Effects of different levels of irrigation and nitrogen fertilizer on the yield and yield components of quinoa cultivar Giza-1

In recent years, the quinoa plant has been used extensively due to its favorable cultivation conditions in harsh climates. The cultivation of this plant is important given that Iran is located in an arid and semi-arid region. In the present study, the effects of different levels of water stress and nitrogen fertilizer were investigated on the yield and yield components of quinoa cultivar Giza-1. A factorial experiment in a completely randomized design based on potted planting with three replications was conducted in the research greenhouse at the Ferdowsi University of Mashhad in 2019. Periodic water stress factor consisted of four levels (without stress (control), stress in the total growth period, stress during the flowering stage, and stress during grain filling stage) and nitrogen fertilizer factor comprised three levels (0, 50, and 100 kg ha−1). To apply stress in different growth periods, the plants were irrigated at 50% of soil field capacity. The results of mean comparisons indicated that height, the number of offshoots, spike length, spike width, stem diameter, grain yield (GY, 134.8 g), and water use efficiency (WUE, 0.27 kg/m3) were significantly affected by water stress at 1% level and the number of spikes at 5% level. The interaction of water stress and nitrogen fertilizer significantly influenced the number of spikes, stem diameter, and GY at the 1% level and WUE at the 5% level. Overall, the highest GY was observed without stress treatment under irrigation at 450 mm and using 50 kg ha−1 of nitrogen fertilizer. The best yield-water-nitrogen production function is a linear function (Y = -0.835 + 0.034 I + 0.012 N) that can be fitted on quinoa cultivar Giza-1 based on the applied statistical indices and ranking of functions in the conditions of this study.