6o Conservation Reader 



upon the materials of the soil and change them into such 

 form that plants can digest them. 



SoU may be supplied with all kinds of plant food in just 

 the right amount and yet, if it is packed hard and is not 

 watered, no living thing can take root in it and grow. 

 Plants drink their food and so we must supply water. They 

 also require oxygen, as do pther Hving things. For this 

 reason we must leave the soil loose, so that the air can enter 

 it and the roots get the oxygen which it contains. 



Thus we learn how wonderfully the soil is made. We 

 learn that it contains many things required by plants. In 

 order that the plants may be thrifty, there must be enough 

 but not too much of these different things. 



