334 MAN'S USE AND CONSERVATION OF SOILS 



fertility, yet it will not continue profitably to produce 

 agricultural crops unless carefully handled by man. The 

 materials taken from it must be replaced by fertilizers. It 

 must also be thoroughly tilled in order (1) to keep in the 

 moisture, (2) to prepare a mellow place where the roots of 

 the plants may spread, (3) to provide air and water and 



LABOR-SAVING MACHINERY 



Two men with a tractor operate two binders and two shockers. The 

 shocker is a new invention which receives the bundles of wheat, auto- 

 matically assembles from 8 to 11 of them into a shock, and deposits 

 the shock right side up. Each shocker saves the labor of at least two 

 men. 



humus needed by the bacteria which build up the solu- 

 ble nitrogen compounds, and (4) to kill the weeds which 

 would use the space and plant foods needed by the grow- 

 ing crops and would choke them out. Proper tillage prob- 

 ably has more to do with thrifty and productive farm- 

 ing than any other one thing. By careful tillage much 

 expense for fertilizers can be saved and the value of the 

 crop produced greatly increased. 



