Influence of cow manure vermicompost on the growth, metabolite contents, and antioxidant activities of Chinese cabbage (Brassica campestris ssp. chinensis)

The effects of cow manure vermicompost on plant growth, metabolite contents, and antioxidant activities of Chinese cabbage were investigated in pot cultures. Five treatments were designed by mixing vermicompost and soil at ratio of 0:7, 1:7, 2:7, 4:7, 7:0 (w/w). Marketable weight of Chinese cabbage was significantly (p < 0.05) higher in the 2:1 treatment than in the other treatments, while plants grown in the full soil treatment (0:7) showed the lowest marketable weight (Fig. 1a). Vermicompost application significantly increased the nutrient content of Chinese cabbage leaves (p < 0.05), especially in the 4:7 treatment, with increases in the contents of soluble sugar (Fig. 2a), soluble protein (Fig. 2b), vitamin C (Fig. 3a), total phenols (Fig. 3b), and total flavonoids (Fig. 3c) by 62%, 18%, 200%, 25%, and 17% compared to the full soil treatment, respectively. The antioxidant activities expressed by 2, 2-Dipenyl-1-picrylhydrazyl-scavenging activity (Fig. 4a), hydroxyl (OH)-scavenging activity (Fig. 4b), and iron (Fe²⁺)-chelating activity (Fig. 4c) were higher by 92%, 40%, and 36% in the 4:7 than 0:7 the treatment, respectively. Vermicompost application significantly increased (p < 0.05) the plant contents of 16 essential amino acids (Table 1); the total amino acid content showed the greatest increase in the 4:7 treatment, 90% compared to the full soil treatment.