The effect of humic acid on growth, yield, and some physiological parameters of wheat under salinity stress

Salinity is a major environmental stress, reducing growth and yield of a wide variety of crops all over the world. The present study assessed effects of humic acid and salinity stress on the growth and some physiological responses of wheat in a pot experiment. The layout was 4×4 factorial experiment in RCBD design with salinity stress levels and humic acid concentrations as main factors in Ilam University during 2016. Treatments were the combination of four levels of salinity stress including stress-free conditions (irrigation by distilled water), and 4, 8, and 12 dS/m NaCl and four concentrations of humic acid including 0 (as a control), 50, 100, and 150 mg/l. The statistical analysis showed that salinity stress and humic acid application had significance effects on the morphological, physiological, and biochemical parameters of the wheat plants. Salinity stress imposed negative effects on plant growth and productivity. Under salinity conditions, growth parameters and yield attribute, relative water content, and chlorophyll reduced, but electrolyte leakage and antioxidant enzyme activity increased. Application of humic acid significantly increased plant growth parameters, chlorophyll content, and antioxidant enzyme activity, and decreased electrolyte leakage content. The highest salinity tolerance was obtained with 150 mg/l humic acid application. In general, results showed that the application of humic acid through affecting physiological parameters decreased adverse effects of salinity stress on the wheat plants.