Doctoring Your Soil:
Testing pH With a Kit, or Red Cabbage
Supplies (additional supplies listed below for the Red Cabbage activity):
pH test kit
the garden, it's all about chemistry. Just as our bodies use chemistry to break
our food down to the point where we can use it for nourishment, plants need the
soil to be "Chemically Correct" for them to grow optimally.
you sow any seeds or plant any plants, you should make sure you know the
nutritional status of your soil. That way, you can "prescribe" the soil
amendments - or changes - that you need to add, to create the best-possible
growing environment for your seeds and plants.
they will be very busy in the spring, you can contact a county extension agent
to have your soil tested. The cost may exceed $25. That may be the best way to
ascertain your soil pH (the measurement of the soil's chemistry, acid vs.
alkaline), and how much salt and lime are in your soil. These professional
tests also can tell you how sandy or clay-textured it is, how much organic
matter is there, and how high or low it is on nitrogen, phosphorus, potassium,
zinc, iron, manganese and copper.
might be more than you really want or need to know, though. The most important
factor is your soil pH. If the soil is too acidic or too alkaline, the
nutrients in the soil won't dissolve in water, and then they won't be available
to the plant roots. So you need to get your soil into proper pH balance.
pH scale runs from 1 to 14. A measurement of 7 means the soil is neutral. Below
7 means the soil is acid, and over 7 means it is alkaline.
ideal pH for most garden plants is about 6.5 - slightly acidic. If you have
clay soils or a lot of organic matter, it may take more lime to raise your
soil's pH than average.
few plants do better with slightly different levels. Carrots, eggplant, sweet
corn and potatoes like acidic soil, about 5.5, while cabbage and cauliflower
will grow fine at that level and also as alkaline as 7.5.
find out where your soil stands, you can purchase an inexpensive pH test at a
nursery center and do the soil test with the kids in the garden club. There are
electronic kits available, but the chemical kits are likely to be more
not to do this shortly after a rain, nor within two weeks of applying
fertilizer to your garden spot.
up a couple of cups of soil from about 6 to 8 inches under the surface and lay
it on a newspaper. Take samples from several different spots in your garden.
Break up any clumps and remove stones and other litter. Follow the test kit
instructions after that, using distilled water and the color chart that should
have been provided with the kit.
can use the results to fine-tune different parts of your garden for different
plants. For example, hydrangeas need extra-acidic soil in order to produce
those gorgeous blue blossoms. Such acidic soil would not be good for most
plants. So if there's a spot in your garden where you are going to plant a
hydrangea bush, you can work bone meal or fireplace ashes in to that particular
spot and not affect surrounding plants.
pH results are easy to respond to:
Too acidic (below 7): add lime
according to package directions. That's called "sweetening" it. Wood ashes are
a good source, although you can buy lime by the bag.
Too alkaline (above 7): add
organic matter such as peat moss, pine needles, leaf mold (decomposed tree
leaves, especially from oak trees), aged sawdust or wood shavings.
it's best to do this in the fall, but if you're starting your garden in the
spring, do this at least three weeks before you plant or sow seeds, to give the
pH level time to change.
note: wear a dust mask when you add lime or ashes to protect your lungs.
sure to keep a record of your pH test results for future reference. You should
have a sketch of your garden plan in a notebook to keep from season to season.
You probably should repeat the pH test every fall after the growing season, to
chart how various plants might be drained their part of the garden of
nutrients. It's best to add soil amendments in the fall and let them settle in
over the winter to be ready to go by spring planting time.
RED CABBAGE pH TEST
blender or knife
One large glass
Six small glass
cream of tartar
muriatic acid or
safety goggles and
clothespins or string
cabbage juice contains a natural pH indicator that changes colors according to
the acidity of the solution. You can make your own pH paper strips using this
Red cabbage contains a pigment, or
color-containing, molecule called flavin. It dissolves in water and is also
found in apple skin, plums, poppies, cornflowers, and grapes. If what you're
testing is very acidic, it will turn a red cabbage solution a red color.
Neutral solutions result in a purplish color. Basic (alkaline) solutions appear
Therefore, it is possible to
determine the pH of a solution based on the color it turns the pigments in red
chop the red cabbage into small pieces until you have about 2 cups of chopped
cabbage. Place the cabbage in a large glass container. Add boiling water to
cover the cabbage.
at least ten minutes for the color to come out of the cabbage. It'll be purple,
way to do this is to put the 2 cups of red cabbage into a blender, cover with
boiling water, and blend.
out the plant material to obtain a red-purple-bluish colored liquid. This
liquid is at about pH 7.
a little out into each of the small glass containers. Then add white vinegar to
one glass, drop by drop. Mix a teaspoon of baking soda into another glass. How
many colors can you make by adding different amounts of each ingredient? Can
you end up with bright blue, shocking pink, and purple?
works because red cabbage water reacts with either acids like vinegar, or base (alkaline)
substances, like baking soda, and changes colors.
tend to turn it pink, and bases turn it blue or green.
can also try adding lemon juice, clear soda water, or laundry detergent.
you can tell which are acids and which are bases. Make a chart.
put coffee filters in a shallow container and soak them in a concentrated red
cabbage solution for a few hours. Hang by a clothespin on string to dry. Cut
the filter into strips and use them to test the pH of various solutions.