The impact of planting density on yield and nutritional value of Glycine max (L.) Merr. under outdoor hydroponics in Armenia

The aim of the research is to investigate the influence of planting density on the yield and nutritional value of soybean seeds under conventional agricultural and controlled hydroponics conditions of Ararat Valley. The obtained data will later serve as a basis for organizing the industrial production of soybean in Armenia. The influence of different planting density (30, 50, 70, and 90 plants m^‑2) on the seeds yield and on the accumulation of most important metabolites (protein, fat, fiber, carbohydrates, etc.) was evaluated in outdoor hydroponics. The experiments were carried out in automatically nourished hydroponic equipment with 2.0 m² surface area, using an EBB & Flow hydroponic system. Plants were nourished 1-2 times a day with the Davtyan nutrient solution. Soil culture was a control variant with 30 plants m^‑2 planting density. It has been shown that the planting density had significant influence on the yield and biochemical indices of soybean. Under hydroponic conditions the soybean seeds yield per plant with the lowest planting density exceeded the densest one by 4.5 times. At the same planting density (30 plants m^‑2), the yield of hydroponic soybean seeds were 1.9 times superior to that of the soil ones. Also, soil plants were distinguished by the highest fat and lowest protein accumulation (1.3 times) compared to the hydroponic plants. The obtained results established the effectiveness of soybean cultivation in Armenia. It turned out that a planting density of 30 plants m^‑2 is the most optimal in regard to financial matters. The regulated hydroponic method ensures obtaining about 1162 g of soybean seeds, 366 g of protein and 256 g of fat m^‑2. For soil culture, the above-mentioned indices are 596, 141 and 173 g, accordingly.