Morphophysiological Changes of Quinoa in Response to Soil Application of Nitrogen Under Salinity Stress of Irrigation Water

In order to determine the effect of different levels of nitrogen on some traits of quinoa (Giza1 genotype) under salinity stress of irrigation water, a factorial experiment was conducted in a completely randomized design with three replications in a greenhouse at Shahed University of Tehran. Nitrogen as the main factor including 0, 50, 100 and 200 kg ha-1 was applied at planting time and before flowering stage. The salinity of water including 0, 3, 6, 9, 12 and 15 dS m-1 was considered as a sub-factor in the irrigation of pots. The initial soil salinity was 13 dS m-1. Results showed that nitrogen fertilizer and water salinity had a significant effect on the measured morphological and physiological characteristics. The highest yield was obtained in the control treatment. Increasing nitrogen up to 200 kg ha-1 decreased grain yield by 8% and increased 1000-seeds weight by 13%. The highest yield (8.79 g pot-1) was obtained in the control treatment of irrigation water. Also, the salinity of irrigation water at 15 dS m-1 reduced grain yield and 1000-seeds weight by 30 and 24%, respectively. The relative water content, sodium and chloride contents of the plant increased with increasing water salinity, and plant height, potassium content and K/Na ratio of the plant decreased significantly. Increasing the salinity of irrigation water up to 15 dS m-1 caused a 6% decrease in potassium and a 9% increase in quinoa sodium. According to the obtained results, quinoa can be recommended in the areas where salinity of irrigation water and soil as well as low soil fertility are limiting factors.