Introduction: Quinoa is a grain and annual plant and is the only plant food that contains all essential amino acids, micronutrients and vitamins. This plant is very resistant to a wide range of abiotic stresses such as cold, salinity and drought and can grow in marginal soils. One of the most important factors determining the productivity of any new product in a specific region is identifying the optimal time to plant a plant that meets its environmental needs. The planting date of quinoa is one of the main factors that play an important role in its production. Planting density is one of the most important agricultural measures that affect crop yield. The optimal density of the plant is a density in which all environmental factors are fully used and at the same time intra-plant and extra-plant competition are at a minimum so as to obtain the maximum possible yield with the desired quality. Considering the importance of quinoa from nutritional aspects and the expansion of its cultivation, the aim of the present study was to investigate the effect of planting date and different densities on the yield and yield components of quinoa under dry conditions in Gonbad Kavos.

Materials and Method: The experiment was conducted as a factorial experiment in a randomized complete block design with three replications at Gonbad Kavos University Research Farm in the 2020-2021 crop year. The planting date factor in six levels included 5 December, 21 December, 4 January, 20 January, 3 February, and 19 February, and the density factor in four levels included 10, 25, 40, and 55 plants per square meter. The Titicaca variety of quinoa was used in this study. The number of planting rows was five lines spaced 37.5 cm apart. The distance between plots was half a meter and the distance between replicates was two meters. Each plot was five meters long and planted about one centimeter deep. At the time of planting, 100 kg/ha-1 of triple superphosphate was used. N fertilizer was added to the soil as a starter fertilizer during planting along with the seeds. During the growth period, weeds were controlled mechanically (hand weeding) and pests (diazinon 1 liter/ha combined with acetamiprid 0.375 kg/ha) and diseases (daconil 2 kg/ha) were controlled chemically. The entire plot was harvested by removing the edge rows and half a meter on both sides of the middle rows. To determine dry weight, the samples were crushed and placed in an electric oven at 70°C until constant weight was reached (about 48 hours). The total rainfall during the entire growing period was 199 mm.

Results and Discussion: The effect of planting date and density on all studied traits was significant. The interaction effect of planting date × density was not significant on any of the traits. The highest plant height was 49.58 cm from the planting date of 5 December and 50.8 cm from a density of 55 plants per square meter. The highest grain yield with 1630.5 kg/ha-1 was on the planting date of 5 December and the lowest with 657 kg/ha-1 was on the planting date of 19 February. The highest and lowest grain yields of 1364.2 and 964.5 kg/ha-1, respectively, were obtained from densities of 40 and 10 plants/m2.

Conclusion: In general, and according to the results obtained in the present study, the appropriate planting time is 5 December and the optimal density is 40 plants per square meter in dry conditions of Gonbad Kavos.