EVAPOTRANSPIRATION OF ONION IN SAHELIAN NIGER

Irrigation responses of three locally adapted onion cultivars were stu died in drainage type lysimeters and under field conditions on a deep sandy loam soil, free of salinity problems, at Maradi in Niger. Evapot ranspiration (Et) was established by the water balance method, and use d to establish the rate of water use. The peak rate of water use was 7 .5 mm per day during the bulb formation stage. Irrigating onions when the available soil moisture to a depth of 20 cm had been depleted by 4 0% increased the yield more than irrigation at 60 or 80% depletion. Th e mean yield from plots receiving frequent irrigation was 33 t ha-1.