Effects Of Stalks On Growth Of Cucumber Seedlings And Soil Microbial Communities

Cucumber is one of the widely popular vegetables because it’s delicate smell and palate ringing in the world, and it has a wide market prospect. In recent years, with the crying needs of cucumber in the market, the area of continuous cropping has increased constantly, thus, resulted in continuous cropping obstacles such as poor growth of cucumber, decline of fruit quality, weakly disease resistance. Studies reported that crop stalks management could improve soil physicochemical property and biological property, then, improve soil continuous cropping obstacles. However, there were different effects of different species crop stalks on the growth and development of same or different receptor plant.In this study, maize stalk, wheat stalk and Jerusalem artichoke stalk were respectively added to soil which has planted cucumber 6 years(12 stubble), to determine the growth of cucumber seedlings, soil enzyme activities, content of soil microbial biomass C and N, and soil cultivable microbial numbers with conventional methods, to determine the soil specific microbial community abundance and community structure with qPCR and PCR-DGGE, and to determine the soil fungal and bacterial community composition with high throughput sequencing, to investigate the effects of crop stalks on growth of cucumber seedlings and soil ecological environment, to provide theoretical foundation and technical support of crop stalk improving soil continuous cropping obstacles in production. The results were as follows:(1) In sum, compared to control, height, stem diameter, fresh weight, dry weight and leaf area of cucumber were promoted by maize stalk and wheat stalk. Jerusalem artichoke stalk increased cucumber growth only at 10 and 20 days.(2) Maize stalk increased soil urease activity and invertase activity, wheat stalk increased soil netural phosphatase activity, invertase activity, and dehydrogenase activity, Jerusalem artichoke stalk increased soil urease activity, invertase activity, and dehydrogenase activity.(3) There was a trend that all stalk treatments increased the content of soil microbial biomass C, and significantly increased the content of soil microbial biomass N, and the content was higher in wheat and Jerusalem artichoke stalk treatments than maize treatment.(4) All stalk treatments declined soil fungal number, and the difference was significant at 10 days. All stalk treatments significantly increased soil bacterial number, in the three sampling dates,soil bacterial number was highest in Jerusalem artichoke treatment, lowest in wheat treatments.(5) All stalks increased the soil Pseudomonas abundance. Additionally, the relative abundance of Fusarium oxysporum was significantly increased by all stalk treatments at 10 and 20 days. At 30 days, all stalk treatments significantly declined the relative abundance of Fusarium oxysporum, but there were no difference among the stalk treatments.(6) The numbers of atlas stripe and diversity index of soil Pseudomonas and Bacillus were increased at first, then declined. And the numbers of atlas stripe and diversity index of soil Pseudomonas and Bacillus were higher in maize and wheat treatments than Jerusalem artichoke stalk treatments.(7) High throughput sequencing showed that all stalk treatments increased the relative abundance of Ascomycota and Proteobacteria, and declined the relative abundance of Basidimycota and Firmicutes. At the 30 days, maize and wheat stalks declined the relative abundance of Verticillium, Nematoctonus, Sarocladium, Gibberella, Corynespora,Stenotrophomonas, Flexibacer, increased the relative abundance of Cellvibrio, Nocardioides,Nitrospira. The trend in Jerusalem artichoke treatment was inverse compared to maize and wheat stalks treatments.Overall, maize and wheat stalks promoted growth of cucumber. In sum, maize stalk increased soil urease and invertase activities, wheat stalk increased soil neutral phosphatase, invertase and dehydrogenase activities, Jerusalem artichoke stalk increased soil urease, invertase and dehydrogenase activities. The three stalks increased the content of soil microbial biomass C and N,and it was higher in wheat and Jerusalem artichoke stalk treatments than in maize stalk treatment.All stalk treatments declined soil fungal number in some extent, increased soil bacterial number,increased abundance of soil Pseudomonas. The relative abundance of Fusarium oxysporum,diversity index of soil Pseudomonas and Bacillus in the three stalk treatmentd were increased at firstly, then declined. All stalks treatemnts changed the soil fungal and bacterial community composition.