusion - This report indicates that more intentional management of fertilizer applications can reduce the overuse of fertilizer and produce a better tea product.