Test Acidity For Blueberries With A Simple Soil Tester

It’s time I got my blueberry bushes the right acidity to produce more blueberries. But that’s easier said than done, as my new soil tester informs me.

by J. Keeler Johnson
PHOTO: J. Keeler Johnson

You know what? It’s time I got my blueberry bushes the acidity they need to thrive and produce a lot of blueberries. But that’s a bit easier said than done, as my new four-way soil tester informs me.

Soil acidity is determined by the soil’s pH level. A 7.0 rating is neutral, but many plants grow well in the range of about 6.5 to 7.5. Anything higher than 7.5 represents alkaline soil, while numbers below 6.5 (especially below 5.5) indicate acidic soil.

Berry Good

Blueberries can be tricky to grow because they need strongly acidic soil in order to thrive. Somewhere in the range of 4.0 to 5.5 is necessary for the plants to extract everything they need from the soil. If the soil is neutral or alkaline, the blueberries will struggle.

I have three blueberry bushes planted in a raised bed in my garden, but they don’t grow very much, and the berries they produce are tiny. They started out all right when originally planted in a mixture of compost and soil from my northern Wisconsin farm. They’ve been fading over the time, though, and I assume unsuitable soil pH is the culprit.

Testing for Acidity

So in an effort to resurrect my blueberries (and open up the possibility of planting more bushes), I acquired a simple four-way soil tester that measures light levels, soil moisture, soil temperature and—most importantly—the soil pH level. Armed with my new tool, I went on a journey around my farm in search of acidic soil.

Perhaps I was a bit naïve, but I didn’t think it would be that difficult to find suitably acidic soil. I figured most of the soil on my farm was in the neutral range, and indeed it was. The vast majority of locations I checked (with a simple press of a button) revealed pH levels of 7.0 or 6.5. (My tester measures in increments of 0.5.) The blueberry bed yielded a 6.5 rating, so it’s no wonder why my blueberry plants aren’t growing well.

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I had read in the past that pine needles are acidic, so I thought perhaps the soil under the stands of Red Pine windbreak trees on my farm would be the right acidity for blueberries. But alas, despite checking many locations, I couldn’t find a pH reading lower than 6.5. After doing a bit of research, it seems pine needles aren’t able to meaningfully lower soil pH levels.

Searching for Soil

And so the search continued. I checked the ground where one of my old compost piles used to sit—6.5. I checked the compost pile from which I’m currently pulling garden soil—6.5. The only time I found a reading below 6.5 was when I tested a mound of decaying sawdust and wood chips generated when cleaning up four windthrown Red Pines, and the reading was only 6.0—still too close to neutral for blueberries.

At this point, I’m going to have to take more serious steps to lower the soil pH in my blueberry beds. Introducing aluminum sulfate or sulfur to the soil will surely do the trick, but I must be careful not to overdo it. Paying for a professional soil test might be the best way to measure the exact pH level and determine with precision the amount and type of additives necessary to reach the right acidity for thriving blueberries. But at least I’m on the right track in seeking a solution.

It’s funny, I’m both disappointed and delighted by the performance of my soil tester. I am disappointed that I can’t find any suitably acidic soil on my farm but delighted that the soil tester worked perfectly and saved me from planting blueberries in pine soil that wasn’t nearly as acidic as I assumed it would be.

Thank you, soil tester!

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