Short‐term alteration of nitrogen supply prior to harvest affects quality in hydroponic‐cultivated spinach (Spinacia oleracea)

• Published in: Journal of the science of food and agriculture 2014-03, Vol.94 (5), p.1020-1025
• Main Authors: Lin, Xian Yong, Liu, Xiao Xia, Zhang, Ying Peng, Zhou, Yuan Qing, Hu, Yan, Chen, Qiu Hui, Zhang, Yong Song, Jin, Chong Wei
• Format: Article
• Language: English
• Subjects: Ammonium Compounds - administration & dosage; Ammonium Compounds - adverse effects; Ammonium Compounds - metabolism; antioxidant activity; Antioxidants; Antioxidants - analysis; Antioxidants - metabolism; Biomass; biomass production; China; Crops, Agricultural - chemistry; Crops, Agricultural - growth & development; Crops, Agricultural - metabolism; Fertilizers - adverse effects; Food Quality; Food science; Functional Food - analysis; Harvest; harvesting; Humans; Hydroponics; nitrate; Nitrates - administration & dosage; Nitrates - adverse effects; Nitrates - metabolism; Nitrogen; Nitrogen Cycle; Nutrients; Nutritive Value; oxalate; Oxalates; Oxalates - adverse effects; Oxalates - antagonists & inhibitors; Oxalates - chemistry; Oxalates - metabolism; patterns of nitrogen supply; Plant Leaves - chemistry; Plant Leaves - growth & development; Plant Leaves - metabolism; Plant Stems - chemistry; Plant Stems - growth & development; Plant Stems - metabolism; Plants (organisms); Solubility; Spinach; Spinacia oleracea; Spinacia oleracea - chemistry; Spinacia oleracea - growth & development; Spinacia oleracea - metabolism; Time Factors; Toxicity; Vegetables; vitamin C
• ISSN: 0022-5142; 1097-0010
• DOI: 10.1002/jsfa.6368

BACKGROUND: Quality‐associated problems, such as excessive in planta accumulation of oxalate, often arise in soillessly cultivated spinach (Spinacia oleracea). Maintaining a higher level of ammonium (NH₄ ⁺) compared to nitrate (NO₃ ⁻) during the growth period can effectively decrease the oxalate content in hydroponically cultivated vegetables. However, long‐term exposure to high concentrations of NH₄ ⁺ induces toxicity in plants, and thus decreases the biomass production. Short‐term application of NH₄ ⁺ before harvesting in soilless cultivation may provide an alternative strategy to decrease oxalate accumulation in spinach, and minimise the yield reduction caused by NH₄ ⁺ toxicity. RESULT: The plants were pre‐cultured in 8 mmol L⁻¹ NO₃ ⁻ nutrient solution. Next, 6 days before harvest, the plants were transferred to a nutrient solution containing 4 mmol L⁻¹ NO₃ ⁻ and 4 mmol L⁻¹ NH₄ ⁺. This new mix clearly reduced oxalate accumulation, increased levels of several antioxidant compounds, and enhanced antioxidant capacity in the edible parts of spinach plants, but it did not affect biomass production. However, when the 8 mmol L⁻¹ NO₃ ⁻ was shifted to either nitrogen‐free, 4 mmol L⁻¹ NH₄ ⁺ or 8 mmol L⁻¹ NH₄ ⁺ treatments, although some of the quality indexes were improved, yields were significantly reduced. CONCLUSIONS: Short‐term alteration of nitrogen supply prior to harvest significantly affects quality and biomass of spinach plants, and we strongly recommend to simultaneously use NO₃ ⁻ and NH₄ ⁺ in hydroponic cultivation, which improves vegetable quality without decreasing biomass production. © 2013 Society of Chemical Industry