Report of Committee on Exchange of Soil Profiles

The activities of the Committee on Exchange of Soil Profiles have been confined, during the past year, to a study of methods for mounting soil profiles which may be used to illustrate as nearly as possible, the general character of soils as they exist under natural conditions. Although a collection of soil monoliths would show to best advantage the general soil conditions which exist in the field, the labor and expense of obtaining such large samples has been the objectionable feature of this method for profile exchange. The only alternative which may be used is to collect small samples of soil from each of the different horizons in the soil profile and prepare them for exhibition. Three methods are being used at the present time by different institutions to preserve such samples for display and study. These methods are as follows: (1) Samples of soil are placed In glass tubes, shell vials, or tall glass jars and the different layers are separated by inserting a paper or rubber disc between them. (2) Loose samples of soil are placed in small boxes with glass windows In the top of the lid so that the samples can be observed without opening the box. The small boxes are placed in a larger box in the order In which the horizons occur in the soil profile. A modification of this procedure is to insert cardboard partitions in a long narrow box at different intervals depending upon the thickness of the different layers of soil which will be placed in it. After the different compartments are filled with soil, a glass is fastened to the top of the box to hold the soil in place. (3) A third method Is to select representative samples of soil from each layer in the profile and smooth one side of each undisturbed block of soil so that it can be treated with lacquer to strengthen the cohesive properties of the soil mass. After the lacquer Is dry the block of soil is fastened to a suitable background by means of glue or any other satisfactory adhesive. In case of sandy soils In which a single grain structure occurs and no appreciable variation in color exists, it is much easier to place loose samples of soil in a glass container or In a series of boxes or compartments with a glass over the top since color variations rather than structural differences are the most important features to be observed. In case of soil layers which have a complex structural arrangement, or are not uniform in color, masses of soil from one half to two Inches in diameter or even larger in some cases are needed to show the soil characteristics to best advantage. It is very difficult to prepare soils for exhibition which have a loose granular development such as that which occurs In the surface horizon of basic soils high in organic matter, or a fluffy condition which la frequently encountered in the surface layers of forest soils. If loose granular soils are dry at the time the samples are obtained they can be moistened and pressed together to Increase the natural tendency of the particles to adhere. This will not destroy the granular condition of the soil and it aids in the preparation of a more durable sample. In order to preserve very loose samples of sandy soil or soil high in organic matter a dilute solution of clear water white lacquer such as that used to protect the surface of linoleum should be applied to the exposed surface of the soil profile and allowed to dry before the samples are removed from the soil face. If this procedure Is followed there is no soil profile that cannot be prepared in minature using solid masses of soil to represent each horizon.