Effect of salinity and sodium adsorption ratio (SAR) of irrigation water on yield and ionic ratios of rapeseed (Brassica napus L.)

Abstract
Background and Objective: The salinity and sodicity of water and soil is one of the most effective factors in reducing the agronomic production. Incorrect management in irrigation, low drainage, and the use of saline water in irrigation, were effective factors in making saline soil. This research was conducted to study the growth diagnosis of two varieties of rapeseed and also, to study the changes of physiochemical characteristics and some nutrient contents in different levels of SAR and salinity.
Materials and Methods: In order to study the effect of salinity and SAR on the yield and physiological characteristics of rapeseed, an experiment was carried out with two varieties of rapeseed, named Talayeh and Okapy in three factorials at a completely randomized design (CRD) with four replications. In this experiment, salinity with 3 levels 0.35(control), 6 and 12 dSm-1, SAR with 4 levels 0, 6, 12 and 18 from NaCl and CaCl2 were conducted. In this research, traits consisted of the SPAD index, the number of silique, grain weight, a+b chlorophyll, a/b chlorophyll, carotenoids, the content of Na, K and Ca were determined.
Results:
The result of the analysis of variance showed that the effect of variety on number of silique, SPAD index, chlorophyll a/b and Ca/Na ratio were significant, the effect of salinity in all of treats were significant, the interaction effect variety and salinity on grain weight, chlorophyll a/b ratio, carotenoids content and K/Na ratio were significant, the interaction effect of salinity and SAR on grain weight, chlorophyll a/b ratio, chlorophyll a+b content were significant. The comparison means of varieties showed in Talayeh variety SPAD index, chlorophyll a+b content K/Na ratio was better than Okapy variety, but silique number, grain weight, chlorophyll a/b ratio and Ca/Na ratio, in Okapy variety was better. The comparison means of salinity showed that with the increase in salinity levels, the SPAD index increased, while silique number and grain weight decreased. The comparison means of SAR showed with the increase in SAR, the SPAD index and Ca/Na ratio increased and the maximum rate obtained in SAR18, in other traits with the increase in SAR, decreased in contents. The investigation of the interaction effect of variety and salinity, in both of variety showed the grain weight in Talayeh was 2.99 grams in pot, while this trait in Okapi was 3.13 grams in pot. In the interaction effect of salinity and SAR, the lowest amount in grain weight was 2.74 grams in pot at EC12 and SAR=18.
Conclusion:
Whereas salinity and SAR causes negative effects on the growth indices of rapeseed, this effect depends on the variety, also, in the traits studied these effects in Talayeh variety were less than those of Okapy. also with increasing in Calcium proportion at salinity source cause the reducing of bad effects in all traits. So in the high salinity water has high Ion calcium, can have better quality for use in agriculture.