Survey of Nitrate Ion Concentrations in Vegetables Cultivated in Plant Factories: Comparison with Open-Culture Vegetables

Abstract

A survey of nitrate-ion concentrations in plant-factory-cultured leafy vegetables was conducted. 344 samples of twenty-one varieties of raw leafy vegetables were examined using HPLC. The nitrate-ion concentrations in plant-factory-cultured leafy vegetables were found to be LOD-6,800 mg/ kg. Furthermore, the average concentration values varied among different leafy vegetables. The average values for plant-factory-cultured leafy vegetables were higher than those of open-cultured leafy vegetables reported in previous studies, such as the values listed in the Standard Tables of Food Composition in Japan-2015 -Seventh revised edition . For some plant-factory-cultured leafy vegetables, such as salad spinach, the average values were above the maximum permissible levels of nitrate concentration in EC No 1258/2011; however, even when these plant-factory-cultured vegetables were routinely eaten, the intake of nitrate ions in humans did not exceed the ADI.

Urban farming in indoor settings: Nitrate limits compliance check of leafy green vegetables under LED lighting

“…Nitrate concentrations in leafy vegetables tend to be higher in hydroponic systems than those under conventional cultivation (in the ground with sunlight) (Gua-Fresh weight, SPAD value, nitrate content and % N of the three tested species in a non-circulating hydroponic system under two different light treatments. dagnin et al, 2005;Chen et al, 2014;Yosoff et al, 2015;Oka et al, 2016). Kmecl (2017) tested cabbage grown outdoors in NO 3 kg -1 with maximum values of 1,964 mg NO 3 kg -1 .…”

Quantitative Nutrient Management Reduces Nitrate Accumulation in Hydroponic Butterhead Lettuces Grown under Artificial Lighting

“…Nitrate accumulates readily in leaves under conditions of high nitrate absorption, and nitrate accumulation contributes to decreases in soluble organic compounds under low light intensity through its osmotic functions (Blom-zandstra and Lampe, 1985). Therefore, nitrate concentrations tend to be higher in vegetables grown in hydroponic systems with low light intensity, such as closed systems with artificial lighting (Oka et al, 2017;Zhou et al, 2013). Furthermore, these growing conditions decrease nutritional quality with decreased sugar and vitamin C levels (Fu et al, 2017;Kirimura et al, 2015).…”