Nitrogen fixed by legume root nodules accounts for 40% of total biological nitrogen fixation.

豆科植物的根瘤固氮占生物固氮总量的40%。

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Some of them, such as nitrogen, oxygen, argon, neon, and so on, may be regarded as permanent atmospheric components that remain in fixed proportions to the total gas volume.

其中一些气体，如，氮，氧，氩，氖等，作为空气的永久组成成分，总是以固定的比例存在于大气中。

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Some of them, such as nitrogen, oxygen, argon, neon, and so on, may be regarded as permanent atmospheric components that remain in fixed proportions to the total gas volume.

其中一些气体，如，氮，氧，氩，氖等，作为空气的永久组成成分，总是以固定的比例存在于大气中。

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