Influence of various fertilizer regimes on phenological characteristics, polyphenol content, and antioxidant capacity of Amaranthus caudatus L.

In this study, the effects of different doses of organic (OF), vermicompost (VC), and chemical (CF) fertilizers on phenological characteristics, polyphenolic compounds, and antioxidant capacity of Amaranthus caudatus L. were evaluated. The study was carried out using a randomized block design with four replications. The findings revealed that the fastest germination occurred in the CF-6 L/da group, with a mean time of 7 days, while the slowest germination was observed in the OF-1200 mL/da group, with a mean time of 16 days. Regarding flowering time, the earliest flowering occurred on the 68th day in the CF-3 L/da group, while the latest flowering occurred on the 79th day in the OF-1200 mL/da group. The longest vegetative period was observed in the OF-1200 mL/da group with 215 days due to the effect of fertilizer applications and the fact that the study was carried out in the summer season. The closest vegetative period to the control group was 187-190 days in the CF-6 L/da group. The treatment groups' total phenolic content (TPC) and total flavonoid content (TFC) exhibited a range of 0.29-2.46 mg GAE/g and 0.50-1.26 mg QE/g, respectively. The highest TPC and TFC values among the treatment groups were determined in the OF-300 mL/ha and VC-2 L/ha groups, respectively. The IC50 values of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of methanol extracts exhibited a range of 3.34 to 6.80 mg/mL, with the OF-300 mL/da (50 mg/mL) group demonstrating the highest radical scavenging activity, exhibiting an 89.95% inhibition rate.