Effect of Water Logging Stress at Specific Growth Stages in Onion Crop

Water-logging is one of the major abiotic stress that severely limits onion productivity world-wide. In onion, bulb size and yield are the economically important parameters that are getting seriously hampered due to frequent flooding events during Kharif season. An experiment was conducted under artificial waterlogging condition to identify the most sensitive growth stage for water logging stress in onion variety Bhima Super during Kharif 2017. The 45 days old seedlings were transplanted in plastic pots and the entire growth period of onion crop was divided into 11 different growth phases. Plants were subjected to water-logging condition created in pit for continuous 10 days during each growth phase and thereafter normal irrigation schedule was followed through-out the growth period. Data interpretation showed that the crop growth period from 20 to 90 days after transplanting (DAT) is found to be sensitive to water logging stress as the plants showed reduction in various morphological traits, survival rate, bulb quality traits (phenol, pyruvic acid, flavanoids, antioxidant activity, total soluble solids) and failed to produce marketable size bulbs. However, the growth period from 20-30 DAT (Bulb initiation stage) is found to be the most critical one as it failed to initiate the bulb formation with overall reduction in crop growth and quality. In contrast, the flooding during early vegetative stage (1-20 DAT) and towards the bulb maturity stage (90-110 DAT) was found to be less damaging as most of the plants are able to survive with better performance and able to produces marketable size bulbs. The study thus identified 20-30 DAT (Bulb initiation stage) is the most sensitive growth stage in onion crop for water-logging stress.