Effect of Supplementary Irrigation with Different Salinity Levels on Yield of Rainfed Wheat in Qazvin

In order to investigate the effect of single irrigation water quality on rainfed wheat yield, a study was conducted in Qazvin region. Treatments included four levels of water salinity with electrically conductive equal to 0.5 (S0), 4.9 (S1), 6.4 (S2) and 8.7 (S3) dS. m-1 and a rainfed treatment (D). The field experiment was conducted in plots with dimensions of 3 × 3 m. Statistical analysis was performed in the randomized complete block design. Irrigation was done as a single spring irrigation in stage of wheat clustering. The results showed that the effect of irrigation water quality on the total biomass, straw and grain yield of wheat was caused an increase of 18%, 12% and 26%, (in S0 treatment) an increase of 10%, 7% and 15%, (in S1 treatment) a decrease of 8%, 4% and 13%, (in S2 treatment) and a decrease of 21%, 13% and 34%, (in S3 treatment) respectively, in relative to rainfed conditions. Therefore, single irrigation up to salinity level of S1 was acceptable and more than, that was not recommended. Grain yield compared to straw yield increased in S0 treatment and decreased in S3 treatment, by a more intensity. So that salinity stress intensified the decrease in wheat grain production. On the other hand, the amount of water productivity in D, S0, S1, S2 and S3 treatments was calculated equal to 2.26, 2.462, 2.3, 1.93 and 1.644 kg. m-3, respectively. Also, a linear equation was presented for estimate the amount of water productivity, based on the water salinity amount. The general result is that the using of water resources with salinity up to S1 level in single irrigation of rainfed wheat, will increase the production and economic efficiency in Qazvin agricultural sector.