3 



THE IDEAL SOIL 



Air and Water in Soil. Figure 16 will help us to 

 understand how the roots of plants are supplied with both 

 water and air. The roots of most farm and garden 

 crops grow fastest just at the bottom of the layer of soil 

 that is turned by the plow. The soil above this point 

 is better supplied with air than that below, while the 

 subsoil, which is the part below this point, is better sup- 

 plied with water than that above. The place where the 

 plowed soil rests on the subsoil is, therefore, best supplied 

 with both air and water. 



Tiledicun 

 FIG. 1 6. Water in the soil. 



Kinds of Soil. A soil made up of particles so fine that 

 they can be seen only with a microscope is called a clay 

 soil. It is sticky when wet and is apt to "bake," or harden, 

 on drying. A clay soil can be improved by manuring, by 

 the addition of sand or ashes, and sometimes by the use 

 of lime. A soil made up largely of particles of sand is 

 called a sandy soil. It dries out rapidly and is not sticky. 

 A silt soil is made up of particles halfway between clay and 

 sand in fineness. Most farm and garden soils consist 

 mainly of a mixture of clay, silt, and sand. Such a soil 

 is called a loam. The best soil for growing crops contains 

 sand enough to let surplus water move downward, and 

 clay enough to hold sufficient water for the use of crops. 



Drainage Necessary. If the pores of a soil remained 



