Effect of biochar on growth characteristics and sodium to potassium ratio of summer savory (Satureja hortensis L.) under NaCl stress

Salt stress is one of the important reasons of different problems in agricultural productions. Also, because of competition between sodium (Na+) with essential cations that necessary for cellular function, salinity cause to limit in absorption of mineral contents and growth reduction. One way of exciting salt from soil profile is using organic amendments such as biochar that recently has been extremely considered as a result of the weather modifications and soil management. Due to the characteristics of organic matter biochar, in this research the effect of biochar on growth traits, sodium (Na+) and potassium (K+) concentration of summer savory leaf under salt stress resulting from irrigation with NaCl were investigated. In order to investigate the effect of biochar on growth characteristics, sodium (Na+) and potassium (K+) concentration of summer savory ( Satureja hortensis L.) leaf under NaCl stress, a pot experiment was performed as factorial based on completely randomized design with four replications in greenhouse condition at Horticultural Research Station, Ferdowsi University of Mashhad, Iran, in 2017. The factors of the test included three levels of biochar (0, 1 and 2 % w/w of soil of each pot) and irrigation with salty water in three levels of salinity (0, 40, 80 mM NaCl). In order to produce biochar, the woods of mulberry (Morus alba) three put in electrical furnace with 530 C temperature for 14 h. Then the biochar crushed in very small pieces, sieved and added to the soil. The growth parameters included height, number of branch let, stem diameter, number of nodule, stem fresh and dry weight, leaf fresh and dry weight were measured by common methods. The amount of Na+ and K+ from the leaf samples were also measured. Data analysis were done with Minitab 17 software. The results of analysis of variances showed that the interaction effects of salinity and biochar treatments on number of branch let, stem diameter, number of nodule, stem fresh and dry weight, leaf fresh weight, Na+ , K+ and K/Na ratio in P<1% and on height and leaf dry weight in P< 5% were significant. The mean comparison of data indicated that the highest plant height (32.17 cm), number of branches (18.92), number of nodule (10.25), stem diameter (11.88 mm), stem fresh (1.75 g/plant) and dry (0.6 g/plant) weight, leaf fresh (3.44 g/plant) and dry (0.82 g/plant) weight were observed at the treatment of 2% w/w biochar without salinity were observed. Furthermore, the highest Na+ (1.69% leaf dry weight ) and K+ (3.39% leaf dry weight) were observed at 80 mM NaCl without using biochar and the treatment without salinity and biochar (control( , respectively. With increasing salt concentration, the K/Na ratio decreased and at the highest salt concentration (80 mM) reached to the lowest amount (1.71%). Salinity stress through limitation in mineral element, disrupting ionic balance, deficit in available water of plant and toxicity of mineral element cause to reduce cell growth. Competition between Na+ and K+ is one of the important physiological mechanisms of salinity stress resistance. K+ deficit is one of the events that occur due to the competition between Na+ with K+ for absorption in the roots. Therefore, it seems that in this experiment application of biochar resulted in increasing the tolerance to salinity by decreasing absorption of Na+ with plant and increasing K/Na ration. The results of this study showed that salinity cause to reduce the growth of summer savory and application of biochar in this condition cause to balance the harmful effects of salinity. In the treatment 80 mM NaCl without using biochar, the highest reduction in studied traits was observed. Moreover, adding biochar by absorbing Na+ of soil cause to reduce Na+ of plant. Due to the results of this research, correct application of biochar could be a suitable biological way for increasing the tolerance of plants to salinity