华北平原典型农田土壤微生物生物量碳氮磷库的县域分布特征——以河北省曲周县为例

Spatial Distribution of Microbial Biomass Carbon,Nitrogen and Phosphorus Pools in Typical Farmland Soils in North China Plain—A Case Study of Quzhou County

土壤微生物生物量是土壤中的活性养分库,直接参与土壤碳氮磷硫等元素的形态转化与生物地球化学循环过程,是反映土壤肥力与质量的重要生物指标。基于网格法采样,运用地统计学方法分析华北平原典型农田土壤微生物生物量碳氮磷库的空间分布特征及影响因子。结果表明:河北省曲周县域农田耕层(0~30 cm)土壤微生物生物量库在空间上呈斑块状分布,具有中等变异强度和明显的空间自相关性,微生物生物量碳(MBC)、微生物生物量氮(MBN)、微生物生物量磷(MBP)库储量分别为(C)64.14×10^(3)t、(N)24.55×10^(3)t、(P)2.80×10^(3)t,作物产量与MBC和MBN存在显著正相关关系。不同种植体系下单位质量土壤MBC、MBN、MBP的量存在显著差异,小麦/玉米轮作体系下单位质量土壤微生物生物量的平均量高于棉花连作。土壤微生物生物量库的大小和空间分布均受种植体系和土壤肥力的影响,其中土壤有机碳含量是影响土壤微生物生物量库容及空间分布的一个主要因子。研究结果表明土壤微生物生物量库是我国北方典型农田土壤中不可忽视的潜在有效养分库。

【Objective】Soil microbial biomass(SMB)is a pool of soil available nutrients,directly participating in the transformation and biogeochemical cycling of soil carbon(C),nitrogen(N),phosphorus(P)and sulphur(S).Soil microbial biomass carbon(SMBC),soil microbial biomass nitrogen(SMBN),and soil microbial biomass phosphorus(SMBP)are main components of the SMB,which serves as a hub for material cycling in the pedosphere.Since SMB is sensitive to environmental conditions,any change in SMB will affect turnover of soil elements.Therefore,SMB is considered to be a sensitive and effective indicator of soil fertility and biological quality.The study on rules of spatial distribution of SMB pool is of important significance to grasp how soil nutrients recycle in situ and how to manage soil nutrients regionally.【Method】In the present study,to explore how SMBC,SMBN and SMBP distribute spatially and what their influential factors are in the farmland ecosystem.A soil survey was conducted in Quzhou County,a typical agricultural county in the North China Plain with 56740 hm^(2)of farmlands.Using the grid sampling(2.5 km×2.5 km)method,soil samples were collected from the topsoil layer(0-30 cm)of a tract of farmland for analysis of spatial distributions of SMBC,SMBN and SMBP pool with the geostatistical method.【Result】Results show:(1)The average reserve of the SMBC,SMBN and SMBP pool was 64.14×10^(3)t,24.55×10^(3)t and 2.8×10^(3)t,respectively,in the topsoil(0-30 cm)layer of Quzhou County.SMB was distributed in patch,featuring moderate spatial variability and obvious spatial autocorrelation;(2)Crop yield was significantly and positively related to MBC and MBN;(3)The mean content of carbon,nitrogen and phosphorus in soil microbial biomass per unit weight varied sharply with planting system,being higher in the wheat/maize rotation system than in the cotton monocropping system,which indicates that rotation system is superior to monocropping system to some extent,and favorable to maintaining a large soil microbial biomass pool;(4)Size and spatial distribution of SMB pools were governed by planting systems and soil fertility.MBC,MBN and MBP were closely related to soil fertility(e.g.,soil organic carbon,total nitrogen,available phosphorus,available kalium),among which soil organic carbon is the most important factor.【Conclusion】For the first time,sizes of SMBC,SMBN and SMBP pools were quantified,and spatial distribution pattern and influential factors of SMB were specified in the farmland of the North China Plain.In the farmland soil of Quzhou County,soil organic carbon is the most important factor affecting SMB pool,which suggests that soil microorganisms are limited by C.Therefore,it is advisable to strengthen application of organic manure,return straw to the field and reduce mineral fertilizer application rate so as to regulate and utilize the SMB pool in the future.All the findings in this study indicate that soil microbial biomass is a potential available nutrient pool in farmland in North China and may serve as a scientific basis for regionalized nutrient management and precise agriculture.