JWSS - Journal of Water and Soil Science

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In this paper, the effect of irrigation water salinity levels on seed germination, dry matter weight of seedlings at eight-leave stage, and the salt tolerance of 8 rapeseed cultivars was investigated. Relative yield reduction in saline and non saline conditions, salt sensitivity index and Van Genuchten-Hoffman methods were used to determine the salt tolerance of the cultivars. Results showed that the effect of different salt levels, cultivars and their interactions on germination and dry matter weight of seedlings was significant at 0.01(the higher the salt level, the lower the germination and dry matter). Also, using the Van Genuchten-Hoffman method, the irrigation water salinity corresponding to 10%, 25%, 50% and 90% reducts in germination and dry matter of seedlings were determined. Statistical analysis showed that a single cultivar gives different responses to salinity during growth stages and it may be tolerant in one stage, but sensitive to salinity in another growth stage. In this research, ACSN1, Falcon, and Shirali in germination stage and ACSN1, Falcon, and Cobra in seedling growth stage were salt tolerant. The three cultivars Oyerka, Global, and Ceres and the next three Shirali, Global, and Oyerka were sensitive to salinity in germination and seedling growth stages, respectively. Finally, the ACSN1 and Falcon cultivars were introduced as salt tolerant, and Oyerka and Global were considered as salt sensitive.

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Canola (Brassica napus L.) in response to salinity represents various resistances with respect to its phonologic stages. Most plants such as Canola are resistant at germination stage. However, at seedling or earlier growth stages, plants become more sensitive to salinity but their tolerance increases with age. Salt tolerance of various plants has been extensively studied however, the results have either been qualitative or expressed as average values over root zone salinity for the whole growth season. Thus, developing appropriate models for quantitative characterization of plant response to salinity at different growth stages is essential. Canola which is considered as high economic value plant was selected for this study. Two productive stages for canola are recognized as flowering and ripening. To determine the effect of salinity on canola at vegetative growth stages, a greenhouse experiment was conducted on a natural saline loamy sand soil, using salinity treatment including one non-saline water (tap water) and 8 saline waters of 3 to 17 dS.m^-1. The canola plants were irrigated with tap water before the desired stage and then salinity treatments were imposed. The Maas and Hoffman (1977), van Genuchten and Hoffman (1984), Dirksen et al., (1993), and Homaee et al., (2002b) models were used to predict relative transpiration (T_a/T_p ) and relative yield ( Y/Y_m) as a function of soil salinity. The maximum error (ME), root mean square error (RMSE), coefficient of determination (CD), modeling efficiency (EF) and coefficient of residual mass (CRM) statistics were calculated to compare the models and their efficiencies. The results indicated that the van Genuchten and Hoffman (1984) model provides best prediction at flowering stage. However the Homaee et al. (2002b) model offers better prediction at ripening growth stage.