Effects of the Application Times and Strength of Additional Fertilizers on Onion Bulb Quality Parameters at Harvest and during Storage

Abstract

Excessive application of basal and additional fertilizers strongly affects the physiological responses of onion bulbs, including yield, quality, and decay during long-term storage. This study evaluated the effects of additional fertilizer application times and strength on onion bulb number and yield at harvest and bulb quality attributes during storage at ambient temperature and relative humidity. Relative to the recommended levels of additional and conventional fertilization for standard onion cultivation, 0.5-, 1-, 1.5-, and 2-fold application strengths and 1, 2, and 3 application times were tested in individual experiments. Although onion bulb number and fresh weight per bulb size were not affected by the application strength of additional fertilizer, onion bulb yield increased at the application strengths lower or higher than the recommended levels. Bulb fresh weight loss and bulb decay severity were the highest at the 2.0-fold application strength of additional fertilizer. With the increase in the application times of additional fertilizer, bulb yield increased gradually but bulb number and fresh weight per bulb size remained unchanged. Furthermore, bulb weight loss and decay severity were the highest when additional fertilizer was applied thrice. Therefore, heavy and repetitive application of additional fertilizers may reduce the quality of onion bulbs through weight loss and severe decay during storage at ambient temperature, regardless of the high bulb yield at harvest.