Sprinkler Irrigation Improves Flavor and Sensory Quality of Ning Black Autumn Tea: A Comparative Analysis

Ning black autumn tea from Jiangxi, China, is often neglected by farmers due to quality decline under hot and arid autumn conditions. In this study, four soil moisture levels (T1–T4, ranging from 32.75% to 18.36%) were established through different sprinkler irrigation frequencies to investigate their effects on tea quality. T2 (27.98% soil moisture) exhibited the highest content of total free amino acids (13.77 mg/g), which was 13.33% higher than that in T4 (12.15 mg/g). Notably, T2 had the highest content of umami amino acids (6.75 mg/g) and the lowest content of bitter amino acids (3.07 mg/g) among all treatments. The total non-esterified catechin content in T2 (18.92 mg/g) was 2.74-fold higher than that in T4 (6.90 mg/g). Among the 55 volatile compounds identified, trans-nerolidol reached its highest odor activity value in T2 (11.77), contributing to a distinctive fruity and floral aroma. Sensory evaluation confirmed that T2 had the highest taste score (89.7), with significantly reduced bitterness and astringency, consistent with its enriched umami amino acids (6.75 mg/g) and lower bitter amino acids (3.07 mg/g). These findings demonstrate that maintaining soil moisture at approximately 28% through moderate sprinkler irrigation effectively balances flavor-related metabolites and improves autumn tea quality, offering a practical strategy to reduce resource waste and increase economic returns.