利用15NO3-标记法研究土壤微生物量氮的化学及生物有效性

采用加入含15N的硝态氮培养方法标记了土壤微生物量氮 ,然后利用碱解扩散法测定了标记土壤有效氮含量 ,温室培养法评价了小麦对标记的土壤微生物量氮的吸收情况。结果表明 ,碱解扩散法对土壤微生物量固持的15N的提取比率 (即提取液中15N原子百分超 /土壤15N原子百分超 )在 1 47～ 2 83之间(平均 2 0 1 ) ,碱解氮中约有 3 0 1 %～ 61 6% (平均 42 9% )来自土壤微生物固持氮。植物体15N丰度在0 749%～ 1 1 62 %之间 ,明显高于15N的自然丰度 ,表明土壤微生物固持的15N在小麦生长期间发生释放 ,为植物利用。土壤微生物固持氮对植物的有效性比率 (植物地上部分15N原子百分超 /土壤15N原子百分超 )在 3 7～ 7 1之间。可见 ,土壤微生物量固持氮有较高的化学及生物有效性

EVALUATING THE CHEMICAL AND BIOLOGICAL AVAILABILITIES OF SOIL MICROBIAL BIOMASS NITROGEN WITH THE 15NO3--LABELED METHOD

In this study soil microbial biomass nitrogen (SMBN) in 6 soil samples were initially labelled with the ¹⁵NO₃^- in the incubation experiment.Then the NaOH hydrolyzable method was adopted to measure the alkali hydrolyzable-N in the soils, and winter wheat was grown on the soils in a greenhouse to evaluate the availability of SMBN to plants.It found that the extractability ratios of the NaOH hydrolyzable-N to the SMBN were in the range of 147 to 283, with an average of 201;there was about 30.1%~61.6% (averaging 42.9%) of NaOH hydrolyzable-N in the soils derived from SMBN.The atom % of ¹⁵N in the plant shoots grown on the soils ranged from 0.749% to 1.162%, which were higher than the natural atom % of ¹⁵N in soil, indicating the release of ¹⁵N immobilized by SMBN in soils.Therefore, it is concluded that the chemical and biological availabilities of SMBN are high.