Abstract: Microbial comunlty in soil of soybean continuous cropping was analyzed, soil fungi were found to be abundant. soybean was inoculated with dominant fungi. The soybean growth is strongly inhibited by Penicillinm Purpuroggnum Stoll 891. Crude crystals of Rubratokins of P.purpurogenum Stoll 891 were extracted. The inoculation experiment with Rubratoxin Ashows that its concentration in water culture actives at 5μg·ml^-1, the soybean root system is injured. At 30μg·ml^-1, the primary roots are seriously necrosised and the secondary roots are almost stunted. At 200μg·ml^-1, some seedlings of soybean varieties are died within a couple of weeks. It is suggested that Pedologic mycotoxin generated by P.Purpurogenum Stoll which is abundant in soybean continuous cropping soil may be one of major factors leading to soil sickness.

Key words: Soybean, Soil sickness by continuous cropping, Mycotoxin, Penicillium purpurogenum, organic carbon storage, active organic carbon, total organic carbon, carbon pool management index, winter cover crop