Sweet Onion (Allium cepa) Plant Growth and Bulb Yield and Quality as Affected by Potassium and Sulfur Fertilization Rates

Abstract

<jats:p>‘Vidalia’ onions are sweet, short day, low pungency, yellow Granex-type bulbs that are popular in the United States. The relationships of sweet onion bulb yield and quality with potassium (K) and sulfur (S) concentrations are not fully understood. The objective of this study was to evaluate the effects of K and S fertilization rates on sweet onion plant growth and bulb yield and quality. Experiments were conducted at the Horticulture Farm, Tifton Campus, University of Georgia, in the Winters of 2012–13 and 2013–14. The experiment had five treatments (K/S rates: 56/80, 112/126, 168/172, 224/218, and 280/264 kg·ha<jats:sup>−1</jats:sup> of K and S, respectively). K/S rates had no effect on onion biomass of roots, bulbs, and shoots during the growing season. Marketable and total number and weight of onion bulbs and individual bulb weight were also unaffected by K/S rate. Incidences of bolting, double bulbs, Botrytis leaf blight (<jats:italic>Botrytis cinerea</jats:italic>), and sour skin (<jats:italic>Burkholderia cepacia</jats:italic>), and bulb dry weight, soluble solids content (SSC), and pungency (pyruvate concentration) were unaffected by K/S rates. In conclusion, K/S rates had little effect on plant growth and bulb yield and quality. The lack of response of onion plants to K/S rates, even at the lowest rate suggests that some of the K absorbed by plants originated from K already present in the soil before planting. The average K content of sweet onion whole plants was 80 kg·ha<jats:sup>−1</jats:sup> K. Thus, under our experimental conditions, application of K rates above the recommended value (84 kg·ha<jats:sup>−1</jats:sup> K) are unnecessary and will likely not improve plant growth, yield, or quality. Regarding S, rates higher than 80 kg·ha<jats:sup>−1</jats:sup> S are probably unnecessary and will not enhance either plant growth or bulb yield or quality of sweet onion.</jats:p>

Impact of the Hydroponic Cropping System on Growth, Yield, and Nutrition of a Greek Sweet Onion (Allium cepa L.) Landrace

“…Here, the high moisture percentage (>91%) confirm that Nerokremmydo should be treated as a fresh mild onion with reduced shelf life [70], implying a relatively short period of availability in local markets. According to our findings (Table 5), bulb %DM averaged 8.17%, which is similar to that of other sweet onions [72,73]. The development of plant % DM (Table 4) shows that its greatest increase occurred after bulbing and up to harvest, in agreement with relevant findings of other researchers [74,75].…”

Sweet Onion (Allium cepa L.) as Influenced by Organic Fertilization Rate: 1. Plant Growth, and Leaf and Bulb Mineral Composition

“…In another report, the addition of nutrients via soil or foliar biofertilizer was unable to supply the required nutrients and was responsible for generating imbalances which decreased the growth and development of the onion crop (Menezes J unior et al, 2013). The mean mineral nutrient concentrations of onion bulbs under organic fertilization in the present study differed compared with the bulb nutrient concentrations under inorganic fertilization of the K and S study (Díaz-P erez et al, 2016). Bulb N (1.84% vs. 2.00%), S (0.22% vs. 0.48%), and Zn (14 vs. 61 mg · kg -1 ) concentrations were lower whereas concentrations of P (0.45% vs. 0.30%), K (2.14% vs. 1.24%), Ca (0.64% vs. 0.25%), Mg (0.24% vs. 0.10%), B (24 vs. 17 mg · kg -1 ), Fe (76 vs. 40 mg · kg -1 ), and Mn (163 vs. 141 mg · kg -1 ) were higher in this study compared with the K and S study, indicating that utilization of organic fertilization resulted in more mineral nutrient-rich bulbs.…”

“…In a study on the effects of K and S inorganic fertilization rates on sweet onion conducted on the same farm as the present study, simultaneously, and using the same cultivar and cultural practices, mean root, bulb, and shoot dry weights of mature plants (at harvest time) were 1.3, 23.1, and 12.7 g/plant, respectively (Díaz-P erez et al, 2016). Results of the present study showed that compared with the onion plants of the K and S study, root growth was enhanced by up to 31% in plants under organic fertilization (at rates $180 kg · ha -1 N).…”

“…Plants at low organic fertilization rates started to display leaf chlorosis 4 weeks before harvest. Plants fertilized organically, regardless of the rate, showed more chlorotic foliage compared with plants (same cultivar and planted the same day) of the adjacent K and S fertilizer study (Díaz-P erez et al, 2016).…”

Comparative Analyses of Four Chemicals Used to Control Black Mold Disease in Tomato and Its Effects on Defense Signaling Pathways, Productivity and Quality Traits

“…Potassium (K + ) is a macronutrient required for fundamental physiological and molecular processes in plants [ 20 ]. It is probably involved in the development of stronger cell walls for preventing the entry of plant pathogens into the cell [ 21 ].…”