Prior to the 1920s, biological N fixation was the primary source of N used to maintain and sustain the fertility of agricultural soils. In order for this form of N to be used by plants, it must be mineralized by organisms in the soil food web so that it becomes a plant-available, inorganic form.
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Step 1: Biological nitrogen fixation — specialized microbes (symbiotic rhizobia in legumes, free‑living diazotrophs and cyanobacteria) use the enzyme nitrogenase to reduce atmospheric N2 to ammonia (NH3), which is rapidly incorporated into microbial and plant Show more…
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The major biological process that makes nitrogen available to plants is nitrogen fixation carried out by soil microarthropods. Nitrogen fixation is also carried out by mycorrhizal fungi. Additionally, nitrogen fixation can occur abiotically and convert nitrate to nitrogen gas. Another source of nitrogen fixation is the symbiotic relationship between soil and plant bacteria.
Rabeya Z.
Nitrogen-fixing bacteria a. reduce atmospheric nitrogen. b. can live independently in the soil. c. are usually associated with legume plants. d. break $\mathrm{N}=\mathrm{N}$ bonds. e. All of these are correct.
Which of these occurs through symbiotic nitrogen fixation? a. The plant benefits from using an endless source of nitrogen. b. The soil benefits from being naturally fertilized. c. Bacteria benefit from using photosynthates from the plant. d. All of the above occur.
Sri K.
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