Date of Award:

5-1953

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Soils and Irrigation

Committee Chair(s)

S. A. Taylor

Committee

S. A. Taylor

Committee

D. W. Thorne

Committee

O. W. Israelsen

Committee

Rolland Perry

Abstract

It is generally recognized that many of the chemical and physical properties of soils are dependent upon the surface activity of the finer soil fractions. The importance of the magnitude of the surface areas to such properties as base exchange, water-holding capacity, absorption of gases, and the plasticity of soils has been demonstrated. Attempts have been made to determine or estimate the surface of soils and soil fractions by various methods and to relate the values obtained to the physical and chemical characteristics exhibited by these materials. Most determinations have been based on calculations of surface area from mechanical analysis data, heats of wetting, hygroscopic coefficients, and other methods, but the results in general have only been approximations.

Recent studies of the clay minerals have determined that many widely different characteristics of these materials can be attributed to the variation in surface area. Because of the effect the various minerals have on the properties of the soil, a great amount of work has been done in attempting to separate and identify the mineral components of soils. Most methods are complex and time-consuming. In recent years there has been a growing realization that the surface area may be a more important criteria of many of the properties of clay minerals than the mineralogical composition. Recently a simple method for determining the total surface, external surface, and internal surface of clay and clay fractions of soil has been developed. Although the method may not be highly exact, it appears satisfactory for exploratory research.

The permeability of soils is an important characteristic, especially in regard to irrigation. This phenomena is difficult to characterize. Various methods have been proposed and developed to attempt to evaluate this property in soils. These methods have varied widely in basis and technique. A number of useful relationships and indices between the movement of water in soils and certain soil properties have been developed. At present it does not appear that there is any method entirely satisfactory for characterizing the water movement in soils.

The water retention characteristic is an important property of soil. This factor is extremely useful in irrigation work. Some knowledge of the relationship between soil moisture and soil moisture tension is necessary in sound irrigation practices. Suitable methods have been developed to determine the moisture retention characteristics of most soils. These methods require considerable time and labor for measurements. A more simple method or means of estimating the moisture characteristic from some commonly measured property of soil would be extremely useful. The total surface area of soils thought to be related to several physical and chemical properties of a soil may be such a common property.

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