There is a growing interest in organic fertilizers because of increased demand for organic sweet onions and other vegetables. There are, however, limited studies on sweet onion bulb yield and quality in response to organic fertilization. The objective of this study was to evaluate the effects of organic fertilizer rate on sweet onion bulb yield and bulb quality before and after storage. Experiments were conducted at the Horticulture Farm, Tifton Campus, University of Georgia, in the Winters of 2012–13 and 2013–14. There were five organic fertilization treatments (organic fertilizer 3–2–3 equivalent to 0, 60, 120, 180, and 240 kg·ha−1 N). Total and marketable yields and individual bulb weight increased quadratically with increasing organic fertilization rate and responses failed to reach a plateau. The fraction of extra-large bulb increased with increasing organic fertilization rate. Incidence of onion bolting was maximal at 60 kg·ha−1 N and decreased with increasing organic fertilization rate. The percentage of bulb dry weight was highest in the unfertilized control and decreased with increasing organic fertilization rate. Organic fertilization rate had no consistent impact on bulb soluble solids content (SCC) and pungency (measured as pyruvate concentration) in the two seasons. Total antioxidant capacity (measured as gallic acid equivalents) values were among the lowest at 60 and 120 kg·ha−1 N. In conclusion, onion bulb yields increased with increasing organic fertilization rate, whereas incidences of bulb diseases responded differently to N rate. Botrytis rot was the main cause of postharvest bulb decay in all organic fertilization rates.

‘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−1 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 (Botrytis cinerea), and sour skin (Burkholderia cepacia), 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−1 K. Thus, under our experimental conditions, application of K rates above the recommended value (84 kg·ha−1 K) are unnecessary and will likely not improve plant growth, yield, or quality. Regarding S, rates higher than 80 kg·ha−1 S are probably unnecessary and will not enhance either plant growth or bulb yield or quality of sweet onion.

Vidalia onions (Allium cepa L.) are sweet, short-day, low pungency, yellow Granex-type bulbs that are popular in the United States because of their mild flavor. There are limited studies on sweet onion plant growth in response to organic fertilization rate. The objective of this report was to evaluate the effects of organic fertilizer rates on sweet onion plant growth, and leaf and bulb mineral nutrients. Experiments were carried out at the Horticulture Farm, Tifton Campus, University of Georgia, in the Winters of 2012–13 and 2013–14. There were five treatments [organic fertilizer 3–2–3 equivalent to 0, 60, 120, 180, and 240 kg·ha−1 nitrogen (N)]. During the season and at the mature plant stage, root, stem, and bulb biomass increased whereas the root-to-shoot ratio decreased with increasing fertilization rate up to 120 kg·ha−1 N. Foliar concentrations of N and Ca decreased whereas Cu concentration increased with increasing organic fertilization rate. Bulb Mg and Mn increased whereas P and Cu decreased with increasing organic fertilization rate. The accumulation of mineral nutrients by onion whole plants increased quadratically (N, P, K, and S) or linearly (Ca and Mg) with increasing fertilization rate. The N use efficiency decreased with increasing organic fertilization rate; the agronomic efficiency of N (AEN) decreased quadratically and the marginal yield decreased linearly with increasing fertilization rate. Chlorophyll indices (CI) were highest with 240 kg·ha−1 N and lowest with 0 kg·ha−1 N. In conclusion, onion plant growth increased with increasing organic fertilizer rate probably because of augmented soil N levels. Observation of nutrient deficiencies late in the season, even at high organic fertilization rates, indicates that preplant application of organic fertilizer was sufficient to cover plant nutritional needs only partially and that applications of N fertilizer later in the season may be necessary. High application rates of organic fertilizer (above those required by the crop) may have resulted in significant N leaching because it is unlikely that the crop used most of the N that was mineralized. Bulb concentrations of P, K, Ca, Mg, S, B, Fe, Cu, and Mn were higher compared with values reported in the literature for onions produced with inorganic fertilizers.

No abstract

Pumpkins are difficult to produce for fall markets in the southeastern United States. Diseases, particularly aphid (Myzus persicae and Aphis spp.)-transmitted virus diseases, make fall pumpkin production difficult. Controlled-atmosphere (CA) storage may offer a method of overcoming this problem by using spring-or summer-produced pumpkins held in CA storage for fall sales. The objective of this study was to evaluate CA storage of pumpkins from spring and summer production. Pumpkins (Cucurbita pepo L.) were stored under ambient conditions (≈ 70-90 • F, ≈ 40%-60% relative humidity [RH]) and CA conditions (3% O 2 , 5% CO 2 , 50 • F, and 60% RH) to compare postharvest storage and shelf life. Pumpkins stored under CA conditions had significantly less damage than pumpkins stored under ambient conditions. There were significantly more marketable fruit after CA storage. Cultivar did not affect results. Although there were differences between storage methods, CA-stored pumpkins still had significant loss due to fungal pathogen activity. In 2007, 14% of pumpkins from CA storage were unmarketable fruit, with an additional 55% showing some damage. In 2008, 40% of pumpkins stored under CA conditions were unmarketable. Additional steps including surface sanitization would likely be required prior to widespread adoption of this technology.