Measuring and modeling spatially variable fluxes in the soil-plant system

The research is carried out in cooperation with KU Leuven, Forschungszentrum Jülich and Kasetsart University in Bangkok, Thailand, and aims at improving our understanding of how spatial variability in soil properties and vegetation characteristics control water flow and transport processes in the soil at the field scale, and how it determines resource use efficiency of agro-ecosystems. It focuses on the spatio-temporal dynamics of water contents and competition for water uptake in mixed cropping systems. The emphasis is on spatial variation that is caused by the cropping pattern and landscape. To this end, a set of monitoring techniques will be used with which spatial patterns of crop status and subsurface soil water contents can be imaged in a non-invasive manner. Soil water content distributions will be determined using geophysical methods: electrical resistivity tomography and time domain reflectometry. The state of the crop and its spatial pattern will be monitored using leaf area index (LAI) sensors and an infrared camera. These techniques will be complemented with ¹³C stable isotope analysis of plants, which is a measure of the integrated stress of the plant over the growing season. In order to interpret the obtained datasets, a soil-crop model will be developed which considers light interception, photosynthesis and stomatal control, water flow within the plant, root growth and root water uptake, and heat fluxes within the canopy in more detail than in currently available crop growth models.