Effect of Salicylic Acid Spraying on Shallot Yield under Salinity Stress Conditions

In this research, the effect of irrigation water salinity and salicylic acid spraying were investigated on the yield of shallot (Qazvin local variety). Water salinity treatments at four levels of 2(S1), 4(S2), 6(S3), and 8(S4) dS.m-1 and salicylic acid at four concentrations of 0(A1), 0.5(A2), 1(A3) and 2(A4) mM were applied in the greenhouse. The experiment was performed as factorial and in a completely randomized design, with three replications. Soil moisture was measured daily, and irrigation scheduling was done based on it. Results showed that salinity stress reduced crop water uptake and shallot tuber weight. Salicylic acid application improved crop water status and increased tubers weight under salinity stress. A4 treatment was the ideal concentration for maximum yield. Application of 2 mM salicylic acid at salinity levels of S1, S2, S3, and S4 increased tubers yield by 11.6%, 32%, 40% and 91%, respectively, compared to the control (A1). The response of dry yield to evapotranspiration showed that by increasing salinity stress, percentage of yield decreased more than the percentage of evapotranspiration. Use of salicylic acid decreased dry yield sensitivity to salinity stress, such that from treatment S1 to S4 yield response coefficients (Ky) were between 1.01- 1.62 (in A1 treatment), 0.93- 1.3 (A2), 0.48- 1.09 (A3) and 0.31- 0.97 (A4). The effect of salicylic acid on water productivity were calculated between 2.13- 1.14 (in A1), 2.15- 1.68 (A2), 2.26- 2 (A3), and 2.38- 2.19 kg.m-3 (A4). In conditions of using saline water for crop irrigation, application of salicylic acid will increase water productivity. Based on the experiment results and in conditions of lack of high-quality water for irrigation, salicylic acid spraying on crops will be a suitable method to reduce the harmful effects of salinity stress.