Paudel, I., Department of Environmental Physics and Irrigation, Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Israel
Noar, A., Golan Research Institute, PO Box 97, Kazrin 12900, Israel
Gal, Y., Ministry of Agriculture and Rural Development, 10200 Kiryat Shmona, Israel
Cohen, S., Department of Environmental Physics and Irrigation, Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Israel

Measurements of xylem sap flow (SF) and its response to soil and plant water status and climatic parameters can help to develop better water status indicators, which may help to manage irrigation based on orchard specific conditions. SF was measured with thermal dissipation probes in drip-irrigated 12-year-old nectarine (Prunus persica var. nectarina) trees in Northern Israel. SF probes, automatic sensors for monitoring soil and plant water status, and a meteorological station were installed in standard irrigated plots and in a separate plot for experimental drying and wetting. Mid-day stem water potential (MSWP) was monitored periodically in all plots. SF and leaf conductance increased with leaf area development at the beginning of the season. Variations observed in the drying and wetting plot during four drying cycles before, and one after harvest, were instrumental in finding relationships between SF and canopy conductance and soil and plant water status and climate variables. SF was more variable and less sensitive than other water status measures. During drying, SF decreased by up to 40% and relative to ET0 it decreased by up to 60%. When expressed relative to the irrigated trees SF decreased by up to 35%, and MSWP by 70%. Similar responses were observed in the postharvest period. Signal to noise ratios were calculated for the sensors. During the drying cycles SF and conductance were significantly correlated with MSWP, and responses to reduced soil water were quantified. © ISHS 2013.