Humic acid supplementation improves salt tolerance in chili by modulating morpho-physio-biochemical variables

Abstract

As agricultural challenges related to soil salinity continue to grow, incorporation of humic acid into cultivation practices could contribute significantly to global food security and sustainable agriculture. This study assessed the effects of different doses of soil applied humic acid (0, 50, 100, and 200 mg/kg w/w soil) on the growth, photosynthetic pigments, and antioxidant potential of chili grown under varying concentrations of salt (0, 50 and 100 mM of NaCl). The results showed that a linear decrease was noticed in the growth, biomass, and photosynthetic pigment attributes of the chili plants by increasing salt level. More reduction was noticed at the higher levels of salt stress as compared to the control, primarily due to lowering of total chlorophyll concentrations and increased sodium accumulation in leaves. Dry biomass significantly increased with humic acid treatments, regardless of the stress level. The reduced enzymatic activities associated with ROS detoxification underscored the pivotal role of humic acid in maintaining redox homeostasis. Optimal use of humic acid (200 mg/kg) showed promising results in comparison with the rest of the treatments in minimizing Na⁺ uptake in the chili plants. This study demonstrates that the application of humic acid activates physio-biochemical defense responses against salt stress in chili plants and provides a significant pavement for the cultivation of chili in soils containing moderate levels of salt.