To make a wash test, use a half-gallon mason jar. If any other type of container is used, be sure it is round so the water and soil can be swirled around rapidly. Put half a cupful of soil into the jar and then half fill it with water. Pull down the top tightly and swirl the soil and water for half a minute. Allow this to settle and then swirl again. Repeat several times.
With each mixing, more and more coarse particles will drift to the bottom and more and more clay particles will drift to the top, with silt settling out between them. Some of the clay particles may not settle out for several days: they are so fine they form a colloidal solution in water.
Interesting information on a soil can be uncovered with the wash test. For example, a soil which one gardener complained was always cracking and was so high in clay he couldn't work it, produced an entirely different picture when washed. It contained only about 15 per cent clay, but about 45 per cent silt. In this proportion, clay and silt particles intermeshed so completely that they worked like the cement in a concrete mixture. The addition of steamed cinders to this soil worked wonders with its texture.
In soil testing laboratories, where samples are dried and sieved into their component parts, a much more accurate reading is possible, but these tests are not necessarily of more value than the
simple home-made wash test which gives a pretty good idea of the proportions of various soil ingredients.
FERTILIZER ELEMENT TRIALS
Serious students of soils will want to find out how plants respond to various fertilizer elements. A lawn is the best place for such investigations. Tests of chemicals are not difficult but do require the use of an accurate fertilizer spreader. The hopper is filled with a chemical that supplies only one fertilizer element and a strip of it is laid down across the lawn. Other single-element chemicals are applied in the same way, until the entire lawn is covered with strips of various elements. Be sure to leave one or more grass strips untreated to serve as a check.
Next, apply strips of the same materials in the opposite direction, creating a checkerboard. This will give a reading both of single elements such as nitrogen, phosphorus, potash and others, as well as of any stepped-up effect when two are used in combination. Results of tests of this kind are often surprising. Certain treatments show little or no response while others will produce dark green islands of vigorous growth among the other tests. Usually the combination giving the best response is the one for your soil.