INTRODUCTION 
9 
SOIL CLASSIFICATION. 
Soils are grouped according to texture into soil classes, a soil 
class being made up of soils having the same texture, though 
differing in other respects. A fine sand, for example, may be 
light colored and of alluvial origin, while another fine sand.may 
be dark in color and of residual origin, while a third fine sand 
may have been blown into sand dunes by the wind, yet all of 
these soils would belong to the same class, because the greater 
proportion of the soil grains have the same size or texture. Thus 
we may have different kinds of clays, loams, sands, etc., and the 
class to which any soil will belong depends upon the size of the 
individual soil grains of which it is composed, and not upon its 
color, origin, topographic position, or agricultural value. 
SOIL CLASSES 
Soils Containing Less Than 20% Silt and Clay 
Coarse sand.—Over 25% fine gravel and coarse sand, and less than 50% 
of any other grade of sand. 
Sand.—Over 25% fine gravel, coarse and medium sand, and less than 
50% fine sand. 
Fine sand.—Over 50% fine sand, or less than 25% fine gravel, coarse 
and medium sand. 
Very fine sand.—Over 50% very fine sand. 
Soils Containing Between 20-50% of Silt and Clay 
Sandy loam.—Over 25% fine gravel, coarse and medium sand. 
Fine sandy loam.—Over 50% fine sand, or less than 25% fine gravel, coarse 
and medium sand. 
Sandy clay.—Less than 20% silt. 
Soils Containing Between 20-50% of Silt and Clay 
Loam.—Less than 20% clay, and less than 50% silt. 
Silt loam.—Less than 20% clay, and over 50% silt. 
Clay loam.—Between 20 and 30% clay, and less than 50% silt. 
Silty clay loam.—Between 20 and 30% clay, and over 50% silt. 
Clay.—Over 30% clay. 
Soils may be grouped in another way. Where soils are closely 
related through similar sources of the material from which de¬ 
rived, mode of origin, topographic position, etc., so that the dif¬ 
ferent soils constitute merely a graduation in texture of other¬ 
wise uniform material, such a group is called a soil series. It 
corresponds to the family which is made up of different indi¬ 
viduals having the same parentage. The Miami series, for ex- 
