Effects of irrigation and fertilization on the quality of 'Super Pinoy' onion (Allium cepa L.) bulbs

Cultural management practices like irrigation and fertilization affect the quality and storage behavior of onion bulbs his study, 'Super Pinoy' onions at a farm Brgy. Sta. Rita, Sto. Domingo, Nueva Ecija from January to March 2019 were subjected to various irrigation regimes (drip irrigation at 3-, 5- and 7-day intervals and flooding every 9 days) from 45 to 97 days after transplanting. Each plot measured 1.4 m by 7 m with 12 rows. Water from elevated reservoir was distributed to six laterals in each plot to emitters with 30-cm spacing with drip of 0.71 L-h-1. Flooding was done at 13.35 L-s-1 for 79 s. On the other hand, two fertilization treatments (90-80-40 based on soil analysis and 114-85-54 based on farmer's practice) were employed. Split plot design with triplicates per treatment was done. Bulbs were harvested at commercial maturity and were cured at ambient condition then profiled using different quality parameters. Higher proportion (31.51%) of large-sized bulbs was obtained in flooded plots compared to those subjected to drip irrigation (14.28-16.78%). Fertilization did not affect bulb size. Flooding appeared to increase the susceptibility of bulbs to insect damage. The incidence of bulbs with wide neck, however, was lowest in flooded plots. Flooding when combined with fertilization using the farmer's practice further increased susceptibility to insect damage. On the other hand, flooding in combination with fertilization regime that was based on soil analysis had more mechanically damaged bulbs. No differences in misshapen, diseased and split bulbs were obtained between treatments. Physic-chemical properties of the bulbs like pungency, total soluble solids, and total phenolic content were almost similar in all treatments. The free-radical scavenging activity of bulbs was higher in plots drip-irrigated at 7-d interval in combination with soil analysis-based fertilization. Mechanical properties (stiffness, boiyield and rupture points) did not vary among treatments.