The C and N cycles in soil are tightly coupled, but research on N cycling has largely ignored the role of microfauna and their interactions with plant roots, bacteria and fung. We will set up multitrophic experiments controlling for the presence of specific nematode trophic groups, to assess how herbivorous nematodes control rhizodeposition, the cascading of this root derived C to the microbial community, bacterivorous and fungivorous nematodes, and the feedback mechanisms on plants. We will use 13C stable isotope labelling to track the rhizodeposition, and its redistribution over the soil decomposer community. We will monitor the evolution of root trait development using both destructive and non-destructive methods, and assess how the activity of microfauna controls this development, both directly and indirectly. We will also investigate for the first time how specifically designed nematode trophic groups affect soil N cycling and plant performance in field conditions.