Effects of Different Irrigation Regimes and Nitrogen Fertilization on the Physicochemical and Bioactive Characteristics of onion (Allium cepa L.)

Abstract

The availability of water and nitrogen in the soil affect the metabolism of onion bulbs. The synthesis of metabolites and bioactive compounds are the most affected, along with the quality of the onion bulbs However, it is necessary to know the effects of different water levels and nitrogen fertilization to optimize the quality of the onion. The objective of this research was to study the effects of the different conditions of hydric stress and nitrogen fertilization during the development of onion (Allium cepa L.) crop, regarding its physicochemical and bioactive properties. Onions were grown using four available irrigation regimes (25, 50, 75 and 100%) and four doses of nitrogen fertilization (100, 150, 200 and 250 kg N ha−1). Onion without any treatment was considered as a control. The treatments low in irrigation and nitrogen fertilization increased the pH level (5.7 to 5.9) and bulb coloration in bright white/yellowish tones. An increase was observed compared to control in titratable acidity (0.13%) just in the nitrogen content, ascorbic acid (46%) and antioxidant capacity with DPPH (12.3%) and ABTS (93.7%). A decrease was shown in soluble solids (14.6%), firmness (3.5 kg cm−2), dry matter (6.6%), total phenols (50%) and FRAP (33.2%) values. Pyruvic acid remained constant (1.5 µmol g−1 FW). The onion bulb extracts showed an erythroprotective effect with a hemolysis inhibition percentage higher than 95%. Finally, the onions had low pungency, and were soft and extra sweet. The treatments with 25% usable humidity and nitrogen fertilization of 150 and 250 kg ha−1, favored the physical, chemical and bioactive quality of the onion bulb.

Response of Onion Fresh Weight, Nutrients Uptake, Nitrogen Use Efficiency, Yield, and Bulb Quality to Different Nitrogen Fertilization Levels and Plant Density

“…Nitrogen may play a significant role in increasing an onion's vegetative growth by enhancing its color, vigor of the leaf canopy, and meristematic activity, which contributes to the increase in cell number and cell elongation, and ultimately, its overall size [27]. These results are in harmony with those recorded by Barrales et al [28]. At 100 days after transplanting, the present study found that the lowest plant density (4 rows/ridge) yielded the best growth metrics in both growing seasons.…”

Water Productivity Indices of Onion (Allium cepa) under Drip Irrigation and Mulching in a Semi-Arid Tropical Region of Colombia

“…TBY ET act (5) where RCWP (kg m −3 ) is the real crop water productivity index, TBY is total bulb yields (kg), and ET act is the actual seasonal crop water consumption by evapotranspiration (m 3 ha −1 ). When considering this relation from a physical point of view, one should consider transpiration only [42,43].…”

“…It is widely consumed in both fresh and processed forms, including powdered, essential oil, and spice formats, owing to its distinctive aroma and flavor, which enhance food palatability [3]. The consumption of onions spans various culinary traditions and cultures, as they are valued for their nutritional properties and medicinal uses [4,5]. Onions are typically consumed either as dry bulbs at maturity or in their early green stage.…”

Analysis of Spectral Characteristics of Cotton Leaves at Bud Stage under Different Nitrogen Application Rates

“…Nitrogen deficiency in crops leads to decreased photosynthesis of plant leaves and growth retardation [36,37]. However, excessive application of nitrogen fertilizer reduces the tillering of crops [38]. The biological basis of monitoring crop growth via hyperspectral technology is that the difference in the internal structure and material content of crop leaves leads to a difference in spectral reflectivity, and then information on the material composition and internal structure of leaves can be obtained by studying the difference in spectral reflectance.…”