Abstract

R. Anlauf*, P. Rehrmann and H. Schacht

To optimize ebb-and-flow irrigation on concrete floors, the relative importance of substrate type, flooding depth and flooding time on water uptake of growing media in containers is important information for the grower. Describing water uptake and distribution in the container with a dynamic simulation model may overcome the disadvantages of the static parameters such as container capacity and air capacity. Water uptake and redistribution was investigated for two different growing media, a coarse white peat and a fine seedling substrate, two flooding depths (1 and 4 cm) and three flooding durations (5, 10 and 15 min). The results were used to evaluate the use of the simulation model HYDRUS1D to describe water uptake and redistribution. The hydraulic functions water retention curve and hydraulic conductivity needed for the simulation model were determined in the laboratory. The results show that substrate properties and flooding height are the main parameters determining water uptake during ebb-and-flow irrigation while flooding time has a minor effect only. Therefore, the slope of concrete floors should be at a minimum to ensure an even flooding depth for all containers. The longer flooding times and the longer drainage durations have a very small effect on water uptake. The simulation model HYDRUS1D is able to describe water uptake and redistribution in containers filled with the two growing media sufficiently well only if the hysteresis of the water retention curve is taken into account.