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This study aims at assessing the effect of limestone mining by-product from the Irati Formation on soil calcium, magnesium, and sulfur contents, as well as their accumulation in the onion biomass. The study was carried out in a greenhouse. A Eutrophic Haplic Planosol (SXe) and a Eutrophic Yellow Argisol (PAe) soil were used. The treatments included the control, limestone by-product, dolomitic limestone, calcium (Ca) + magnesium (Mg) carbonates, and Ca + Mg carbonates + gypsum. Onions were grown in pots containing 10 dm3 of soil kept at a moisture level close to the field capacity. The onion biomass harvest (bulb + leaves) was performed 77 days after transplanting. Afterwards, the soil macronutrient content and the dry onion biomass were determined, as well as its production. The by-product application increased Mg2+ content in both soils (+74% in SXe and + 182% in PAe) and Ca2+ and sulfate (S-SO42-) contents, respectively, in the PAe (+62%) and SXe (+124%). There was an increase in S accumulation due to the onion biomass cultivated in both soils (about 85%). Regarding Ca and Mg accumulations, no difference was observed in the by-product treatment when compared to the control. Therefore, it is possible to infer that the limestone mining by-product from the Irati Formation is potentially useful as a source of secondary macronutrients and proves to be a clean environmental solution for soil fertilization, increasing the sustainability of the local production system. [ABSTRACT FROM AUTHOR]

Severe root rot was observed in onion seedlings growing in nursery seedbeds in Changnyeong, South Korea in September 2021. The diseased onion seedlings showed symptoms including water-soaking, browning and blight, followed by seedling collapse. Three isolates were obtained from diseased onion seedlings, and their morphological characteristics were found to be similar to previously described Pythium species. Artificial inoculation with isolates produced identical symptoms to those observed in the original infection. Based on morphological characteristics, sequencing of rRNA gene internal transcribed spacer, ribosomal large subunit gene region, and cytochrome c oxidase subunit I gene region, and pathogenicity testing, the causative agent of root rot on the onion seedlings was identified as Globisporangium irregulare (formerly Pythium irregulare). This is the first report of root rot caused by G. irregulare on onion seedlings in Korea. The results of this study suggest that root rot may pose a severe threat to onion seedling cultivation. [ABSTRACT FROM AUTHOR]

Potential yield of onion (Allium cepa L.) in semi-arid regions is reduced by abiotic (soil infertility, poor agronomic practices, and unbalanced fertilization) and biotic (use of low yielding varieties, insect pest, and diseases) challenges. Soil infertility causes up to 60% yield loss in onion. This study was undertaken to assess the influence of manure and phosphorus (P2O5) fertilizer levels on growth and bulb development of onion under semi-arid conditions. Manure at 30 or 60 kg/5 m2 or 0.24, 0.48 or 0.62 g/plant for phosphorus and treatments combined at each application rate were used. Application of phosphorus and manure at 0.24 to 0.48 g/plant and 30 kg/5 m2 plot, respectively, improved vegetative and bulb development and weight. A combination of 30 kg/5 plot manure and 0.48 g/plant phosphorus produced an economic benefit based on number and weight of marketable bulbs. Application of 0.24 to 0.31 t∙ha−1 of P2O5, increased number of unmarketable bulbs. 'Red Bombay' performed better than 'Red Mantle.' Individual or combination application of P2O5 at 0.12 to 0.31 t∙ha−1 and organic manure at 60 t∙ha−1 may produce adequate yield, and 'Red Bombay' maybe a better choice than 'Red Mantle' under semi-arid conditions. Application of manure and phosphorus improves vegetative and yield in onion cultivars. Use of 30 kg/5 m2 of manure and a combination of 30 kg/5 m2 and 0.48 g/plant manure and P2O5, respectively, appear to improve yield. [ABSTRACT FROM AUTHOR]

Root and basal rot disease (RBR) of onion,Fusarium oxysporumf. sp.cepa(FOC), is one of the most important diseases, which cause tremendous losses in onion-growing areas worldwide. In this survey, various onion genotypes, including eight main and dominant Iranian seed sets and two exotic ones, were tested against FOC incidence in greenhouse and field conditions of various growing stages. The incidence of the RBR was determined at three stages, such as early, flowering and seed-setting stages, on the basis of disease severity. The genotypes reacted differentially to FOC within and between various stages with a very high significant level. The genotypes were classified in five scoring scales, accordingly. Highly infected ones tended to be associated with the highest mean scores of 75–100% severity and the least infected genotypes had the lowest scores of 0–10%. Moreover, the examined genotypes were ranked from 1 to 10 according to their markedly differing reactions to FOC at various stages. Variance and cluster analysis also showed similar results among the genotypes with various levels of infections. There was a direct, positive and enhancing correlation for every genotype to infection as the growing stages were reaching to the maturing stage. [ABSTRACT FROM AUTHOR]

Field experiments were conducted at Bugri and Binduri in northern Ghana in the 1996-97 and 1997-98 onion growing seasons, to determine the optimal irrigation regime for onion: morning and evening daily, morning daily, evening daily, morning and evening alternate days, morning or evening alternate days on bulb yield and yield components of onion cv. Bawku Red. Bulb yield of onion and yield components were significantly (P < 0.05) influenced by irrigation interval. Mean height of onion plants that received irrigation morning and evening, or morning or evening daily were about 39 cm while plants in other treatments were only 34 cm in height. Mean foliage weight when onion was irrigated morning and evening daily was 1.7 kg/plot compared to 1.4 kg/plot when onion was irrigated every other day. The highest bulb yields of 39.8 Mt-ha-1 were obtained when transplants received irrigation morning and evening. Onion bulb yield and yield components generally decreased significantly (P < 0.05) with increase in irrigation regime. Irrigation regime did not have any significant (P < 0.05) effect on the percent total sugar in onion bulb. Over 50% of the farmers in the trial preferred irrigating their onion crop once daily in the morning, thereby confirming the agronomic results obtained in the study. [ABSTRACT FROM PUBLISHER]

Optimum age of onion (Allium cepa L.) transplants for use in current and expanding onion-growing areas in Ghana is not well understood. Field studies were conducted at two locations in Ghana during the 1996-97 and 1997-1998 onion growing seasons. Transplants that were 20, 30, 40, 50, 60 or 70 days old, and of uniform size at each age, were used. The effect of transplant age on bulb yield components of onion was determined. The tallest plants were developed from 40-day-old transplants and the shortest were developed from 70-day-old transplants. Harvest index (bulb weight/total biomass weight) of onion decreased significantly as transplant age increased. The heaviest onion bulbs, 57.2 g, were from plants derived from 40-day-old transplants, and the lightest, 26.1 g, were from plants developed from 70-day-old transplants. Plants developed from 20- to 40-day-old transplants produced the highest yields. The results indicate that using 20- to 40-day-old transplants will give optimal bulb yields. [ABSTRACT FROM PUBLISHER]

The current spatial arrangement and density of onion plants adopted by producers in Northern Ghana was found to limit onion production. A study was carried out at two onion-growing locations in Northern Ghana, during the 1996-97 and 1997-98 onion growing seasons, to evaluate the response of onion cv. Bawku Red to eight spacings, i.e., 0.18 X 0.15, 0.15 X 0.15, 0.18 X 0.10, 0.15 X 0.13, 0.15 X 0.10, 0.13 X 0.10, 0.10 X 0.10, and 0.8 X 0.8 m, which gave the following plant densities: 37.04; 44.44; 51.28; 55.56; 66.67; 76.92; 100 and 156.25 plants/m2, respectively. The experimental variables measured were plant height, number of leaves, number of marketable bulbs, number of culls, neck diameter, mean bulb weight, bulbing index and bulb yield. Plant population density significantly (P < 0.05) affected bulb yields and yield components of onion. Bulb neck diameter, mean bulb weight and plant height decreased as population density increased. Total bulb yield increased significantly (P < 0.05) as population density increased. Number of marketable bulbs increased significantly (P < 0.05) with higher planting density. Onion bulb yield in the study ranged between 20.9 and 33.1 t_ha-1. It was concluded that sowing onion at densities above 76.92 plants/m2 increased marketable onion bulb yields. [ABSTRACT FROM PUBLISHER]