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Nixwell Mudau, Puffy Soundy, and Elsa du Toit

Bush tea (Athrixia phylicoides) belongs to the Asteraceae family. It is a popular beverage, commonly used as an herbal tea and for medicinal purposes. In some parts of South Africa, people consume or drink it as an aphrodisiac. Bush tea was grown under varying nitrogen (N), phosphorus (P) and potassium (K) levels in the four seasons to determine the seasonal nutrient requirements for improved quality. Treatment consisted of 0, 100, 200, 300, 400, or 500 kg·ha–1 N, P, or K in a randomized complete-block design under 50% shade nets. Three N, P, and K parallel trials were conducted per season (autumn, winter, spring, and summer). Total polyphenols were extracted using Folin-Ciaocalteau reagents and analyzed in a spectrophotometer. Results for the N trial suggested that total polyphenols increased quadratically in response to N nutrition during summer, winter, and spring, but not in autumn. The optimum N level was 300 kg·ha–1. The highest total polyphenol was 51.1 mg·g–1 in winter. For the P trial, total polyphenols also increased quadratically in response to P nutrition regardless of season. Again winter had the highest total polyphenols (46.8 mg·g–1). The optimum P level was 300 kg·ha–1. In the K trial, regardless of season, total polyphenols plateaued at 200 kg·ha–1 and the highest polyphenols were in winter (43.3 mg·g–1). Therefore, for improved total polyphenol content, 300 kg·ha–1 N and P and 200 kg·ha–1 K are recommended regardless of season.

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Nixwell F. Mudau, Puffy Soundy, and Elsa S. du Toit

Bush tea (Athrixia phylicoides) belongs to the Asteraceae family. It is a popular beverage used as an herbal tea and as medicine for cleansing or purifying the blood, treating boils, headaches, infested wounds, and cuts, and the solutions may also be used as a foam bath. In some parts of South Africa, people drink bush tea for aphrodisiac reasons. Bush tea was grown under varying N, P, and K levels in all four seasons to determine the seasonal nutrient requirements for improved plant growth. Three parallel trials for N, P, or K one at each season were laid out in a randomized complete block design (RCBD) with six treatments replicated eight times. Treatments consisted of 0, 100, 200, 300, 400, or 500 kg·ha–1 N, P, or K. Parameters recorded were plant height, number of branches and leaves, fresh and dry stem mass, fresh and dry root mass, stem girth, fresh and dry shoot mass, leaf area and percentage leaf and root tissue N, P, and K. Results of this study demonstrated that, in all trials regardless of season, N, P, or K nutrition increased bush tea fresh and dry shoot mass, plant height, number of leaves, number of branches and leaf area. Regardless of season, the optimum level of N, P and K fertilization for bush tea on growth parameters was 300 kg·ha-1 N or P and 200 kg·ha-1 for K. No significant differences in number of flowers and buds (fall and winter), stem girth, fresh and dry root mass as well as fresh and dry stem mass were obtained.

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Itani Tshivhandekano, Fhatuwani Nixwell Mudau, and Thilivhali Emmanuel Tshikalange

Bush tea is a popular South African herbal and medicinal tea with the potential for commercialization. The objective of the study was to investigate the effects of different rates of applied nitrogen (N) and timing (early and late) of N application on yield, chemical composition, pharmacologic activity, and cytotoxicity of bush tea. Factorial treatments consisted of timed N application rates (0, 75, 150, and 225 kg·ha–1) for both early and late N application. The treatments were arranged in a randomized complete block design with five replicates. The results show a significant positive response of bush tea fresh and dry leaf and twig weight, chlorophyll, leaf tissue N, total polyphenols, and total flavonoids in response to applied N rates, regardless of the timing of N application, reaching a maximum at 225 kg·ha–1 of N. Later, regardless of the timing of N application, total tannins and total antioxidant activity increased with increasing applied N from 0 to 225 kg·ha–1, reaching a maximum of 150 kg·ha–1 N. The results of this study suggest that, with the exception of antimicrobial activity, most of the parameters recorded increased with increasing rates of N applied. The results further denote that parameters recorded were consistently greater on early applied N compared with late applied N. However, there was no significant difference between the minimum inhibition concentration (MIC) and minimum microbicide concentration (MMC) of early and late applied N. Bush tea applied with 75 N and 150 N had a significant MIC value (3.1 mg·mL–1) for Escherichia coli and Klebsiella pneumonia compared with 6.3 mg·mL–1 reached at 225 kg·ha–1 N. Among N rates applied, the MIC for Klebsiella oxytoca, Proteus vulgaris, Salmonella typhi, Serratia marcescence, and Staphylococcus aureus were not significantly different. Hence, N rates applied did not have a significant effect on bush tea MMC values of all microbial species tested. The cytotoxicity of bush tea leaf and twigs harvested from early and late N application were significantly reduced with increasing nitrogen levels reaching a maximum at 225 kg·ha─1. There was a wide variation of compounds despite rates of N applied as well as timing of application, with most compounds such as norfenfluramine, phytol, caryophyllene, propylene glycol, α-copaene, and squalene detected in greater quantities.