Allelopathic effects ofPolygonum aviculare L. I. Vegetational patterning.

Polygonum aviculare was observed to spread rapidly into heavy stands ofCynodon dactylon (L.) Pers. resulting in death of the latter. This indicated a strong interference againstCynodon dactylon. Measurements of selected soil minerals and physical factors indicated that competition was probably not the chief cause of that interference. Soil collected under deadPolygonum was very inhibitory to all test species exceptSporobolus pyramidatus (Lam.) Hitchc., suggesting the presence of inhibitory compounds. Tops and roots ofPolygonum, root exudates, and leachate of the tops inhibited seed germination and seedling growth of most test species. Therefore, allelopathy apeared to be the dominant component of the interference, with competition probably accentuating its effects.Polygonum aviculare was inhibitory toGossypium barbadense L. andSorghum bicolor (L.) Moench, indicating that allelopathy is an important component of the interference byPolygonum against crop yields.