Determination of the Optimum Concentration and Time of Salicylic Acid Foliar Application for Improving Barley Growth under Non-Saline and Saline Conditions

In a 2yrs field study the effect of concentration and time of salicylic acid (SA) foliar application on growth of barley under non-saline and saline (2 and 12 dS m-1 of NaCl, respectively) conditions was evaluated in National Salinity Research Center of Iran, Yazd, central Iran during 2012-2014 growing seasons. The treatments of SA (11 treatments) included without SA and SA foliar application at 0.0, 0.35, 0.70, 1.05, 1.40 and 1.75 mM applied at tillering stem elongation ear emergence or stem elongation ear emergence. Salt stress led to significant decreases in seed yield and yield components; however, grain yield of barley plants were considerably increased when subjected to SA. This positive impact of SA was due probably to its effect on grain number. Average of grain yield in 0.0, 0.35, 0.70, 1.05, 1.40 and 1.75 mM SA concentrations were 496.1, 539.7, 538.5, 553.8, 517.4 and 501.3 g m-2 under non-saline and 189.2, 212.5, 219.1, 206.9, 200.3 and 182.3 g m-2 under saline conditions, respectively. Considering the negative correlation between sodium concentration in shoot and grain yield, modulating role of exogenous SA on adverse effect of salinity might be related to a SA-induced lowered Na concentration in such organs. The appropriate treatment seems to be SA foliar application at 1.05 mM for non-saline and 0.70 mM for saline conditions applied at stem elongation ear emergence, as they increased grain yield by 16.6% and 18.6%, respectively. The result of this study revealed that higher concentration or frequency of SA application could be associated with negative impacts on barley.