106 FIRST YEAR SCIENCE 



agricultural crops unless carefully handled by man. The 

 materials taken from it must be replaced by manures. 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 humus needed by the germs 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 

 probably 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. 



GOOD SOIL. 

 A truck farm. 



49. Value of Soils. Many different factors enter into 

 the determination of the value of a soil. Soils which in 

 one locality would be of great value are almost valueless in 

 other localities. Light sandy soil far from a market, un- 

 less transportation facilities are exceptionally good, is 



