Evaluating th The effect of biochar fertilizer and foliar application of humic acid on the quantitative and qualitative characteristics of Roselle (Hibiscus sabdariffa)

In order to investigate the effect of biochar fertilizer and humic acid foliar application on quantitative and qualitative characteristics of Roselle (Hibiscus sabdariffa) a split plots experiment in a randomized complete block design was performed with three replications in the Research Field of Islamic Azad University, Arak Branch during 2017-2018 and 2018-2019. Experimental factors included 3 levels of biochar (non-consumption or control, 4 tons ha-1, and 8 tons ha-1) and the second factor of foliar spraying of humic acid 82% at 4 levels (non-consumption or control, 100 mg/l, 200 mg/l, and 300 mg/l. Interaction of biochar and humic significantly affected fruit yield. In the treatment with 8 t/ha biochar and 200 mg/l humic acid, the fresh weight of shoots was 465.1 g plant, showing an increase by 32% compared to the minimum value obtained from fertilizer control. At different levels of humic acid, consumption of 8 tons per hectare biochar always increased fruit yield compared to non-biochar treatment and consumption of 4 tons per hectare biochar. The interaction of biochar and humic acid on color intensity was significant. In the combined treatment of 8 tons per hectare of biochar and 100/l of humic acid, a red index of 14.67 was obtained. At different levels of humic acid, consumption of 8 tons per hectare biochar increased the red color index. Considering the fact that the intensity of red color in Roselle indicates the quality of the product, the consumption of 300 mg per liter humic acid and 8 tons per hectare biochar increased this trait, improving its functional traits.