CHAPTER X 

 SOILS AND SOIL MANAGEMENT 



84. From what we have learned, we recognize that 

 the proper management of soils should be such as to: 



(a) Provide the plant with an adequate supply of 

 available soil moisture at all times. 



(b) Put the soil in such tilth that the roots can find 

 abundant supplies of the important soil nutrients. 



(c) Provide for the removal of the surplus water 

 (drainage) that would fill up the air spaces and prevent 

 the proper development of the roots. 



(d) Make the soil sufficiently loose so that the oxygen 

 of the air and the water in the soil may circulate freely. 



85. Classification of Soils. Before we can intelli- 

 gently discuss the problems of soil management we should 

 learn more about the properties of the different kinds 

 of soils. By "soil" we mean that layer of the earth's 

 crust which is formed from finely broken-up rocks and 

 decayed plants and animal remains. Soils are variously 

 classified according to origin*, method of formation, 

 chemical composition, physical properties, or adaptations 

 to kinds of crops. It will be advisable for us first to 

 learn more of the properties of the substances that 

 compose the various kinds of soils. 



86. Origin of Soils. The geologist classifies soils 

 according to their origin and conditions of formation. 

 He tells us that all soils have been formed by the gradual 

 breaking up of rocks. Fig. 33 shows a mountain of rock 



*See chapters on Erosion in any text-book on geology or physical geography. 

 (52) 



