464 INVESTIGATION BY CULTURE EXPERIMENTS 



TABLE 88. CROP YIELDS IN ILLINOIS SOIL EXPERIMENTS: BLOOMINGTON 



FIELD 



1 No commercial nitrogen applied after 1905. 



2 Clover smothered out by previous very heavy wheat crop. After the clover 

 hay was harvested, all ten of the plots were seeded to cowpeas, and the crop was 

 plowed under later on all plots as green manure for the 1907 corn crop. 



nitrogen (plot 104) produced nearly as large an increase as the 

 increase by phosphorus with nitrogen (plot 106) ; whereas on the 

 Sibley field phosphorus with nitrogen (plot 106) produced more 

 than twice as large an increase as the increase by phosphorus with- 

 out nitrogen. 



It should be stated that a draw runs near plot no on the Bloom- 

 ington field, and the crops on that plot are sometimes damaged by 

 overflow or imperfect drainage. Otherwise, all results reported in 

 Tables 87 and 88, including more than 150 tests, are considered 

 trustworthy, and they furnish much information and afford many 

 interesting and instructive comparisons, as, for example, between 

 plots 104 and 106 and between 108 and 109 on the Sibley field where 

 no legumes are grown in the rotation; also, between plots 103 and 

 106 and between 107 and 109 on both fields. 



Wherever nitrogen was provided either by direct application or 

 by the use of legume crops, the addition of the element phosphorus 



