Rational application of combined fertilizers improved tea growth and quality components

BACKGROUND: The excessive and sole use of chemical fertilizers has been found to deteriorate tea quality components. Therefore, to explore the effects of rational application of combined organic and chemical fertilizers on tea growth and quality, a pot experiment was conducted with six treatments of rational and combined organic fertilizer (OF) and chemical fertilizer (CF) which were as follows: control (no fertilizer was applied), 0OF/CF100 (only CF was applied), 25OF/75CF (25% OF + 75% CF), 50CF/50OF (50% OF + 50% CF), 75OF/25CF (75% OF + 25% CF), and 100OF/0CF (only OF was applied). The biomass of tea plant, net photosynthetic rate, chloroplast ultrastructure, and tea quality components including tea polyphenols (TPs), flavonoids, sugars, catechins, caffeine, total amino acids (TAAs), chlorophyll pigments and TP/TAA were measured. RESULTS: Compared to control, all fertilization treatments significantly improved tea growth, biomass, and quality components including soluble sugars, TAAs, catechins, caffeine, polyphenols and flavonoids in tea leaves. Among all fertilization treatments, 75OF/25CF and 50OF/50CF treatments had higher plant shoot biomass; 75OF/25CF and 100OF/0CF treatments significantly improved chloroplast ultrastructure and increased net photosynthetic rate, and had higher TAAs, polyphenols, catechins and caffeine contents; while 75OF/25CF treatment had higher sugar content and lowest TP/TAA. The principal component analysis (PCA) further explored that 75OF/25CF and 100OF/0CF treatments improved quality components in tea leaves in comparison to the application of only chemical fertilizers. CONCLUSION: The 75OF/25CF and 100OF/0CF treatments enhanced both tea growth and quality, which indicate that rational and combination of organic and chemical fertilization or organic management had high potential to improve tea growth and the production of high-yield and better-quality tea leaves.