Effects of storage duration and bulb sizes on physiological losses of Agrifound light red onion bulbs (Allium cepa L.)

Abstract

Abstract. The effect of storage duration and bulb sizes on physiological losses of the Agrifound light red onion bulbs stored in an Improved Naturally Ventilated Storage Structure-INVSS (constructed using locally available materials like; sand, cement, wood, corn stalks, wire mesh and grasses) under room condition was studied in 2012. Dry and wet bulb thermometers were installed to measure ambient temperature and relative humidity. Wind velocity was measurement by hand held Anemometer. The onion bulb samples were sorted and graded into three standard size categories (small: <50mm; medium: 50-70mm and jumbo: >70mm in diameter) and kept in the INVSS at the Department of Agricultural and Environmental Engineering Research Farm of Modibbo Adama University of Technology (MAUTECH), Yola. The samples were monitored and data taken on a daily basis for a period of twenty (20) weeks. The data were analyzed with ANOVA in CRD and the means were separated using LSD at p<0.05. The results indicated that storage duration had significant effects (p≤0.05) on weight, rot and sprout losses. Jumbo size onion bulbs had the highest Storage Weight Loss (SWL) by a mean of 5.1%, followed by medium and small size onion bulbs with means of 4.8% and 4.2%, respectively. Storage Sprout Losses (SSL) studied in the three of onion bulb sizes showed higher SSL among the small size Agrifound light red variety than the medium size onion bulbs with respective mean values of 5.0% and 3.8%, while the least value of SSL (2.6%) was observed in Jumbo size onion bulbs. Similar comparison was also made in terms of Storage Rot Losses (SRL) and it showed that relatively higher SRL among the Jumbo size onions (3.3%), followed by medium sizes (3.1%) while the least was observed from the small sizes (2.3%). The findings recommend that the INVSS should be used to store Jumbo and small size onion bulbs for at least 5 months to achieve minimum storage losses. Though, it is not cost effective to store medium size onion bulbs in the INVSS for more than 4 months.