The Effects Of Welsh Onion-Cucumber Rotation And Its Relationship With Root Exudates

Cucumber (Cucumis sativus L.) is one of the main vegetables for protected cultivation,and continuous cropping obstacles have become an important factor in restricting highproduction and sustainable development.Rotation with welsh onion is an efficient measure in reducing the harm of cucumbercontinuous cropping but the internal mechanism is not clear. In this study the plants growthand the soil properties were studied in welsh onion-cucumber rotation cropping system. Theplants growth and the soil environment of cucumber that treated by welsh onion root exudateswere studied either. The purpose of this study was to explore the effector mechanism of welshonion-cucumber rotation cropping system and provide the theory basis for setting areasonable cropping system. The main results were as follows:1. Compared with continues cropping cucumber, the plant height, stem diameter, yield,content of chlorophyll and the photosynthetic rate of rotation cucumber can be promotedobservably. The photosynthetic rate of rotation cucumber can be rised by27.79%and theyield increased by48.49%.2. Compared with continues cropping cucumber, the increasing amplitude of soil pH andthe decrease amplitude of soil EC of rotation cucumber were bigger. The content of availableN in the rhizosphere soil was higher in the early growth stage but has no significantlydifference later, the content of available P in the rhizosphere soil was higher in the earlygrowth stage and became lower later, the content of available K was higher all the time. Theactivities of urease, phosphatase and catalase were higher. There were more bacteria andactinomycetes in the soil but the amount of fungi was smaller. The rate of fungi inmicroorganism became lower.3. The DGGE analyse of the soil microbial community showed that the diversity andevenness of soil bacteria and actinomycetes of rotation cucumber were higher while thefungi’s was lower. The change of bacteria community and actinomycetes community inrhizosphere can be affected by growth period obviously while the fungi community can beaffected by cultivation mode.4. The growth of cucumber seedlings can be promoted by welsh onion root exudates, thefacilitation was strengthened and then weakened with the increasing of concentration of welshonion root exudates. The plant height, stem diameter, content of chlorophyll, photosynthetic rate and root activity were significantly improved by proper concentration of welsh onion rootexudates.5. Proper concentration of welsh onion root exudates can raised the soil pH and reducedthe soil EC obviously. The content of available N, available P and available K, the activitiesof urease, phosphatase and catalase, the number of bacteria, actinomycetes and fungi can besignally increased either. The rate of fungi in microorganism was reduced.6. The diversity and evenness of soil bacteria and fungi can be increased by welsh onionroot exudates while the change of actinomycetes was little. There were some kinds of bacteriaand fungi get together in the rhizosphere soil of cucumber seedlings treatmend by highconcentration of welsh onion root exudates.