58 



Elementary Principles of Agriculture 



Diameter of ffl gram in miUimettn 



93. Size of Soil Particles. In recent studies on Ameri- 

 can soils, much attention has been given to the deter- 

 mination of the size of the particles in good agricul- 

 tural soils. Fig. 34 

 shows how two soils 

 may differ in this 

 respect. In noting 

 the size of the soil 

 particles, we should 

 distinguish between 

 the actual size of 

 the minute particles 

 or fragments of rocks 

 and the soil floccules, 

 or granules formed 

 by the sticking to- 

 gether of a number of 

 very small particles. 

 93a. Examination to 

 Observe the Size of the 

 Soil Granules. Secure a 

 half-dozen lumps of soil 

 from the moist layers 

 beneath the surface, and 

 put into a fruit jar three- 

 fourths full of water. 

 Screw on the top and 

 shake vigorously for 

 some minutes, and allow 

 to settle. Describe the layers formed after standing one hour or 

 more Note the differences in size of the granules of the soil. Apply 

 the same treatment to a handful of garden soil; to a sample of stiff 

 clay soil. 



93b. Secure a good handful of soil and moisten and work till 

 a very thin, even paste is formed. Place in a jar, as in f 92a, and 

 shake. Allow to stand until the particles have all settled to the bot- 



Diamila of Ike gram m millmelcn. 



Fig. 34. Showing the amounts of the particles 

 of different size in two kinds of soils. From 

 Bureau of Soils, United States Depart- 

 ment of Agriculture. 



