Weed management for rice in Egypt.
In a survey of rice fields in 1986-88, Echinochloa crus-galli, E. colonum, Cyperus difformis, C. rotundus, Scirpus tuberosus, Ammannia spp., Eclipta alba, Bergia capensis and red rice (Oryza sativa) were the major weeds. Delaying transplanting of rice cv. Giza 175 from June to July resulted in greater numbers of weeds, especially C. difformis and broadleaved weeds and lower grain yields. Av. yield losses from weeds were 54, 62 and 78% at spacings of 10 × 20, 20 × 20 and 30 × cm, resp. Pre-em. application of thiobencarb at 3.6 kg/ha increased the period of weed control. In broadcast sown rice, chemical control of weeds decreased at high weed densities. Continuous flooding to a 10 cm water depth improved the effectiveness of herbicide treatments. High sowing rates were necessary to control C. difformis and broadleaved weeds whilst quinclorac + thiobencarb at 0.6 + 1.2 kg/ha, applied when E. crus-galli was at the 0.5- to 1-leaf stage, controlled grass weeds. Quinclorac + thiobencarb and thiobencarb + propanil (at 2.4 + 2.6 kg/ha) were recommended for control of mixed weed populations in either drill-sown rice cv. Reiho and cv. Giza 181 or mechanically transplanted rice cv. Reiho.