"Topsoil" and potting soil are two different materials. Since the definition of "topsoil" is that it is the top 4 to 6 inches of soil. That means that anything can be labeled "topsoil".
Potting soil is made to be used in containers and does not have any of the mineral component that real soil has. Potting soil will be made from peat moss, coir, finely ground bark, or a combination of those. Potting soil is meant to be used in some kind of container where drainage is an issue and is formulated to drain fairly quickly. Potting soil is not a substitute for real soil.

Bummer,

I guess the issue started when I wanted to grow some plants in a raised bed that's lower in PH than the regular soil around here (7.5). I purchased some top soil from a local hardware store thinking erroneously that the bag soil would be neutral (7.0). In retrospect, transportation cost means the soil probably came locally so will probably have the same PH problem. In addition, there does not appear to be regulation on what constitute top soil, so it's hard to figure out what's in the bag.

My thought was perhaps to use potting soil since the stuff is likely to be more neutral and more consistent than top soil.

How do you suggest I proceed?

Paul

You could ask at ace or call/email them about the product or find contact information on the bag. They might not have to monitor the ph, but that doesn't mean they don't anyway.

If you have an area to get some of your own soil (perhaps dig a pond or put in path or patio) you could mix in an amount of sphagnum peat moss (ph 4.5) and compost to end up with a nice soil.

You might also look up something like "ammending blueberry soil" here or elsewhere to find more information on how people lower soil ph and keep it lowered over time - some of it will be specific to the blueberry plant but I think you will find some good ideas.

Best of luck!

So far I notice that vendors have very little information on their products. My garden stores offers bulk compost and topsoil but has no info except for a brief brochure from the manufacturer. In the case, of bagged stuff, it will even vary by location, so stuff in one state is probably not the same as another state.

Paul

Using bagged potting soil to fill a raised bed is a very expensive way to go and is not really necessary. If you have access to bulk soil products, all that is really necessary to build a decent bed soil is whatever is sold as "topsoil" (or even better, "planting mix") mixed with a reasonable amount of compost. If you need to lower pH, including peat will help or add an appropriate amount of sulfur. To achieve a faster result, you could mix in cottonseed meal, which is a natural acidifier and a decent organic fertilizer in its own right.

FWIW, raspberries will grow quite well in a soil of around 7.0 or neutral pH.

The pH of compost is neutral and it can help lower pH of an alkaline soil, and help raise the pH of an acidic soil.

In your case, use the local soil, plus compost, plus aluminium sulfate to lower the pH. You will have to periodically continue to add the sulfates over time, as adjusting the pH is a continual process.

FWIW, It's easier to change your plant selections than to change your soil.

I'd be very careful about adding aluminum sulfate....aluminum toxicity is very easy to achieve with repeated use of this product and that is going to be far worse an outcome than a less than ideal pH. And it won't alter the pH any faster than just plain garden sulfur will.

And I'd agree about focusing on plants appropriate to existing soil conditions if this were an inground planting situation. One of the primary benefits of a raised bed IS the ability to tailor the soil according to your specifications.

He never did say what he was attempting to grow, strawberries, blueberries, hydrangeas?

You can buy other sulfates, including elemental sulfur for pH adjustment, but as with any soil manipulation, amendments can all cause problems, if used incorrectly, including compost.

H,

I am just trying to grow bottle gentian and rue anemone. The plant data said they should have PH of no more than 7.2 and should have PH of around 6.5.

I use a simple probe tester on the soil recently and it does appear that the soil is more acidic than the soil outside the raise bed, so may be the plants are dying for other reasons (like too much rain).

Paul

You can buy other sulfates, including elemental sulfur for pH adjustment

Just as a point of clarification, sulfur is not the same as sulfate. Sulfate is an SO4 (a sulfur atom with 4 oxygen atoms).
The elemental sulfur will acidify through microbial action. (the products of which are sulfate and free hydrogen). The free hydrogen drops the pH and the sulfate does not.

When sulfates acidify, it is a chemical reaction and actually has virtually nothing to do with the sulfate itself.
For example, take iron sulfate. It's very soluble and disassociates readily. The sulfates float off to do nothing to the pH. Iron then splits water molecules (hydrolosis) into OH- (hydroxyl) and an H+ (free hydrogen). OH- bonds with iron (oxidation) to form iron hydroxide (Fe(OH)2), which is pretty insoluble while the free hydrogen (as noted above), decreases the pH. Yes, some of the hydrogen will hook up with sulfate to make sulfuric acid (H2SO4) but this is incidental. It also makes nitric acid (HNO3), carbonic acid (H2CO3), etc... The hydrogen will drop the pH whether the sulfate is there or not. On the flip side, sulfate can't drop the pH without the free hydrogen.
Same thing happens with aluminum sulfate and, to a lesser extent, magnesium sulfate.

I know I tend to bore folks but I think it's important to really understand this stuff to avoid confusion in the real world. For example, if you think it's the sulfate that decreases pH, you might go out and by a bunch of gypsum (calcium sulfate) or potash (potassium sulfate) to decrease your pH, wasting your time, your money and your energy and not accomplishing the pH change you need.

If you are amending soil to grow natives, aren't you kind of defeating the purpose of growing natives?

And where did you get the pH recommendation for those plants, its seems way off.

Have you ever seen the soil where rue anemone grows? It doesn't need that low of a pH or even much soil. It grows very well on thin soils over a rocky limestone base. And its a spring ephemeral, it may be starting to die back right now, but it should come back with a vengeance next spring.

Bottle gentian is a bit more picky about growing conditions and does prefer a rich moist soil. I don't grow that one myself because it needs full sun (something I don't have much of on my woody lot). According to the Illinois Wildflower site, (which I like to refer for native plant growing conditions) bottle gentian prefers a calcareous soil. (Which is actually on the high side of the pH range, not the low...)

Here is a link that might be useful: Illinois Wildflowers

Hmmm. No one ever talks about the microbes. Microbes make top soil unique - definitely not the same as sub soil. Microbes act as the interface between the organic material in soil and the plants. Plants will suffer in sterile soils, not matter how rich the soil is, without microbes - unless of course, the soil is treated with synthetic fertilizers and/or hormones. Plants in soil without microbes (and no fertilizers) will essentially starve.

Dirt is not an appropriate synonym for top soil. The two are quite different things. Top soil is almost impossible to store, as the microbes require oxygen. The oxygen only penetrates a few inches in the best of soils, to about 8 inches max. Heavy soils can have top soils that are only fractions of an inch deep, or even none at all. Deprive the microbes of oxygen, and the microbes die in hours. Plastic-bagged, manufactured top soil, will not have appropriate conditions for microbes to survive if they were ever present. Even true top soil, if harvested through grading and stored in piles, will only be true, healthy top soil on the top few inches of the mound. Within hours all of the microbes below the top layer of the mound will have died. True top soil is a living thing. Top soil needs to be harvested and properly placed in a very short period of time.
Take a yard of dirt (or at least a good pile) from below the top soil, mix it with fertilizer-free compost, mound it up in a remote area of your yard and watch what happens - nothing. Nothing will grow on that pile, even though it is dirt amended with compost, because it essentially sterile. After one to two years, the microbes will begin to permeate the top layer of the pile and plants will start to show up. With true top soil, the mound would explode with plants after the first rain.
Manufactured mixes "cheat" by stuffing the created mix with fertilizers. This works, but is lousy for the environment in many ways, and "hooks" your plants on synthetic fertilizers like drugs. When you hear such names as Monsanto, Miracle Gro, etc. think "pusher".
Microbes do not like synthetic fertilizers, so once using fertilizers, you are stuck using them unless you do a lot of work to fix the situation, or wait until the soil regains a proper ecological balance.
Plants will grow well in many types of media, even water, if given proper aeration and proper nutrition, i.e. fertilizer. But this is needlessly expensive and again, potentially problematic for our environment.
True top soil is magic. It's ecology is wonderfully complex and is only barely beginning to be understood. No manufactured mix will do what true top soil can do for your garden. Growing plants really needs to be thought of first as growing your soil.
True top soil, air, and water are vital to most life forms on Earth. We would all starve without true top soil, unless we were able to subsist on fungi.
Labeling requirements for growing mixes are virtually non-existent. Those ingredients that might be listed will be very vague. Notice that no synthetic fertilizers are listed, even if they are there in quantity. Anyone can sell any dirt as topsoil, and people often do as a means to avoid disposal fees for dirt.
Get top soil from people removing their raised beds, those who have graded the top few inches of an area, people taking out lawns, etc. or from your own backyard. If there are unused areas of your yard that support a dense mat of weeds, at least during wetter, warmer months, then that is true top soil. Yes there will be weeds, but a good mulch will take care of most of that problem.
My advice to any gardener is to start with good top soil, nurture that soil by continually adding organic material, worm castings and compost tea, and use a good mulch. These items are 80-90% of the battle for the vast majority of plants.

r "Microbes do not like synthetic fertilizers, so once using fertilizers, you are stuck using them unless you do a lot of work to fix the situation, or wait until the soil regains a proper ecological balance."

I understand why people believe this. Studies with incredibly heavy agricultural applications have shown a decrease in soil biota. But to then extend it to any synthetic fertilizer application kills soil biota is ridiculous. How do you think labs culture microbes, with manure? Of course not, they use synthetic nutrients. Dosage makes the poison. The good part of the link provided is "“Aerated Compost tea appears INFERIOR [you read that right �" inferior] compared to fertilizer in its ability to increase microbial biomass, microbial activity” and a few other things. Hmmm…I’d been told that microbes hated synthetic fertilizer. I guess not all microbes agree. In terms of the fertilizer used, it was a 30-10-7. I didn’t see it explicitly stated in the article, but I’d bet it was a synthetic fertilizer called Arbor Green Pro. It was applied at what I would consider a heavy dose."

Here is a link that might be useful: compost tea study shows fertilizer leads to more microbes.

"Take a yard of dirt (or at least a good pile) from below the top soil, mix it with fertilizer-free compost, mound it up in a remote area of your yard and watch what happens - nothing. Nothing will grow on that pile, even though it is dirt amended with compost, because it essentially sterile."

This is a load of bs as anyone who has dug a foundation could tell you. Give that pile water and you will grow plenty of plants that like depleated and disturbed soils commonly known as weeds.

We do know how important microbes are to soil. Having said that...

If people knew how hard it actually is to truly sterilize soil, the idea that fertilizers make it sterile would make you chuckle.

Subsoil even has lots of microbes. No, it's not the same as good topsoil, of course. But topsoil is nothing but the upper layer of subsoil that has organic matter, a soil food web, and contact with air. Give it all that and it will grow plants just fine.

Cheap topsoil purveyors like the ones who supply Ace Hardware with budget priced topsoil bags do not bother to add fertilizers. I too have found in questioning an Ace manager that they know very little about those bags. I showed one a couple years ago that his cheap 'compost' bags were mostly soil, and he said he would 'check into it.' Whatever.

Let's also remember that tissue culture would be impossible if plants couldn't grow in a sterile cuture. Microbes can be great and helpful, but they aren't magic.

Tissue, plants, bacteria, and fungi do not grow in a sterile environment. The equiprment used to grow these cultures is sterilized so that you can grow what you want without foreign materials also growing in that medium, but once sterilized the equipement is then contaminate with what you want to grow.
Soil is composed of the mineral portion, the sand, silt, and clay particles, plus organic matter, the stuff that feeds the soil bacteria that feed your plants, plus air and water. Clay soils lacking adequate levels of organic matter will not have the air plant roots need to use the moisture and nutrients locked up by the clay soil particles. Sandy soils will have a pore structure that will not hold adequate amounts of moisture and nutrients and will have too much air unless adequate levels of organic matter are added.

ok thats a fair semantic nitpick kimmsr.

"Let's also remember that tissue culture would be impossible if plants couldn't grow in a sterile cuture."

Change one word - 'culture' to 'medium' - and its indisputably correct and I'm sure is what you meant in the first place. I don't think that deserved a lecture on the components of soil, but what do I know. :-D

you are correct tox.