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Late bud burst or dieback in grapevine after severe cold and drought winter could be the result of insufficient recovery of xylem conductivity from embolism caused by low root pressure in early spring. To test this hypothesis, precipitation effects were excluded using a polyethylene film-roofed frame during the experimental period. The treatments on 11 years old ´Campbell Early´ grapevine were: no irrigation in winter and spring (NIWS); no irrigation in winter but irrigation in spring (NIW); and irrigation in winter and spring (IWS). Soil water potential among the treatments showed no difference during winter because of enough residual moisture in mid-October. In middle and late March, soil water potentials (Ψ_(soil)) in NIWS and NIW were between -16.6 and -21.9 ㎪ in comparison with -5.5 to -7.1 ㎪ in IWS and Ψ_(soil), in NIWS decreased to -22.4 to -34.6 ㎪ in April and May. Xylem embolism occurred more than 93% in all treatments in mid-November and continued till March. Root pressure in mid-April showed no significant difference among the treatments, ranging from 45 to 58 ㎪. In early May, it was 110 ㎪ in NIW, 97 ㎪ in IWS, but 56 ㎪ in NIWS. Xylem conductivity seemed to recover from winter embolism with positive root pressure in March and April. In early May, embolism in IWS and NIW decreased to less than 5%, but 17% in IRWS, which were related with soil moisture status and root pressure. Even in different hydraulic conductivities among the treatments, there was no difference in bud burst rate and subsequent shoot growth.
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