Weed control through crop plant manipulations

Weeds are able to establish in agricultural systems when and where resources are in excess of what the crop is able to utilize. We discuss four strategies for manipulating crop plants in order to increase resource utilization and improve weed suppression. First, cover plants can be used to usurp resources and suppress weeds during fallow periods between cash crops. In some cases, cover plants can also suppress weeds in subsequent cash crops by changing soil resource availability, production of allelopathic substances, and/or persistence of physically suppressive residues. Second, intercropping two or more functionally diverse cash crops can reduce weed abundance by increasing total resource utilization by the crop community. Thirdly, manipulating the density or spatial orientation of cash crops can reduce weed abundance by enhancing the competitiveness of the crop population. Finally, breeding for competitive cultivars by selecting traits that increase a crop plant’s ability to acquire resources has the potential to enhance the ability of crops to suppress and/or tolerate weeds. Weed suppression via crop plant manipulations is enhanced when multiple tactics are combined and will result in benefits such as reduction in the need for tillage and herbicides and their associated negative environmental impacts.