Weeds Dine Out on Nitrogen and Phosphorus

Cultural weed control methods are becoming more important where efficacious herbicides are limited or herbicide resistance has become prevalent. Manipulating crop fertilization may be one method of reducing weed interference in crops. Nitrogen (N) fertilizer can break seed dormancy of certain weed species and thus may directly affect weed infestation densities. Added N can markedly alter crop-weed competitive interactions. Depending on the species and density, N fertilizer can increase the competitive ability of weeds more than that of the crop. Research indicates that fertilizer placement can alter weed competition with crops. Nitrogen fertilizer placement in narrow insoil bands has been found to reduce the competitive ability of downy brome (Bromus tectorum), foxtail barley (Hordeum jubatum), and wild oat (Avena fatua) more than surface broadcast. However results vary, and other