Soil Classification

The ability to classify the soil will give you an advantage

Soil classification is important. Understanding your soil type is the first step to turning your unproductive garden soil into a glorious gardener loam. Once you understand where you are, you can begin to figure how to get where you want to go.

Here is a soil classification according to particle size:

Soil Classification by pH

Years ago, Dr. Edgar T. Wherry devised a soil classification by degrees of acidity; it is still useful but should be qualified by the fact that many plants spill over into two or more classifications while some are relatively sensitive to pH.

Under his system, soil classification is as follows:

Superacid: Bogs, largely of sphagnum origin, with a pH range of 3.0 to 4.0. Only a few plants thrive under these superacid conditions. Because bacteria and fungi cannot function at this low reading, organic matter breaks down slowly or not at all. (It is interesting to see that two plants which do well in superacid soils – pitcher plants and sundews – do not rely upon soil for nitrogen, but are carnivorous.)

Mediacid: Bogs of sedge and sphagnum where no run-off from lime-bearing soils drains in. The pH is from 4.0 to 5.0. Broad-leaved evergreens thrive on moist mediacid soils, while hemlock, spruce and oaks grow on somewhat drier areas.

Subacid: Older gardens and fields from which lime has been all but exhausted, resulting in a pH of 5.0 to 6.0. Also includes old upland woods and some swamps.

Minimacid: Gardens and fields which are limed from time to time; woods on soils over limestone; old untilled grasslands or soils under oaks. The pH ranges from 6.0 to 7.0.

Minimalkaline [including Neutral]: Marshes and lowlands into which water drains from lime-rich soils. Contain debris from limestone ledges and cliffs, and leaf mold from hardwood forests except, under most instances, from oaks. The pH is from 7.0 to 8.0.

To the above soil classification we might add a group for gardeners who live in the Great Plains area where rainfall is too light to leach out alkalizing chemicals, resulting in alkali- and salt-sick soils typical of such regions with a pH of from 8.0 to 9.0.


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