Could I use nothing but mulch for a giant earthberm?

My property starts from the rd at only 30ft wide for a driveway and thenopens up to 200 ft wide behind the neighbor in front of me. Id like to make a 15ft to 20ft tall berm to block the site and sound of my neighbor and rd. Problem is, its within 200ft of a creek which means id have to pull a permit and submit an erosion control plan and get a civil engineer involved if i were to do this with dirt. I may or may not be doing other thimgs on site that the department of making you sad may or may not frown on, and so for this reason as well as my repugnancy towards the state, id rather find another way... also i cant get free dirt and that would cost me a fortune. However, i can get all the free mulch i wanted delivered by the dumptruck load for free bc theres a lot of tree services in the area looking for places to dump.  My thought is to just pile the mulch up into a berm, as it decays ill add to it, and when it seems like its tall enough that after its full decomposition itll be sbout 15 ft, then ill plant it with trees adding topsoil to each of the tree holes. With it being as tall as i want it to be, id expect it would be upwards of 60ft wide. Ill have to be able to drive my tractor along its ridge as in order to continue adding mulch while it decays. With mulch so deep, will it ever become firm enough to drive a tractor on top? Also what are your other thoughts on the idea, does it sound feasible or unrealistic?

Ground here is nearly flat so i wont have to worry about it washing away.

My own concern would be in planting trees that could become large into the berm.  I believe that large root systems should be grounded into real dirt and rocks to anchor them.  One does not want a wind storm to knock over their trees especially if they become large.

My other concern is that I would want the roots to reach into the natural dirt to get out the nutrients and minerals.

That being said, most trees will grow in berms made out of decaying wood chips, but like you said you will need to top dress every year as the wood chips compost and shrink exposing the roots.  Evenually, you might get tired of all this extra work,

There might be another concern about the trees growing too much leaves from the nutrient rich composted and less fruit.

That being said, under the circumstances of not being able to bring in dirt and only wood chips, I definitely would profit from these berms as lots of edible plants and scrubs will grow in the compost.  I would just avoid growing trees that can grow large.

One always have to work with what resources and limitations they have, which is what you are aiming to do.  Thinking outside the box....

Keep us posted with lots of photos as you progress on your project so we can all learn with you.

Hi Nick.

I would be concerned with the effect of weathering, even on a flat piece of land. I would suggest digging a trench to start, and reserve the topsoil and mineral soil that results for periodic layering as you put down the mulch. I would seed this all with as many local pioneer species as you can get your hands on. Pioneers should be able to establish themselves in the minimal soil provided, which will secure the surface of your pile of mulch. You can chop and drop these before they go to seed, but I would let them get established to the point where they are self-seeding. Never pull them out by the root systems, as they are what's turning your freeform pile of mulch into a berm capable of growing things.

I would also suggest that you think about innoculating the whole thing with mushroom spore of whatever edible varieties are local to you. One of their prime functions is to break down woody matter, and to create nutrient, mineral, and water transportation pathways in the soil, or in your mulch pile. And you might get yummy mushrooms.

Also, if you can plant and harvest green manures for the layering from around the grow site or on it before you dig and fill, you'll be able to mix up the consistency of the pile. It will compost if you get the proportions right. You can also treat it with compost teas or just pee on it regularly, and it will break down more readily to a form that will grow plants without assistance.

Before even thinking of trees, I would think about natural meadow succession patterns to develop your berm. Go from small to large. Think about strategically placed hosts for nitrogen-fixing bacteria around your berm site, preferably perennial and mulch-dropping ones like black locust. If you placed two rows of nitrogen-fixing bacteria hosts, probably low-growing shrubs, on either side of the ridge that you want to be able to drive on with your tractor, it will definitely help keep things in place as you compact it.

On the tractor note, however, I wouldn't do it that way. I would start with a trench. Any larger woody matter that you can get your hands on would be very beneficial. If you take the mushroom spore route, which I encourage, innoculate everything. You can make not only a structural pile of larger woody material on the bottom, but shape it to better hold what you put on top of it. You could incorporate large limbs and logs on the perimeter of the trench to trap bits that roll of while you're building, or in subsequent weather events. I like to use these as actual berm walls, almost like a loose log cabin structure, on my berms. They keep the bottoms more vertical and contained, allowing the berm to grow taller while maintaining a more svelte footprint. If you start that way and then layer with mulch, fresh chopped green manure, any real manure you can find in any quantity, and the top and mineral soil from your trench excavation, it will hold more water and establish itself as more than just a woody sound barrier, and you will be able to plant food crops for yourself on it that much sooner.

Having said that, if you just dump a 20' tall, 60' wide berm of mulch, it will eventually break down. I would be concerned with it blowing away, but as soon as it starts maintaining a moisture equilibrium, it will start hosting living things. The reason I suggested innoculation with culinary mushroom spore is that some kind of fungus will eventually take up residence and help breaking down your pile of mulch. I just think it would be better to be able to eat their fruit, especially if you're just going to dump the mulch and forget about it. It will also start accumulating the trace sediments and dusts that are carried on the wind and making its own soil. It will just take longer, and you will have less control over the outcome.

In any case, let us know how it goes. Good luck.

-CK

As the others have mentioned, trees on a berm (even if it were made of dirt or soil) will eventually topple over.
The accepted norm is to have trees, shrubs and bushes start at the junction of berm to soil not on the berm itself because of the issues berm settling creates for trees, shrubs and bushes.
I would consider planting trees on the flat ground behind the berm, and perhaps cover crops all over the berm for the first year to get lots of roots into the mulch berm to stabilize it.
From that point you can use the berm to plant vegetables and cover crops every year without having to worry a lot about the effects of settling.
If you wanted bushes such as blue berries, those could go next to the berm foot and out from those would be where the trees went in.

Think of this as if it were a hugel mound and you should be fine.

Redhawk

Ditto to what others have said above: trees would not be a long-term solution if your berm is made of wood chips.  One good wind storm and they'll go tumbling over.  However, you might wish to plant a few trees with aggressive root systems as sacrificial trees that will get cut-down in a couple of years.

In our area, we have a lot of palm trees, the most common being the California fan palm.  Queen palms, Date palms, King palms, Pindo palms . . .  there are a dozen common palm trees here.  They all have root-systems that are comprised of hundreds of small fiber-like roots.  Palms are built to grab onto sandy soil and anchor themselves therein.  So they are very effective for erosion control --- all those pencil-thin roots going in every direction, interweaving and interlocking.  When I see a common fan palm growing volunteer on my steep hillside, I let it go for a couple of years.  I like the fact that the root system will hold the soil in place as well as add all that additional bio-mass to the soil.  I'll cut it off and kill it after it gets 4 or 5 feet tall.

So perhaps you could create some pockets of soil on top of your mulch berm.  Nothing more than a five-gallon pail of soil would be needed.  Then plant some "weed trees" or easily grown palms in those soil pockets.  Once the trees are a few feet tall, cut them back.  The right kinds of trees can be coppiced and re-cut annually.  Their root systems will go a long way to keeping your berm stable.  If there are multiple trees throughout the pile, their roots will eventually intertwine and lock things together.

Not much will grow in those wood chips for the first two years but if you get an active fungal colony chewing through all that fiber, it'll reduce those chips to beautiful black soil by the third year and you'll be amazed with how good it is to grow stuff in.

Thanks everybody! Solid points all around. Two ideas, a) what about planting the whole berm with some kind of large bamboo? That way ill get blocking higher up and ill get a building material out of it. I would of course but some kind of root barrier on either side to keep the bamboo contained. Or, b) what about planting super densely loads of trees that recover well from coppicing, and letting goats rotate through once in a while? Thatll keep the trees small enough from toppling and ill get a dairy yield out of it. My main concern here would be the goats causing erosion by running all over it. Your thoughts?

I like your idea of coppiced trees, but I think instead of rotating goats through you could develop your berm as a sort of tree hay goat food bed. I do think though that you should consider seriously the recommendation to see your berm through a proper succession. You can build it tall fast and then just pioneer crop it for years and get all the benefit, and then once it has settled into a legitimate piece of topography start thinking about larger woody goat fodder, and then longer term have an epic place to plant more permanent trees.

Nick,

Where do you live?  Climate and geography would be helpful to the discussion.  What zone do you live in?

Bamboo is a grass and it will spread like grass over the years.  There are running bamboos that get pretty invasive very quickly --- you don't want that.  Clumping bamboo will still spread, albeit much slower.  But like any grass, bamboo can be a bit of a nitrogen pig.  I doubt it would grow well right on top of the pile, but if you were to plant it around the edges, it might serve as a living fence to keep the chips in place.  Once the chips begin to break down, you'll need to continue to replenish them so you'd need access to the pile --- you couldn't completely surround it with a living fence of bamboo, but growing in on the back side of your pile might be a nice way to keep things tidy (with the added benefit of having the bamboo for garden projects and such).  It would be a privacy screen as well.  As the chips begin to break down, I have no doubt that bamboo would colonize it and you'd find new bamboo culms shooting up out of the rich black humus of your former chip berm.

I don't know much about goats.  I would imagine that if there is a hill to climb, they would certainly love that.  Do you want to keep goats?  I've heard that they can be a pain in the butt.  However, if you can get them to poop and pee on the top of a chip pile, it will assist in the chips breaking down twice as fast.  Nitrogen is an important part of decomposition.  

Is your climate warm enough to plant moringa?  Once established, it's a tough tree that is fantastic for food for people, and fodder for chickens or any other animal.  Chaya is great as well --- it grows easily, is fairly drought tolerant and makes great fodder.  I like chaya better than spinach.  Moringa is an easy tree to coppice—its a very soft wood that you can easily trim back with a machete.  We eat moringa almost every day -- I threw a handful into my scrambled eggs this morning, and another big handful in the salad I made tonight.  Berry plants might do well if you planted them initially in a pocket of good soil.  Raspberries or thornless blackberries might be a good choice.

I'd love the opportunity to experiment with such a project!  It could be really cool.  Make sure you take lots of pictures and keep careful records.  Those are some of my favorite threads on this site ---- the ones where people try some kind of epic project and then come back and regularly update us on their progress.  The guy who created ponds with his pigs on a site that was nothing but gravel --- that's a cool thread.  I think you should go for it.  Best of luck.

Oh yes this is right outside atl, ga.Zone 7b-80

When i get to work on this project, should i post pictures here on this thread or start a new thread?

There's no reason not to use this thread. You've indicated that whatever you do, your berm will be mostly mulch. That is still consistent with your original question. And I want to see pictures.

So I was thinking about my earlier suggestions. I definitely think that you could beef up the internal structure with some branches and logs, and I would still start with a trench of some kind, just so you have more to work with than just a pile of woody debris that will need to decompose fungally before it can host plant life. The layering of organics and the mixture of top and mineral soils should speed things up markedly.

I know that I advocated the accelerated natural pasture succession path, too, but I think that it is the quickest path for you towards having an earth berm, as opposed to a mulch berm that fills the air with, depending on moisture conditions, the smell of either dry or fungal wood decomposition. Considering the size of the berm in question, probably both. That is largely unavoidable, at least in the short term. But there are things you could do to speed matters.

You could capture and culture your local lactobacillus strains, then innoculate the berm with said microbiota in a dilute solution. This method, or spraying with raw milk solution, introduces healthy microbiota to an environment to, for instance, improve pasture health, boost compost effectiveness and reduce smell, and just generally introduce soil life where there is none present, which can also kill soil pathogens, or outcompete them.

But apart from being in a 7a/8 hardiness zone and being outside Atlanta, we need a few more details, if you wouldn't mind. How deep is your soil, and how hard, in the spot where you wish to locate the berms? How deep is the watertable? What does seasonal flooding look like in your area? Is it an issue, or has it ever been (or is the spot in the floodplain)? Do you want your berm to retain water in dry weather, or do you want it to regulate soggy conditions, or is it perhaps both at different times of the season? These are a few important considerations when dropping a pile of loose debris that you wish to keep in a pile. What is the prevailing wind direction with respect to the future berm, and what is the average windspeed, and the normal maximums you'll see?

I definitely agree with RedHawk that it will behave and is best thought of as a hugelbeet. I have realised in writing this that most of my suggestions have stemmed from a subconscious assumption that this is a hugelbeet, and eventually, especially if you help it along, it will be. My chief concern beyond all else is that you want it to stay in one place, as a berm, which is fine. But the natural tendencies of the macrobiota that will come to eat your pile of woodrotty goodness and the effect of the elements will shorten the height and widen the base without some thought to giving it structure and physical containment, like  perhaps a nest-like ring of larger woody debris encircling that trench I mentioned. Just doing that will give it a footprint, and physically retain the base of the pile. It would even give you something to stake, should the pile start to shift in an undesirable way, for whatever reason. In your position, I would see if there are gnarly knotty bits that the arborists keep out of the mulchers for fear of damage. You could totally use these on the perimeter of the trench.

Also, I would love a description with regards to orientation of this berm and your property. Where is North with regards to the berm? Does it run north-south, or east-west, or something between? Is it out in the open, or is it sheltered in any way? And what food production do you see on this berm? Are you going to grow any annuals on it, or will it be all perennials? Apart from topping it off seasonally with more stuff at need, were you planning on spending any time managing it, or are you designing it to look after itself (is it closer to zone 2, or is it in your zone 4)?

As to accelerating decomposition, if you do nothing else, make sure it stays damp. That will enable the fungi already present in the chips and environment to do their thing. They are your absolute bestest buddies for this project, if you aren't introducing large amounts of culinary spore (then they'll compete, most likely).

I would seriously do the trench and layering with topsoil and mineral soil thing, because that gives you more options for acceleration. If you have goats to feed (I think you mentioned dairy), especially if you can keep that pile moist, you might want to see if you have any local willow by the creek you're within 200' of. Make sure your goats like it, but you could seriously just stick fresh willow wands on the perimeter and up the first third of the berm. The goats could eat it all, as soon as its established, and the roots would stay in place, firming your berm and giving off new shoots for the next browse. I don't know if you could do this all the way up, but if you could, your goats would have no problems climbing to the top. I would add in browser-friendly pasture crops along with a complete pasture mix (all the necessary actors including but not limited to nitrogen-fixing bacteria hosts like clovers and dynamic hyperaccumulators, deep taprooted plants and plants with shallow, netlike root and/or rhizomal structures) and there you have structure reinforcement and accelerated nutrient cycling in one somewhat complex process. I don't know if your goats would eat stuff like sunflowers and hemp, but that kind of stuff would be worth trying. Obviously, the methods could be tweaked to grazer-friendly selections if you were dealing with, say, sheep.

If you have access to chickens, I would also run them over the berm. They will definitely impact the surface population of wood-decomposing macrobiota, but they will also break things down on the surface of the berm. The smaller the particles, the smaller the macrobiota that can consume them. They will also effectively be processing processed woody material (in the form of the macrobiota eating the mulch) into a form that, for instance, Black Soldier Fly Larvae and worms prefer. As soon as things are sufficiently broken down in structure, you will see it colonised by worms. If the mulch is older, you might see worms sooner, but I would expect them later, when non-woody vegetation starts decomposing on the berm.

Sorry for the ramble, but I have been working on and off in a similar situation, but on the backyard scale. I can't build giant mulch berms, nor can I get a truckload dumped, for the smell that it will cause, but I can go grab about four large garbage wheelie bins worth at a time and work with them that way. I don't have goats to work with, but I hope to move beyond the current compost, Effective Microorganism, BSFL and redworm process to one that includes chickens, biochar, and an initial culinary mushroom phase. Acceleration of woody material into soil is important in my particular case, so I'm trying to develop a soil creation regimen, making my kitchen and backyard something of a soil bioreactor. I hope some of my suggestions will be useful for you.

Oh that is a good point I forgot. Do you have any experience or want to experiment with biochar? I mean, you have access to literally tonnes of woody biomass. You would need to work with a gallon-sized biochar retort, and probably a rocketstove made of like 4 sets of cinderblock channels, but that would address issues of soil structure if it made up any part of the berm, and even if you did only one retort-full of biochar on top per truckload of fresh mulch, that would still mean more variety and structure to your berm, and lots of tiny spots for fragile but voracious microbiota to live. You might even be able to, if the water table is high enough and grass fires aren't an issue, do a trench setup where you start a burn in your trench, top it with mulch as soon as there's a coal bed, top with wet cardboard and some of the excavated mineral soil to kill the oxygen and trap the heat, and let it go out. You'd have to excavate carefully, and there might be need for temperature probes (or lengths of rebar thrust into the buried charred mulch and an instant-read thermometre), but you could then gradually add in that biochar in layers, and in greater quantity than you could have managed in a retort.

Good on you, though, if nobody's said it so far, for recognising a "waste stream" that can be a solution for your berm issue.

Good luck, and please post updates, and those pics!

-CK