Effects Of Different Cover Modes On Cucumber Growth And Soil Environment In Greenhouse

In the intensive cultivation system facilities, the traditional continues cropping and simple rotation mainly rely on the use of pesticides and fertilizers with large input, but this may cause series of problems such as soil degradation and brought obstacles to plant growth, which lead to the reduce of vegetable yields. How to control the soil function degradation, improve and maintain the soil quality of facilities, so as to make the vegetable production of production facilities achieve sustainable development is a problem which urgently need to solve. Cucumber(Cucumis Sativas L.) as one of the main crops in the facilities, the phenomenon of continuous cropping in recent years has been increasingly serious and has aroused the attention of many scholars.The main aim of this study was to investigate the effects of different cover modes on soil health keeping of cucumber in greenhouse. Plant growth, soil enzyme activities, soil physical and chemical properties, soil microbial communities and soil phenolic compound contents of cucumber were studied by conventional chemical method, PCR-DGGE, real-time PCR and high performance liquid chromatography(HPLC) methods. Cucumber(Cucumis sativus) was the main crops, scallion(Allium fistulosum), oilseed rape( Brassica campestri) and wheat(Triticum aestivum) were different season cover crops. The experiment was carried by pot experiment with 3 years of continuous cropping of cucumber soil in greenhouse. Main results of this paper were as following:(1) Cucumber yield, plant height and dry matter of cucumber plant in scallion and rape were significantly higher than wheat in the first two planting seasons, while results of the last two were in contrast.(2) Compared with cover scallions and rape, cover wheat in summer was conducive to suppress the occurrence of cucumber Fusarium wilt disease.(3) Wheat treatment was more advantageous to improve the soil urease, neutral phosphatase and invertase activities than that of scallion and rape.(4) Different cover modes, with the increasing planting times, soil available potassium content trended to increase and then decrease; soil EC were lower than before planting except the autumn season in 2013; soil p H kept neutral as a whole. In conclusion, all cover modes could keep the soil with relatively low EC, avoid soil acidification, which in summer cover wheat was the best.(5) PCR-DGGE results showed that the soil bacterial and fungal community structures were quite different of different cover mode under different planting season. scallion treatment increased the diversity indices of bacterial community and reduced the the diversity indices of fungal community; wheat treatment remained the relatively higher bacterial diversity indices; rape treatment maintained a relatively higher fungal diversity indices.(6) q PCR results showed that the sizes of soil bacterial, fungal and Fusarium communities were different among different cover modes. Wheat treatment significantly increased the number of bacteria and reduced the number of Fusarium than the other two treatments.(7) Seven phenolic compounds were detected by the HPLC method in both the before planting soil and the different cover modes soils in all crop times. 7-Hydroxycoumarin was the most abundant in all the soil samples, followed by vanillic acid > p-hydroxybenzoic acid > ferulic acid > syringic acid > vanillin > p-coumaric acid in cover modes soil samples. With the increasing of crop planting time, all kinds of phenolic compounds content in the soil are increased.(8) The allelopathic strength of different cover mode were different in different planting seasons.Overall, all cover modes had a certain impact on cucumber growth, soil nutrient condition and soil microbial environment, and led the soil environment changed. Each cover mode had his good points to keep greenhouse soil health: scallion and rape treatments could promote the growth of cucumber in a short time, and improve soil enzyme activities and microbial diversity to a certain extent; wheat treatment could maintain relatively higher soil enzyme activities and soil microbial community diversities, reduced the number of Fusarium at the same time, and remained relatively low soil EC, avoid soil acidification. Therefore, we should be based on the specific situation and choose the appropriate cover mode in production.