492 



Journal of Agricultural Research 



Vol. XII. No. 8 



had been sterilized. At the end of four days tests were made on the 

 dry and on the watered soil. The acidity of both appeared unchanged. 

 From the results of the foregoing experiments it appears that dry 

 Colby soil can be sterilized and sterile water added until the soil is half 

 saturated, without interfering seriously with the original reaction of 

 the soil. Therefore this method of sterilizing soil was adopted for all 

 of the pure-culture work. 



INFLUENCE OF CALCIUM CARBONATE, MAGNESIUM CARBONATE, AND LIME- 

 STONE ON THE AMMONIFICATION OF BLOOD MEAL BY PURE CULTURES 

 OF BACTERIA IN SOIL 



Colby silt loam. — One-hundred-gm. portions of dry soil were each 

 treated with calcium carbonate, with magnesium carbonate, and with 

 limestone separately. To the soil of the entire series 2 per cent of dried- 

 blood meal was applied. The treated soil was placed in 300-c. c. Erlen- 

 meyer flasks and sterilized as previously stated. Sterilized water was 

 then added to bring the soil to half saturation. The sterilized soil was 

 then inoculated with water suspensions of Bacillus tumescens and B. 

 suhtilis. The flasks were incubated at 27° C. for seven days and at the 

 end of this period the ammonia in each flask was determined. In Table 

 XIV are recorded the complete data for this experiment. 



Table XIV. — Influence of calcium carbonate, magnesium carbonate, and limestone on 

 the am.monification of dried blood with pure cultures in Colby silt loam 



Treatment. 



Ammonia nitrogen in loo gm. of dry soil. 



Bacillus tumescens. 



After 

 7 days. 



Increase. 



Bacillus svbiilis. 



After 

 7 days. 



Increase. 



None , 



One-fourth calcium carbonate. . . . 



One-half calcium carbonate 



Full calcitmi carbonate 



One-fourth limestone 



One-half limestone 



Full limestone 



One-fourth magiiesium carbonate 

 One-half magnesium carbonate. . . 

 Full magnesium carbonate 



Mgm. 



Mgni. 



•3 



15- S 

 16.4 

 16.4 

 II. 2 

 14. 6 

 14.8 

 15-7 

 16. s 

 17. 1 



Mgm. 



II. o 



Mgm. 



4.2 

 5-1 



S-i 

 -o. I 

 3-3 

 3-5 

 4-4 

 S-2 

 S-8 



16.0 

 16.0 

 II. 7 

 13- o 

 13-9 

 12- 5 

 17.6 

 21.0 



50 

 S-O 



0.7 

 2.0 



2.9 



1-5 

 6.6 

 10. o 



The data in Table XIV show clearly that the ammonification of dried 

 blood by Bacillus tumescens or B. suhtilis was increased when the 

 sterilized soil was treated with calcium carbonate or with magnesium 

 carbonate or with limestone. Magnesium carbonate gave better results 

 than did calcium carbonate, while the latter gave better results than did 

 the limestone. In every case full treatment with any of the compounds 

 gave the largest increase of ammonia. This is in agreement with results 

 obtained in unsterilized Colby silt loam two months after treatment with 

 the limestone or calcium carbonate. 



