Buckwheat and nitrogen fixation

Buckwheat is not a legume. There are a few non-legumes that sequester atmospheric nitrogen. I have heard that buckwheat can fix nitrogen, but never thought much of it because there are a lot of garden myths and nonsense around.

Then I stumbled across a thesis written in 1997 published on the FAO website: Nitrogen fixing microorganisms of the buckwheat rhizosphere and their influence on the plant productivity.

From this study it sounds as though if buckwheat is properly inoculated it not only fixes nitrogen, the grain yield is also increased by 15-20%. That is intriguing.

I am trying to read more into buckwheat and nitrogen fixation. Does anyone have any other research on buckwheat and nitrogen fixation that they can link?

Another study shows significant increases in soil nitrogen after growing buckwheat as a cover crop (page 32) and states “Despite the fact that buckwheat is not a nitrogen scavenger, concentration of nitrogen in soil significantly increased in both soil layers indicating stimulation of biological nitrogen fixation by bacteria in the rhizosphere”.

https://digitalcommons.fiu.edu/cgi/viewcontent.cgi?article=2044&context=etd

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I plant the garden each fall with buckwheat and treat it as a green cover crop that I chop into the soil in early spring just before seed heads are appearing. In this way it is a nitrogen fixer with all that green biomass that gets tilled into my soil just before I plant the garden. This not only helps aerate soil but is feeding the microbes as they break down the nitrogen fixed in the biomass.
Dennis
Kent, wa

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Interesting. No, I don’t have any sources for you, but I’ll definitely read the paper you posted. Buckwheat sure ACTS like nitrogen fixer, growing green and lush even when enduring soil moisture and fertility that would stifle most plants.
We hear and talk about nitrogen fixation as though we all know what it is, yet it seems much more a vague generalizable concept than just a small subset of root nodule inhabiting bacteria associating with a small subset of plants.
I’m no expert, by any means, by a cursory glance would show you that it’s all about microbes rendering nitrogen bioavailable by their metabolic doings. Elemental nitrogen, or any other element for that matter, is not stable nor usable in the environment. Nitrogen, in one form or another, IS ubiquitous though. While

Here’s a small section of the Wikipedia entry for nitrogen fixation.

Reading it makes me realize how generalizable the concept is to life on the whole. I suppose there is a time factor, but it seems there could be other ways a plant might foster or induce nitrogen fixation besides harboring some specific type of bacteria in nodules on its roots.

Reading down a bit (I realize this is a Wikipedia based analysis, fwiw) there ARE cereal crops that form synopsis with Cyanobacteria toward similar ends:

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I concur with hobilus. Nitrogen gets fixed even in the absence of legumes, so there are a number of N fixing bacteria and those that associate with legumes are just the best of many. In point of fact results from cover cropping indicate that a rye daikon cover crop provides more nitrogen to the subsequent crop than a winter legume. Part of it is biomass, part is deep roots, and part is just non legume N fixing.

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i had read that somewhere as well but dont remember the source. i discussed this with a local farmer that his family has been growing buckwheat for nearly a century. he said buckwheat is the only crop they dont fertilize the field before planting and the next crop grown in the field the following year does very well, so he believes that its true from his experiences.

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Buckwheat is a great nutrient scavenger. It tends to send down a nice deep root, that gets below what other seasonal plants do. This allows nutrients that have leeched down, to be brought back up to the surface and be stored in the green biomass of the stalks and leaves. Once crimped over, or tilled in, those decomposing buckwheat stalks release the scavenged nutrients in the top of the soil profile, to be used by the next crop.

We’ve been planting buckwheat for years with great results for the next years growth.

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Interesting topic. Though I’m skeptical concerning the nitrogen fixation.

i have a 15’ x 60ft steep ditch that i planted some red Takane Japanese buckwheat 3 yrs ago from rareseds.com. from the 2 small packets its managed to cover about 80% of that area and gets bigger every year. its actually out competing the wildflower mix i originally seeded there. looks nice mixed with the calendula in there

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When I started growing vegetables 20 years ago, the common refrain was that buckwheat is a phosphorous scavenger, meaning that it is better at taking up P from the soil than other plants. When the buckwheat is tilled back into the soil, the P is in an available form for the following crops. I wouldn’t be surprised if the same mechanisms that allow the buckwheat to transform P also allow it to access other nutrients. I’m guessing the trick is acids or enzymes exuded from the roots, but that’s above my pay grade.

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I’ll try to find the study, but corn can also supposedly fix nitrogen under the right circumstances. If I recall correctly, it has something to do with the aerial roots.

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The second link I posted above seem to indicate that there is an increase in nitrogen in the soil after using buckwheat as a cover crop, I guess this is probably all I need to know, but I am curious as to why there is a significant nitrogen increase.

There seem to be three possibilities with buckwheat, perhaps a mix of all three is occurring.

  1. Deep roots can gather resources from lower in the soil and move it into its leaves and stems that mulch down later.
  2. Chemically changing the form of resources already present in the soil. I believe this is what buckwheat does with phosphorus.
  3. Sequestering nitrogen from the atmosphere through bacterial action.

The first link indicates that there may well be bacterial nitrogen fixation occurring. Given the economic significance of buckwheat I find it odd that this phenomenon would not have been studied much.

Sorry to drone on about this, but I find it fascinating.

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everything being said here makes sense, my ditch is nothing but regular road gravel yet the buck wheat grows to nearly 4ft. before laying down. no fertilizer. no watering and all the other plants around it are growing well also so somethings good about it that’s for sure.

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I considered buckwheat for a cover crop this year, but decided on peas and oats as I’ve heard the buckwheat can get aggressive- but now I’m wishing I’d done buckwheat!

The field I was going to do has very compacted soil and I think the deep taproot would have been better.

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