Effect of humic acid on some vegetative traits and ion concentrations of Mexican Lime (Citrus aurantifolia Swingle) seedlings under salt stress

Effects of humic acid on some vegetative characteristics and mineral concentrations of Mexican lime were investigated under different salinity concentrations. Four doses of humic acid (0, 1500, 3000 and 4000 mg/kg soil) and four salinity levels (1500, 2500, 3500 and 4500 µmos) were applied on Mexican lime seedlings. Experiment was conducted as a factorial arrangement based on a completely randomized design. The results showed that humic acid had a positive influence on plant height under salinity stress. Shoot number was significantly increased by application of humic acid under salinity stress conditions. In 4500 µmos salinity, application of 4500 mg/kg humic acid caused an increase in shoot fresh and dry weights, root dry weight and shoot potassium concentration. Percentage of sodium was decreased by application of 3000 mg/kg humic acid in the shoot of plants that were exposed to 4500 µmos salinity level. humic acid at 1500 mg/kg caused a reduction in shoot sodium percentage under 3500 µmos salinity level. When compared to the non-treated plants, application of humic acid led to a decline in chloride percentage in Mexican lime seedlings. In conclusion, 3000 and 4000 mg/kg humic acid can be used to reduce the toxic effects of salinity and also to decrease the uptake of toxic elements such as sodium and chloride in Mexican lime seedlings.