84 ELEMENTS OF AGRICULTURE 



granulated condition. If such a soil is worked while wet, 

 and if it then dries, it will be greatly injured, sometimes 

 so much as to damage the crops for several years. 

 Working a clay soil when wet makes "bricks" of it. The 

 crust that is formed on the surface of soil after rains is 

 due to the breaking down of compound particles. 



If such a soil is too finely pulverized, it "runs together" 

 and bakes because the granules have been broken up. (See 

 Fig. 43.) 



The relative fineness of the soil is called its texture, 

 just as the word is used in speaking of the texture of cloth. 

 If a soil is composed of very small particles that are floc- 

 culated, it may yet be of a coarse structure. Structure 

 refers to the arrangement of soil particles. If the small 

 particles are united, it is possible to have a soil of fine tex- 

 ture and coarse structure. 



SOIL WATER 



86. Importance of Soil Water. In an agricultural 

 sense, the most important use of soil is to act as a store- 

 house for water. The productiveness of a soil is limited 

 by the amount of water that the soil can hold, and by the 

 extent to which growing crops are able to remove the 

 water. The soil water is important, not only because it 

 is the chief plant food, but because it acts as a carrier of 

 all the other plant foods that come from the soil (page 

 66). 



Soil water is very different from rain water. It con- 

 tains all the plant foods in solution. The solution is very 

 dilute, but plants use a large amount of it. Plants will 



