Abstract:
Onion (Allium cepa L.) is one of the most important commercial vegetable crops grown by
small-holder farmers in Kenya, for both local and export markets. Losses in storage which are
mainly due to rotting and sprouting contribute greatly to post-harvest losses which average 40%.
Nitrogen (N) is one of the most important crop nutrients affecting growth and quality but with an
impact on shelf-life of the crop. An investigation was therefore conducted with an objective to
optimize N and time of application for onion bulb yield and storage life. The experiment was
carried out in 2014 and 2015 at the National Agricultural Research Laboratories and the bulbs
stored at room temperature for 3 months at the University of Nairobi botany laboratory. Nitrogen
was applied as Calcium Ammonium Nitrate at five levels including (0, 26, 52, 78 and 104kg N
ha-1) at different times (3 weeks, 6 weeks, 9 weeks and 12 weeks) after transplanting. Two
commonly grown varieties, Red creole and Red Tropicana F1 hybrid were used. The treatments
were laid in a Randomized Complete Block Design (RCBD), with a split-split arrangement and
replicated three times. Analysis of variance (ANOVA) showed that N application had significant
effect on bulb splitting and neck thickness at harvest and adversely affected storage life through
increased PLWand rotting and sprouting of bulbs. Time of application also significantly affected
these parameters, with early application leading to increased PLW, rotting and late application
splitting and sprouting of bulbs. The Red creole variety exhibited a better shelf-life compared to
the Red Tropicana F1 hybrid. Nitrogen application is important for increased yields but
excessive application beyond 52 kg N ha-1 should be avoided for bulbs intended for storage.
Application time is increasingly important in enhancing quality of onion before and after storage |
