Effect of potassium humate and growth stage on phenolic compound and vitamin C accumulation in kale (Brassica oleracea var. sabellica)

Kale is one of the top economically valuable crops in the world because of its high antioxidant content. Research shows that the antioxidant profile of Brassica crops varies with growth stages due to soil fertility, temperature, light and other agronomic factors. This study aimed to analyze the effect of potassium humate on phenolic compound content, the greatest contributor to the antioxidant properties of the highest-ranking superfood kale ( Brassica oleracea var. sabellica ). Our results showed that potassium humate at different growth stages elicited phenolic compounds in the studied samples. Leaves of 22 weeks old plants accumulated phenolic compounds about two times higher than those of 7 weeks old plants. Vitamin C content was increased by potassium humate treatment at 7 weeks. At 22 weeks levels in controls and treated kale leaves did not significantly differ.