Optimizing Selenium Application for Enhanced Quality and Nutritional Value of Spring Tea (Camellia sinensis)

Tea (Camellia sinensis) is a globally cherished beverage, valued for its flavor and health benefits, largely attributed to bioactive compounds like polyphenols and amino acids. Selenium (Se), an essential trace element for humans and animals, plays a dual role in promoting plant growth and enhancing human health, yet its impact on tea quality remains underexplored. In this work, the effects of selenium application rate (with 0, 150, 225, and 300 g·ha−1 of Se) on soil selenium availability, enzyme activity, and the biochemical composition of spring tea, including chlorophyll, polyphenols, free amino acids, and polysaccharides, were studied. Results show that selenium application significantly increased soil selenium availability, with higher rates promoting its conversion into bioavailable forms. Soil enzyme activities, such as sucrase and urease, were notably influenced by selenium. In tea leaves, selenium content and glutathione peroxidase activity increased, while chlorophyll content initially rose but declined at higher application rates, with the Se225 treatment (225 g·ha−1 of Se) yielding optimal results. Selenium reduced polyphenol content, increased free amino acids, and lowered the phenol-to-amino acid ratio, improving tea sensory quality. Polysaccharide content also peaked at the Se225 treatment. These findings highlight the potential of selenium-enriched tea as a functional food and provide a scientific basis for optimizing selenium application in tea cultivation.