Effect of different ratios of nitrate and ammonium on seed yield, oil yield, physiological attributes and fatty acid composition of canola under conditions of salt stress

Canola is a major oil seed crop worldwide, and it is also an important crop in Mediterranean areas where salinity is an increasing problem. In this paper, the effect of different ratios of nitrate and ammonium on seed yield, oil yield, physiological attributes and fatty acid composition was evaluated under salt stress. Two field experiments were carried out over two crop seasons on SLM046 canola cultivar. In the first experiment different ratios of nitrate and ammonium were compared to each other and the best ratio was tested in the second experiment in composition with phosphorus and potassium fertilizers under mild and severe salt stress conditions. Soil salinity was induced by saline water over the entire crop cycle. The results from Experiment I showed that there was significant difference among nitrate and ammonium ratios so that 50:50 ratio showed the best influence on above mentioned traits. Seed and oil yield, photosynthesis, nitrate reductase activity and fatty acid percentage increased due to application of 146 kg ha(-1) ammonium nitrate which has equal proportion of nitrate and ammonium (50:50 ratios) while proline accumulation decreased as a result of this treatment. In addition, seed and oil yield and linolin, linoleic and oleic acid percentage increased by application of 146 kg ha(-1) ammonium nitrate when applied with the phosphorus and potassium fertilizers, simultaneously, in the second experiment. In general, considering the results of both experiments, application of 146 kg ha(-1) ammonium nitrate recommended under salt stress conditions along with phosphorus and potassium fertilizers.