| This paper through scientific siting investigation at different farm areas for three years showed that:the weeds in Huai Bei area were belongs to 13 families and 35 species, the main weeds were Leptochloa chinensis, Echinochloa crusgalli, Cynosurus indicus, Digitaria sanguinalis, Eclipta prostrata, Monochoria vaginalis, Monochoria korsakowii, Sagittaria trifolia, Ludwigia prostrate, Ammannia baccifera, Rotala indica, Fimbristylis miliacea, Fimbristylis fusca, Cyperus serotinus, Cyperus difformis; the main weeds were Echinochloa crusgalli, Leptochloa chinensis, Fimbristylis miliacea, Fimbristylis fusca, Monochoria vaginalis, Eclipta prostrata, Cyperus serotinus, et al.. The density of the whole weeds was 235/m2. The main weeds said above distributed everywhere in Huai Bei area, but the species and ratio were different with the change of area and farming system. In fine, the grass weeds were the predominant weeds in direc-seeding rice field, the ratio of which to the whole weeds was nearly 61%, secondly, were the Cyperus weeds, the ratio of which to the whole weeds was nearly 26%, but the ratio of broadleaf weeds to whole weeds was only 10%.The weeds in direct-seeding rice field of Huai Bei have two germination peaks, the first one is 10 to 15 days post planting of rice, the mainly of weeds were grass weeds, such as Monochoria vaginalis, Eclipta prostrata; the second one is 25 to 40 days post planting of rice, in the prior period, the mainly weeds were and in the late, the mainly weeds were Cyperus weeds. In 60 days after the rice seeding, very few weeds will geminate.Through the study of the relationship between the germination of different weeds and the loss of yield, found clearly that:firstly, the different grades of weed damage lead to different loss of yield, that is The higher the hazard level of weeds on the direct seeding rice yield loss caused by the greater; secondly, the greater density of weeds in the same kinds of direct seeding rice yield loss caused by the greater; thirdly, at the same density, the difference of the plant-type and coverage between the weeds were bigger, the difference of the yield was larger. The threshold of economic control in direct-seeding rice field of Huai Bei was 20 to 24 plant per square metre. In 29 to 31 days after rice seeding is the critical period of competition.Producted the special soil closed herbicide in direct-seeding rice field of Huai Bei, which is the mixture of 36% butachlor·oxadiazon EC, the 40 days after spraying, stem control effect could reach 95.3%. Through the screening of different herbicides and the demonstration trials, found that:the soil closed herbicide in direct-seeding rice field could select 36% mixture of butachlor and oxadiazon EC, the mixture of 30% pretilachlor EC and 10% bensulfuron-methyl WP, the mixture of 55% bensulfuron-methyl·metolachlor·pendimethalinWP; according to the weeds in field, the leave treatment herbicides could select 10% cyhalofop butyl EC,2.5% Penoxsulam OF (daojie) or the mixture of 50% quinclorac·bensulfuron-methyl WP. The dose of the herbicides will change with the different ages of weeds, at the safe dose, the larger age of the weeds, the larger dose will need. Use the herbicide in the right stage and at the right dose, could reach very good control effect and is safe to the rice. Thus, could reach good social, economic and ecological benefit. |
