Harvest date affects yield and postharvest quality of nondried, short-day onions

Short-day onions (Allium cepa L.) grown under humid, subtropical conditions at two locations were evaluated for bulb size and yield at five harvest dates (H1 to H5) ranging from 94 to 132 days after transplanting (DAT) for 'Granex 33' and from 115 to 153 DAT for 'Texas Grano 1015Y'. Maximum yields were attained by H4 for both cultivars and were attributed to increased bulb size rather than differences in plant (bulb) population. Nondried, large bulbs (>7.6 cm diameter) from each harvest were trimmed and stored at 1 or 10 degreesC and 80% relative humidity (RH) for 2 weeks plus 2 weeks at 20 degreesC and 80% RH to simulate commercial storage and handling. Initial respiration rates of bulbs of both cultivars decreased >60% between H1 and H4. Bulbs also retained higher fresh weight during storage as harvest was delayed. Storage for 2 weeks at 1 degreesC suppressed sprouting of immature (H1) 'Texas Grano 1015Y' bulbs, but not of 'Granex 33' bulbs from one location. Storage at 10 degreesC did not suppress sprouting of either cultivar, Decay became more prevalent with delayed harvest, but 'Granex 33' was more resistant to decay than was 'Texas Grano 1015Y', which developed up to 40% decay after 2 weeks at 20 degreesC. Harvest at 115 and 132 DAT resulted in acceptable yields for 'Granex 33' and 'Texas Grano 1015', respectively, and satisfactory postharvest quality of nondried bulbs following 2 weeks of storage at 1 degreesC and 80% RH plus 2 weeks at 20 degreesC.