42 

 0. 



O 



LJ 

 O 



tr 



MISCELLANEOUS PUBLICATION 95 2, U.S. DEPT. OF AGRICULTURE 



180 

 170 

 160 

 150 

 S40 

 130 

 ,120 

 .1(0 

 (00 



.090 



IS YEAR ROTATION 



3 YEAR ROTATION 



CONTINUOUS WHEAT 



1915 



1934 

 YEAR 



1946 



1956 



1915 



1934 

 YEAR 



1946 



956 



Figure 5. — Average nitrogen and carbon content under three cropping systems as 

 influenced by treatments and length of cultivation at Manhattan, Kans. Data 

 from Fritschen and Hobbs {22) . 



