A STUDY OF SOIL PARTICLES 9 



1. Stones: particles of soil so large that they interfere 

 with tillage operations. 



2. Gravel: particles smaller than stones but larger than 

 one twenty-fifth of an inch in diameter. 



3. Coarse sand : one twenty-fifth to one fiftieth of an inch 

 in diameter. 



4. Medium sand: one fiftieth to one hundredth of an inch 

 in diameter. 



5. Fine sand: one hundredth to one two hundredth of an 

 inch in diameter. 



6. Very fine sand : one two-hundredth to one five-hundredth 

 of an inch in diameter. 



7. Silt: one five-hundredth to one five-thousandth of an 

 inch in diameter. 



8. Clay: one five-thousandth to one two-hundred-fifty- 

 thousandth of an inch in diameter. 



These different-sized particles of soil are spoken of as soil 

 components or physical soil constituents. All soils do not 

 contain all of these components. Some of the most fertile 

 soils do not contain stones or gravel, yet all of the fertile 

 soils contain the three other constituents, sand, silt, and clay. 



While all soils contain most of the different soil constit- 

 uents, very few soils contain these constituents in exactly 

 the same amount. One soil will have the sand particles 

 predominating, another soil the silt particles, and a third 

 soil the clay particles. Thus there will be different types 

 of farm soils produced as the amounts of these different 

 soil constituents vary. The leading types of farm soils 

 formed by varying amounts of these different soil constit- 

 uents are given in the following list : 



