Continuous Cropping Soybean Allelopathy And Allelochemicals Types Identified

The continuous croppings in our country leads the decrease of yields and quality of soybean. One of the reasons is allelopathy. In thsis thesis, the continuous cropping soil of soybean was extracted and isolated by various means. With the combination of bioassay, the extracts were identificated and quantified by GC/MS.The germination and radicel length of soybean seeding were inhibited by the acidic, neutral and alkaline extracts from soybean soil samples before sowing in continuous cropping and continuous cropping soil samples. The allelopathic effects became stronger with the increase of concectration. The allelopathy of acidic, neutral and aldaline extracts from continuous cropping was greater than those from rotational cropping. The allelopathic inhibition on germination and radicel length of soybean seeding were different between the various polarity extracts from continuous cropping and rotational cropping. The allelopathy were heavier with the increase of concentration. The most polar fraction had the strongest inhibition.The allelochemicals in the soil around rhizosphere collected in the maturing stage of soybean were identificated by GC/MS as organic acids, alcohol, ester, ketone, aldehyde, benzene, phenol, hydrocarbon and so on. Allelochemcials in continuous cropping soil were more than those in rotational cropping soil. The results showed that there were allelopathic compounds inhibiting the germination and radicel length of soybean seeding in continuous cropping soil of soybean.The quantity of hexadecanoic acid and octadecanoic acid were analysized by GC/MS, the amount of hexadecanoic acid in continuous cropping soil was 16.26mg/kg; the amount of octadecanoic acid was 11.72mg/kg.