Spatial Variation in Soil Humidity - Implications for Yield and Irrigation Management of 'Conference' Pear

Drip irrigation is a technique frequently used to prevent water stress and to achieve a maximal fruit yield and fruit quality in pear orchards cultivar 'Conference' in Belgium and the Netherlands. The irrigation scheme in an orchard is often based on measurements performed at only a few trees per orchard disregarding the spatial variance in soil moisture throughout the orchard, which occurs due to slopes, differentiation in soil profiles and differentiation in planting regime. To evaluate the importance of this spatial variation in soil moisture an intensive survey was set up in a Belgian fruit orchard in 2010 and 2011. Soil water content (theta(v)) and stem water potential (Psi(stem)) were monitored weekly at different positions alongside a slope in the fruit orchard. The variation in topography caused variation in soil moisture which lead to variations in fruit yield in the high fruit size classes. This yield variation was successful related to Psi(stem) illustrating its value for revealing water stress. A model was suggested to predict Psi(stem) based on theta(v) and ETo when no direct observations of Psi(stem) are available.