Correlation and Pathway Analysis of the Carbon, Nitrogen, and Phosphorus in Soil-Microorganism-Plant with Main Quality Components of Tea (Camellia sinensis)

The contents of carbon (C), nitrogen (N), and phosphorus (P) in soil-microorganisms-plant significantly affect tea quality by altering the main quality components of tea, such as tea polyphenols, amino acids, and caffeine. However, few studies have quantified the effects of these factors on the main quality components of tea. The study aimed to explore the interactions of C, N, and P in soil-microorganisms-plants and the effects of these factors on the main quality components of tea by using the path analysis method. The results indicated that (1) The contents of C, N, and P in soil, microorganisms, and tea plants were highly correlated and collinear, and showed significant correlations with the main quality components of tea. (2) Optimal regression equations were established to estimate tea polyphenol, amino acid, catechin, caffeine, and water extract content based on C, N, and P contents in soil, microorganisms, and tea plants (R² = 0.923, 0.726, 0.954, 0.848, and 0.883, respectively). (3) Pathway analysis showed that microbial biomass phosphorus (MBP), root phosphorus, branch nitrogen, and microbial biomass carbon (MBC) were the largest direct impact factors on tea polyphenol, catechin, water extracts, amino acid, and caffeine content, respectively. Leaf carbon, root phosphorus, and leaf nitrogen were the largest indirect impact factors on tea polyphenol, catechin, and water extract content, respectively. Leaf carbon indirectly affected tea polyphenol content mainly by altering MBP content. Root phosphorus indirectly affected catechin content mainly by altering soil organic carbon content. Leaf nitrogen indirectly affected water extract content mainly by altering branch nitrogen content. The research results provide the scientific basis for reasonable fertilization in tea gardens and tea quality improvement.