Study Of Soil Microbial Community Diversity Under Long-term Straw-returning And Fertilization

Straw-returning in farm land have drew more attention in recent years, long-term straw-returninghas a profound impact upon both in soil properties and crop yield. Soil microbe, especially bacteria andfungi, plays an important role in the cycling of soil nutrients. Therefore soil fertility can be assessed bythe changes in diversities of soil microbial community. Yet, the response mechanism of microbialcommunity to long term straw-returning is still unclear.In this study, we take long-term straw-returning and fertilization experiment on fluvo-aquic soilwith typical rotation system as winter wheat and summer maize in Hengshui of North China as researchobject，the experiment is implemented as a double factors test，the main factor is inorganic fertilizer rateassigned as‘A’，the input of nitrogen is pure nitrogen and phosphorus is P2O5（kg·mu-1）：A1-N0P0（CK），A2-N6P4，A3-N12P8，and the side factor is straw-returning rate assigned as ‘B’，the inputof straw is as follows（kg·mu-1）：B1-0，B2-150，B3-300，B4-600。Microbial community diversityhas been investigated using Biolog analysis and PCR-DGGE fingerprinting technique. The main findingobtained are as follows：1.Microbial community functional diversity has changed under long-term straw-returning andfertilization：（1）the general Average well colour development（AWCD） of carbon sources onbiolog-eco plate increases most quickly in24h-120h of all treatments, implies the microbe grows mostquickly at that time;(2) straw-returning and fertilization has a impact on soil microbial functionaldiversity, but there is not a necessary significant difference between different treatments;（3）themicrobial communities that use Miscellaneous as carbon source are in a weak position of all treatmentscompare to those which use other kinds of carbon sources；in accord with general AWCD，AWCD ofAmines/amides、Amino acids、Carbohydrates、Polymers in single large quantities of chemical fertilizerstreatmen（tA4B1）is lower than other treatments，especially of Carbohydrates and Polymers，while thereis no significant difference of the utilization in the other two carbon sources；AWCD of Miscellaneousand Carboxylic acids in combined application of large quantities of chemical fertilizers and straw（A4B4）is significant lower than other treatment.2.Microbial community genetic diversity has changed under long-term straw-returning andfertilization：（1）impact of fertilization to soil bacterial community diversity is depended on its amountand soil organic matter，in this research，bacterial species haven’t been changed by long-termstraw-returning and fertilization but the abundance. More specific，the bacterial community diversity isthe lowest among all the treatments，which is the most close to ck（A1B1），application of suitableamount of straw and fertilization can increase bacterial community diversity such as the treatmentsA2B3、A2B4and A3B2；（2）the fungal community diversity can be increased by application ofchemical fertilizer，while the application of straw do not cause such（.e.g.）Fungal community diversitiesunder the small amount of straw（B2）are in order as A4B2>A3B2>A2B2>A1B2，and the4fungalcommunity diversities under the large amount of fertilizer（A4）are higher than the others；（3）The environmental factors that are correlated with soil bacterial community diversity are in the followorder：Total K>OM>C/N>Available N> Available P>Total P>Total N；The environmental factorsthat are correlated with soil fungal community diversity are in the follow order： AvailableK>AvailableP>Total P> Available N>Total N；（4）In this study，soil fungi is effected more easily bylong-term fertilization than soil bacteria. In fungi DGGE image, the treatments such as A2B3and A3B4show some peculiar patterns and there is none in bacteria DGGE image.