Nitrate smoothly accumulates in leafy vegetables and poses serious health hazards if connected excessively to the human diet. The objective of this study was to improve the cultivation method of low-nitrate lettuce grown in plant factories.
A substantial decrease of nitrate content (NO3-) in three lettuce cultivars was subjected to short-term pre-harvest treatment combined with a lowing nitrogen supply of nutrient solution to half concentration and high photosynthetic photon flux density (PPFD) by LED lighting. The lettuce (Lactuca sativa L. cv. Frill ice, Lvzhu, Ziwei) was hydroponically grown in the full strength of nutrient solution based on the Yamasaki formula up to harvest time within a controlled environment under two light sources using fluorescent lamps and LEDs.
The results demonstrated that subsequent 3-day treatment of additional PPFD from 250 µmol m-2 s-1 to 350 µmol m-2 s-1 from 18 days after transplanting and half concentrations of nitrogen (NO3--N) in a nutrient solution which is composition to standard resulted in the decrease of nitrate content as compared to plants grown under initial PPFD and full concentration of NO3--N composition. The gradual decrease in nitrate content was accompanied by an increased concentration of nutritional carbohydrates. Another important indicator of nutritional quality such as vitamin C content exhibited some variation, fresh weight of cultivars in cv. Frill ice and Ziwei were observed higher with fluorescent lamps and for cv. Lvzhu with LED treatment section followed by lowest nitrate content of fresh leaves, respectively.
Further, presented results disclosed that to avoid high accumulation of nitrate in leafy vegetables, the strategy of lowering nitrogen supply and increasing light intensity prior to harvest benefits growers and consumers by improving the quality of the product and also making it consumer-friendly.
Khan, Khurshied & Yan, Zhengnan & He, Dongxian. (2024). Impact of Light Intensity and Nitrogen of Nutrient Solution on Nitrate Content in Three Lettuce Cultivars Prior to Harvest. Journal of Agricultural Science. 10. 99-99. 10.5539/jas.v10n6p99.
Source: Research Gate