Nitrogen fixers for composting wood chips

I was wondering if growing nitrogen fixing plants in my woodchip compost pile would speed up decomposition. Would the nitrogen fixing action allow for the release of nitrogen into soil . Or do the plants have to be grown and chopped and mixed into the soil? I am unsure of how the nitrogen action works.

it depends on the plant. Things like Comfrey need to be chopped and then either dropped or processed into a tea. Other nitrogen fixers are hosts for proper microbes that allow for the natural nitrogen production. certainly an interesting question, what are you thinking for this? from reading this, the first idea that comes to my mind is planting something like Goumi berries around the woodchip pile.
Yarrow might be a really good option for this too, as yarrow leaves are believed to help kickstart compost ( Composting With Yarrow: Does Yarrow Speed Up Decomposition (


If you pull a nitrogen fixing plant you’ll notice that the roots have nodules. On these nodules there is bacteria that fixes nitrogen from the air into an organic compound. The chopping of the plant adds carbon and other nutrients back into the soil but the nitrogen comes from these nodules.

Will it add nitrogen? Sure. Will it be a significant amount? Maybe? Depending on what your parameter for significant is? Wouldn’t your pile be better in a shaded area where it doesn’t dry as opposed to a sunnier area where the plants would grow better? Is this a pile you manage for quick turn around or a set-it-and-forget-it pile?

Honestly there are better sources of nitrogen. Heck look up urea… One load of that probably outperforms the entire output of a nitrogen fixing plant, and you generate urea every single day. Water down 5:1 ratio and you will not have odor issues.


Thanks for that. Very good info and points concerning sunlight. I get a 12 cubic yds load of wood chips each spring to mulch around trees in yard. Over time starting to use less and less. As I replace old chips I am starting to have a large pile to finish composting and more of the new pile also remaining. I am blessed with very poor dirt(no topsoil) so I use the finish compost to improve overall soil condition. 4 years doing so has improve large swats of planting are but need more work. More chips!!! Wife gave me 5 years before she demands a lawn. Time is almost up.

Thanks for that read. I was just musing over that idea. I cannot use urine even though it does well. My pile is to close to neighbors fence and don’t want the smell as an issue on such a large pile and urine amount required. I was thinking adding nitrogen fixing plants growing in partially decomposed mini piles.

Urine on wood chips is not going to smell.

1 Like

Ok, so you have a ton of carbon and would need a ton of nitrogen to even come close to put a dent on that.

  • Urea, specially at the recommended dilution, will not smell early on and will get decomposed quickly enough. I would pick this provided that your household doesn’t go on strike over it.

  • Horse manure. I just pick half a pick up truck to start building my pile for next year. Call me weird but I actually like the smell of horse manure, it smells like horses. Get a bag and see if your neighbor minds.

  • Push comes to shove, straight nitrogen fertilizer. Find something like 28-0-0 and sprinkle liberally, wet well. Bacteria will go to town on your pile in record time.


Urea (by that I mean the commercial fertilizer) is what I use out of necessity. Hard for me to believe you could get enough from N-fixing plants to do the trick on any reasonable time frame.

If you can get it in reasonable quantities, it would be very hard to beat chicken manure.

As it is, a large pile of wood chips, (my annual pile is about 10-13 heaping wheelbarrows full) requires. not only a large amount of N in the initial 3 mos. or so, but steady additions afterwards, if you want to get it so that it can be incorporated into the soil without sucking up all the N in the plot.

A large pile of wood chips continues to be a steady consumer of N for many months after the first few months.

Disproportionately load most of your N source at the top half of the pile. It takes a few days for the pile to develop absorbency. Before the bacteria starts to chew through the sides of the cellulose cells, the chips shed water like crazy.

Keep the pile moist at all times. This can require some attention if the pile gets hot.

I actually had my finished product tested. Mixed finely sifted product with some other stuff as if I were making potting soil and paid for a soil test.

As you would expect, NPK were great. Product was very acid as you would also expect.

Micros were a mixed bag as you would also expect. I visualized my pile spread out 3” deep on the ground, and added the micros based on the hypothetical square footage. using things like boric acid, copper sulfate iron sulfate and Zinc sulfate.

If you are under the gun for results it’s worth the expense and trouble to get it right.


When expressed as “urea…” It is meant as an euphemism for human urine.

Im not sure if anyone has mentioned it yet but grass clippings are the easiest, cheapest natural and neighbor friendly way to turn wood chips into compost that are in a pile not on bare ground. (other than urine).

For the nitrogen fixing plants- white clover in the aisles is what i do… also pulls in pollinators like crazy. I know that most people cant go without mowing so its hard for them to let it bloom and re-seed.

If your orchard area floor is teeming with biome you wont need to compost your wood chips… they and the worms will dessimate whatever you put around your trees and send it down into the topsoil.

Stephan Sobkowiak has a video on this and i have found it to be true. In a healthy orchard you wont be able to keep up with adding woodchips… nature composts it very quickly. (same with cane fruit rows).


In my dry climate, no. You need to affirmatively add N. (And affirmatively keep the pile moist).

We don’t have extensive lawns around here, but yes, that is a good addition if it can be easily scavenged.

Cowpeas! This won’t work if wood chips are in a pile, but if you can spread them out and toss in a few handfuls of cowpeas, you will get enough nitrogen to compost the wood chips. This may not work in northern states as cowpeas need a lot of heat to grow rapidly. Here in the hot humid southeast, it is an extremely effective way to add nitrogen and produce an edible crop at the same time.

How do I know this works? Neighbor does it every year.

1 Like

FeMo-Cofactor enzyme is the primary nitrogen fixation enzyme of symbiotic microbes.
They don’t need a plants roots.
They need a small amount sugar or starch.
The enzyme contains Iron, Sulfur & Molybdenum.
There is a variation with a Cobalt replacement of an Iron, one with a Vanadium replacement of Molybdenum, and one with both replacements, plus a variation with no Molybdenum just Iron & Sulfur.
Plus one for Mycorrhiza & Yeast which contains Nickel.
Cheap “Mild Steel” which rust quickly Contains a near perfect blend of Iron, Molybdenum, Nickel, Cobalt & Vanadium.
So adding (Steel Wool, Gypsum & sugar) to a compost pile & spraying with water causes growth of nitrogen fixation bacteria, wild yeast & Mycorrhiza.


ive watched all his vids. hes about a 2 hr. drive due west of me. someday ill get out there if Canada isnt in a civil war before.:wink:


This is a very misunderstood term. In peer-reviewed biological science papers it refers to plants that have a symbiotic relationship with some genera of soil fungi or bacteria where the plants and microbes exchange nitrogen compounds for micronutrient salts and chelates .

Important: the plants and microbes use the nitrogen compounds to produce more cells. While alive, they do not transfer it to the soil.

Herein lies the age-old practice of crop rotation. Every 3-4 years 1/4th of the crop fields are planted with alfalfa or another nitrogen-fixer and small numbers of livestock are put to graze there at intervals. In the Fall (or Spring in areas without winter grasses) the “fallow” field is tilled. Presto - the soil is resupplied with nitrogen compounds from the dead cells and other nutrients from the livestock defecation.

Now fast forward to the 20th century where the practice is extended to deeper-rooted perennial row crops; e.g. grapes and cane berries. A low-profile N-fixer suitable for local soil-microbes is sown between the rows in the Spring and tilled during main crop dormancy.

Richard, it is bacteria, not fungi. Fungi are still part of the process but the nitrogen fixing legumes are from bacteria growing in nodules on the roots. This is an example of symbiosis where two very different organisms support each other to mutual benefit. The nitrogen is a toxic waste product to the bacteria. The plant needs nitrogen to grow. The plant has a surplus of carbohydrates from photosynthesis. The bacteria needs carbohydrates to grow.

Decay of wood chips requires nitrogen for the basic cellulose + nitrogen = proteins for fungal growth. Nitrogen fixing bacteria in legume root nodules produce excess nitrogen which enables fungal growth on the wood chips. Some types of bacteria get in on the feast adding their growth and reproduction to the breakdown cycle of the wood chips.

“Legumes (peas, vetches, clovers, beans and others) grow in a symbiotic relationship with soil-dwelling bacteria. The bacteria take gaseous nitrogen from the air in the soil and feed this nitrogen to the legumes; in exchange the plant provides carbohydrates to the bacteria. This is why legume cover crops are said to “fix” or provide a certain amount of nitrogen when they are turned under for the next crop or used for compost.”


Thanks for the heads up. I only recall reading about fungi exchanging mineral ions for N compounds. But on second look … I shared an article here 4 years ago about legumes and bacteria! :slight_smile:

Which nitrogen(s) do the pine wood bacteria utilize?
Wouldn’t it be more efficient to spray the chip pile a few times a year with the nitrogen(s) in water-soluble fertilizer form?

Any form of nitrogen made available will be converted to a form useful to the organisms breaking down cellulose. Bacteria and fungi are very adept at slurping up nutrients. It is certainly easy to spray on some liquid nitrogen or toss a handful of nitrate pellets on the woodpile. But the question asked is what nitrogen fixers to use for composting wood chips. The answer is that any plant that fixes nitrogen will be beneficial, however, some plants are better for the purpose than others. That is why I suggested cowpeas above. They can fix about 70 to 80 pounds of surplus nitrogen per acre. My neighbor loves to have the power line crew dump a load of wood chips on the end of his garden. He spreads it with his tractor and tosses several handfuls of cowpeas on the mix. The cowpeas can be harvested and the wood chips will finish decaying over winter.

To more directly answer your question, urea is highly effective while ammonium nitrate or sulphur nitrate have to be converted to free nitrogen first. It is difficult to find ammonium nitrate in the market currently which means most of us have to use sulphur nitrate and count on adding lime to counter the acidifying effects of sulphur.