First, congratulations on your new gig. Second, how deep is the topsoil that was added and where is the bed(s) with the heathers and other dying stuff? I ask because mortar and cement leach lime and can also affect the pH. Beds near buildings or atop old building sites can be affected. Elemental sulphur is about all I use. Because of the many sulphur compounds in garlic, I am experimenting with garlic tops cut after harvest worked in the soil and used as a mulch. Trying this on blueberries but won't know it's effectiveness for some time.

tj

Sulfur is about the only thing that will drop the pH much at all. The iron sulfate, aluminum sulfate, ammonium sulfate, etc won't have much effect. Aluminum sulfate is also not a very good idea to use in general if you plan to grow anything for eating, because the aluminum can build up in the soil.

For the sulfur to give the most benefit, dig it into the soil and water it in. I treated a chlorotic maple tree by drilling holes a couple of feet deep with a bulb auger and filling them most of the way with sulfur, then putting soil back on top. It's difficult to tell if you have enough because it takes months for the sulfur to take effect. On the bright side, the effects will last a long time. I suspect that the acidic soil around the new soil will help lower the pH over time, also (as will the things that contribute to your native acidic soil). So if you can get the sulfur to bring it close to where it needs to be, you may not need to repeat the process. Since my native soil is high pH, lowering the pH is always temporary.

As you have discovered you cannot assume anything about what someone is selling you, you need to check it out your self. Buying something labeled "topsoil" is always a waste of your money since no matter the source what you get is around 95 percent of what you already have (the mineral portion of soil) and maybe 5 percent of what you need, organic matter. You would have been further ahead just purchasing leaf mold, or compost to amend the soil already there.

Paul: When you say "a couple of loads" what do you mean? Truck loads? "Scoops"? How high did you build with the new soil?

I'm wondering if the pH hasn't already meandered down some since that test? If not ammended would it naturally come to match the native soil? And you did say that you added sulfur in the fall.

I know this sounds stupid, but what makes your native soil acidic? What makes my native soil alkaline? The minerals, organic matter, water, etc? If unammended by man, do changes occur only over hundreds of years, thousands, 2?

Karen

paulns - Nova Scotia has always been a favorite vacation area for me. Indeed the soil there is very different in relation to southern New England. I noticed on many breakfast occasions that the eggs had almost white yolks and figured that sulfur was a rarity up there. Whereas down here the yolks are quite yellow indicating the presence of sulfur. Bpgreen is right in that elemental sulfur has to be dug in, it doesn't leach well. There are fertilizers for acid loving plants that will also have some effect. And as Kimmsr will attest, add plenty of compost/organic matter in order to approach neutrality. Best of luck neighbor.

To perhaps mention as well, pH measurement is logarithmic, and your soil, at 7.15 isn't far at all from neutral. What would be your ideal pH?

Around here, surface soil is around 7.8, and sub soil 8.2. Trying to acidify that is a whole other issue.

I found this line of thinking to be a bit odd:
you cannot assume anything about what someone is selling you, you need to check it out your self.
Immediately followed by:
Buying something labeled "topsoil" is always a waste of your money.
That sort of sounds like an assumption to me.

In regards to the original post: There isn't much to be done now. Next time you can use a backfill for acid loving plants. Live and learn. In the meantime, one option is to hit the plants with chelated micronutrient cover sprays at the manufacturers label rate and frequency, which many would not even consider as an option. I leave that one up to you.
Another option is to acidify the irrigation water. You can get your hands on small, fairly affordable, injectors to push sulfuric acid. You would have to have your water analyzed to come up with a setting for your injector. But, you have to use that continuously because it will acidify the soil solution, but the buffering capacity of the soil will most likely push the pH back into the alkaline range if you stop acidifying the water.
Iron sulfate actually does help acidify the soil in the backfill but, like soil sulfur, only affects the soil as deeply as it is incorporated. Scratching it in only takes care of the first centimeter or so of the root zone. The rest of the root zone won't be affected. Granular acidifying products at this point would be a waste of money unless you are going to tear out plants and start over.

That's interesting about the garlic, and soil texture, and acidifying the irrigation water, and that 7.15 is not as outrageously alkaline as it seems to me.

This area is known for its gypsum outcrops, even karst topography, and that means plenty of sulphur, right?

The heath and heather bed is 12x12' bounded by 6x6" wood beams. It definitely needed to be raised with imported soil because much of the ground there is rock/fill. We felt lucky to get sandy loam because that is easy to amend with compost, which we brought by the cubic yard from home. Plus the peat moss. Altogether the new soil is about 10" deep.

It was two truckloads - maybe 10 cubic yards each? - of topsoil.

Heaths and heathers, like blueberries, are truly acid-loving. They require, not prefer, a pH of 4.5-5.2. But heaths are more forgiving of higher pH than heathers, which fact was borne out by the look of the two types this spring.

The two hardware/garden supply stores, both ~20 miles away, that used to carry garden sulphur don't anymore. They do, ridiculously IMHO, carry aluminum sulfate just for turning hydrangeas blue. Luckily last fall we had a can of sulphur on hand at home. Seemingly little things like this become complicated where we live - a remote area.

Since none of this bed is for edible crops, couldn't I give the plants some aluminum sulfate? Or potassium aluminum sulfate/alum, which we have a small box of in the spice rack?

The website below says iron sulfate acts quicker than sulphur. What if I buy ferrous sulfate vitamin pills at the pharmacy and water them in? Maybe lift the heathers and replant in soil amended with more peat moss? Besides caring about the gardens, my dignity is at stake - we were hired to do them on the strength of the wonderful gardens we've created at home.

I'll get another test this week, on the amended soil, see what's going on.

Here is a link that might be useful: acidifying

I'd use iron sulfate before I'd use aluminum sulfate, but neither will have as much effect as sulfur. I may be wrong, but I think the main reason that iron sulfate is faster acting than sulfur is because one of the effects of high pH is iron deficiency. The iron sulfate doesn't bring the pH down nearly as much, but unless you've got pH like David52 and I have, the iron sulfate will provide some readily available iron right away (around here, the pH is high enough that the iron in iron sulfate is not available).

Something that can very quickly (and very temporarily) lower the pH are to add a quart or twoo of vinegar to a 5 gallon bucket of water and use that to water.

If there are pool supply places nearby, you can probably buy some granules that can be added to the water to drop the pH in pools. I think most of these have sulfur in them and turn the water into either sulfurous or sulfuric acid.

If you get really desperate, you can use muriatic acid (I think it's something like 15-20% HCL). If you use muriatic acid, make sure to add the acid to the water and not the other way around.

These approaches are fast, but very temporary. With your weather and native soil, a temporary fix may be enough, since that'll give time for the soil to move toward the norm for your area.

Karen--A number of things contribute to making soils either acidic or alkaline. Weather is actually a big factor. Areas that get a lot of rainfall tend to have more acidic soil and areas that are arid tend to have alkaline soil. This is mostly due to the minerals and elements that get washed away with the water (somewhat related to this, arid areas often suffer from problems with salt buildup). In recent years, the acidifying effect of rain has become even more pronounced where acid rain is an issue.

There are other factors, as well. For example, there are areas in Colorado and Utah that have acidic soil despite being arid. The reason is that the soil content is mostly crushed granite. I would assume that southern Ohio gets enough water, so your alkalinity must be due to the makeup of the soil itself.

'...This area is known for its gypsum outcrops, even karst topography, and that means plenty of sulphur, right? ...'

Yes, and plenty of calcium as well. Generally, gypsum is pH neutral. Having said that, it also raises the sulphur content and can help with sulphur deficient soil if that soil is sandy. In the southwest it can RAISE the pH. Go figure.

tj

Here is a link that might be useful: Value of Gypsum

I find that the soluble sulfates do a fairly quick job of lowering the pH, and that the effect is reasonably long lasting. It is remarkable to me how quickly my blueberries noted the change years ago when I put ammonium sulfate on. I would also pick ammonium sulfate of aluminum sulfate to avoid the soluble Al, but would not worry much if only the aluminum sulfate is available. The Al binds quickly in the soil, and it isn't being used for food. If you apply the soluble sulfates, I suspect you will see effects in a week or so. You can also add some sulphur for a longer lasting effect, dealing with the assumed buffering capacity of the soil. Don't give up! The soluble sulfates act quickly.
Renais

Thanks for helping me put this in perspective and explaining some of the chemistry...To tell you the truth I'm p*ssed at having to learn about and deal with such a wide range of pH's, when I was expecting only to amend our native soil. In all my gardening years I've never tried to grow things that needed extreme soil amendment - I just went without those plants. Anyhow. In the past few days a few things have happened.

Saturday: bought Ferrous sulfate pills at the drugstore. The pharmacist was amused and very interested when we told her what it was intended for; we waxed poetic about heathers, and she told us about the heather she'd had in her wedding bouquet.

Next we bought a small bag of aluminum sulfate at the nursery, whose owner thought it should do the trick. He commiserated about the high (for here) pH topsoil, wondered where it could have come from, and conjectured that lime had purposely been added to it.

The wording on the aluminum sulfate bag is optimistic - use it liberally on everything! just about. "Soil acidifier - Recommended for begonias, blueberries, dogwood, fuschias, hollies, hydrangeas and other acid-loving plants...Apply 1 KG evenly over 200 sq. ft."

This sounds like a lot. Ironically, dogwoods, hollies and blueberries grow well here without amendment.

Lastly, yesterday I was chatting on the phone with a lady not three miles from here who has plants to donate to the museum gardens, and she told me pink heather grows in a great patch behind her house, and we are welcome to take a half dozen plants. That was delightfully ironic! So if our expensive purchased little plants are dead we'll replace them with mature, proven plants, free of charge - always the best kind.

Now that I have an arsenal consisting of minerals, vinegar and peat, I'm going to try, cautiously, some of each in different spots and see what happens. An almost uncontrolled experiment, my second-favourite kind. We've had three days of rain though so this will have to wait.