The store people and even some landscapers will tell you that you need to buy garden soil if you're going to put in a garden. They'll tell you to buy more every year. When I was first starting out, that's what I did, until I learned, via experience, it's a scam.
No, really, it is. I grow things better in fill dirt subsoil than in that plastic-bagged garbage from the store. Yes, it is garbage. Tree trimmer wood chips, composted sewage sludge, animal waste, etc. Not that those don't make good fertilizers, but the ratios those bags have are often strongly wood chips, which means any fertilizer in the bag is tied up decomposing the wood chips, and not feeding your plants.
Those that aren't high in wood chips will feel like a solid mud clod, because they are. Live soil is full of-well- life. You take that away, shove it in a mostly non-breadthing plastic bag and mush it on a pallet and it dies. It's then just compacted dirt. It maybe mostly organic matter compacted dirt, but it's not healthy soil.
Because it's not healthy soil, the microbes in the soil which help plants grow vs. The ones that decompose stuff is in favor of decomposition. Which means your microbes will be working against you until they re-balance to your garden. This means your plants are more likely to get sick, which means more pests.
Think that's bad enough? There's more: weeds and decomposition. Yes, they can carry weed seed. So while you carefully weed everything from your garden, you then apply soil which brings them back. Joy.
It's the end of the season. You completed a season with adding fertilizer to your garden soil, staving off disease and pests, and weeding the plants it brought in. What else could go wrong? As you admire your garden, you notice that it looks a little low in soil. Want to know why? The store bought soils are mostly organic matter, which means when they are fully decomposed, they leave your garden bed via volatilization or in your plants. The wood chip type do this more than the mud clod type because the wood chips decompose taking up less space. What you have at the end ofthe season is more work and money to refill your bed of magic disapearing soil.
I switched to using subsoil, some peat moss, organic matter on hand, compost, organic fertilizer, and time. Subsoil is full of micronutrients, a strong matrix of stuff (no need to discuss soil chemistry) that doesn't magically disappear in in a year and allows natural air pockets to develop, it's usually local which means the local microbes are adapted to it. What it lacks to kick into real good soil can be developed in 3 years by adding 4 things:
Organic fertilizer (this mimics naturally decomposed stuff and animal poo that would be in a healthy soil. I apply liberally as the plants need it.
Compost from your yard. This adds local microbes and places to live without bringing in new weeds. It doesn't need to be fully decomposed. Healthy soil isn't fully composted, it's always got some of both.
Organic matter on hand. This is to draw the worms in and get them making air holes and work their magic.
Peat is local here. It's another food and ratio thing to get the ecology kick started. If I had lots of compost, I may leave this out. It's not weedy, so since I have to buy some decomposed organic matter, I buy this. Even still, I only add a little, just to help compensate for our high in clay and very low in organic matter subsoil.
Time. The first year I imagine the plants are sort of hydroponic. They get about all their food from what I add via fertilizer. They may need more water too. I don't expect high yields. I mostly want them to be edible cover crops. Year two I still give them more fertilizer, but the yields increase. The soil is still a little rough, but the yields are about what you'd get in a normal garden. Year three I get my neighbors asking for advice because not only am I getting higher yields, but I am also not schlepping bags of soil, dealing with much pest, or doing much weeding. True story.
I agree with every word. I sort of backed into gardening as an adult (although my mom was an organic gardener when I was a small child and I did a lot of unwilling forced garden labor then in site preparation and collection/introduction of soil amendments) and I was appalled and dismayed by the modern internet garden wisdom, all of which boiled down to "dig a hole or build a box, then, go to the store and buy bags of stuff to fill your hole or box." I started very small with five gallon buckets and was very unhappy with the quality of what came in those bags to fill 'em!
I do agree that the ones sold as "subsoil" or "soil" are probably the best of a bad lot, but won't differ a whole lot from the native dirt under one's feet wherever one is. Which means that in most situations (unless one is a renter, or in a very flat, highly coiffed urban/suburban situation) one can probably find a creative way to dig some up for free where one lives, or somewhere disturbed nearby.
In my location (central Oklahoma) the native dirt pretty much turns to concrete in a container or raised bed unless amended very heavily with organic matter, which may not be readily available in sufficient quantity. I find that "working it" for a year is the best way to make soil. Making compost isn't easy here (too hot and dry, and requires possibly-scarce inputs) but if I fill a calf tub 5-gallon-bucket or any watertight container half full of native dirt (preferably screened for rocks and broken glass) and throw in a few water chestnuts in the spring, then top up with water, they'll grow all summer long. I keep these all over my garden, and it's where I throw pulled weeds, split tomatoes, sun-scalded peppers, half-bug-eaten anything, squished hornworms, pinched flowers from the basil, weed cuttings from my garden paths, anything that might normally go to a compost pile. All that organic matter rots, or is eaten by the frogs and tadpoles that live in the water (they also eat the mosquito larvae). I water these tubs when I water my plants, and dragonflies breed in them and live among the reeds. Come winter they freeze out and I turn over the tubs, and what I've got is something much closer to soil (full of roots and decomposed organic matter) than I started with. I use this stuff for the bottom half of next year's raised beds or containers (that way any water chestnuts that I don't harvest don't make it into the open air) and older better soil goes on top. It's slow, but I progress.
Another thing I do is maintain larger water garden features (those plastic kid's sandboxes in the shape of a frog are awesome for this, especially if you buy them cheap at garage sales and raise them up on a couple of pallets) where I bring small potted plants that have dried out, to soak and rejuvenate. These start the year with dug-up native subsoil in the bottom, and aquatic plants growing in them. I'll bring in dirt all year long in the form of potted plants that don't make it, which I empty into the ever-growing swamp. I also throw in grass clippings and such. Or if the aquatic plants get out of control I'll wad up a huge ball of them and flip them back in, submerged, to break up and rot. As I'm potting things up during the year I'll reach in and grab a mix of red/grey muck from the bottom (my original subsoil) and black muck (organic decay products and recycled potting soil) and stir them together into my container. Even with this borrowing, by the end of the year I always have four inches of rich muck that dries out and becomes available to use wherever.