Successional Allelopathic Interactions of Amaranthus palmeri S. Wats. and Cereals

Plant allelochemicals can affect the germination and growth of other plant species. Petri and pot experiments were conducted to detect the interaction of Amaranthus palmeri with cereals (barley, oat, wheat, and triticale). Aqueous extracts of different tissues of A. palmeri and cereals at several concentrations were used to measure the inhibitory effects on the germination of other plants in the Petri experiments. A. palmeri plants and cereals grown at two different densities were incorporated into a potting mix at two different growing stages to determine the inhibitory effects on the germination and growth of other plants in pot experiments. The relative germination inhibition of A. palmeri was present in the following order: barley > oat > triticale > wheat. The relative germination inhibition of cereals was present in the following order: oat > triticale > barley > wheat. The above-ground parts of the plants were more effective than the roots. The germination of A. palmeri was only affected by wheat, while barley was better at reducing the dry weight in pot experiments. Wheat was found to be the only cereal affected by A. palmeri. Despite the prevailing hypothesis that these plants do not affect each other’s germination and development in nature, it was concluded that using wheat and barley as a cover crop can support A. palmeri management, and delaying wheat planting in the presence of A. palmeri can protect cereals from allelopathic interference.