Blueberry shrubs and soil pH

ericwiApril 14, 2011

Here in Madison, Wisconsin, we have native soil with pH around 7.6, too high for growing blueberries. I began growing blueberries back in 1994, & learned in the first few years that I had to test the soil before making additions of sulfur to lower pH. For several years I used a Hanna Instruments pH meter, and got good results, but eventually the meter died, so I began using dye indicator solutions, in a effort to find a less expensive method. I am now using bromocresol green indicator, and it works very well for this purpose. A soil sample is mixed with an equal volume of de-ionized water, and the slurry is then filtered using a small funnel and paper filter. A few drops of bromocresol green is added to the filtrate, and the solution will turn yellow at pH = 3.8, blue at pH = 5.4, and varying shades of green if pH is between the two endpoints. The pH results obtained with bromocresol green indicator agree with pH results obtained with a calibrated pH meter. However, dye indicators do not have the same resolution, so a given result is actually a range of about 0.3 pH unit. If the test result is 4.1, the real pH might be 4.0, 4.1, or 4.2. My experience has been that this method works very well for growing blueberries, however, I do not expect dye indicators to replace conventional pH meters in the laboratory. Given that conventional pH meters are expensive and fragile, metal probe type pH measuring tools have been developed and marketed to the public. If two different metals are placed in a solution to be tested, there will be a voltage generated that corresponds to the rate of corrosion, and this voltage can be used to infer pH of the solution. However, a solution of pure water and sodium chloride will also result in corrosion of the metal probe pH measuring tool, and the voltage generated does not correspond to solution pH. For this reason, metal probe type pH measuring tools are not always accurate, and they will not replace conventional pH meters in the laboratory. They do give useful results in certain soils, and there are many people using this type of tool to successfully grow blueberries. Bromocresol green indicator will be hard to find locally, but it can be gotten from HMS Beagle, online. Two dollars will buy enough solution for about 100 soil tests.

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In the last 7 years, about how often did you have to add more sulfur to the plants?
Or how long did the pH stay around 4.2?

    Bookmark   April 14, 2011 at 10:54PM
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I am an hour west of you and I grow Blueberries fine? Never really soil tested as the plants do OK and I get berries. My oldest plant is only three years old so I am not getting buckets full yet. I sprinkle a teaspoon of sulfur around the plants in the spring and monthly coffee grounds on them.
I know to keep them away from cement (lime leaches in to the soil) but I might do a PH check. I have one of those meters with a arrow, though i don't even know if it works correctly?

    Bookmark   April 15, 2011 at 10:40AM
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Typically I will add additional sulfur every two years, and the quantity added might be 1/4 lb per shrub. It takes about two years for granulated agricultural sulfur to be metabolized by soil bacteria. Soil pH might drop 1/2 unit, or 0.5, during the growing season, if there is sulfur available at the soil surface. I don't think soil pH changes much over the winter, as soil microbes are dormant during the cold weather. When the available sulfur is all used up, soil pH might rise 0.5 unit per year.

    Bookmark   April 15, 2011 at 10:43AM
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Berryman, based on my experience, a three year old blueberry shrub might yield one pint of fruit, if the pH is between 4 and 5, and if growing conditions are good, with regard to sunlight, moisture, and fertilizer. If the soil pH is between 5.5 and 6.5, the yield might be one cup of fruit. However, the leaves will be green, and the shrub will be healthy. Pale green leaves, or yellow tinted leaves is a sign of high pH, above 6.5.

    Bookmark   April 15, 2011 at 11:07AM
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Thanks for the info.

    Bookmark   April 15, 2011 at 2:22PM
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hmmm we have clay here in Milwaukee pretty alkaline i tried using pine needles, peat moss,and such to recondition the soil i guess it doesnt correct the ph fast enough

    Bookmark   April 21, 2011 at 11:38PM
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We have some clay in our soil here in Madison, as well. I mix it with compost made from shredded tree leaves when preparing a hole for planting a blueberry shrub. I use a lot of compost, maybe 60% compost and 40% dirt. Blueberry shrubs do well in soil that is heavily amended with vegetable fiber of some sort or other, but they still need the pH to be lowered to around 4.5, and that takes sulfur.

    Bookmark   April 22, 2011 at 10:38AM
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I'm located 35 miles south of Madison (Monroe). Would very much like to grow some blueberries. I prepared a plot about 900 sq ft and tilled in about 20 lbs of granulated sulphur. I planted the plants in a 18" hole with 50% peat moss and the rest with equal parts native soil and compost. Haven't tested soil for PH yet. My plot is on a hill with high winds and don't know if the BB will be able to withstand the winter. I planted Patriot,Northblue,and Chandler from Jung's in Madison. Any suggestions would be greatly appreciated.

    Bookmark   June 20, 2011 at 3:23PM
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Since blueberry shrubs need to be kept watered, we growers often end up putting down considerable well-water during the summer, typically August. If the water used is hard, that is, if it contains dissolved limestone, from an underground aquifer, then the soil pH will rise a bit every time the shrub is watered. It is for this reason that I test soil pH both in the spring and in the fall, every year. It will be easier to keep soil pH down if rainwater, or surface water from a pond or stream is used to irrigate blueberry shrubs. I have seen wild blueberries growing in very exposed locations, where they would see lots of sun and wind. However, wild blueberries typically get covered in drifting snow during the winter, and get some protection from the weather. We have Patriot and Northblue here in Madison, and these varieties generally do well over the winter, until the local rabbits get hungry for browse...

    Bookmark   June 20, 2011 at 7:41PM
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wayne_5 zone 6a Central Indiana


I suggest that you mulch/winterize your Chandler...mine died over winter and I think Chandler is a bit suspect on full hardiness.

    Bookmark   June 20, 2011 at 9:46PM
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