Emergence of weed species and their competitive characteristics in direct-seeded rice (Oryza sativa). 1. Distribution and growth of weeds in direct-seeded rice.
It was found that 14 (2 grasses, 8 broadleaved species and 4 sedges) and 12 (1 grass, 7 broadleaved species and 4 sedges) weeds occurred in dry- and water-sown rice, resp. Dominant weed species in dry-seeded rice, in descending order of importance, were Lindernia procumbens, Cyperus difformis, Cardamine flexuosa and Cyperus serotinus. The main species in water-seeded rice were Cyperus difformis, Scirpus juncoides and Lindernia procumbens. The dry weight of weeds increased up to 75-90 days after sowing. Regardless of the number of weeds that emerged, the most dominant weeds present until the late stage of growth were Cyperus difformis, Bidens frondosa, Digitaria ciliaris and Echinochloa crus-galli in dry- sown rice, and Cyperus difformis, Echinochloa crus-galli and Scirpus juncoides in water-sown rice.