Validatie van de Virtuele Lysimeter: de Virtuele Lysimeter getest en gevalideerd op praktijkbedrijven

Strict rules to reduce water-related emissions require growers to comply with the ‘duty of care’ to align fertigation with crop demand. To enable growers to do this, the ‘virtual lysimeter’ (VL), a combination of a transpiration and a soil model, calculates the inputs and outputs of water flows for a specific soil crop situation. It forms a powerful tool for growers, showing an overview of the crop water balance, potential leaching, and soil moisture contents in three layers, calculated from available climate data. This gives the grower insight into his soil and allows optimized irrigation with minimal leaching. The VL was validated in the period 2020 – 2022 on farms with chrysanthemum and organic fruit vegetables, based on the measured drain of the installed physical lysimeters. It turned out that the calculated water fluxes over longer periods (weeks, full cropping cycles) corresponded well with measured values, but for short periods (days) the deviations are large. The patterns and trends in soil-moisture levels matched those measured with soil-moisture sensors. All by all, the VL is sufficiently robust to be a useful tool for growers to adjust the irrigation to the need and thus meet the ‘Duty of Care’.