Effects of type and rate of potassium fertilizer on agronomic and physiological traits of two durum wheat varieties under salt stress

To evaluate the role of potassium on salt tolerance of two durum wheat varieties، Behrang and Yavaros، a pot experiment was carried out as factorial experiment based on completely randomized design with three replications in College of Agriculture، Shahid Chamran University of Ahvaz، in 2013-2014. The experimental treatments were control، NaCl 150 mM، NaCl 150 mM together with two levels of 300 and 450 mg of potassium sulfate per 1 kg soil and two levels of 30 and 45 mg of potassium nano chelate 27% per 1 kg soil. Results showed that salinity stress lead to decreasing 68%، 51%، 58%، 22%، 15% and 61% of the grain yield، biological yield، stomatal conductance، greenness index، relative water content and K+ concentration، respectively، and increasing 3. 9 fold of the Na+ concentration of flag leaf compared with control treatment. In contrast، the application of different types of potassium under salinity condition alleviated the negative effects of salt stress on grain yield، biological yield، stomatal conductance، greenness index، relative water content and K+ concentration (25، 27، 22، 36، 7 and 35%، respectively)، and was caused the lower Na+ accumulation (2. 8 fold) compared with control. The variety responses to different levels of potassium were different، so that the second levels of potassium sulfate and nano potassium in Behrang variety caused to decrease the grain yield، while the grain yield of Yavaros variety was not affected. Results showed that Behrang variety was more tolerant than Yavaros in response to salinity. Generally، the application of potassium under salinity conditions was caused to maintain photosynthesis by adjusting the osmotic potential and relative water content and increasing the stomatal conductance as well as preventing loss chlorophyll، hereby reduces the salinity effects on yield performance of the durum wheat.