Abstract:

Crop management practices，such as fertilization and straw returning，have great impact on weed community.However，little is known about the effects of longterm fertilization and straw returning on weed community.In this study，we investigated the characteristics of spring weed community in ricerape seed cropping system with different longterm crop management regimes in 2007 (the site located in Wujiang County，Jiangsu Province，and the experiments started in 1987).There were significant differences in spring weed community composition among different management patterns.Low biodiversity and total biomass of spring weed existed in the plots with longterm chemicalorganic fertilizer (chemical fertilizer plus pig manure and straw returning).Longterm nonnitrogen fertilization significantly increased the total density of spring weed which was up to 1 810 ind./m2.In addition，〖WTBX〗carolina cranesbill〖WTBZ〗 gradually became the dominant weed in the nonfertilization plots，its relative density reached at 87.9%；〖WTBX〗Alopecurus aequalis〖WTBZ〗 S.gradually became the dominant weed in cropstrawreturningin autumnandsummer (chemical fertilizer plus rice and rape straw returning) plots，the relative density reached at 69.7%.Straw returning in autumn decreased the total biomass of spring weed，but increased weed biodiversity.Spring weed community could be controlled through adjusting the regimes of fertilization and straw returning in ricerape seed cropping systems.

Key words: fertilization/ straw returning/ ricerape seed cropping system/ weed community/biodiversity