An investigation of effects of humic acid on changes in nutrients concentration of leaf, root and stem of Satureja khuzestanica under salinity stress

To investigate the influence of humic acid on the amount of absorption and allocation of elements on different parts of Satureja khuzestanica under salinity stress conditions, a greenhouse experiment was done as factorial based on a randomized complete block design in four replications. Factors included humic acid (zero, 10, 20, 30 and 40 mg kg-1 soil), and salinity stress (zero, 25, 50, 75 and 100 mM NaCl). It was found that the shoot dry weight was decreased with increasing the intensity of salinity stress; at a level of 100 mM sodium chloride, the average of this trait was reduced by 16%. In contrast, the use of humic acid, particularly 60 mg/kg soil, increased the shoot dry weight by 25% compared to the control. The effect of humic acid, salinity, and their interaction were significant (P≤0.01) on measured characteristics except stem and leaf nitrogen. Results showed that among organs (root, stem and leaf), the highest amount of sodium, potassium, phosphorus, zinc and nitrogen (5064, 9000, 13, 19.92 and 3.91 mg kg-1 dry weight) were observed in leaf in the S1H5, S2H2, S1H4, and S1H5 treatments, respectively. Among different organs, maximum iron content (759.9 mg kg-1 of dry weight) was observed in roots under S2H1. In general, with increasing salinity and decreasing humic acid, the concentration of salts such as sodium increased whereas the concentration of useful and essential elements for the plant decreased. According to the results, it can be stated that probably soil application of humic acid at high amounts (40 and 60 mg/kg soil) can moderate the effects of salinity stress by affecting the nutrient changes of plant organs.