Water stress detection in a 'Conference' pear orchard in a temperate climate using sap flow monitoring

Drip irrigation in ‘Conference’ pear trees in Belgium and the Netherlands is used to maximize fruit yield. Belgium is situated in the temperate climate zone with a relatively low average evapotranspiration and a high but variable rainfall. Current irrigation scheduling techniques are based on soil water balance models or soil moisture sensors. Continuous plant based measurements can improve the precision of these irrigation scheduling techniques because they are more connected to metabolic and physiological processes. However continuous plant based measurements in field conditions in a temperate climate are scarce. In this experiment sap flow monitoring was used to detect water stress in a pear tree orchard in Belgium in 2011. Stem (Ψstem) and soil water potential (Ψsoil) were measured in a control irrigation (CI), partial irrigation (PI) and non-irrigation (NI) treatment. Thermal dissipation probes were used to detect differences in sap flux density (Jp) between the treatments. Between the PI and the CI treatment no differences in Ψstem or Jp were observed. A lower Jp tendency was observed in the NI treatment. The detection of Jp differences under low evaporative conditions, applying moderate water stress, opens the door for plant based irrigation scheduling in pear trees in a temperate climate.