Estimation of water requirement in a young peach orchard under irrigated and stressed conditions

Sap flow measurements on single branches of 8 peach trees (cv. 'Suncrest') were performed for 3 consecutive years after planting (1996-98) to estimate water requirements during the growing season and to evaluate the effect of water stress on growth and productivity of a young peach orchard. Starting from the end of May of each year, irrigation was witheld on half of the trees. Heat balance sap flow sensors (Dynamax Inc., Texas, USA) were applied on a single branch, well exposed to sunlight, of each tree for 4-5 periods of 7-20 days each from May to October. Data on total leaf area per tree and leaf and xylem water potential were also collected during the same periods. At the end of the growing season, total leaf area for each tree was assessed. Data on sap flow showed different water requirements, expressed on a m2 leaf area basis, in different years according to canopy size; in 1996 water consumption appeared to be higher than in the consecutive years. Water consumption per tree was affected by total leaf area and water availability in the soil. Because the type of soil and very large root expansion, the first symptoms of water stress were not recorded until 20-30 days after suspension of irrigation. Water consumption of stressed trees ranged between 80 to 20% of that of irrigated trees depending on vapour pressure deficit and pre-dawn leaf water potential. Data on sap flow during recovery from the stress are also shown for 1997 and 1998