两种测定土壤微生物量氮方法的比较初探

用氯仿熏蒸-0.5mol/L的K2SO4直接浸提,280nm紫外比色法和熏蒸-淹水培养法测定了20种有机质、全氮和速效氮差异较大的土样的土壤微生物量N。研究结果表明,两种方法测得20种土样的土壤微生物量N数值呈极显著正相关;280nm紫外比色法操作步骤简单、产生误差的环节少、测定所需时间短、且测定数据比熏蒸-淹水培养法有更好的重现性。初步认为,280nm紫外比色法来反映土壤微生物量的大小。结果还表明,两种方法的测定结果都与土壤的全氮含量呈极显著正相关关系,与有机碳含量有一定的正相关关系,与速效氮无明显的相关关系;但在不同的土壤类型上,与全氮、有机碳和速效氮的相关性有所不同。用280nm紫外比色法测定两种土壤的新鲜和风干样的微生物生物量的结果说明,可用风干土经预培养后测定土壤微生物生物量。风干土样的预培养时间初步确定为10天。

Comparison between two methods of determination soil microbial biomass nitrogen

Two techniques were compared that uses the UV absorbance at 280nm of 0.5mol/L K_2SO_4 extracts of fumigated and unfumigated soils and fumigationwaterlogged incubation to estimate the concentrations of nitrogen in the SMB.Using 20 Ningxia and Shaanxi soils,with a wide range of organic carbon(5.16～24.6g/kg), total nitrogen(0.75～2.66 g/kg) and available nitrogen(25.7～119.0 mg/kg),it was demonstrated that the increase in UV absorbance at 280nm after soil fumigation was strongly correlated with the soil microbial biomass N(SMBN,r=0.79),as determined by fumigationwaterlogged incubation method.The 280nm UV absorbance technique has the advantages as followed,simple steps,less error,less time needed and better repeatability than fumigation/waterlogged incubation method.The SMBN determined by two methods all have remarkably positive correlations with total nitrogen,have positive correlation with organic carbon and no obviously relation with available nitrogen.In different soil types,it showed different correlation with total nitrogen,organic carbon and available nitrogen.In addition,the microbial biomass in fresh and dry soil were measured by 280nm UV absorbance technique,the results also showed that dry soil can be used to measure the(microbial) biomass after pre-cultivate,and the cultivating period is 10 days.