nitrogen Fixation – a deep dive (From 1)

About two years ago I wrote a post where I celebrated the nitrogen-fixing plants as one of the keys to getting a step closer to the forest horticulture lofty goals of the self-creating fertility. In the same post I presented as a table with quite a variety kvävefixerare, ranked by their ability to capture the nitrogen from the air and make it available to other plants. Although I have not found any direct factual errors in the post, it has in the last months turned up a lot of questions about kvävefixerarnas proper role and possible limitations. It started when I was wondering how it actually works - what mechanisms underlie nitrogen fixation, how much nitrogen plants can capture, how much of it they can spread to their neighbors and how they do it? What factors influence their nitrogen-fixing ability? And how many kvävefixerare needed for them to make a difference? Unfortunately, it appears that there are no simple answers to these questions. Nitrogen fixation depends on numerous factors and is a surprisingly poorly studied phenomenon. In the following posts I still want to make an attempt to find answers to questions. Welcome to comply with the proper delving!

All nutrients are important, but the subject nitrogen (N) is perhaps the most important of them all. It needed to build amino acids that are the building blocks of all proteins, even those proteins called enzymes, which control virtually all biological processes in plants. In addition, we need to form chlorophyll, it helps to absorb other nutrients and stimulates growth both above and below ground. A plant suffers from lack of nitrogen is characterized by pale yellow leaves and poor growth.

Without nitrogen there will be no beautiful green leaves which in this part of my woodland garden.
Without nitrogen there will be no beautiful green leaves which in this part of my woodland garden.

The plants we call kvävefixerare, however, does not really bind nitrogen from the air themselves but collaborates with highly specialized bacteria that capture nitrogen from the air and convert it into a form that plants can absorb. These usually live in small bumps that sit on the outside of the roots. The best known nitrogen-fixing plants belonging to the family of legumes (Fabaceae). These cooperating with bacteria that either belong to the genus Rhizobium or the genus Bradyrhizobium [1]. In addition to the countless legumes are the woodland garden grower interesting plants in other genera that have entered into a symbiosis with nitrogen-fixing bacteria of the genus Frankia, such as alder (Alnus glutinosa) and sea buckthorn (Hippophae rhamnoides). There are more types of nitrogen-fixing organisms, but they are not relevant to forest horticulturist [2].

Seabuckthorn is a kvävefixerarna cooperating with Frankia bacteria.
Seabuckthorn is a kvävefixerarna cooperating with Frankia bacteria.

Whatever microorganisms which capture nitrogen, it is always the enzyme nitrogenase that catalyzes the uppspjälkningen of atmospheric nitrogen molecules (N2) and converts them into ammonia (NH3). Enzymes are catalysts that chemical reactions that otherwise would not have been. We can think of them as the oven when baking bread. To water, flour and yeast to become bread, they need to be baked and it takes a lot of energy. In biological nitrogen fixation, this energy from the sun, whose light has been converted into energy through photosynthesis. This energy is used to break the enormously strong (triple)the bond between the two nitrogen atoms that form each kvävmolekyl. It is clever is that the nitrogenase enzyme remaining after the reaction has taken place - just as we can use the oven several times to make bread.

Så kan nitrogenase se ut i modellform. To form the enzyme thus requires, even iron, molybdenum and sulfur. Source: PatríciaR, Wikimedia Commons.
Så kan nitrogenase se ut i modellform. To form the enzyme thus requires, even iron, molybdenum and sulfur. Source: PatríciaR, Wikimedia Commons.

In nature there are only two processes that add new nitrogen to the terrestrial ecosystems: den ena, dominant process is the biological nitrogen fixation by bacteria. The second occurs during thunderstorms, When Lightning DEVICES enormous energy splits up atmospheric nitrogen molecules, which then combines with oxygen and nitrogen oxides are subsequently raining down and be absorbed by the vegetation. Everything else nitrogen circulating in the ecosystem is recycled nitrogen which once was picked out of the atmosphere by either bacteria or during thunderstorms. A lot disappears course also, either back to the atmosphere as a result of various degradation processes or by leaching into watercourses, so there is a continuous supply of nitrogen from the atmosphere to the biological systems to keep them running. In modern times, however, we have disrupted this system properly by both the combustion of fossil fuels (where the nitrogen compounds formed later raining down and provides nitrogen present in the atmosphere for millions of years ago) and by the excessive use of fertilizers manufactured by artificial and energy-consuming way fix nitrogen from the atmosphere. Man's conversion of atmospheric nitrogen currently exceeds all natural nitrogen fixation processes together [3].

Since we are in the forest gardening do not want to use chemical fertilizers are nitrogen fixation using plants very important to bring new nitrogen to the system. But how will the nitrogen available to plants actually? More on that in the next post.


[1] Brady, N.C. and R.R. Because, The nature and properties of soils. Upper Saddle River, N.J.: Prentice Hall, 2002.
[2] Santi, C., D. Bogusz, and C. Franche, Biological nitrogen fixation in non-legume plants. Annals of botany, 111(5): p. 743-67, 2013.
[3] Rock Power, J., W. Steffen, K. Noone, A. Persson, F.S. Chapin, E.F. Lambi, T.M. Lenton, M. Scheffer, C. Folke, H.J. Schellnhuber, B. Nykvist, IT. the White, T. Hughes, S. van der Leeuw, H. Rodhe, S. Sorlin, P.K. Snyder, R. Costanza, The. Svedin, M. Falkenmark, L. Karlberg, R.W. Corell, V.J. Fabry, J. Hansen, B. Walker, D. Liverman, K. Richardson, P. Crutzen, and J.A. Foley, A safe operating space for humanity. Nature, 461(7263): p. 472-475, 2009.

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14 thoughts on “nitrogen Fixation – a deep dive (From 1)”

  • brilliant Philipp! Have thought and wondered a lot about this yourself then it just figures some rather vague (or without references) claims in the literature about forest gardens. Just as you type.
    One aspect that deserves mention can also be fungi (mykorrhiza) ability to assist the nitrogen-fixing bacteria with access to phosphorus. With that, I know not so much about… Looking forward to the next part!

  • Do any information on nitrogen-fixing plants in perennial crop? When I studied as they spoke mainly of nitrogen-fixing plants in a mixture förgröda nutritional consuming vegetables. There are some templates to count on. But some plants, t.ex. Red clover can in good conditions bind large amounts of nitrogen. The condition in which the involvement of the carbon-rich plants (usually different grass species). With “Right” carbon / nitrogen ratio so tied this in green mass and does not leak out.

    There seems to be widespread in permakulturkretsar that it is enough to cultivate some nitrogen-fixing plants near other plants. But I have seen many very bad examples of it when lush herbs to compete with young fruit trees such as. with very poor establishment as a result.

    In vegetable cultivation so count on (yep, count, think it is law t.o.m. – Eutrophication is one of our biggest environmental problems) industry bound in green mass, which then makes available industry after the first and second year when the plants decompose.

    It must be added that the nitrogen-fixing plants usually grow on poor soils. In nutrient-rich soils hampered symbiosis and nitrogen fixation is not as great. Therefore, usually professional growers habitually always inoculate the bacterial strains at each sowing.

    To make this work effectively in perennial crops, I think you have to think slowly and long-term (Permaculture is certainly well on slow flows?). I en juvenil odling kanske en stor andel kvävefixerande växter ska odlas för att år fram i tiden successivt mogna. Precis som många naturliga miljöer där olika arter tar över varandra i successioner och strävar efter något slags klimax.

    Typ detta scenario:
    1. Störd mark med maskiner, packningsskador
    2. Örter med kraftiga rotsystem och som pga av enorm fröspridning finns i fröbanken börjar komma upp (typ åkertistel, gråbo, rödklöver)
    3. Gräsarter
    4. Trädpionjären, t.ex. Asp
    5. Sekundärarter, t.ex. I

    Varje artförberederförutsättningarna för att nästa ska kunna växa.

    Hoppas jag fick fram någon poäng eller tips 🙂


    • Tack för bra och utförliga kommentarer Johan! Jag håller med ditt successionsförlopp, Thus, a large proportion kvävefixerare in the young forest garden and more sensuccessionsarter in the mature forest garden. Will try to put together a post about it in the spring. Please continue to share your experience!

  • Marcus,
    fun you took up mycorrhiza. Yet another super exciting topic. Recommend to check up on Paul Stamets and his ideas and research into fungal importance of resilience in ecosystems mM.

    Mycorrhiza can help plants with nutrient supply. It does so in part through the “extends” the plant root system and secrete enzymes that have the ability to degrade more sparingly soluble compounds of phosphorus. Mykorrhizza and nitrogen-fixing bacteria, I have not read anything about. But fungi in general seems to be strong foundation in all mature (forests) plant environment,.

    Do also remember that I read that organic soils ecosystems are more mushrooms dominant, while those fertilizer used is more dominant bacteria. Soluble nitrogen is apparently beneficial bacteria growth of fungi expense. However, it has been associated with the saprophytes (spoilage organisms). How it is with nitrogen-fixing bacteria I have poor track.

  • great post! One question that I would think would be interesting in this context is exactly how much energy is required in the production of a certain quantity of fertilizer per square meter type (expressed in an understandable comparison) …om du snubblar över någon sådan information 🙂

  • Fast vid förbränning av fossila kolväten så är det huvudsakligen själva värmen som skapar NOx av luftens kväve. Detta blir faktiskt ännu värre om man har en katalysator som arbetar på hög värmesamma effekt som i blixtens urladdning för övrigt. Detta var bara en kommentar till att förbränning av forssila kolväten släpper fritt kväve som fanns i atmosfären för länge sedan.

    Men jag letar egentligen efter en referens på hur mycket kväve som fixeras av jordbakterier utan någrakvävefixerande växter”. Kommer inte ihåg var jag läste om det, trodde det var här. Har du nån aning? It's actually surprisingly much as fixed by the bacteria that live freely in the soil.

    Sincerely, Magnus

  • Magnus,
    Clostridium and azobacter learn to fix 3 kg / hectare (per year). Can not find the source now ..,
    The green manure mixtures think you count on the 30 kg.
    I think most this can give hints yet. There are so many parameters that come into play for how much nitrogen fixation in the soil is.

  • Annevi,
    would be interesting to see such figures. But I think you need to be more specific if you find the right information. Nitrogen fixation by legumes, for example, would not be able to replace commercial fertilizers from phosphate rock or kalimagnesia eg.

  • Yes, I find nor source, Remember that I said was not. But I remember that it was a not insignificant nitrogen fixation by bacteria, even without symbiosis, and it was strongly influenced by how poor the world was on the nitrogen in the starting point (less nitrogen in the soil more fixing =).

    It would have been interesting to test, and also fairly easy. For example, if you have a large “pot” (one 1000L plastic tank with avskuren top). Fills with soil, or more preferably sand or gravel. plants comfrey, which is very nitrogen hungry without fixation. Watering with rainwater, fertilize optionally with fertilizer without nitrogen. Cuts and weighs harvest.

  • 2/4 – 3/4 of nitrogen is indicated to come from nitrogen fixation, residue from soil. read in “Gröngödsling” in the binder “Organic vegetable garden in the open”. But it is in contexts other than forest gardens.
    Do a carefully selected composition (with perennial herbs) and a green manure by-the-book in a couple of years before the establishment of a forest garden can provide good effects. The vegetable is valuable.
    But with green fertilization, other effects too, which in turn increases nutrient uptake and the soil's ability to supply nutrition. It feeds the soil.
    Do not follow in your experiment with comfrey, that is not a plant that has symbiosis with bacteria.
    Do you think that the existence of any free-living nitrogen-fixing bacteria in the gravel in Sant case? They survive in gravel? Also note that rainwater contains some nitrogen. Think you count on 6kg / year and hectare when farmers make their nutrients calculations.

  • Yes, I guess that nitrogen-fixing bacteria survive in the gravel in the same way as in soil, but it is only an assumption.

    The reason for the gravel is to have as little stored nitrogen in the soil as possible from the start, although it may not be so important because nitrogen is not stored particularly well in soil. And the reason to use rainwater is precisely in order to be able to count on the amount of nitrogen is added to the road.

    The reason to plant comfrey is that it is easy to care for, dominant (some weeds) and nitrogen hungry. It is then expected that the nitrogen content of the soil is kept very low, something that stimulates nitrogen fixation. Dessutom tål vallört att beskäras kontinuerligt. Beskärt material vägs (helst torkat) och mängd kväve som har tatt ut från systemet är då lätt att beräkna, och det som tas ut måste ha fixerats asymbiotiskt (korrigerat med kväve tillfört med bevattning).

    Resultatet är att mängden asymbiotisk fixerat kväve i systemet lätt kan beräknas, dessutom över tid, utan några laboratorieanalyser.

  • Hi, hoppas det finns liv här även i äldre intressanta bloggtexter. Tittat på skogsgödslingen och vad som lovas där. Stämmer följande länk nedan, ger den någon del av svar på Annevis fråga? Jag har inte studerat not 3, but now wonder if it contradicts what is said of this company, clock enegivy?

    (An occasional thought for Permaculture can get hiccups of this manure systems.)

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