Polk County Master Gardeners
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Soil Testing
So who needs a soil test, anyway? Well, you probably do unless all your
flowers and trees and your vegetable garden are thriving and healthy. The local
office of the University of Arkansas Cooperative Extension Service can send off
the soil sample and even help you understand the results when they come back.
Best of all, there is no charge for the service!
Plants need a number of different nutrients to grow well, and a soil test can
tell you what levels are needed in your garden for whatever you plan to grow
there. The big three, of course, are nitrogen, phosphorous, and potassium - the
numbers on the fertilizer bag refer to these three. You want just enough for
healthy plants and to avoid adding more nutrients than will be needed because
the excess can run off and pollute ground water. A soil test can tell you just
what and how much you need to add.
Another important bit of information you can get from that soil test is the
pH of your soil: how acid or alkaline it is. This is reported on a scale of 0 to
14, with 7 being just about neutral. Most plants do well in a slightly acidic
soil (in the 6.0 to 7.0 range). A few, however, are decidedly picky.
Strawberries are happier at 5.7 to 6.5; blueberries like it still more acid at
5.0 to 5.2. Azaleas, Calla Lillies, and Magnolias want the pH below 5.5. Sweet
Peas. Nasturtiums, Geraniums, and Morning Glories want the soil much sweeter:
above 7.0. Your Hydrangeas will be blue if the soil is acid or pink if it is
alkaline.
If your soil is not at the proper pH for the plants you want to grow, you can
lower it by adding sulfur, iron sulfate, or aluminum sulfate. To raise the pH
and make the soil more alkaline, you can add lime. And that handy soil test will
tell you how much of what you need to add.
To put together a sample of soil to be tested, you should dig a small amount
of soil (about ¼ cup) from several different areas of the bed you want to test.
Mix these together well. You will need a total of about one pint. If the soil is
very wet, spread it out on newspaper and let it dry for a day or so. The samples
are sent through the mail, and the Post Office is not a happy camper if it ends
up with muddy water seeping out of your sample. Put it in any handy container
and take it to the Agricultural Extension Office at 211 DeQueen Street here in
Mena. There you can transfer it to a mailing container that the Extension Office
furnishes. In a couple of weeks, you’ll get the information you need to make
your plants happier.
By Barbara M. Tobias
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