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We are making numerous raised beds and have been playing around with various combinations of bagged garden soil, compost, etc. to fill them but this method is both expensive and providing less than perfect results. Just read a gardening book that talked about instead using a soil less mix involving three materials: compost, peat moss and vermiculite. I had no problems finding the first two but the vermiculite I can only find in very tiny and expensive bags. When you compare the vermiculite package with the peat moss package, it reads like both products do the same thing. So can I just use the peat moss mixed with the compost/manure to make my soil less mix?

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The mix needs to contain three basic types of ingredients: something to retain water (the peat moss in your recipe), something to provide nutrients (the compost in your recipe), and something to provide drainage (the vermiculite in your recipe).

If you make a mix of just peat and compost, it may not drain well enough.

Here are some ingredients that you could use for each of the three basic types:

Retain Water

  • Peat moss
  • Coir (this will likely be more expensive than the peat)

Nutrients

  • Compost
  • Manure
  • Fertilizer

Drainage

  • Vermiculite
  • Perlite
  • Sharp sand (aka washed sand, winter sand). You don't want to get "sandy fill" even though it may be the cheapest thing on the menu at your local sand & gravel yard, because this will probably be too silty and won't provide good drainage.

I suppose if you use sand, it's maybe not technically a "soilless" mix, but I find that sand works well.

A recipe that I use that works very well for plant-starting potting soil and costs very little; it would work well in raised beds:

  • 1 part well-composted horse manure (mine also contains composted kitchen scraps and some poultry manure). Since my horse manure contains a stall bedding product made from wood, it has really good moisture absorbing properties, so this meets both the water retention and nutrient requirements.
  • 1 part washed sand (this is the only part I might pay for, but sometimes I get free sand)
  • 1 part good garden soil -- obviously, if you are building brand-new garden beds, you won't have this

Sometimes I'll mix in peat moss if the compost portion is more compost-y and not as manure-y.

If you want to build a low-cost mix for new raised beds, look around your local area to see what you can get cheaply. In many areas, if you own a pickup, you can find a horse stable or a dairy farm where you can get free or cheap composted manure. (The last time I went "off farm" for manure, I paid $20 for a pickup-truck load of well-rotted cow manure that the farmer loaded for me with his tractor. I also made a few trips to horse farms where I had to shovel it on the truck, but it was free for the taking.)

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    +1, but watch out on the manure, can be easy to overdo, if not burning things, then can get too much green growth... Depending on what you are growing. Also how organic lettuce gets E. coli.
    – Grady Player
    Commented May 7, 2012 at 3:12
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Since I've watched "Back to Eden" about mulching with woodchips I'm convinced to give that a try.

Why?

Because it seems the most natural and logical thing to do. In nature there is no mix with peat, compost and vermiculite on a 1-1-1 basis.

I would start with grassclippings, compost on top of that and mulch with woodchips. Add little manure on top and later on some bonemeal, bloodmeal or anything else when needed. Every next year, just some woodchips and little manure.

To me, that's the most natural way to get good healthy soil.

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    Interesting idea. I might suggest using autumn leaves instead of woodchips. First, woodchips will grab a lot of nitrogen while they are breaking down (to be fair, you're compensating for this with grass clippings and blood meal). Second, producing woodchips requires a fair amount of energy, while acquiring leaves is generally much less. Third, if you're aiming for natural, a layer of fallen leaves is what you would generally find in forest soils; bits of wood are less common.
    – bstpierre
    Commented May 8, 2012 at 12:27
  • Yes, woodchips will take a while before breaking down. But if you drop them in autumn, they have some months to get decomposed a bit. Mixing leaves with twigs etc. makes it more natural yes. But you want the soil to be covered the whole year. After months the leaves will be gone and the wood won't.
    – Aschwin
    Commented May 31, 2012 at 12:59
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You could try replacing vermiculite with expanded clay aggregate. It may be more available than vermiculite (here, in Poland, it is) and can provide the same function (drainage and loosening of the soil).

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You might consider another major soil substrate, or conditioner, named coco peat, which is famous for its air porosity, high water retention and root propagation.

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