Allelopathic activities to barnyardgrass in rice and yield reduction due to barnyardgrass infestation.
Seven germplasm accessions that varied in their allelopathic activity to barnyardgrass (Echinochloa crus-galli) based on previous tests and 2 semidwarf cultivars from the USA plus one blank plot (no rice) were evaluated. Four of the accessions originated at the IRRI, Los Banos, Philippines (PI 338064, PI 350468, PI 355150 and PI 373026), two were from China (Guichao and Teqing) and one from Taiwan (PI 312777). The two non-allelopathic cultivars from the USA were Rexmont and Lemont. The average grain yield reduction in the barnyardgrass infested plots was 3424 lb acre-1 or 48.9% (PI 350468 and PI 338064 had the highest grain yield reduction, 2173 lb acre-1 or 36.7% and 2519 lb acre-1 or 37.2%, respectively). Rexmont and Lemont had the highest percentage yield reduction (4609 lb acre-1 or 68.1% and 3815 lb acre-1 or 59.5%, respectively).