Different soil water tension values were tested to evaluate the effects on onion yield of two drip irrigated onion cultivars. The experiment was carried out at Lavras, in the State of Minas Gerais, Brazil (21° 14' S, 45° 00' W and 918.8 m), from June to October 2008. The statistical design used was randomized blocks with a factorial scheme 2 x 6, with four replications. The treatment levels were two onion cultivars (hybrid Optima F1 and the non hybrid Alfa tropical) and six critical soil water tension levels (15, 25, 35, 45, 60 and 75 kPa). It can be concluded that the hybrid Optima F1 presented the best response in relation to the following analyzed variables: total bulb yield, marketable bulb yield, average marketable bulb mass and water use efficiency. In order to obtain larger bulb yield (total and marketable) and average marketable bulb mass, for both cultivars, the irrigation should be provided when soil water tension reaches 15 kPa at 0.15 m depth. The total soluble solids, presented a quadratic polynomial response in relation to soil water tension. Water use efficiency increased linearly with increase in soil water tension.
trickle irrigation; tensiometer; Allium cepa L.
