The allelopathic potential of several rice varieties on barnyard grass (Echinochloa crus-galli L. Beauv.)

A total of 148 rice varieties were tested for their allelopathic potential on Echinochloa crus- galli using the relay seeding technique . Seven days after the rice seed germinated, non-dormant seeds of E. crus-galli were placed close to the rice seedlings. The effect factor (EF) of the rice varieties was calculated as (relative root length + relative shoot length + relative seedling dry weight)/3 and used as the indicator of the allelopathic potential of the rice varieties. Reduction of weed growth was calculated as (1 - EF) x 100, whereby 1 is the control factor in which no reduction occurs.Significant differences among the rice varieties with regard to their effects on root length, shoot length and dry weight were observed and these ultimately produced the significant differences in the effect factor . The results showed that there were 12 varieties with highly inhibitory effects on the weed growth. The percentages of growth reduction were Makmur (44%), MR 14 (40%), Acheh Puteh (37%), Manik (37%), MR 59 (37%), Seberang (36%), Sekencang (35%), MR 15 (34%), Anak China (33%), Anak Ikan China (33%), Anak Ikan China (33%) and Y1021 (33%). The weakly allelopathic rice varieties identified were Lembut Ketanl (1%), MR 212 (3%), Chempaka 173 (4%), MR 109 (5%), MR 219 (5%) and MR 58 (7%). The following three varieties namely Janda Berhias, Muda 2 and Mayang Seroi 70 caused 8% growth reduction in the E. crus-galli seedlings.