310 LUTHER BURBANK 



Cultivation also goes far in keeping insects 

 and diseases under control. Many insects' eggs 

 and Iarva3 and many disease germs are found in 

 the soil. When the field is stirred frequently, 

 these are brought to the surface and exposed to 

 the hot sun and many of them are thus destroyed. 



Soil is of a very complex composition, and 

 furthermore it is continually changing. A worm 

 burrows into the soil and on his way replaces and 

 rearranges thousands of soil particles. 



As the root hair penetrates among the particles 

 of soil it affects a change. 



The passing of moisture from one particle to 

 another makes changes which are of extreme im- 

 portance from the standpoint of fertility. 



Because of this ever changing condition, it is 

 necessary to pay close attention to cultivation in 

 order to keep the conditions as near uniform as 

 is possible. 



A soil that is not given the proper care as to 

 cultivation often holds its valuable food elements 

 like a deposit in a bank that bears no interest. 



Every business man knows that it is an ex- 

 tremely bad policy to allow resources to lie idle, 

 but farmers too often do not consider the ele- 

 ments in the soil as resources. 



There are three important ways to make avail- 

 able the supply of plant food in the soil: One 



