Effect of Nitrogen Concentration in the Nutritional Solution and Harvest Time on Nitrate Content in Baby Leaves of two Swiss-Chard Cultivars Crop in a Hydroponic System
Vanegas David(1), Contreras Antonia(1), Tapia María Luisa(1), Lizana Luis Antonio(1,2), Escalona Víctor(1,2).1:Centro de Estudios Postcosecha. Facultad de Ciencias Agronómicas. Universidad de Chile.2:Departamento de Producción Agrícola. Facultad de Ciencias Agronómicas. Universidad de Chile. Santa Rosa 11315, La Pintana, P.O. Box 1004, Santiago, Chile. website: www.cepoc.cl
The development of baby leaf vegetables has increased due to its fast processing operations and its attractiveness as a gourmet product. Despite these benefits, its high level of nitrates in tissues will create serious health problems. To reduce these levels, the dose of nitrogen fertilization and harvest time are essential. The objective of this study was to evaluate the nitrate content in two cultivars of Swiss-chard (baby leaf) changing the N2 content of nutrient solution and time of harvest. For this, two independent assay were performed, where the nitrate content, nitrate reductase activity (NRA) and quality parameters such color, dry weight, height of leaf were measured in two cultivars of Swiss-chard (Beta vulgaris L. var. Cicla) with a red (E1) and orange petiole (E2), respectively. A randomized split-plot design was performed, where the main plot corresponded to N2 dose (100, 200, 300 and 400 mg N2 L¯¹) and subplots of different harvest times (9, 12 and 21 h). In E1, the time of harvest was the main factor on the nitrate content, where high N2 levels were founded at 8 h, and low levels at 12 and 21, probably due to different carbohydrate levels and reducing supplying powers available to activate the NRA, which had its maximal activity at 12 and 21 h. By contrast, in E2 the N2 concentration in the nutrient solution had a significant effect on the content of nitrates, where high dose caused a high accumulation in tissues. In both assay, increased nitrate content in the petiole and midrib compared to the lamina was obtained.