BackgroundIntroducing new crops to reduce the nutritional gap in Egypt is an important target. One of these crops is Quinoa which is characterized by high nutritional value with multiple food uses. However, it will compete with other winter crops, so it is candidate to grow in marginal lands like calcareous soils. Meanwhile, planting density and N requirements are not known under such conditions; therefore, this work was undertaken in calcareous soil Caco3 > 50%.MethodsThe experiments included three nitrogen fertilization treatments (0, 50 and 100 kg/fed.) and two plant densities (20,000 plants/fed. and 36,000 plants/fed.) on Quinoa (Chenopodium quinoa Willd.) cv. Shibaya Field over two consecutive winter seasons of 2018/2019 and 2019/2020 in calcareous soil. Quinoa seed yield, biological yield, straw yield, weight of 1000-seed, harvest index, total nitrogen percentage in seeds, crude protein content in seeds, phosphorus content in seeds and potassium percentage in seeds were determined. The experimental design was a split plot design with three replications.ResultsThe results showed that applying nitrogen fertilization at a rate of 100 kg/fed. had significantly greater seed yield, biological yield, seed yield, straw yield and weight of 1000-seed. All seed chemical contents except K percentage were significantly affected due to nitrogen fertilization. Increasing plant density from 20,000 to 36,000 plants per feddan significantly increased the biological yield, seed yield, straw yield, weight of 1000-seed and harvest index. The interaction between the two studied factors was significant on all characters of this investigation except, K percentage in seeds.ConclusionIt can be concluded from this study that the quinoa crop responds to the increase in nitrogen fertilization and increases productivity and quality when fertilized with a rate of 100 kg nitrogen per fed.