Ameliorative effects of calcium nitrate and humic acid on the growth, yield component and biochemical attribute of pepper (Capsicum annuum) plants grown under salt stress

The present work was carried out in order to determine the effects of calcium nitrate and humic acid applications either separately or in combination on the growth and fruit yield quality of pepper plants under salt stress condition. Two different concentrations of calcium nitrate (Ca1; 60 mg/kg soil and Ca2; 120 mg/kg soil) were applied to the soil before sowing whereas humic acid applications (HA1; 750 mg/kg soil and HA2; 1500 mg/kg soil) were performed during plant growth (at the third true leaves stage). Plants were irrigated with saline water in a concentration of 100 mM NaCl. Data showed that applications of both concentrations of humic acid and lower concentration of calcium nitrate (Ca1) individually caused significant increases in growth parameters, RWC, photosynthetic pigments, minerals content, non-enzymatic antioxidants contents of the plants under normal and salt stress conditions. Moreover, fruit antioxidant compounds and quality of fruits (capsaicin, lycopene, β-carotene, total phenol, total flavonoids and antioxidant activity) were improved by using theses treatments. The combined treatment of Ca1 and HA2 was the most effective one on the previous criteria under salt stress conditions. Therefore, the usage of humic acid and calcium could be suggested to improve the soil properties, growth and antioxidant capacity of pepper plants and to mitigate the damage caused by salt stress.