THE PROPERTIES OF SOILS 



59 



gravelly loam, and silty clay. In the reports of the state and 

 national soil surveys, certain proper names are prefixed to 

 describe certain types of soils, as Hagerstown Loam, Marshall 

 Silt Loam, Salem Sand, and Miami Clay Loam. 



61. The weight of soils. The coarser the soil is, the less the 

 pore space of the soil and the greater the weight per cubic foot. 

 A cubic foot of dry sandy soil weighs from 100 to no pounds ; 

 of loam, from 80 to 90 pounds ; and of clay soil, from 60 to 



Coarse sand (at left), fine sand (in middle), and silt (at right) under the same magnifica- 

 tion. Particles of clay are so small that they are not visible under the magnification used. 

 (Photographs by Throckmorton) 



70 pounds. The farmer, however, refers to a heavy soil as one 

 which is hard to work, such as a clay soil or a clay loam. 

 These soils work hard because they are fine grained. They are 

 plastic when wet and become very hard when dry. A sandy 

 soil, on the other hand, would be called a light soil by the farmer 

 because it is easy to work. Therefore, that which the farmer 

 knows as a light soil is really one which has a heavy weight per 

 cubic foot, and what he classes as a heavy soil is one which is 

 light per cubic foot. It is also true that the greater the amount of or- 

 ganic matter in a soil, other things being equal, the less it weighs. 



