David Kottelenberg

Agricultural fields harbour many plant species besides crops. Some lower crop yields and are called weeds. Weeds are generally controlled with chemicals, but these can harm nature and human health, and weeds are growing more resistant, so farmers need alternatives. Intercropping, growing two crops together on the same field, is one promising approach. Cereal-legume intercrops work especially well: the cereal suppresses weeds strongly, while the legume adds nitrogen to the soil, which the cereal needs.

In this thesis I studied why such mixtures suppress weeds well and how they can be designed. I approached this from several angles: field experiments across many crop combinations, computer models that simulate individual plants in 3D, and analyses of which weed species appear in each system. Together these showed that the faster-growing cereal usually dominates weeds and legumes, but that careful design can balance weed suppression against the yields of both crops, offering a route towards more sustainable cropping with lower chemical inputs.