Adequate choice of variety, rootstock and irrigation techniques could be, together, sources of improvement of water use. A field experiment was carried out in northern Tunisia on two drip irrigated peach varieties grafted on two rootstocks. Two deficit levels, mild DI1 and severe DI2, were applied. Phenological survey allowed determination of the crop growth stages: initial, development, mid- and late-season. The average lengths of these crop stages were 32, 43, 49 and 136 days for early variety and 33, 49, 63, and 105 days for mid-season variety, respectively. Mean value of crop evapotranspiration (ETc) for the four growth stages was respectively 31, 115, 211 and 420 mm for early variety and 40, 128, 311 and 300 mm for mid-season variety. ETc was restricted with low ground cover to 25, 85, 150 and 280 mm. Tree development, yield and water needs were affected by water status, rootstock and climatic conditions. Threshold values of Ψstem of −1.5 and −2.0 MPa could be considered for mild and severe deficit irrigation. The water use of the soil water seemed to be more efficient with vigorous rootstock under mild deficit. Under extreme watering conditions, rootstock effects were negligible. Lack of chilling affected tree growth inducing reduced water requirements.

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