Response of tea selenium content to concentration and timing of single foliar organic selenium-rich fertilizer application

To investigate the feasibility of producing selenium-enriched tea through a single foliar application of an organic selenium-rich fertilizer, a randomized block experiment was conducted focusing on the concentration and timing of the application. The effects of different treatments on tea yield characteristics and selenium content were analyzed, and a predictive model for tea selenium content was developed. The results show that the spraying time and concentration of organic selenium-rich fertilizer have no significant effect on tea bud density; Spraying organic selenium-rich fertilizer 12 and 6 days before picking significantly increase 100-bud weight by 14.5% to 22.7% (P<0.05), while spraying 24 and 18 days before picking have no significant effect. The tea selenium content shows an increasing trend with the increase of spraying concentration. Spraying organic selenium rich fertilizer at different spraying times has a significant improvement effect on the selenium content in tea (P<0.05), increasing by 0.56 to 44.2 times. Moreover, the shorter the interval between spraying and picking, the more favorable it is for the increase of selenium content in tea. A relationship is established between tea selenium content (C_se), application concentration(c_s), and application-picking interval(t_s): C_se=(8.547×10⁻²)c_st_s^−2.637+0.037, and the predicted values of the predictive model are significantly correlated with the measured values (P<0.001). To achieve precise control of tea selenium content within the selenium rich standard, the single foliar application rate of organic selenium-rich fertilizer is calculated at key time points 6 days, 12 days, 18 days, 24 days, and 30 days before picking, which has strong guiding significance for the production of selenium rich tea.