Effect of sowing date and plant density on seed yield and yield attributes of quinoa (Chenopodium quinoa) genotypes

Quinoa (Chenopodium quinoa) is world-renowned for its nutritional and health benefits and its adaptability to different environments. Despite some research on quinoa cultivation, determining the appropriate planting date and density for different genotypes and regions needs to be studied. The main objective of this study was to determine the effects of planting date and planting density on quinoa seed yield in climatic conditions of Kermanshah. In this regard, field experiments were conducted during two growing seasons (2019-2020) at the research farm of Razi University, Kermanshah, Iran. The experiments were conducted as split-plot factorial in randomized complete blocks design with three replications. Three sowing dates (March 15th, April 15th, and May 15th) were assigned to the main plots, two planting densities (40 and 60 plants m^-2), and three genotypes including Titicaca, Q29, and Red Carina as subplots. The results showed that the highest seed yield (2179.72 and 2267.39 kg ha^-1) were achieved on April 15th, 2019 and May 15th, 2020, respectively. Sowing dates of April 15th in 2019 and May 15th in 2020 with a plant density of 60 plants m^-2 and Titicaca genotype had the highest seed yield for quinoa in Kermanshah climatic conditions. The results showed that panicle length and biological yield had a positive and significant correlation with grain yield in all studied planting dates. There was a positive and significant correlation between grain yield and grain weight per plant, 1000-grain weight, and biological yield at both densities. The path analysis revealed that panicle length had the highest positive direct effect on seed yield followed by 1000-seed weight on the first sowing date in 2019 and 2020, while biological yield and panicle length had the highest positive direct effect on seed yield on the second and third sowing dates, respectively. This experiment showed that genotypes and planting dates are the most determining factors affecting quinoa growth, development, and yield compared with planting densities.