Studies On Relationships Among Major Continuous Cucumber Cropping Obstacle Factors And Its Work Mechanism

Cucumber is the favorable vegetable for Chinese and has become the main variety of greenhouse vegetables. However, Continuous mono cropping often caused cucumber weak growth, inferior fruit quality and specific root diseases and/or insects. To explore the origin of its occurrence mechanisms, agricultural researchers had contributed much work to many single factors including rhizosphere nutrition, soil borne plant pathogens and related soil physical-chemical characteristics. However, the exact causes have never been fully explained. The most limitation of previous studies was that much effort was put on the single factor of cropping obstacle, the interaction among factors should have, but not emphasized ever since. Regarding allelophathic substances in root exudates as the ligament of many factors of continuous cropping obstacles, we analyzed the variation of rhizosphere microbial population in response to continuous cucumber cropping using culture-dependent and -independent approach. At last we trialed the effect of phenolic acid on cucumber seedlings and wilt hypha growth. The main conclusions were as following:Plate count analysis revealed a reduction trend in the number of culturable microorganism both in rhizosphere and bulk soil as cucumber cropping continued. Bacteria showed more sensitive than actinomyces did, and had an apparent decrease extent in CFU number. In a fourth cropping season, the number of culturable bacteria in rhizosphere and non-rhizosphere decreased 31.3% and 25% respectively compared with that in non-replant cucumber soil. Continuous cucumber cropping also caused a slow decline in the number of culturable actinomyces, when to the fourth season, the number have decreased 21% and 20.1% in rhizosphere and nonrhizosphere respectively.Continuous cropping led few fungi populations enriched as well as many decreased, but the number of potential plant pathogens rose. Trichoderma sp., Asp. fumigatus decreased rapidly, Mucor sp., Rhizopus sp., Penicillium sp. have small decline, while the number of Asp. flavus, Verticillium sp.and Alternaria sp. increased...