| During rice growth and development, an investigation was conducted to observe the distribution occurrence and infestation of weeds communities in paddy fields in Jiangsu province by visual scoring the level of weed infestation to rice in seven scales. The relationship between weed communities and ecological factors was analyzed by the principal component analysis (PCA) of the data of survey of weed infestation. , The output of PCA was ecologically interpreted.The weed seed bank was also surveyed in paddy fields of Jiangsu province in order to explore the weed species, the seed number of species and the vertical distribution in soil and the effect of soil water content on the weed seeds for germination in seed bank. The relationship between potential-real weed communities was elucidated after the study of seed bank. A mixture of butachlor and LGC-42153 was selected, which would provide perfect control of weed infestation in paddy fields.A field plot experiment was completed to assess many aspects of a new type herbicide LGC-42153 to paddy weeds in paddy fields, such as target spectrum, application stage, use rate, other techniques for using, safety to rice, effect on yield and so on. The dominant results as follows :The flora of weed in paddy fields in Jiangsu province was simple, 65 weed species belonged to 24 families was found in paddy fields in Jiangsu province. The main weeds were Echinochloa crusgal (L.) Beauv., Echinochlon crusgalli var. mitis (Pursh) Peterm. ,Leptochloa chinensis (L.) Nees,Digtaria sanguinalis Scop,Cyperus difformis L., Linderniaprocumbens Philcox,Rotala indica Koehne, Ammannia baciferal L.,Monochoria vaginalis Presl ex Kunth, Sagittaria pygmaea Miq., Amaranthaceae philoxeroides Griseb.etc. There were plenty of factors that determined the occurrence, distribution and infestation of weed communities in Jiangsu province paddy fields, but the main factorswere soil quality+water condition and herbicides according to the result of PCA. 60 sampling sites could be divided into three groups in paddy fields all over the province. The group of river coastal paddy areas has such dominant species as Leptochloa chinensis (L.) Nees and Eclipta prostrata L. The dominant weeds in the inland plain were Echinochloa crusgalli L. and Ammannia bad feral L In the group of sea coastal paddy fields Ludwigia prostrata Rox& and Amaranthaceae philoxeroides Griseb. were the dominant weeds.The result on weed seed bank indicated that 79 weed species subjected to 19 families was discovered in soil seed bank in Jiangsu province. The trend of distribution of weed seed in vertical direction of soil from underground tended to decline. 48% weed seeds was found in soil layer of 0-5 cm from underground, 35% in 5-10cm, 17% in 10-15cm. Soil water content controlled the germination of weed species. The main weeds between potential and real communities were identical, which occurred at the same place and the same period .Weed seed bank in soil was the source of infestation of real population, which characteristics of species, component and spatial structure have very close relationship with weed communities above ground.The combination between butachlor and LGC-42153 was optimal effective ingredient, which had perfect synergism on weed control, The mixture could provide perfect weed control during the rice growth period at the ratio 28.5:1.5. It has the trait of low cost, safe to rice and good environmental compatibilityThe result of field plot experiment showed that the new type herbicide LGC-42153 in rice fields could provide perfect weed control including grass, sedge, and broadleaf weed during the rice growth period. Their application window was very wide from 3-leaf stage to 5-leaf stage. The optimum use rate of the LGC-42153 30-45g a i/ha. To sure a uniform efficacy in the field, even and fine spray is required and spray overlap or uneven spray need to be avoided. LGC-42153 cannot effectively suppress Leptochloa chinensis. (L.) Nees. |
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