NATURE OF SOIL 229 



n 



with water and shake for several minutes. Set the bottles 

 in a quiet place and let the contents settle. Note which 

 soil settles to the bottom most quickly. Keep a record of 

 the time required for water to become clear in each bottle. 



Meaning of texture. By texture of soil is meant 

 the degree of fineness or coarseness of the particles of which 

 it is composed. The finest soil particles, which will remain 

 in suspension clouding water for hours, are 'called clay. The 

 next finest, which will settle in about one hour, are silt. The 

 coarser particles, which will settle almost at once, are called 

 sand or gravel. 



Most crop soils have all three of these grades or sizes of 

 particles in their make-up. The texture of the soil depends 

 on the proportion of each in the mixture. Soils are named 

 in accordance with the particular one of these elements that 

 preponderates. 



If the very fine particles are in excess, we speak of a 

 clay soil; if the texture is intermediate, of a loam soil; and 

 if coarse, of a sandy or gravelly soil. We also use the terms 

 clay loam, silt loam and sandy loam to describe the texture. 



Composition of three soil types. A mechanical an- 

 alysis of three types of soil texture made by the United 

 States Department of Agriculture shows the following pro- 

 portions of soil particles in each: 



Very 



Fine C'se Med. Fine fine 

 Type of soil gravel sand sand sand sand Silt Clay 



Norfolk sand (truck soil) 3% 15% 22% 38% 10% 8% 4% 

 Wabash clay (river bottom)_0 1% 1% 3% 7% 49% 37% 



Silt Loam (corn soil) 1% 1% 2% 8% 73% 15% 



From this table it is seen that Norfolk sand, which is 

 an excellent soil for truck gardening on the Atlantic, is 

 eighty-eight per cent, sand and gravel, and only twelve per 



