Investigation of Physiological and Yield Characteristics of Quinoa as Affected by Different Levels of Irrigation and Plant Density

IntroductionQuinoa is a dicotyledonous plant from the Amaranthaceae family, with favorable nutritional value and a high potential for growth and production in adverse environmental conditions. Despite being three carbon, it has high water consumption efficiency and as a new crop, due to its wide adaptation to different environment conditions such as salinity and drought, as well as being premature, it is suitable for planting in arid and desert areas and has many factors. Genetic and environmental factors such as genotype, density, arrangement and planting date, soil salinity, and drought stress affect yield. Among these, drought is one of the most important non-living stresses that cause great damage to crops and horticulture in the world every year. And especially Iran, which is considered an arid and semi-arid country. The effect of moisture stress on plants varies depending on which stage of plant growth occurs and plants can work through various mechanisms such as reducing growth parameters, closing pores, reducing photosynthesis, changing regulatory mechanisms of ion transport, and increasing activity. Antioxidant enzymes cope with drought stress to some extent, although such mechanisms are energy-intensive and cause a decline in performance.Materials and MethodsIn order to investigate the optimal density of quinoa at different levels of irrigation, a factorial experiment was conducted based on completely randomized design with three replications at the research farm of the Faculty of Agriculture, Birjand University. The first factor was irrigation levels (based on 50, 75, and 100% water requirement) and the second factor was plant density at 5 levels (40, 60, 80, 100, and 120 plants m-2). Measurement traits included relative leaf water content, stomatal conductance, electrolyte leakage, number of branches, number of grains per branch, branch weight, 1000-grain weight, grain yield, water use efficiency, and grain protein.Results and DiscussionThe results showed that the yield components in response to low irrigation conditions were significantly reduced, so that the highest 1000-seed weight, number of branches, number of seeds per branch, branch weight and yield at the level of 100% water requirement were, respectively, 0.1 (g), 1368.4 (branching per square meter), 132.64 (grains per branching), 2377.8 (grams per square meter) and 3265.25 (kg ha-1) have been obtained. The maximum orifice conductivity measured at 35.66 (mol CO2 per square meter) was obtained at the beginning of flowering at 100% water requirement. Also, with decreasing irrigation level, physiological traits including relative leaf water content decreased significantly and traits such as electrolyte leakage and grain protein increased. The optimal density at the irrigation level of 100, 75, and 50% of water requirement were 113, 105, and 80 plants per square meter, respectively. The interaction of irrigation levels and density also showed that the highest yield was 100% of water requirement and density of 100 plants with 4226.52 kg ha-1. The results showed that at the irrigation levels of 100 and 75% of the water requirement, the highest yield was obtained at a density of 100 plants and with a decrease in density at these levels by 61.2 and 73.2%, respectively, was associated with a decrease in yield, but at the level of 50%. The highest yield was obtained at a density of 80 plants, which was accompanied by a decrease in yield to 40 plants with a yield of 73.5%. The results also show an increase in optimal density with increasing irrigation level, so that the most optimal density at the irrigation level of 100% of the water requirement is 113 plants per square meter and with increasing the stress to 75 and 50% of the water requirement, respectively, density Optimal yields of 105 and 80 plants per square meter have been achieved.ConclusionIn general, the results show that lack of moisture has an adverse effect on quinoa yield such as 1000-seed weight, branch weight, number of seeds per branch, and number of branches in the main inflorescence and reduces the optimal plant density.