Study On The Potato Continuous Cropping Obstacle And Intercropping Regulation In The Mountain Area Of South Ningxia

The mechanism of potato continuous cropping obstacle and intercropping regulation were studied by using the method of field experiment and room culture. Allelochemicals from soil and stubble in long -term potato monoculture were indentified by using gas chromatograph mass spectrometer system(GC-MS). The effect of the long-term potato monoculture to soil microbial community were analyzed by using the hospholipid fatty acid (PLFA) biomarkers、Terminal Restriction Fragment Length Polymorphism(T-RFLP)and Biolog Eco-plate. The soil nutriention in rhizosphere soil were also studied. The soil basic physical and chemical characteristic,soil biological properity and the structure and function of soil microbial community were also separately studied, when the intercropping system were used in the field, three different potato varieties were selected as major crops. The results are as follows:1、The extracts from potato stubble and soil could obviously inhibit the germination rate of seed, the suppression ability from the allelopathy of exotic plants or soils were enchanced with the increasing of the extracts concentration and had a great effect on seed germination and the radical growth. Both of iso-butyl phthalate ester and cis-14- twenty-nine alkenes were detected, the former chemical ingerident can reach 50%, which had a large proportion in the total components. So we could draw a conclusion that the iso-butyl phthalate ester and cis -14-twenty-nine alkene areprobably the main allelochemicals, which could caused potato continuous cropping obstacle.2、After long-term potato monoculture, soil fertility in rhizosphere still have a litter high, and no nutriention deficit were found; After several years of long-term monoculture, the soil phosphatase, urease and catalase activity were declined; The rhizosphere microbial biomass carbon and nitrogen were showed the trendency of decling and then enhancing with the time increasing of,long-trem monoculture, However the ratio of carbon and nitrogen for microbial bomass were still increased.3、The ability of carbon utilization for soil microbial community were the minimum in continuous cropping for ten years, but there were the highest ability of carbon utilization in four years of long-term potato monoculture. The function diversity of soil microbial community were obviously decreased and the microbial population using the carbohydrates、carboxylic acids and amino acid as the metabolism substances were also inhibited significantly. The biomass of C16:1, C16:0, C18:2ω6t, C18:1ω9c marked by the main phospholipids fatty acids (PLFAs) profiles were higher compared with the other PLFA fraction. The content of the different PLFAs fraction were showed a tendency of single peak with the time increasing of continuous cropping. The maximum of biomass marked by PLFA were found at four years. The ratio of bacteria/the total biomass of soil microbial community were increased, while the ratio of fungi/the total biomass of soil microbial community declined with the time increasing of continuous cropping, the soil microbial community structure and the biomass were obviously improved owning to the rotation.4、After intercropped with different potato varieties, soil pH were significantly decreased; Soil nutriention, nearly all of them were both higher compared with long-trem monoculture. Soil nutrient have already been changed when the different potato varieties were intercropped, together. For different treatments, soil enzymes activity also had a big change; soil microbial biomass nitrogen content increased, the microbial biomass carbon decreased and the ratio of soil microbial Carbon and Nitrogen were also decreased.5、The number of bacteria populations were obviously higher for intercropping under the condition of different potato varieties, the number of actinomycetes and fungi populations were showed a decreasing trend, the total number of soil microbial communities have been increased, compared with long-term monoculture.The ability of soil microbial carbon utilization were enhanced, the functional diversity of soil microorganisms were significantly improved,the ability of carboxylic acids and aromatic compounds used as carbon souce of soil microbial communities were obviously increased for intercropping system.6、The results from field yield showed that crop failures are common compared with monoculture, but according to the land equivalent ratio(LER), LER was greater than 1 for intercropping system, it means that there were a higher production efficiency in intercropping system, compared with long-term monoculture. Where Longshu3 and zhuangshu3 were intercropped, the rate of potato yield growth could reach to 17%, zhuangshu3 and qingshu9 intercropped, it could reach to 19%. So, we could get a conclusion that the continuous cropping obstacle could be regulated by using intercropping system, especially for different potato varieties intercropped, together.