Competitive crops are important for sustainable cropping systems. For perennial weeds, below-ground organs, for instance rhizomes for couch grass, constitute the best measure of a crop’s long term suppressive capabilities.
Ringselle et al. found that the type of competition (primarily for light or nutrients) utilised by a crop influences both the suppression rate and the likelihood of whether the crop will successfully alter the weed’s allocation pattern. By competing primarily for light, red clover suppressed the rhizome biomass of couch grass more than perennial ryegrass per gram of produced companion crop biomass. Perennial ryegrass impacted upon couch grass allocation with a higher proportion of rhizomes.