Investigation of Simultaneous Effect of Soil and Irrigation Water Salinity on Final Soil Salinity and Quantitative and Qualitative Yields and Water Use Efficiency of Canola

During the plant growing season, soil salinity changes by irrigation water. Therefore, assuming constant soil salinity during the growing season cannot simulate the actual plant growth conditions in the field. Accordingly, the present study aimed to investigate the interaction of irrigation water salinity (at six levels including 1.2, 4, 6, 8, 10 and 12 dS.m-1) and salinity of soil saturated extract at the beginning of the season (at three levels including 3, 4.5 and 6 dS.m-1) on growth, yield components, quantitative and qualitative yields and water use efficiency of a cultivar of canola, Hyola 401. For this purpose, a factorial experiment based on randomized complete block design with three replications was conducted in the Gorgan region. The results showed that the effect of initial soil salinity and irrigation water salinity on final soil salinity was significant. However, according to correlation analysis and regression equation, the dependence of final soil salinity on irrigation water salinity was higher than the initial soil salinity. The salinity of water and soil had no significant effect on the number of secondary branch and harvest index but they resulted in the significant increase of days to flowering and significant decrease in days to maturity, plant height and height of the first silique, stem diameter, silique length, number of seeds per silique, number of silique per plant, and biological yield. Due to the high tolerance of canola to the soil salinity, seed yield and seed water use efficiency (on the basis of seed yield and economy) were not affected by soil salinity, but the salinity of irrigation water caused a significant decrease of these traits because of the introduction of frequent salinity shocks into the plant. Also, the interaction of irrigation water salinity and soil salinity on oil percent, oil yield, and oil water use efficiency was significant so that an increase in irrigation water salinity from 1.2 to 12 dS.m-1 at different soil salinities of 3, 4.5 and 6 dS.m-1 resulted a decrease of oil percentage by 10.1%, 7.3%, and 10.5% and oil yield and oil water use efficiency by 23%, 18% and 28%, respectively.