I’m not even sure how I came upon this research, but it was a few years back, and I mention it to people all the time, experienced gardeners even, and so far best I get a blank stare. Because I don’t really know what I’m doing, but I do know I’ve read a number of these papers and they sound legit.
So I’m hoping to write this down once so I don’t have to explain it again and again only to see people blink. So if anyone knows anything, hit me up.
So here’s the idea…
The idea is that legume plants (partnering with rhizobia bacteria) , alders (partnering with Frankia alni bacteria) and some other shrubs fix nitrogen via their symbiotic relationship with their respective root bacteria.
It was relatively recently that it was found that various other species can do something similar with different bacteria in, not just roots, but branches, stems, and leaves. And that this was discovered (I’ve traced it to xxx) by xxx growing like weeds in literal gravel pits in British Columbia with no obvious nitrogen inputs.
Papers I’ve read in full, highlighted and filed.
Research Paper #1
- In the above paper they were able to isolate said bacteria(s) culture it, and inoculate other seedlings, resulting in substantially enhanced biomass of 100-311%.
- They noted that strains AN1r, AR1r, and SN1r fixed the most nitrogen. They went into some detail of the inoculation process as well.
- They also gave brief overviews of the culture and inoculation process, which I’ll need to give another look.
- I gave this paper a 10/10.
Research Paper #2
Evidence for Nitrogen-Fixation in the Salicaceae [willow] Family. 2011
- I would say the 2nd most common tree when I look outside my door, even on the gravel is willow, of various varieties. Like cottonwoods they grow out of bare gravel, no problem.
- I know that YouTube is full of videos on how to make rooting hormone from willow, AND Ed Biersky, who lectured authoritatively in my our Alaska Master Gardener’s course, said it worked. So I’m wondering if the willow rooting hormone brew can be turned up a notch in some way but culturing the willows, gravel pit cottonwoods, endophytic diazotrophs. And if those diazotrophs work on rice, soy and corn, if we, or at least I, shouldn’t douse everything I plant with it.
Research Paper #3
Variable Nitrogen Fixation in Wild Populus. 2019.
- “Here we report the first direct evidence of N2 fixation in the early successional wild tree, Populus trichocarpa, [our cottonwoods] a non-leguminous tree, from its native riparian habitat.”
- Research was funded by the USDA
- I gave it a 9/10.
Research Paper #4
Suppressed N fixation and diazotrophs after four decades of fertilization. 2019
- “It was found that N fixation was drastically reduced (dropped by 50%) after almost four decades of fertilization.”
- Strikes me as important. And makes me think the Badgersett Hybrid Hazelnuts, which in their book they go on and on about how they were heavy feeders, might be cold hardy, not ideally bred to survive the future. No wonder mine are so spindly. However, maybe they can be inoculated.
- 10/10 paper!
Research Paper #5
Nitrogen Fixation in Salix and Populus (willows and poplars). 2020ish??
- This one is more of a blog, but they say they do research. Maybe informally like me.
- Regardless, the paper seems good and is well cited. Giving a bit more history of the discovery of endophytic diazaotrophs in cottonwoods and willow going back to the 1980s, but saying nobody did anything with it at the time.
- Worth a read, I gave it 8/10.
Research Paper #6
Use of beneficial bacterial endophytes: A practical strategy to achieve sustainable agriculture. 2022
- Good review, some refs to check, no specifics.
- 8/10
Research Paper #7
- This one was more of an overview. Confirms the general story story but offers little actionable information.
- Ends by calling for genetic modification of the microbes to create a commercial products, which is fine I guess, I’m not looking to wait, years, for others to work this out. I want something sustainable, something local, and something now, should the grid go down before they work out their neoliberalism.
- 6/10
Research Paper #8
Dynamic nitrogen fixation in an aerobic endophyte of Populus. 2024.
The populus in question are populus trichocarpa, otherwise known as black cottonwoods. If I look out any door or window of my abode, I see black cottonwoods like crazy, growing straight out of gravel.
The bacteria this paper speaks most of is Burkhoderia, and they note that it was known to increase rice grain yields up to 29%, increasing pproteincontent in the process.
I gave this paper a 7/10.
Research Paper #9
Plant-microbe networks in soil are weakened by century-long use of inorganic fertilizers. 2019.
- Did not mention endophytic diazotrophs but noted that century long fertilization in the UK decreased richness and diversity of both plants and microbes, resulting in them being less hardy and more reliant on continued artificial fertilization.
I’m very into this idea…
…as I’m all about permaculture, forest gardens, hybrid hazelnuts. And I just so happen to live on 157 acres, about 17 of which is an ex-gravel pit, teeming with willows and cottonwoods, growing like weeds, straight from gravel, with no soil in sight. So I’m sure I’m sitting on the raw material to culture my own diazotrophs assuming it’s not too tech-intensive. FYI, I did graduate summa cum laude from NAU, and while chemistry was not my major I was freshman chemistry student of the year, so I can follow a recipe, despite my becoming a physical therapist instead.
Given we are at, or just past peak oil, and certainly peak net energy, and that peak (then decline) of natural gas is likely to soon follow. And that industrial nitrogen fertilizer is literally made from natural gas, it seems a really good idea to be able to learn to grow food, with little or no external inputs.
Relevant papers for which I have only read the abstracts:
#1 N2-fixation and seedling growth promotion of lodgepole pine by endophytic Paenibacillus polymyxa. 2013.
- I havent read more than the summary, but this one from 2013 seems pretty OG for the lodgepole pine group and th abstract says a lot:
- “Abstract: We inoculated lodgepole pine (Pinus contorta var. latifolia (Dougl.) Engelm.) with Paenibacillus polymyxa P2b-2R, a diazotrophic bacterium previously isolated from internal stem tissue of a naturally regenerating pine seedling to evaluate biological nitrogen fixation and seedling growth promotion by this microorganism. Seedlings generated from pine seed inoculated with strain P2b-2R were grown for up to 13 months in a N-limited soil mix containing 0.7 mM available N labeled as Ca((15)NO3)2 to facilitate detection of N2-fixation. Strain P2b-2R developed a persistent endophytic population comprising 10(2)-10(6) cfu g(-1) plant tissue inside pine roots, stems, and needles during the experiment. At the end of the growth period, P2b-2R had reduced seedling mortality by 14 % and (15)N foliar N abundance 79 % and doubled foliar N concentration and seedling biomass compared to controls. Our results suggest that N2-fixation by P. polymyxa enhanced growth of pine seedlings and support the hypothesis that plant-associated diazotrophs capable of endophytic colonization can satisfy a significant proportion of the N required by tree seedlings growing under N-limited conditions.“
#2 Accessing inoculation methods of maize and wheat with Azospirillum brasilense. 2016.
- Noted that inoculation decreased corn nitrogen fertilization by 25%, and that foliar spraying after seedlings emerged and spraying the furrow at the time of sowing was as effective as inoculating the seed.
- Said balancing dose was important to prevent inhibition, but I have yet to read the details.
#3 Transmission of Bacterial Endophytes. 2017
- Review on how them things get there in the first place.
- “Colonization of roots from soil is the best studied transmission route, and probably the most important, although more studies of transmission to aerial parts and stomatal colonization are needed, as are studies that conclusively confirm vertical transfer. While vertical transfer of bacterial endophytes likely occurs, obligate and strictly vertically transferred symbioses with bacteria are probably unusual in plants. Instead, plants appear to benefit from the ability to respond to a changing environment by acquiring its endophytic microbiome anew with each generation, and over the lifetime of individuals.”
- Another from the logepole pine/gravel pit group. What’s interesting about this one is they used the endophytic diazotrophs from the lodgepoles to inoculate a foreign hybrid white spruce with similar results. Which suggests to me that my idea of using the diazotrophs to inoculate Korean pines has a good chance of working.
#5 Biological nitrogen fixation in logging residue piles of different tree species after final felling. 2022.
- Same authors as the 2019 gravel pit pine study.
- “Results: Although soil N-content at the gravel pit was drastically lower than the forest site, pine tissue N-levels at both sites were identical.”
- For the record, I’m not very interested in logepole pines. I mean maybe it would be fun to build a few teepees. However, my wondering here is if I can inoculate/recruit similar bacteria to grow Korean Pine Nuts, which are reportedly very cold hardy, but reportedly take 25-30 years of growth to produce meaningful numbers of pine nuts. Would endophytic diazotrophs help speed this along?
#7 An Archaic Approach to a Modern Issue: Endophytic Archaea for Sustainable Agriculture. 2022
- Review paper by the lodgepole pine guys. I should fast-track reading this one.
- Interesting in the above was that the C-to-N ratio was higher in branches than in the leaves, and higher in coniferous than in birch.
#9 Bacterial synergies amplify nitrogenase activity in diverse systems. 2024.
- “The 50% reduction of UF application combined EDB addition obtained the fresh cob with no significant difference, compared to 100% recommended urea application. The interaction between the effectiveness of EDB inoculation and UF reduction was clearly different in favor of corn grown on sandy loam soils with low nutrient contents. Both Bacillus A and Bacillus B had the abilities of high yield and good nitrogen fixation with the potential to simultaneously improve soil fertility and corn yield.”
Books of unknown utility on the topic
- Bacterial Endophytes for Sustainable Agriculture and Environmental Management. 2022
- Microbial Endophytes: Prospects for Sustainable Agriculture. 2019.
- Amazon sample has beginning chapters in full, looks worth a read.
Questions I have:
- Can this be done locally, or do I need a lab and an electron microscope.
- Are the listed diazotrops from the above papers commercially available?
- If so, what is their shelf life?
- If I inoculate a generation of trees, will all their children have similar nitrogen fixing ability?
- Do I even need to do anything, or are the diazotrophs already here, in my gravel, and I just need to plant my seeds in it?
- Would blending up poplar biomass and soaking overnight make a workable foliar spray, or seed dip, etc?
- Would summer coppicing my willow/cottonwoods and using the material as a mulch steadily bring the diazotrophs into my better soil than the gravel pit?
- What all can I just put perennials, even annuals, into inoculated ground, out in the pit, and then propagate inoculated cuttings??
- Will this work on potatoes? Wait, maybe yes:
#9 First report of diazotrophic Brevundimonas spp. as growth enhancer and root colonizer of potato. 2020
- Results showed that Brevundimonas sp. TN37 increased growth parameters and nitrogen uptake as compared to non-inoculated controls. Based on the results obtained in this study, it can be suggested that Brevundimonas spp. (especially TN37) possess the potential to improve potato growth and stimulate nitrogen uptake. This study is the first report of Brevundimonas spp. as an effective PGPR in potato.
- Add this to my list of papers to read.
That’s all I’ve got for now.
- Message me if you have an idea how to make any of this happen.
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