900 



Journal of Agricultural Research 



Vol. VI, No. 23 



ammonifying and nitrifying powers of the soil. The results as a whole 

 indicate that the manure increases the nitrogen-fixing power of the soil 

 and it is slightly higher when 10 tons per acre of manure are applied to 

 a soil than when any of the other quantities are applied. Even those 



/S.5 



/S /7.5 SO 



P£& Ce/VT CF WATER s400£D 



Fig. 2. — Curves of the nitrifying powers of soil in pots with varying quantities of manure and 



S3.S 

 water. 



pots receiving 5 , 15, and 20 tons of manure per acre as an average fix 

 more nitrogen than the unmanured soil. 



The results taken as a whole indicate that the application of manure 

 to soils in pot experiments influenced to a very great extent the ammoni- 

 fying and nitrifying powers of a soil, but the influence upon the num- 



