Evaluation of transpiration in adult apricot trees from sap flow measurements

The aim of this study was to assess the accuracy of transpiration measurements obtained using the compensation heat-pulse compared with the transpiration estimated using the soil water balance. The experiment was carried out with 11-year-old apricot trees (Prunus armeniaca L. cv. Bulida, grafted onto Real Fino apricot rootstock) growing in a commercial orchard located in south-eastern Spain under different irrigation regimes from mid-July until the end of November. The results showed the heat-pulse measurements tended to underestimate the transpiration obtained from the soil water balance. This discrepancy was probably associated with the components of the soil water balance equation and perhaps with errors in the sap-flow calculation owing to daily changes in the volume fraction of water in the tree trunk and limitations of the technique as sap flow was reduced during the night. In spite of these limitations, the heat-pulse measurements could be considered a valuable method for measuring transpiration of mature apricot in orchards. The close correlation between sap flow measurements and ET0 Penman-Monteith FAO demonstrates that it is feasible to develop an irrigation schedule for apricot orchards as an additional tool for linking irrigation management to an automated, electronic and plant-based stress indicator.