Remission Effect And Mechanism Of Continuous Obstacle In Vegetable Field Under Intercropping Pattern And Maize Straw Returning

The study materials were the broccoli, green sword bean and the waxy maize which usedfor export. The allelopathic of broccoli straws extracts and soil extracts on the vegetable seedsand seedlings were studied to discuss the mechanism of vegetable cropping obstacles. Thedifferences between the crop yield and quality under the relay intercropping with waxy maizeand straw returning were studied. At the same time, soil microbial biomass and soil nutrientcontent were analyzed. The aim was to make it clear that the effect of vegetable continuousobstacle, so as to supply academic base for summering fallow problems and making full usedof agriculture resource in vegetable field.1The causes for continuous cropping obstacles1.1Allelopathic of broccoli straws extracts and soil extracts on the vegetable seeds andseedlingsThe straw extracts of vegetable and the soil extracts were both affected the germinationrate of vegetable seeds and the inhibition effect was significantly with the concentrationraising. The inhibiting effect of straw extracts on the seeding germination was greater. The inhibitingeffect of the broccoli straw extracts was more significantly on the small seeds than large seeds, and the soilextracts was in contradiction to straw extracts. The extracts from broccoli straw and soil significantlyinhibited the root—top ratio and fresh weight of stem and leaf. The root—top ratio and fresh weight ofstem and leaf in the neutral and acid substances treatments lower than other treatments. Theinhibition of neutral substances and acid substance of the straw extracts in activity ofSuperoxide dismutase (SOD) and Perpxodase (POD) activities was very strong, and thehigher the concentration of the extracts the stronger effect of the inhibition. The neutralsubstances of broccoli straw extracts significantly destroyed the structure of cell and Malondialdehyde(MDA) contents rose with increasing contention of the extracts. The inhibition of Maize straw extracts isweaker, and it was meaned that the maize straw was the best for returning in vegetable field.1.2The analysis of broccoli straws extracts and soil extracts by GC-MSThe GC-MS analysis results showed that broccoli straw extracts had the more kinds ofsubstances than soil extracts. The neutral substances of broccoli straw extracts had many allelochemicals,they was bad for vegetable growth. There were some organic acid substances in acid substances of broccolistraw extracts, they also inhabit vegetable growth.2Remission measures for continuous cropping obstacles2.1Changes of soil character under different intercropping patternsThe microbial biomass and soil urease activity were raised under relay intercropping treatment. The number of microbial was raised and the microenvironment was better thanbefore. Vegetable continuous cropping caused soil nutrient overly consumption and decreasedthe microbial biomass and the activity of urease. As more toxic substances from the root andstraw were released to the soil, this phenomenon made that the activity of soil polyphenoloxidase and catalase in vegetable continuous cropping fields were higher than that in othertreatments, this was bad for soil chemical reaction, and the soil reaction could not be carry on.Relay intercropping decreased the inorganic nitrogen concentration and increased soil organiccontent in vegetable fields compared with sole cropping by making full use of soil nutrition.2.2Effect of soil character in continuous cropping field under maize straw returningStraw returning improved the soil environment and of continuous cropping field by strawcovering. The activity urease was raised and the activity of soil polyphenol oxidase andcatalase were decreased under straw returning treatment. Maize straw had a plentiful supplyof carbon resource for the soil by decomposing. Straw returning treatment increased soilorganic content and increased the inorganic N utilizing rate.3Effect of crop yield and quality under different planting patternsAutumn broccoli yield under relay intercropping was higher than the treatment ofcontinuous cropping, and straw returning in vegetable field would improve the quality ofvegetable. The vitamin C and total phenolics of straw returning were higher than othertreatment. The continuous cropping mode would make the nitrate content accumulate toomuch and vitamin C and total phenolics content were in a low level.