THE SOIL 19 



it modifies the qualities of both; it binds together the particles 

 of sand and enables it to hold more moisture; it makes the clay 

 less adhesive or sticky, and keeps it from baking when it dries. 



Farm Soils. Let us see the application to agricultural soils of 

 these facts about sand, clay, and humus. A farmer will tell you that 

 the four chief classes of soils are sandy, clay, loam, and limestone. 

 These are the most important and most widely distributed. 

 Later, you will learn their special adaptations to crop plants and 

 how their qualities may be modified and improved. 



Sandy Soil. A sandy soil is made up largely of sand. Farmers 

 call such a soil' ' light,' although it is the heaviest in weight. The 

 term is applied to its working quality. It is light and easy to 

 work, because its particles do not adhere closely. It is so open in 

 texture that air and water pass freely through it; thus it recovers 

 quickly from rain and can be worked early in the spring. 



Clay Soil. A clay soil contains large quantities of clay. It 

 differs from sandy land in the fineness and relations of its particles; 

 though it is lighter in weight than sand, farmers call a clay soil 

 1 heavy ' because it is heavy or hard to work. This is due to the 

 fact that its particles adhere closely. Water, air, and heat do not 

 penetrate it readily, but it has great power to absorb and retain 

 moisture. Heavy winter rains make it wet and cold, so that it 

 cannot be worked until late in the spring. If plowed too wet, it 

 runs into a sticky mass and bakes when dry. If plowed too dry > 

 it breaks in hard clods. 



Loam. Loam is composed of a mixture of sand, clay, and 

 humus. According to the quantity of sand or clay, it is called 

 a ' sandy loam ' or a ' clay loam.' Loam is easy to work. Its 

 porous texture enables air and water to penetrate it readily, and 

 its humus enables it to retain water and heat. 



Limestone Soil. A limestone soil is one derived from limestone 



