Comment by thatcat | Hacker News Reader

Comment by thatcat | Hacker News Reader

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The plant roots like the right texture. If you have clay, adding organic matter releases glomalin [0] and creates aggregates that let the water drain more easily, preventing root rot and allowing them to penetrate deeper.

Each of those - sand, clay, organic matter have a pore size distribution and different pressure that it releases water at. The amount of water and the pressure that it's released at form what's called a soil matric potential graph. The important thing is balancing those so that the soil moisture is mostly held at a pressure that the roots can access . There is a soil texture pyramid that illustrates the different soil textures and mixtures.

[0] https://www.dpi.nsw.gov.au/content/archive/agriculture-today...

[1] https://topsoilpros.com/what-is-a-soil-texture-chart/

The guy in the video is calling mulch compost. Compost is supposed to be made of green material which contains nitrogen and other nutrients not bark and wood chips. There are different sources of organic matter that contain different nutrients, pore distributions, etc.

Thanks for the cool links.

I believe he knows what compost is, he is just being lazy about using it interchangeably with what you find at most garden shops. Most commercial bags of garden soil and compost both contain a lot of broken down wood. He is just suggesting you shouldn't really have any organic matter around your roots, except for at the top level. It's good to promote mycorrhizal fungi but only at the top layer etc

I think he mostly ranting about how commercial gardening places just sell "soil" that is mostly always comes with added "compost" e.g. https://shorturl.at/mvwzG

Where as they should sell more clay/silt/sand mixes and encourage top dressing instead.

Most people just fill their pots to the top with those bags and it leads to adverse effects.

Yea, you're welcome. I'm watching it rn, he def knows what he's talking about. I just disagree about the deep organic matter being beneficial, obviously don't use rotting compost as your source in a non porous soil though.

I started a company that fractures soil and injects organic matter deep, filling fractures to create drainage and sequester carbon, we use biochar - it has a sandy texture and doesn't break down very quickly because it's been pyrolyzed (anaerobic combustion that produces a charcoal/activated carbon like material that looks like black sand). Integrated pyrolyzed organic matter is how slash/burn ag works in the rainforest and is why Brazil has some soils that are black.

https://en.wikipedia.org/wiki/Terra_preta

Oh that's such a cool company. I only recently got put onto Terra preta through my personal favorite gardener -> https://www.youtube.com/watch?v=DnTaWiO5Eso (he's funny lol)

I'm going to try make my own ad hoc terra preta plots for fun too. Are you able to share any more information on your company? Who is actually buying this service?

I feel like biochar is going to hit the main stream this year or next.

Going to make a compost tea and soak my bio char in it too.

> anaerobic combustion that produces a charcoal/activated carbon

I wonder if this is the trick though, not that there is organic matter down there, but that is already broken down and fully activated the charcoal.

It would also be great to know if the beneficial fungal processes happen at those depths. So many questions aha

That's awesome! The tea thing is a good idea. No one is buying it yet, but the plan is to have some micro rain gardens installed this spring using the tech to reduce the overall area required due to the increased drainage depth and moisture storage. It's essentially an erosion control measure until there is a carbon market and we increase automation. We will also be doing some testing with trees - remediating poor drainage with living trees that have been already been planted.

Some of the organic material breaks down really slowly, providing some nutrients to bacteria at a rate that allows the gas to escape, but yea essentially the trick is the ultra high surface area and high compressive strength so that it maintains a porous structure instead of compacting into an anaerobic environment.

Yes, beneficial fungi reach much deeper than roots due to the higher penetrative ability of hyphae and they can still extract stuff from whatever depth they reach.

Long term I want to be able to do what the guy in the video is doing but with out all that shoveling...

Never heard of micro rain gardens, googled them, also a good idea for some places in my garden.

And yeah seems like an awful lot of work aha

I'd imagine just getting a bull dozer or something, digging a whole lot of deep rows.

Then putting a sign in my neighbour for everyone to just come dump everything in the ditches, throw some wood on, light it up and repeat several times.

I saw that they are attempting synthetic stuff too which I might research later.

Some useful tips in this Reddit thread -> https://www.reddit.com/r/Permaculture/comments/1558h7/terra_...

Bamboo sounds like something worth investigating.

If you don’t mind me asking, what is/was your educational/career route that led you to the knowledge that you currently have? It seems interestingly diverse, like you have biology, agriculture, but also some mechanical?

I got a degree in biosystems engineering (it covers electrical mechanical and chemical eng broadly from a systems perspective focused on bio production) and worked on research farms (organic academic and private viticulture). Then did some academic soil formulations research in greenhouse / nursery setting. Currently I'm employed part time on upwork doing chemical formulations reverse engineering for green products.

Fascinating, thank you - I have some more questions if you don't mind! Was that your first degree or did you switch to this domain from something else? Would you care to name/recommend your degree program, and any key texts, for someone interested in following in your footsteps?

I got a visual comm degree, worked in video production for awhile, but decided to change fields. It kinda took a lot of time and set me back, but I prefer this kind of work. UC Davis has a good ag program, I think Purdue is highest ranked, Arkansas and NC state are good too. I went to UTK, it was not bad. The course work was just generic engineering stuff until junior level - then you get some really interesting bioprocess industry stuff and Sr level is focused completely a series of design projects. Learned the most there really, because it's about being able to quickly do research and apply it to a design that has to be presented for critiqued review. It's pretty fun for me to get presented with a new little niche problem and go down the rabbit hole trying to figure it out - after you do that a bunch of times you build up a pretty diverse knowledge base and it makes things quicker.

If you tell me which subject you're trying to learn more about I could recommend something. There's not really any text that covers that field broadly, you might start with a soil science book - I'd recommend Soil Science Simplified as intro or The Nature and Properties of Soils for a complete in depth text. Those won't tell you anything about nursery soils though, only field soil.

I added my email to my profile, feel free to hmu.

Much appreciated, thank you for sharing!

I don't have a specific interest at the moment, but have been more curious about this area recently after getting into regen ag podcasts.

David has a guest video by a lady working above hardpan clay:

https://www.youtube.com/watch?v=goUfl4x8URc

Essentially all of the permaculture advice for breaking up clay appears to be failing on her hardpan, so she's started using broadforking, which is a sort of compromise between tilling and building soil from the top down. The speaker in this video is being a little more aggressive with the broadfork than most people suggest. The idea is to open the subsoil without blending the upper layers together, resulting in the organic matter-consuming bacterial bloom you get with tilling.

One variant of keylining accomplishes a similar trick on an even smaller scale: you put one long slice into the ground. Water and organic matter seep into that cut and fan out from there.

There are also "subsoilers" that you can pull behind a tractor that kind of lifts up the soil 36" deep and then drops it creating breaks.

Is it beneficial in anyway to use wood that burned in wildfires (very hot fires that burned most trees and shrubs down through the roots, but also left a lot of nearly fully burned trees and shrubs above ground) as part of the mix or is only pyrolyzed material useful?

That left over bit is technically also pyrolyzed material because very hot fires create anaerobic conditions. Integrating it into the soil seems like a good idea.

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