Coupled atmosphere-land surface models are important tools for assessing the impact of global climate change on a regional scale. The quality of regional climate simulations is critically dependent on an accurate representation of land surface exchange processes. Soil-plantatmosphere interactions play a key role here. In the first phase, we have integrated the advanced crop growth model GECROS with the land surface model NOAHMP. In the second phase, we will test the capability and robustness of NOAHMP-GECROS with regard to simulating soil water regime, crop growth and land surface exchange. Model testing and, if necessary, further development are based on our long-term eddy covariance and soil water measurements. As part of the Atmosphere-Land surface-Crop Model ALCM (NOAHMP-GECROS coupled with WRF) NOAHMP-GECROS is an important component of the Integrated Land-system Model System (ILMS). In cooperation with the other projects of the Research Unit, ILMS will be used to study feedbacks in the land system (Kraichgau and Swabian Alb) under climate change. Within this joint effort, we will investigate, among others, the question in which detail soil processes and crop growth have to be considered to reliably simulate landscape functions such as crop production and water regime.