74 



The processes are both important factors in soil fertility ; they doubtless 

 respond to many of the same agencies ; the degree of their activity is cer- 

 tainly one index to the crop producing power of arable lands. It would 

 be logical to expect, therefore, that soils showing high nitrifying powers 

 would exhibit likewise unusual qualities for fixation. For the sake of com- 

 parison a number of cultivated soils with outstanding properties in either 

 process were chosen that the two qualities might be noted with reference to 

 the same soil. These comparative figures are presented in Table V. 



TABLE V. Comparing Certain Cultivated Soils, as to their Nitrifying and 



Nitrogen Fixing Power. 1 



The soils employed in Table V include all cultivated soils from Table 1 

 which produced as high as 13 mgs. nitrate per 100 grams soil and all those 

 which fixed as high as 10 mgs. nitrogen per 10 grams soil in 100 c. c. Ashby's 

 medium. The total number is 23 and of this number 11 showed nitrifying 

 and fixation powers which may be regarded as commensurate one with the 

 other. In the remaining 12 there is apparently no relationship between 

 the two processes. 



In the light of the above results there is no basis for assuming that nitri- 

 fication and fixation are favored by the same influences ; that they are 



lr The minus sign following a number indicates that the nitrifying and fixation powers of that 

 soil do not appear to be correlated. 



