How can deep-rooting catch crop mixtures be optimised to give main crops such as maize better access to subsoil resources? The project investigates how deep-rooting and shallow-rooting intercrop species can be combined to create effective root channels within the short winter period. The aim is to improve access to nutrients and water in the subsoil to meet the challenges of increasing drought risks and limited nutrient availability in the topsoil. Field experiments on different soil types and the simulation of a drought scenario evaluate the effectiveness of catch crops under different conditions.

The aim of the project is to develop optimal catch crop mixtures for maize cultivation. The root canals of deep-rooted catch crop mixtures are intended to make it easier for the following crop, maize, to access the subsoil and the water and nutrient resources stored there. In view of increasing dry periods as a result of climate change, this is intended to ensure the supply of nutrients to the maize. The principle of niche complementarity is utilised in the intercrop mixtures. Shallow-rooted and deep-rooted catch crops (cruciferous plants, grasses, legumes) are combined to generate deep-rooting root channels even during the short winter season. The chemical and microbiological characterisation of intercropping root canals and their interactions with the rhizosphere of maize provides information on the usability of intercropping root canals by the subsequent crop maize. Tracer methods were used to analyse the fast and efficient access of maize to underground nutrients and water via the root canals. and water via the root canals of catch crops was documented. Using drone-based thermography, an upscaling of water and nutrient utilisation by maize to the field level was developed. The integration of this data into cultivation models makes it possible to predict the maize yield as a function of cultivation.

The results of the project suggest that catch crop mixtures with grasses in particular have the potential to improve nutrient and water uptake from the subsoil for maize as a subsequent crop and to contribute to longer-term carbon storage in the subsoil. In the first funding phase, the RootWayS project concentrated on winter-hardy catch crops in order to minimise nitrogen losses in spring. However, the inclusion of non-hardy catch crops can improve the ability of the main crops to colonise and reuse the biopores generated by the roots of the catch crops. In the second funding phase, the trialled catch crop mixtures are now to be supplemented with non-hardy mixture components.