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This study aimed to compare the responses of two Peruvian quinoa cultivars “ cv. Hualhuas” and “ cv. CICA-17” to water salinity and different levels of nitrogen under greenhouse conditions. A completely randomized experiment was conducted under artificial conditions. Irrigation was carried out at two levels of salinity (0.0 and 200 mM NaCl) with three levels of nitrogen supply [50 ppm low nitrogen(LN), 250 ppm moderate nitrogen (MN) and, 450 ppm high nitrogen (HN)]. In general, the growth-related parameters measured in this study were negatively affected by salinity, the effect was worst under LN, as it was not favorable even under control conditions. At LN; salinity decreased plant fresh weight (FW) by 45.01% and 60.06% in Hualhaus and CICA-17 plants, respectively. Plant height was significantly decreased by 45.10% and 47.46% for Hualhaus and CICA-17, respectively. The leaf number per plant and surface leaf area was reduced in response to salinity for both cultivars. Osmotic potential (Ψs) of all plant organs was decreased significantly with saline water irrigation. Under LN, salinity caused lowering K+ overall with some exceptions and over-increasing Na+. At LN treatment, salinity did not significantly affect the leaf pigments contents in Hualhaus cultivar but led to an increase in those of CICA-17 plants by 30.23%, 26.08%, 36% for chl (a), chl (b), and carotenoids, respectively. In addition to the profound changes caused by the salinity in all the studied CO2 exchange parameters of both quinoa cultivars. Under salinity and LN conditions Net CO2 assimilation rate (Anet) was significantly reduced reached about 54.94% in Hualhaus and 76.90% in CICA-17 of the control values. This was accompanied by significant decreases in stomatal conductance (gs) resulting in significant reductions in transpiration rate (E) which led to significant improvement in photosynthetic water use efficiency (PWUE) for both cultivars. Also, the seed yield was negatively affected for both cultivars. As a general trend, increasing of nitrogen level led to improve in the most of morphological and physiological characteristics of both cultivars, whether under non-saline or saline conditions. Under non-saline conditions, FW of the Hualhaus cultivar was significantly increased by about 150.68% and 24.77% in response to MN and HN treatment, respectively, and by 95.91% and 56.08% for CICA-17 cultivar at MN and HN treatment, respectively. Although under saline conditions, the effect of nitrogen was less obvious, it improved the FW of the Hualhaus cultivar by 19.44% and 12.84%, and for CICA-17 by 33% and 47.35% in response to MN and HN levels, respectively. Moreover under saline conditions, HN level gave the lowest values of (Ψs) (more negative values) in most of the tested organs (roots, adult leaves and juvenile leaves) for both cultivars. In addition to increasing the number of leaves per plant and leaf area per leaf. Increasing of nitrogen levels also significantly increased the yield of Hualhaus cultivar by 167.86% and 105.63% under non-saline conditions and by 16.14% and 32.93% under saline conditions in response to MN and HN treatments, respectively, compared to LN. Likewise, the seed yield of CICA-17 plants increased by 133.44% and 66.49% to MN and HN treatments, respectively under non-saline conditions, and by 48.96%and 9.62% to MN and HN treatments, respectively, under saline conditions. from these results and under these experimental conditions, it was found that a moderate nitrogen level could be an optimal level to sustain growth and productivity for quinoa plants grown either under non-saline or saline conditions.