秸秆覆盖下土壤养分与微生物群落关系研究

Study on the Relationship Between Soil Nutrients and Microbial Community Composition After Cornstalk Mulching

以我国17省的85个土壤样品为研究对象,定量添加玉米秸秆置于30℃培养90d,研究处理后土壤有机质(SOM)含量及养分变化与微生物群落之间的关系。结果表明:土壤各理化指标除全氮、碱解氮、全磷含量在处理后部分土壤减少以外,全钾、速效钾、速效磷含量均显著增加;SOM变化差异显著,根据其变化量将土壤分为I_1组有机质增量(I)>12.05g/kg,I2组0.25<I<9.0g/kg,I3组-112.3<I<-0.3g/kg。I_1和I_3组初始SOM含量高且相似,处理后SOM却出现显著增加和显著降低2种截然相反的结果,而初始SOM较低的I_2组增加,但不显著;初始可培养细菌远高于可培养真菌和放线菌,但处理后真菌增量显著高于细菌,I_3组最为明显;处理前后,I_2和I_3组部分土壤的微生物生物量碳(MBC)变化不显著,部分则显著下降,而I_1组MBC含量在处理后多为显著上升;磷脂脂肪酸(PLFA)测定结果表明I_2组土壤微生物受环境和养分胁迫较I_1和I_3组高,I_2组处理后MBC均值降低了10.3%。秸秆对土壤的添加效果除了受土壤本底养分等条件影响外,很大程度上决定于土壤原有微生物的类型和组成。PLFA可用于预测秸秆添加效果。

There are lots of researches about dynamics of microbial decomposition and soil nutrients during straw returning to soil,but the differences in soil properties between different soil types were neglected.To investigate the changes of soil organic matter（OM）and relationships between soil nutrients and microbes by adding corn-stalk,85 soil samples were collected from 17 provinces in China and placed under 30℃and cultivated for90 days.The results showed that：except the contents of total nitrogen,available nitrogen,and the total phosphorus reduced in part of the samples,total potassium,available potassium,and available phosphorus contents were increased in all of the samples after treatment.Based on the changes of soil OM,all the samples were divided into 3groups：I1group with OM increment〉12.05g/kg,I2 group with OM increment between 0.25g/kg and 9.00g/kg,I3 group with OM reduction between-0.30g/kg and-112.30g/kg.Soils in I1 and I3groups had the similar higher original OM content,however the totally opposite trends of OM matter variation occurred after treatment,and group I2 with the lower OM than I1 and I3experienced insignificant increase in soil OM.The cultivable cell number of bacteria was significantly higher than those of fungi and actinomecetes in all original soil samples,however straw mulching stimulated the multiplication of fungi and actinomecetes but restrained the growth of bacteria at the same time,especially in I3 group.Compared with the original soils,soil microbial biomass carbon（MBC）of I2 or I3were either no significantly changed or significantly decreased after adding cornstalks.On the other hand,most of the I1 group soil samples MBC after adding cornstalks increased significantly.PLFA results depicted that I2 group samples faced the most stress on nutrient and environmental perspectives among the 3groups which could attribute to the average 10.3% decrease of MBC in I2 samples.Overall,this study indicated that the effect of straws adding on the soil quality depends much more on the original soil microbial community and composition than on the soil original nutrient background,and the method of PLFA could be used to predicate the effect of straw adding.