Does mulch create too much soil eventually?

As mulch breaks down you then add more mulch, year after year. Doesn't this soil level get very high eventually?

My garden bed is ground level and I'd like to keep it that way because it would be expensive to put boards to keep soil spilling over into my yard.

I have lived here now for 23 years, and there are places that constant mulching built soil up quite a bit, but after a few years of no mulching, it settled back down.

In nature, under normal conditions, it takes 600 years to make 1 inch of top soil, but with mulching a person is basically speeding up the material laid down significantly.

Ultimately the choice is yours. For me, when I first started building this house and landscaping, I mulched a lot and soil was building up like you describe, to overflowing on flat areas to the point of having to contain it. But then my interests waned from landscaping and so with it, less mulching and so the soil settled out as the decomposition continued. Also my flowerbeds changed as my house morphed, so I would not be too concerned if I was you. You might think, "I love this area and I will never change it", bow, but views on things change over time. It may not even be your view that changes. Often times my wife might say, "You know, if we took this out, and did this..."

We had a saying when I worked for the railroad. "Things are not a problem, until they become a problem." Your fine for now I think.

It usually does, but also depends on how much production you are getting from it.
If you add mulch over clay soil, soil level gets higher each year. Not mainly because of the mulch though, even though it does bring material in. What makes the difference is that air gets in and soil gets fluffed up. Mulch will be consumed by worms and etc, meanwhile they will create tunnels and those will create voids. So, say, initially your soil is compacted and has 5-10% voids (shared between water and air) (rest is say minerals), gradually your soil will de compact and in ideal case might reach up to 45-50% voids (water and air) and 50-55% solids (minerals (40-45%) and organic material (5-10%)). Since amount of minerals are the same, the total volume increases. Almost doubles actually. Final organic materiel is only 5% of that final volume. So mulch itself increases the volume (5-10%), but it is decompaction that makes the main difference, assuming you will try to keep mulch thickness the same. (Percentages might be wrong, I wrote what I remembered. Correct me if they are wrong. But you get the idea :) )
I don't have an experience about how it works in sandy soil.
If you are using bio intensive techniques, production is so intense that it kinda "consumes" soil. You will need to add a lot of material to keep the soil level.
Raised garden beds are known for settlements. You will actively work to keep the soil level the same. Only in my carrot beds soil level doesn't change a lot. I suspect it is because of high sand percentage.

Luckily then that I dug out a lot of the heavy clay soil beforehand, and what's left is fluffed up already and a bit below ground level. When I initially dug up the soil the volume more than tripled, it had been so compacted!

If it ever beomes an issue, just redistribute some of that nice soil olas a top dressing on your lawn. Grass likes nice soil as much as any other plant.

I have a friend who doesn't mulch per se, but he keeps chickens and he puts the spent bedding on his garden which takes up his entire back yard. The back yard has indeed raised by about 4 inches, and he was facing having to remove some soil because of the drainage issues this was having on his house.

But that isn't really why I posted this. I've been thinking a lot recently about annual vege gardens. We know all natural systems have this long cycle of maturity. And yet even permies tend to fight against nature in an attempt to keep a garden from maturing past the herbaceous plant stage. I'm wondering if we should instead acknowledge the signs of maturity and transition the spaces into a more mature system instead.

So when you have too much soil, then it's probably time to transition to a perennial food system and find somewhere else to grow tomatoes. Same deal with shade.

This year I've given up on one of my garden beds due to the shade thing. Trees around the property have grown up and it's inhibiting veges growing in this bed. But it's fine for perennials and so I'm planting berry bushes in the bed. The garden bed has come of age so to speak.

My friend also stopped gardening because of a creeping charlie infestation. I'm wondering if it's nature's way of saying to him that his backyard is ready to be a forest.

My father has always used raised mounds, not beds, no boards or anything to keep things in place. So if your only objection to increased height is needing boards, don't worry, it isn't necessary.  I do find raised beds make things easier to contain in small areas, like my 1/10 acre suburban lot, but he's in the same situation, small lot, and manages just fine.

Tim Kivi wrote:Luckily then that I dug out a lot of the heavy clay soil beforehand, and what's left is fluffed up already and a bit below ground level. When I initially dug up the soil the volume more than tripled, it had been so compacted!

All soil and rock does this, which is known as "bucket swell." Every type of material "fluffs up" or "swells" at different rates, so calculating this means knowing what is to be dug up.

This is well known in the mining and earth moving business. For instance I have a gravel pit that is 8 acres in area, and has an average depth of 32 feet. That is 407,000 cubic yards. BUT because gravel has a 25% bucket swell percentage, I will actually have 500,000 cubic yards of gravel to sell. That is an additional 100,000 cubic yards, but at $2 a cubic yard, this phenomenon really adds up.

For earthwork contractors, that must be accounted for because it costs a lot of money to move that much more material...and having to know where to move it too. Granite for instance has almost 95% bucket swell so it really must be accounted for.

In Permicultural Applications, this must be calculated in for digging ponds if a person wants to calculate in how long they should rent a particular machine for. Taking how many cubic yards of material the pond will remove from the earth INCLUDING bucket swell, basing it on average cycle times of the machine, and the machines capacity; a time frame can be calculated. So can fuel consumption and other averages for the machine. For instance a 34,000 pound excavator can move 3/4 of a cubic yard per bucketful, and move it from point A to point b in an average of 30 seconds. So in an hour it can move 90 cubic yards, or 900 cubic yards per day. So a 1/4 acre pond, 10 feet deep should take about 2 days of machine rental of a 32,000 pound excavator, figuring in a little time for final shaping.

Nick Kitchener wrote:So when you have too much soil, then it's probably time to transition to a perennial food system and find somewhere else to grow tomatoes. Same deal with shade. ... I'm wondering if it's nature's way of saying to him that his backyard is ready to be a forest.

Haha I don't know why I failed to see that! Of course, isn't permaculture meant to be about working WITH nature and not against it?

Unfortunately I have a small yard in suburbia so I'll never be able to just move on to another patch of ground to start over.

So just mound the soil up in the centre of the bed. Make an undefined mounded bed. Grow up the slope to the peak and down the back. If you need structure to the pile, maybe collect some deadfall if there's any available, use an edging tool or a trenching tool to define the perimeter of your bed, drop in the deadfall, and mulch overtop.

If you don't use other methods, just make sure you're shaping the perimeter of your bed to increase infiltration of water and to trap your soil as it seeks to run away with the water. Controlling your hydrology, even in a case as small as a garden bed, can obviate both the need for expensive infrastructure to hold your soil, and the eventuality of a waterlogged, neighbour-visiting garden bed.

-CK