Most every part of the USDA's chain of Cooperative Extension Service Universities will tell you that around 5 percent organic matter in the soil is optimal. I try for 8 percent.
I doubt there is a real need for you to buy something called "topsoil", just get compost to add to the soil you already have. While most people think they know what "topsoil" is they have in their minds a picture of loam which is 45 percent sand, 25 percent silt, 25 percent clay and about 5 percent organic matter. Most often what they get when buying "topsoil" is the same soil they already had with a bit of organic matter added to it.

Because you are doing raised beds, you do need to buy topsoil. I would not fill raised beds with just compost.

I would probably ask for something between 5 and 10% compost.

I would also ask them for information on the topsoil that they are providing. What are the percentages of sand, silt, clay and organic matter in the base soil that they use and where does it come from?

Buy the cheapest period, you can't create a finish soil regardless of what you buy so buy cheap. Now the process has started, in 3 years or so it will start to work well and not before.

All these questions and blends are running the price up for no benefit.

Buy the cheapest period, you can't create a finish soil regardless of what you buy so buy cheap. Now the process has started, in 3 years or so it will start to work well and not before.

I think that's a rather restricted view and not necessarily correct. It makes a good deal of difference what the consumer is buying and how it is put together, but it is entirely possible to purchase a prepared soil mix and have it immediately produce a healthy and productive garden.

The importation of commercially prepared bulk soil mixes is very common in newer, upscale developments and to replace existing soils that have been removed during the construction process or to add to or amend poorer or depleted soils in established gardens. Many of these have been "designed" to provide the optimum structure and fertility necessary to immediately provide good, strong plant growth.

And I'm not sure I understand or accept the notion of a "finished" soil, anyway. Organic matter will always need to be replenished as it is consumed by soil organisms and decomposes, so is a good, healthy, fertile growing medium ever "finished"?

Bulk suppliers in my area offer 3- or 5-way planting mixes that include various combinations of soil (loam, topsoil, humus, whathaveyou) together with compost, composted manures, bark fines, sand or other amendments to provide an organically rich, porous, well draining soil with adequate fertility to grow virtually anything. 60-30 or 75-25 blends are the most (with compost or composted manures being the smaller number) and they do the job perfectly well. Fine-tuning and continued amending over time will always be necessary.

Sorry, early morning math errors.....make that a 70-30 mix :-)

gardengal,

What you're talking about sounds very similar to what they do at the local place where I'm going, with the exception that they don't use manure. They have top soil, garden soil (don't remember what the difference is), compost, composted bark, and garden soil blend where you choose what % of compost you want added to the garden soil, and top soil blend. It's quality stuff - I know someone who used some and was impressed.

Deanna

Only 5-10%? Sounds to me like I've been a little too eager with my first bag of compost (mixed quite a lot of it into my new planting beds). Is there such a thing as "too much compost" and is it severely detrimental to most plants? Though mine don't seem to be complaning....yet.

Deanna, what do these various mixes cost? And give me a little more of a discription?

"Topsoil" is a meaningless term. The dictionary defines "topsoil" as the top 4 inches of soil so the seller can call whatever he has "topsoil" and be correct while what you are expecting will be something altogether different. Just get compost and mix it into the soil you already have and the total cost will most likely be less than attempting to find good "topsoil".
Now if you could find loam, which does have a very clear definition, that would be the ideal but there is not enough loam around to be of any help and loam is what most people think of when the talk about "topsoil" and that is not what "topsoil" is.

Lots of commercial blends will work fine, but I'm a total cheapskeat. So, hot on the heals of what kimmsr says, I personally would get my hands on some compost or nitrogen stabilized organic (i.e. nitrolized fir bark with 90% passing a 1/4 screen) and till it in. A good rule of thumb is to get enough organic matter to cover the area 2 inches deep and incorporate it down to 6 inches. That's pretty much 75% mineral to 25% organic by volume, which is going to be roughly 95% mineral to 5% organic by weight. The exact ratio depends, of course, on the bulk density of both materials. But, it'll be close.

The OP is filling raised beds. Unless she removes garden soil from elsewhere in her garden she needs to import soil to fill them. If not too rocky or otherwise filled with debris, any purchased soil - regardless of terminology - will work if sufficient quantities of OM are added.

gardengal48, I'm not sure why you are re-stating in bold that she is using raised beds. The suggestions for adding OM to existing soil (whether it's been moved around in the yard or not) makes perfect sense as a low-cost alternative to purchasing a custom blend; in raised beds or at original grade. Raised or not-raised isn't really the issue.

actually empty raised beds is the issue, because being built "above grade", without adding some amount of soil [whatever kind], it would require 100% compost to fill, and to get the "ratio" you folks are suggesting would require "tilling in" to a depth at least 4 times the depth of the new raised height ... or using less compost and moving soil from elsewhere in the yard, apparently not an option

usually "topsoil" means the material someone has skimmed off an area for new construction, commercially, "garden soil" means s made up blend of topsoil and other amendments meant for use in a garden

I say fill'er up with compost, if that's cheaper than the mixes - you'll have a good crop the first year, and a lower level in the bed by the second year, to which you can add whatever .... I have mostly raised beds on my pit-run gravel lot, and they all got started with a fill of compost, added to every year

Bill

Ah...I think I see the confusion now.
... or using less compost and moving soil from elsewhere in the yard, apparently not an option
I must have missed (and am still missing, quite frankly) the part where gardenfanatic stated that moving soil from elsewhere in the yard isn't an option. The way I understand the original post is that she doesn't have enough compost. I got that crazy idea from this line in the original post.
I won't have enough compost to blend with the soil myself
Making compost the limiting factor, not "the soil".
Commercial blends are fine, but I threw in my 2 cents as a good and economical option for getting a fair amount of organic amendment into the soil she has on hand; again, whether it's a raised bed or at original grade.

And as a side note, I find this phrase:
and to get the "ratio" you folks are suggesting would require "tilling in" to a depth at least 4 times the depth of the new raised height ...
particularly baffling.
To begin, we don't know the height of the beds. If it were a 6 inch bed she could fill the first 4 inches with dirt from around the yard, toss in 2 inches of OM to fill the bed the remainder of the way, and till just those 6 inches to get a good 75% mineral to 25% OM by volume (not counting the OM that's probably already in the native). Sure it will settle a bit but as gardengal48 stated (and rightly so, I believe) It would be best to add more OM every year anyway.

Sorry, I meant 8 inch bed with 6 inches of soil and 2 inches of OM on top. Early afternoon math and all.

Moving dirt from another area of the yard is not an option. I've done that in the past, and there's no more "extra".

The company I'm talking about is called "Missouri Organic". Their definition of their top soil is:

"sandy loam mix pulverized and screened for constant texture and ease of application"

The definition of their compost is:

"humus rich organic matter made from lawn, garden, and tree trimmings, thoroughly processed using bacteria, heat, and aeration to a state most readily and effectively used by the soil"

It's lab tested for contamination from herbicide and pesticide contamination, free of weed seeds and harmful pathogens.

It's way cheaper and better quality to buy this stuff in bulk, than to buy bags at Home Depot.

Deanna

Deanna, this will work fine just like it is, now how much does it cost by the yard?

What you are buying is yardwaste compost and soil removed from where ever they can get it which is fine.

well, I guess I wasn't too far wrong, keinley, so no matter the depth of the raise, getting to 25% means tilling well to 4x the depth

I still say go with the best price, if that's pure compost, mix in your own compost, dig it over a bit, and go with it, it'll work fine unless you're planting trees - any reduction can be made up next year, when you'll want more organics anyway .... in my experience you can't have "too much" if you can keep it watered

Bill

If I mix 5 to 8 percent organic matter in to my sand the level of that bed is raised about 6 to 8 inches, even after the entrained air is allowed to settle out. If you get enough organic matter into your soil and fill in the pore spaces between the mineral component the level must raise, at least for a time. If you keep adding sufficient quantites of organic matter the level will remain where it was. So purchasing "topsoil" or "garden soil" (whatever that might be) is unnecesary.

I know if I just add compost, it will shrink and the plants will sink down. Especially when we're talking about 8 inches of it. It's for a perennial bed, and I don't want to have to raise the plants every year. Been there, done that, big pain in the neck. Pure compost doesn't provide the soil structure plants need.

Missouri Organic charges $32.95/cubic yard for the garden soil blend and $23.95/cubic yard for pure compost. I think that's pretty reasonable, especially since it's good quality stuff. I'm definitely going to get the blend for my new raised beds, and since I'll be starting out the spring with such a small amount of compost, I'm thinking I'll buy some compost too, to put on my existing beds.

You don't need to till-in the compost or organic matter, if you just apply it thickly as a mulch each year the soil microorganisms and worms will do the work for you.

This is especially easy in an annual bed, where you start anew each year. But I also apply a new layer of leaf and coffee ground mulch around perennials ocassionally during the year.

As for new raised beds, the one in my front yard consists of roughly 50/50 mix of plain soil and composted mulch topped with alternate layers of coffee grounds and shredded leaves.

Before:
{{gwi:140942}}

After:
{{gwi:140943}}

Buy the soil compost mix the first time, fill completely, plant and walk away then compost every year till you die.