Abstract: An analysis of field yields and pot biomass during 1983 and 1984 indicated that corn, soybean, sunflower and sweet clover all caused evident soil sickness due to continuous cropping. The sickness could be released by means of soil sterilization. The inoculation with cultured enrichment liquids of soil microorganisms from continuous cropping plots restrained crop growth to a certain extent. Meanwhile, continuous cropping increased the number of fungi (F)and nematode, decreased the number of bacteria (B), root nodule and the B/Fratio in soybean root zone and root surfaces.

Key words: Toxoptera aurantii, Leis axyridis, Kairomone, Odor source, Behavior response