Autotoxicity of continuoulys cropped passion fruit (Passiflora edulis Sims) soil

We determined the soil autotoxicity in the rhizosphere soil of passion fruit continued cropping up to 3 years, and analyzed the changes in the enzyme activity, microbial quantity and diversity in rhizosphere soil. The results showed that the autotoxicity of passion fruit rhizosphere soil increases with the increase in continuous cropping years. The microbial biomass carbon, microbial respiration, and the activity of enzymes (protease, urease and catalase) in passion fruit rhizosphere soil decreased with increases in passion fruit continuous cropping years. Contrarily, the activity of polyphenol oxidase was opposite, showing an upward trend. The results of BIOLOG eco-plate showed that the differences in soil carbon sources between different continuous cropping years were mainly amino acids, carboxylic acids, phenolic acids and amine carbon sources. The ratio of bacteria, bacteria/fungus ratio, actinomycetes, protozoa and total marker PLFA in the rhizosphere soil decreased significantly with the increase of soil planting years, while the total PLFA of fungi increased. Thus, with the increase of continuous cropping years of passion fruit, the soil autotoxicity was intensified and the soil enzyme activity and soil microbial diversity decreased.