Effects of cultural practices at harvest on onion bulb quality and incidence of rots in storage

Abstract

A field study was carried out over two seasons to investigate the effects of maturity of onions (Allium cepa L.) at harvest and different curing conditions on bulb quality and the incidence of storage rots. Onion plants were lifted at one of three stages of maturity: 10, 70, or 90% leaf collapse (top-down). Foliage was removed (topped) either before or after curing, and bulbs were subjected to one of three curing treatments: field curing with additional water, field curing without additional water, or heated forced air curing. Additional water applied during field curing increased the proportion of onions with stained skins and rots. Forced-air curing of onions reduced the incidence of rots regardless of harvest method. Forced air drying also reduced skin staining in most harvest method treatments.

Quercetin Content in Field-Cured Onions (Allium cepa L.): Effects of Cultivar, Lifting Time, and Nitrogen Fertilizer Level

“…As a general rule, onion foliage should be allowed to desiccate as much as possible after lifting and before topping (46). The greatest number of rotted bulbs in storage has been shown to occur when onions are topped before field curing, probably as a result of rainfall within 12 h after topping (38).…”

Effects of cultural practices at harvest on onion (Allium cepa) bulb quality and incidence of bacterial soft rot and fungal moulds after simulated shipping

“…At higher temperatures the concentration of natural pigments in the outer skins of bulbs is enhanced, resulting in darker bulbs (Sanguansri & Sutherland 1991). Although skin colour does not affect storage performance, the intensification of skin colour of PLK to a dark gold or brown is regarded as a desirable characteristic (Wright & Grant 1997). Bulbs that were stored at cool temperatures after harvest "darkened up" when they were returned to warmer temperatures.…”

“…The United Kingdom and Europe are the biggest markets for New Zealand onions, taking over 75% of total onion exports (Statistics NZ). The production of high quality onion bulbs that are able to withstand long transportation distances to export markets is fundamental to the New Zealand onion export industry (Wright & Grant 1997). Onions from New Zealand are transported by ships either loose in containers, in large wooden bins, or in netting bags or large netting bulk bags (Wood 2001).…”

“…Desirable quality characteristics of harvested onions include bulbs that are free of diseases and that have clean, unblemished skins that do not split or are loose, and have a colour appropriate to the cultivar (Tucker & Drew 1982). Research carried out in New Zealand and internationally has demonstrated that the methods by which onions are harvested and cured, and the prevailing weather conditions during harvest, can have important effects both on onion quality characteristics and storage life (Currah & Proctor 1990;Wright & Grant 1997).…”

“…To meet consumer demand and obtain premium prices many New Zealand growers have started to use non-traditional harvest practices to produce onions of higher quality (Wright & Grant 1997;Wright et al 2001). Perhaps as a result of this, the incidence and severity of bulb rots, and bulbs with poor skin quality (split skins, staining, and fungal moulds) on arrival at export destinations has also markedly increased in recent years (Wright & Grant 1997;Wright et al 2001).…”