Effect of trace element supply on plant growth and mineral nutrition of Cyclopia longifolia Vogel L. a Honeybush tea plant growing on a farmer's field in the Cape fynbos, South Africa

Cyclopia longifolia Vogel L. is endemic to the Cape fynbos, and cultivated for the production of Honeybush tea, a herbal beverage with health benefits and economic potential in the cosmetic and nutraceutical industries. In this study, field plants were supplemented with different levels of Cu, Mo, Mn and Zn using 0, 0.5, 1.0 and 1.5 mM solutions of Na2MoO4.2H2O and MnSO4.2H2O and 0, 1.0 and 1.5 mM solutions of ZnSO4.7H2O and CuSO4.5H2O in a split-application. Plant shoots were harvested at 300 days after fertilization for biomass determination and analysis of mineral nutrients. The results showed significantly increased shoot dry matter yield of C. longifolia in response to Mn, Cu, Zn and Mo supplementation under field conditions, and was highest at the 1.5 mM level of each applied micronutrient. These results suggest that field fertilization of Cyclopia plants can lead to increased plant growth and greater tea yield, in addition to overcoming nutrient mining from the annual harvests of plant shoots for making tea. Furthermore, supplying Mn, Zn, Cu and Mo to C. longifolia also significantly increased the concentrations and amounts of P, K, Ca, Mg, Cu, Zn, Mn and B in shoots relative to the zero controls, suggesting an increase in tea quality with trace element supplementation. However, the shoot concentrations of N and Fe were markedly reduced with increasing supply of Mn, Cu, Zn and Mo to C. longifolia plants, an indication of mineral-to-mineral antagonism in the plant rhizosphere.& COPY; 2023 Published by Elsevier B.V. on behalf of SAAB.