Irrigation Regimes and Nitrogen Rates as the Contributing Factors in Quinoa Yield to Increase Water and Nitrogen Efficiencies

Sustainable field crop management has been considered to reach the food security issue due to global warming and water scarcity. The effect of deficit irrigation and nitrogen rates on quinoa yield is a challenging issue in those areas. In this regard, the interaction effects of different N rates (0, 125, 250, and 375 kg N ha⁻¹) and irrigation regimes [full irrigation (FI) and deficit irrigation at 0.75 FI and 0.5 FI] on quinoa yield and water and nitrogen efficiencies were evaluated with a two-year field experiment. Increasing nitrogen fertilizer application levels from 250 to 375 kg N ha⁻¹ under FI and deficit irrigation did not cause a significant difference in seed yield and the total dry matter of quinoa. Furthermore, 20% and 34% reductions were observed for nitrogen use efficiency (NUE) and nitrogen yield efficiency with the application of 375 kg N ha⁻¹ compared with that obtained in 250 kg N ha⁻¹ nitrogen fertilizer, respectively. Therefore, a Nitrogen application rate of 250 kg ha⁻¹ and applying 0.75 FI is suggested as the optimum rate to reach the highest seed water use efficiency (0.7 kg m⁻³) and NUE (0.28 kg m⁻³) to gain 4.12 Mg ha⁻¹ quinoa seed yield. Under non–limited water resource conditions, an FI and N application rate of 375 kg ha⁻¹ could be used for higher seed yield; however, under water-deficit regimes, an N application rate of 250 kg ha⁻¹ could be adequate. However, questions about which environmental factors impressively restricted the quinoa growth for optimizing the potential yield need further investigation.