Feb. 25, 1918 



Influence of Carbonates on Soil Bacteria 



489 



INFLUENCE OF CALCIUM CARBONATE, MAGNESIUM CARBONATE, LIME- 

 STONE, AND MONOCALCIUM PHOSPHATE ON THE NITRIFICATION OF 

 GELATIN IN SOIL 



In order to study the effect of calcium carbonate, magnesium car- 

 bonate, limestone, and monocalcium phosphate on nitrification in Colby 

 and in Plainfield sand to which nitrogenous material was added, a series 

 of tests was made. After the soils had been treated w^th the forenamed 

 substances separately and allowed to incubate for three months, loo-gm. 

 samples were drawn and to each portion 23.6 mgm. of gelatin were added. 

 The soil was placed in tumblers, which were covered with glass, and 

 incubated for six weeks at 27° C. At the end of this time the nitrate 

 content was determined. The results of this experiment are given in 

 Table XII. 



Table XII. — Influence of calcium carbonate, magnesium carbonate, limestone, and mono- 

 calcium, phosphate on the nitrification of gelatin in Colby silt loam and in Plainfield 

 sand 



Treatment. 



Nitrate nitrogen in loo gm. of dry soil. 



Colby silt loam. 



After 6 

 weeks. 



Increase. 



Plainfield sand. 



After 6 

 weeks. 



Increase. 



None , 



One-fourth calcium carbonate 



One-half calcium carbonate 



Full calcium carbonate 



One-fourth limestone 



One-half limestone 



Full limestone 



One-fourth magnesium carbonate 



One-half magnesiiun carbonate 



Full magnesium carbonate 



0.1 per cent monocalcium phosphate 



0.1 per cent monocalcium phosphateH-one-fourth calcium car- 

 bonate 



0.1 per cent monocalcium phosphate-t-full calcium carbonate. . 



Mgm. 

 20.87 

 22.31 

 25.00 

 28.43 

 20.87 

 23.12 

 25.00 



23-12 

 26. 12 

 25.09 

 22.31 



23-12 

 28.43 



Mgm. 



1-44 

 4-13 

 7.56 

 .00 

 8. 25 

 4-13 

 3.25 

 S-25 

 4-13 

 1.44 



3.25 



7-56 



Mgm.. 



9.06 

 11.70 

 10.57 

 zi. 12 

 II. 70 

 II. 70 

 II. 12 

 II. 12 

 13.09 

 12.24 



9.06 



13.09 

 12.24 



Mgm. 



2.64 

 1.51 

 2.06 

 3.64 

 3.64 

 3.06 



3. 06 



4-03 



3- 18 

 .00 



4-03 

 3- 18 



In reviewing Table XII it will be seen that with the exception of one- 

 fourth limestone treatment in Colby loam, and phosphate alone in 

 Plainfield sand, there was an increase in nitrification in the treated 

 soils. The increase in most cases was very slight, especially in the sand, 

 where only about half of the nitrogen of gelatin apparently was nitrified, 

 while in the Colby loam the greater part of the nitrogen of gelatin was 

 nitrified. A comparison of the amount of nitrate formed in the soil to 

 which magnesium or calcium carbonate was added, both with and without 

 the addition of gelatin (Table XI), showed a relatively greater nitrate 

 formation in the soils to which no organic nitrogen was added. These 

 results were to be expected, since it is likely that some of the ammonia 

 formed from the gelatin in the neutral or partly neutral soil escaped. 

 On the other hand, the combined effects of the gelatin and the carbonates 

 increased the multiplication of bacteria beyond that of the soil treated 

 with gelatin alone. The great gain in the number of bacteria is no doubt 



