Disentangling the effect of nitrogen input and weed control on crop–weed competition suggests a potential agronomic trap in conventional farming

Weeds are commonly assumed to induce yield loss because of resource competition. However, there is growing empirical evidence that the picture much more complex, fertilizer inputs, by modifying level resources and weeding removing some weed species, affect outcome crop-weed interaction. We assess how two important crop production inputs - nitrogen (N) fertilization weed-control a fundamental non-chemical means management, competition, in real field conditions 56 winter cereal fields, which 23 were organically farmed. used factorial design with levels (absence/presence) input control but our case, “control” (i.e., presence level) for both practices was usual practice farmer (which therefore varied). found aboveground biomass grain positively related amount Ntotal (N soil plus N fertilizer), while species assemblages negatively affected, showing lower richness abundance number plants). also detected contrast between farming systems: conventional fields (CF), managed higher total control, showed yield, compared farmed (OF). Importantly, findings competition crops weeds largely favor plants CF even absence control. In OF still crop, at lesser extent than fields. The patterns similar unfertilized plots, though effective low amounts N, suggesting intense required N-rich maintain production. Overall, we argue these results may underlie an agronomic trap: increased supply generally increases it benefits weeds, requiring efficient