Planting Densities Affect Nitrate Concentration in Spinach (Spinacia oleracea L.) Cultivated in Root Floating Hydroponic System

Light is one of the main factors involved in the accumulation of nitrate in plants especially under low light intensity. The aim of this work was to evaluate concentration of nitrates in baby spinach leaves, growing at different densities in a floating hydroponic system root expressed as dry mass. Also others parameters such leaf area index and nitrate reductase activity were measured. The planting densities were 862, 1296, and 1728 plants/m². Three harvest periods were performed when the leaves reached 8–12 cm of length (day 28, 32, and 38 after transplants). The density 862 plants/m²showed a significant high dry mass compared to the highest density. Nevertheless, the leaf area index was bigger at higher density (4.61 cm²) compared to other treatments (2.96 and 3.61 cm²). A higher concentration of nitrates and low nitrate reductase activity were found in the highest density. The nitrate reductase activity was 0.47 μmol/g FM per hour for low density compared to 0.22 μmol/g FM per hour obtained in high density. It was concluded that high concentration of nitrate in baby spinach leafs was affected by the planting densities. Accumulated nitrates were higher in petiole than leaf. This work was financial supported by the Project FONDECYT-CONICYT, Chile Nº 1120274 and Ms A. Machuca CONICYT PhD Grant Nº21120299.