Best Way To Lower Soil pH?

So I got it into my head to try some in-ground gardening this year. I’ve been composting for a few months now, and today I bought a pH tester to see what would be my best bet for choice of crops. The pH was a bit under seven…not horrible, but I’d been hoping to plant blackberries, and the recommended range for most variaties seems to be 5 - 6. The instructions that came with the meter were pretty vague – add organics/fertilizer to the soul to lower pH, add lime to raise.

Any green-thumb dopers with something a little more specific advice? I’m living in the Tucson suburbs, so I can’t do anything too odor-offensive.

Normally, you add sulphur to the soil to lower the pH and add lime to raise the pH. There are also fertilizers that will lower soil pH too.

Here’s a good link:


Sulfur is a slower PH acidifier that feeds bacteria that change the PH. Aluminum sulfate is a quick fix acidifier that directly affects the soil.

Your soil is slightly acidic and I wouldn’t worry about the need to make it more acidic. I especially wouldn’t add the aluminum sulfate to adjust it for this.

I’ve got a fairly vigorous blackberry garden that I started three years ago. I’m digging out another as soon as I can this spring. I live in central Kentucky and have silt loam soil, so YMMV.

Assuming that you haven’t started the garden yet, what I would do is (after the ground has thawed, of course) completely dig out the area where you are going to plant the blackberries, setting the soil aside. Blackberries have fairly shallow roots, but you’ll still want to dig to a depth of a foot or so. Fill the pit half way full with peat moss, which should be available at your local megamart like Lowes or Home Depot. Gradually mix your soil back in a shovelfull at a time until you’ve got a full pit full of well-mixed soil. Actually, keep it up until the pit is raised a bit; it’ll settle quite a bit later. The blackberries will thrive in the organic soil, and the pH will be exactly where you want it. If you can, you’ll want to keep the berries mulched every year with pine straw, which will also keep the soil pH nice and low and continue to contribute organic matter to the soil.

If you want to stay on the organic path, add bone meal (heck, add it anyway) which will provide plenty of phosphorous and a bit of nitrogen. If you don’t mind chemical fertilizer, Muracid (as noted) or anything advertised as “good for azaleas” works great. I’d avoid adding sulfur if you haven’t had much experience with it–it’s easy to add to much and burn your plants, especially if yo have new transplants.

If you live near any forests/wildlife, be warned that bone meal has the potential to attract raccoons, possums, and plenty of other scavengers that might dig up the plants while they’re still seeds/seedlings. This happened to 2 people I knew who used it. Both of their properties lined a small patch of woods though, so I’d imagine it’d be much easier to use in a city/suburban setting.

True, and good point. Fortunately, mine is an “urban farm” protected by two semi-ferocious dogs!

Thank you all very much for the advice, and the caveat about bone meal. I had issues with the goddamn neighborhood cats digging up my container garden last year just for the hell of it; I definitely don’t want to put down anything that will attract them more than fresh-turned dirt already will. (Little bastards are also the reason I want a thorny blackberry variety.)

I’ve always heard that pine needles make the soil acidic. Is using them a good or bad idea?

They do make the soil acidic, which is a good thing for plants that thrive when the pH is <6 such as blackberries and blueberries. I certainly wouldn’t (and don’t) mulch my asparagus with them!

Was it your soil or compost that was just under seven pH? Because compost is usually fairly acidic (like peat moss).

Many farmers inject sulfuric acid into the soil. It’s nasty stuff though.

Soil. I haven’t put down the compost yet.

You can’t really change the ph in your soil in any significant way. Best way to grow blackberries in Tucson would be in big pots.