Sheet mulching with compost only

Hi, I am new in planting. And I want to restart a weed covered side yard.
I have been reading about sheet mulching and the idea sounds fantastic. Only question is, the area I want to cover is about 700 square feet, instead of doing lasagna and gather all different materials, can I just use a thick layer of straight compost from soil supply company to put on top of cardboard and wait a season?  

You could! I've made quite a few beds by putting down paper sacks and covering them with bedding from my duck house and/or woodchips. A few things grow through the papersacks (they probably wouldn't as much with cardboard, especially if you overlap it well). It might be good--depending on how much rain you get at any given time, to cover the compost with some sort of mulch (grass clippings that don't have seeds, leaves, woodchips, etc) just so the compost doesn't wash away or have it's nutrients wash away. Compost is rather expensive, and not always of the highest quality, so I think people like to do lazagna gardening as a way to smother the grass with things that might be free for them. But, if you have the money and access to good compost, this should work well. You might want to make your first planting in the bed something that will shade the bed, like squash or potatoes or sweet potatoes so that the weeds have even less of a chance.

I've found that potatoes seem to do a pretty good job of shading out whatever plants try to grow through/sprout in beds like this, and so my go-to method for making a new bed is: (1) Lay down a barrier of paper sacks/paper feed sacks, (2) cover with mulch/duck bedding, (3) Plant potatoes and "hill up" the potatoes with some additional mulch as I find it, to help suppress any weeds that may squeeze through the layer of paper.

As Nicole mentioned, not all compost is good compost. I would give that soil supply company a quiz about; how the compost is made, what materials go into the compost, where do those materials come from, are there any known pesticides or herbicides used on those materials.
These days it is imperative you know the answers to those questions or you might spend money to stunt or kill the plants you want to grow.

Mulch that is a minimum of 4 inches thick when laid down will suppress most first succession plants (weeds), a barrier layer such as cardboard or paper sacks under that mulch layer increases the effectiveness of the mulch.
When using such barrier materials be sure to soak them with water just before spreading the mulch so that the barrier layer will let water pass through it instead of sheading it off to the sides.

Once you have such a mulch system installed, you don't have to wait to plant (unless you want to do that) you can poke holes through the barrier and plant into the soil below, this works best with transplanting rather than direct seeding.

Redhawk

Buying that much compost would be expensive.  And because finished compost has already broken down to a point of a fine structure, it's not the best for a heavy mulch application like you are taking about.  Half-finished compost with chunks of stuff still in it would actually be better.  Any finished compost laying on the soil surface will lose much of its nutritional benefit within a couple of weeks if it isn't protected by a layer of carbon on top, or at least shaded by plants.

If you're mainly concerned with creating a healthy mulch layer, a much cheeper option would be straw, spoiled hay, wood chips or some other less "refined" biomass.  

The "Back to Eden" method of sheet mulching is to put down a layer of cardboard or newspaper, followed by a 2 inch layer of compost, and then covered with a thick layer of wood chips.  This does a couple of things.

1.  The compost is filled with microbes and is generally higher in nitrogen, so putting it on top of the cardboard helps to quickly break-down the cardboard and grass/weeds below the cardboard.

2.  The heavy carbon "blanket" on top of the compost (straw, wood chips, whatever) keeps the sun from irradiating all the microbial life in the compost and killing it.  Basically, if you've spent good money to buy all those wonderful microbes, you'll want to spend a bit more to make sure you keep them alive and working for you.

3.  The wood chips (or straw or hay) act as a nitrogen sink.  Compost will continue to decompose and gas off.  You don't want all that lovely nitrogen to just gas off up into the atmosphere where it originally came from.  You want to keep it in your garden soil profile.  The heavy carbon blanket takes the brunt of the sun and wind, but leaves your expensive compost active and (relatively) stable underneath.  

4.  A layer of compost sitting on the surface will quickly dry out, making it an unwelcome place for worms.  If you bury it under a nice layer of chips/straw/hay, it remains moist and thus becomes a magnet for earthworms and other soil biota.

5.  Wood chips last a long time as a mulch.  A 6 inch layer should last you for a full growing season before breaking down.  A layer of compost will be gone within months.


Save yourself a few bucks and buy just enough compost to cover your cardboard to a depth of 2 inches or so, and then put something cheap and more durable on top.  

I love this website!  I learned a lot from everyone.  Thanks
I will certainly check out what the compost is made of, the company seems knows what they are doing, and $20/yd is within reach.
We are getting couple days of rain before the dry summer season so will be perfect time to soak the cardboard.
When doing general planting, I have heard some people prefer to mulch with compost product (mostly broken down compost blend)  instead of bark/wood chip, saying it will still suppress weed and supple more nutrient vs. bark mulch will take nutrient from soil as least at beginning.  I have always wonder what's the real deal of the chip/bark mulch, it's a good point that at least for doing sheet mulching, I should still have wood chip on top to keep the nutrient underneath especially through the summer.

Hi Tian,
You might want to check Charles Dowding"s works. He has a very informative book and a great youtube channel. He used to be around here, answering questions making comments (permies). He lives in a wet climate and slugs are major problem so he uses finished compost for his beds. He is a no-till advocator.
Hope it helps

My go to method of sheet mulching is to always mow or chop down the area in question, and then water it extensively before adding the cover (in my case cardboard).  This watering activates the worms, enhances breakdown of the sod/weeds, and allows the area to get water since the cardboard will be a barrier to that for a while.  Like Nicole, I go for potatoes first.  I cut a hole in the cardboard and chop a bit of the sod up and put a sprouting potato in, cover with a bit of soil, move a foot or so and do it again.  If the cardboard is overlapped well, the only place I need to weed is the small potato holes and this is done with a pair of scissors in a short time.  At any rate, as far as compost only goes, that can be a bit nutrient rich for some plants, and the others gave good advice.  You should have no problem with potatoes in compost, particularly if the compost was made from woody waste as that tends to be acidic and fungal.  Potatoes are a great plant for establishing a new area/soil system.  

Thanks s. ayalp, noted, I am right at the wet and sluggy land!
Thanks Roberto.  We got more rain as expected this couple days which is awesome. Get to soak the soil one day and lay the cardboard to get soaked the next day!  The ground isn't flat, so it's kinda bumpy and imagine there'll be air pockets underneath.  Hope it will be ok with the soil down...   I am planning to plant some small bushes and seed perennials in the fall, so I suppose the compost should be milder by then.

Susan Hutson wrote:Morning Tian,

The information that Bryant supplied about compost is not to be taken lightly and as Marco pointed out it will be expensive.

My question would have to be if this compost is purchased turns out to be NBG or even as a precaution would it be an option to spray it with a GOOD compost tea.

Kind regards
Susan

That is a great question.  You would want to use a compost tea and perhaps one of the Steiner preparations (check my thread on those and how to create good preparations with out so much hassle).
It is sad that with so much chemical use in vogue over the years, commercial products like compost almost are certain to have something in them we don't want to put into our soil.
Mushroom slurries and good compost teas are our main ways to remediate the possible problems we could encounter from having to purchase those amendments.

Redhawk