28 



SOILS AND PLANT LIFE 



17. How we may get More Air into the Soil. — From 



the western limit of the Corn Belt to the Atlantic Ocean 

 and in all the land subject to irrigation, there is need of 

 plenty of air in the soil. This does not mean that large 

 air spaces, such as are caused by clods or small piles of 

 weeds or straw, are necessary ; it means rather that much 



Fic. 9. — Farmer plo^ving. 



of the air which finds its way into the small spaces in 

 mellow, well-tilled land is needed. 



The amount of air in the soil is influenced first by cul- 

 tivation or tillage; second, by manuring; third, by 

 drainage ; fourth, by rotation of crops. 



The plow turns up particles of soil which may have 

 been shut off from a supply of air. Then, too, the bottom 

 of the furrow is in direct contact with the air until it is 

 covered on the next round. 



