EFFECT OF IRRIGATION REGIME AND NITROGEN-FERTILIZATION ON BULB YIELD AND WATER-USE OF ONION (ALLIUM-CEPA)

A field experiment was conducted during the spring seasons of 1991 and 1992 at New Delhi to study the effect of irrigation regime and nitrog en on water use and yield of 'Pusa Madhavi' onion (Allium cepa L.). Ir rigations at 1.25 irrigation water: cumulative pan-evaporation (IW: CP E) ratio (14-16 irrigations) and 1.75 IW:CPE ratio (19-21 irrigations) were at par, giving 69.6 and 72.8% higher bulb yield respectively tha n 0.75 IW: CPE ratio (9-11 irrigations). The seasonal consumptive use was 500,636 and 784 mm with irrigation at 0.75, 1.25 and 1.75 IW: CPE ratio respectively. The water-use efficiency was maximum (50.3 kg/ha/m m) at 1.25 IW: CPE ratio. N application up to 120 kg/ha gave significa ntly higher dry matter/bulb. 100-bulb weight, bulb diameter and bulb y ield than 60 kg/ha. The net return/Re investment on N was Rs 12.4 at t he optimum level of 131.4 kg N/ha. Increase in N level from 0 to 120 k g/ha increased the consumptive use and water-use efficiency from 560 t o 628 mm and 38.1 to 52.1 kg/ha/mm respectively.