Abstract: 1% fermentation matters from four weeds ( Artemisia princeps Pampan, Cayracia jap onica Gagn, Ste llaria media Villars, Trifolium rep ens L. ) were respectively added into pot soils which contained high density propagules
of vesicular􀀁arbuscular mycorrhizal fungi for culturing trifoliate orange ( Poncirus trifoliata Raf. ) seedlings. After 70 days, mycorrhizal infection rates were high in all treatments. But compared with the control, fernentation matters signi􀀁ficantly stimulated the growth of trifoliate orange seedlings, reduced the mycorrhizal formation in roots of seedlings, and there were lower infection rates in treatments of fermented weeds than in that of fermented liquids; High concentration of nitrogen also could reduce the mycorrhizal formation level; The phenomena of parasitism and growth depression in mycorrhizal citrus took place when the mycorrhizal infection rate was too high.

Key words: Weeds, Fermentation, Citrus, Trifoliate orange ( Poncirus trifoliata Raf. ), Vesicular Arbuscular mycorrhiza