Abstract
Surplus absorption of elements that contribute little to crop productivity and quality can be avoided, and fertilizer consumption costs minimized, by applying elements quantitatively to the nutrient solution fed to the plants. The aim of this study was to determine the minimum macronutrient requirements of spinach (Spinacia oleracea L.) with a desired plant size, so that fertilizer management in plant factories can be maximized. Spinach plants were grown in a plant factory (20°C/17°C day/night temperature, photosynthetic photon flux (PPF) of 350 μmol·m-2·s-1 for 12 hours per day using cool-white fluorescent lamps, 1,000 μmol·mol-1 CO2). Spinach grew and developed rapidly, and reached its desired marketable size in only 12–15 days after being transplanted to the study conditions. At day 15 of cultivation under the treatment conditions, the required quantities of macronutrients per plant (90 grams in fresh weight) were determined as follows: 191 mg N, 31 mg P, 345 mg K, 34 mg Ca, 38 mg Mg, and 13 mg S. In conclusion, a quantitative nutrient managing method with low nutrient concentrations is feasible and resource-saving for hydroponic vegetable production in plant factories.
Highlights
Hydroponic systems have currently been widely established, and they are applied for vegetable and flower production worldwide
Addition of nutrients is usually controlled by the electrical conductivity (EC) of the nutrient solution
Photosynthetic photon flux (PPF) in the chamber was provided by cool-white fluorescent lamps at 350 μmol m-2 s-1 for 12 hours per day, and CO2 concentration was maintained at 1,000 μmol mol-1
Summary
Hydroponic systems have currently been widely established, and they are applied for vegetable and flower production worldwide. Management of the used nutrient solutions is considered as an effective way to control the quality and productivity of the crops, since nutrients are one of the main factors influencing plant growth and development. Addition of nutrients is usually controlled by the electrical conductivity (EC) of the nutrient solution. Nutrients can be optimized to get a desirable level of plant growth and development. Many studies have been conducted to evaluate the effects different nutrient solutions can have on the growth, morphology, and antioxidant contents in various cultivars of tomato [1,2], and leaf lettuce [3]. Nutrient solution composition has been modified to obtain low-potassium lettuce and tomato for dialysis patients [4,5]
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