Assessment of allelopathic potential of barnyard grass (Echinochloa crus-galli) on rice (Oryza sativa L.) cultivars

Laboratory, greenhouse and field studies were conducted to assess the allel opathic potential of 44 rice cultivars (Oryza sativa L.) on barnyard grass (Echinochloa crus-galli P. Beauv. var. oryzicola Ohwi). Rice cultivars exhi bited marked differences in the inhibition of barnyard grass growth and dev elopment. In the laboratory, Gin shun rice cultivar extracts exhibited the greatest activity on the weed seedling growth, reducing dry weight by 61%, while Kasarwala mundara cultivar extracts exhibited the greatest activity o n seed germination, reducing germination by 23% and germination speed by 46 %. In a greenhouse study of a residue mixture, the Philippine 2 cultivar sh owed the greatest inhibition percentage on seedling emergence (57%), total seedling length (74%) and dry weight (73%). In the field study, the Juma 10 cultivar demonstrated the most inhibitory effect by reducing barnyard gras s tiller number (80%), leaf area (49%) and leaf (61%) and stem (74%) dry we ight (68%). These results suggest that there are differences among the vari eties for allelopathic inhibition of barnyard grass, and that the developme nt of barnyard grass suppressive rice cultivars that have greater allelopat hic potential may be possible. (C) 2001 Elsevier Science Ltd. All rights re served.