Soils 31 



farmer raises in ponds and streams could not persist were it 

 not for the yield of the land. When the barns are bursting 

 with great yields, the land is to be praised. We are not to 

 think of soil as mere dirt, beneath our notice. The farmer 

 buys his land and cares for it ; the more knowledge he has of 

 it the better should be his practice. The proper care of the 

 soil is perhaps his first duty. He must understand tillage and 

 the reasons for it. The robbing of the land of its fertility is 

 not only poor farming for the present, but it destroys the her- 

 itage of the future, impoverishing those who come after us. 

 A farmer should not leave worn-out land to his children ; and 

 the children are to learn how to care for it, to be ready when 

 it comes their time to have control. 



12. Constituents of soil. From the farmer's standpoint, 

 that part of the earth's crust in which roots can or do find a 

 place to grow is soil. It is composed of broken-up rock particles 

 mixed with animal and vegetable matter. The rock particles 

 are known as mineral matter; the animal and vegetable sub- 

 stances, as organic matter. The particles are of various sizes 

 and shapes and of different stages of decomposition ; some are 

 hard and resistant to decay ; s some are so decayed that they are 

 easily broken. When the organic matter of soil decays until 

 it loses all trace of its original structure, it forms what is called 

 humus. We shall read much about humus in the following 

 pages, for soils without sufficient humus are practically worth- 

 less. Humus enriches the soil, makes it darker in color, helps 

 to make it crumbly and easy to cultivate, aids in holding water 

 for the use of the plants, and improves the soil structure. 



In addition to mineral matter and organic matter, water, 

 air, bacteria, and plant-food are essential constituents of pro- 

 ductive soil. These are discussed in detail later. 



The term surface soil is applied to the top layer of soil and 

 subsoil to that layer just beneath it. The top soil contains 

 more humus than the subsoil, is darker in color, more porous, 

 and can be worked into garden condition more easily. The 



