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测定了位于北京西北郊的本所农场耕地及附近几个土样的土壤总Nδ15N值,农场耕地的δ15N值为6.39±0.42‰,本所庭园土壤为5.03±0.26‰,圆明园土壤为1.66±0.49‰。农场耕地土壤总Nδ15N的垂直变化为6.09±0.77～7.71±0.67‰,水平变化为6.52±0.55～7.13±0.73‰。 无N营养液砂培大豆的测定结果表明,根瘤富含15N,δ15N值为8.32±0.16‰和10.54±0.30‰,地上部贫化15N,δ15N为—2.25±0.48～—4.16±0.75‰,说明在固N2过程中和固N2产物输送转化过程中发生了N同位素的分馏,固N2分馏因数β=1.0023～1.0042。 用15N天然丰度法估计不同大豆品种的％Ndfa表明,不同大豆品种的N素自给能力不同。固N2植物的δ15N值明显低于非固N2植物的δ15N值,一般相差3～5δ15N,说明用15N天然丰度法评价这些植物的固N2状况是可能的。然而,不固N02植物也有较低的δ15N值,即便在同一地块上,非固N2植物的δ15N值也很不相同,有待进一步研究。
The total Nδ15N value of the farmland and nearby soil samples of the farm located in the northwestern suburbs of Beijing was measured. The δ15N value of the farmland cultivated land was 6.39 ± 0.42 ‰, that of the original garden soil was 5.03 ± 0.26 ‰ and that of the Yuanmingyuan Park soil was 1.66 ± 0.49 ‰. The vertical variation of total Nδ15N of farmland soil was 6.09 ± 0.77 ~ 7.71 ± 0.67 ‰, and the horizontal variation was 6.52 ± 0.55 ~ 7.13 ± 0.73 ‰. The results showed that the root nodules were rich in 15N, with δ15N values of 8.32 ± 0.16 ‰ and 10.54 ± 0.30 ‰, aboveground depleted 15N and δ15N of -2.25 ± 0.48 ~ -4.16 ± 0.75 ‰, indicating that N isotope fractionation occurred during solid N2 transfer and solid N2 product transport and conversion. The solid N2 fractionation factor β = 1.0023-1.0042. Estimation of% Ndfa for different soybean varieties using the 15N natural abundance method indicates that different soybean varieties have different N self-sufficiency. Solid plant N2 δ15N value significantly lower than the value of the unfixed δ15N N2 plants, general difference of 3 ~ 5δ15N, N2 solid condition described evaluation of these plants with 15N natural abundance method is possible. However, the non-immobilized N02 plants also have lower δ15N values, and the δ15N values of non-immobilized N2 plants are very different even in the same land, which needs further study.