Response of onion (Allium cepa L.) yield to water stress and mineral biofertilization

Abstract

Two field experiments were conducted at the Experimental Station of the Faculty of Agriculture, Mansoura University, Egypt, during the 2006/2007 and 2007/2008 seasons. The results showed that a gradual increase in soil water tension from 24 centibars (cb) (5588.25 m3/ha), i.e. 56.3% field capacity to 36 cb (2634.49 m3/ha), i.e. 41.% field capacity, significantly decreased the average onion bulb weight (g), bulb diameter (cm), bulb length (cm), total bulb yield (t/ha) and marketable bulb yield (t/ha) and significantly reduced the total percentage loss after 2, 4 and 6 months in both seasons. Conversely, this increase in water tension significantly amplified the culled bulb yield (t/ha), bulb dry matter (%) and water use efficiency (kg/m3). Normal water supplies (24 cb) clearly led to high percentage losses in bulb dry weight compared to the other water stress treatments. The results indicated that the application of 75% NPK plus the bio-fertilizer Soft Guard significantly improved the average bulb weight (g/plant), bulb diameter (cm), bulb length (cm), total bulb yield (t/ha), marketable bulb yield (t/ha) and dry matter (%) compared with the other fertilization treatments.