Water fluxes between the earth surface and the atmosphere can be estimated by metorological, plant-physiological and by soil water balance approaches. Estimation of water fluxes below the root zone is mostly done by water balance approaches. Many equations regarding these components are based on average monthly or daily data. However, weighing lysimeters are precise tools to allow the determination of the hydrological cycle components in very short time intervals. Specifically, evapotranspiration ET from weighing lysimeters can be computed from weight changes ΔS, rainfall R, irrigation I and percolation water P (ET = R + I - P - ΔS) and compared with calculated ET. Thus, lysimeter measured ET values allow to adapt ET equations, and to assess the physiological reactions of plants on soil and atmospheric conditions. Interception processes and dew formation and dew evaporation can also be better interpreted and perhaps embedded in ET equations. Similarly, lysimeters with controlled suction at the lower boundary allow estimation of deep water percolation on short time scales, thus giving hints about the occurrence and the extent of preferential flow.

This session aims to discuss innovative process research with the help of lysimeter studies to improve our understanding of soil–plant–atmosphere and soil-groundwater relations. We invite researchers ranging from plant production, climatology and unsaturated zone which are applied to lysimetry research in a broad sense. We especially invite innovative studies to determine evapotranspiration in time steps shorter than one day. Lastly, we invite pioneering research that connects hydrological and grow processes knowledge in the unsaturated zone with respective modeling.