RESPONSE OF ONION (Allium cepa L.) CULTIVARS TO SPACING AND STORABILITY IN THE SUDAN SAVANNAH AGRO-ECOLOGICAL ZONE OF GHANA

Abstract

Low yield and poor quality of onions produced from the Sudan Savannah Agro-ecological Zone of Ghana among other factors attributed to lack of appropriate cultivars for cultivation, poor knowledge of plant spacing and storability. These factors have the potential of lowering income levels of farmers and wasting of precious agriculture land. Field and storage experiments were conducted at Bawku in the Upper East Region of Ghana from 2015 to 2016 to investigate the response of cultivar and spacing on growth as well as yield and shelf-life of onions. Four cultivars namely; Ares, Bawku Red, Red Creole and Top-Harvest and spacings namely; 8 cm x 10 cm, 10 cm x 10 cm, 12 cm x 10 cm and 14 cm x 10 cm were used for the field studies. Levels of the two factors were factorially combined and replicated three times using Randomized Complete Block Design (RCBD). Results showed that Ares was superior to the other cultivars in terms of bulb yield. The order of superiority among cultivars in terms of bulb yield was as follows: Ares > Red Creole > Top-Harvest > Bawku Red. Plant height, leaf length, leaf number, chlorophyll content, girth of bulb neck, root number per plant, root biomass per plant, average bulb weight, bulb diameter, percentage of bulbs with girth of 10-19 cm and percentage of bulbs with girth ≥ 20 cm increased with increasing plant spacing. However, leaf area index, days to hundred percent bulb initiation, biomass accumulation, days to maturity, total bulb yield and percentage of bulbs with girth < 10 cm increased with decreasing plant spacing. In general the results from the 2015 cropping season were lower in magnitude values as compared to those of the 2016 cropping season. After harvest, bulbs were stored in building with thatch roof and building with corrugated iron sheet roof. Results from the storability showed that the thatch roofed storage structure was superior to the corrugated iron sheet roofed structure. Bulb rot, bulb sprout, and total bulb weight loss were lower with the thatch roofed structure as compared with the corrugated iron sheet roofed structure. Cultivars such as Ares and Red Creole having large bulbs size recorded the highest losses in terms of rot, sprout, and total bulb weight loss as compared with Top-Harvest and Bawku Red that had smaller onion bulbs. Percentage bulb rot, bulb sprout and total bulb weight loss increased with increasing spacing. Bulbs harvested from 8 cm x 10 cm spacing stored better probably because these were those with high percentage of bulbs of smaller sizes.