Competitive rangking of transplant aman rice cultivars against barnyard grass

A pot experiment was conducted at the Bangladesh Agricultural University, Mymensingh to evaluate the competitive abilities of ten rice cultivars namely BR11, BRRI dhan30, BRRI dhan31,BRRI dhan34, BRRI dhan39, BRRI dhan41, Nizershail, Kalizira and Basiraj against barnyard grass [(Echinochloa crus-galli (L)P.Beauv]. The varieties were in pure stands and in mixtures with the weed. Monocultures of the weed and rice were also maintained.Per plant dry weight of rice and the weed under monoculture and mix culture were recorded. Competitive ability was measured by aggressivity at crop anthesis stage.The present reduction of plant growth in rice due to the weed and that in weed due to rice was calculated. Correlation between aggressivity and plant characters of rice and the weed was studied. The most competitive cultivar was BRRI dhan34,which exhibited the greatest weed suppression but produced the lowest grain yield. The making of the varieties was BRRI dhan34>Nazirshail>Kalizira>BRRI dhan41>BRRI dhan40>BRRI dhan39>BRRI dhan30>BRRI dhan31. The plant height and tillers per plant of rice were positively related to the aggresivity but grain yield was not related to the aggressively but grain yield was not related. No correlation was noted between aggresivity and API in rice but the aggresivity was negatively related to API in weed.