Normal Soil and Its Requirements 7 



ent depths of the same soil. Brown' has shown that 

 bacteria are generally more abundant in the upper 

 eight inches. Table i, adapted from Brown throws 

 much light on this phase of the problem. 



Table i 



Bacteria as Found in Various Depths of Soil and Under 

 Different Cropping Systems ' J,* 



' BiDwn,P. E., Iowa Agr. Expt.Sta. Research Bul.8 ; 283-321, 1912. 

 'Plot No. 601. — Continuous com. 602. — 2-year rotation, com 

 and oats. 604. — 3-year rotation, com, oats, and clover. 



