Apr. 28,1923 Effect of Changing Reaction of Soils upon Azotohacter 293 
Table IV .—Effect of basic compounds upon longevity of Azotohacter in an acid soil {B)^ 
Sample 
No. 
Basic compounds added. 
Potmds 
per acre, ft 
Ph. 
Azotohacter cultures. 
Feb. 9. 
Mar. 18. 
May 7. 
I 
4. 3 
2 
4. 3 
_ 
_ 
_ 
3 
0. 01 per cent CaCOg. 
300 
4.3 
— 
— 
— 
4 
. 05 per cent CaCOg.. 
I, 500 
4-4 
— 
— 
— 
5 
. 10 per cent CaCOg. 
3,000 
4 - 7 
— 
— 
— 
6 
. 50 per cent CaCOg.1 
15, 000 
5-3 
+ 
— 
— 
7 
I. 00 per cent CaCOg.. 
30, 000 
6. 5 
+ 
+ 
‘ + 
8 
2. 50 per cent CaCOg... 
75,000 
7.0 
-f 
9 
I. 01 per cent NagCOg. 
300 
4.3 
— 
— 
— 
10 
. 05 per cent NagCOg. 
I, 500 
4.8 
— 
— 
II 
. 10 per cent NagCOg. 
3,000 
5-2 
— 
— 
12 
. 50 per cent Na^COg. 
15,000 
5-8 
— 
— 
13 
I. 00 per cent NagCOg. 
30, 000 
6. 5 
— 
— 
— 
14 
2. 50 per cent NagCOg. 
75,000 
c8. 6 
— 
— 
15 
. 01 per cent Mg.COg. 
300 
4.3 
— 
— 
— 
16 
. 05 per cent Mg.COg. 
I, 500 
4.3 
— 
— 
17 
. 10 per cent Mg.COg. 
3,000 
4*3 
— 
18 
. 50 per cent Mg.COg. 
15,000 
5-4 
— 
19 
I. 00 per cent Mg.COg... 
30, 000 
6.6 
+ 
4 - 
20 
2. 50 per cent Mg.COg. 
75, 000 
7.8 
+ 
o + = Presence of Azotohacter. — = Absence of Azotohacter. Experiment set up Jan. 21, Moisture 
content optimum. 
6 3,000,000 pounds soil. 
c Greater than 8.6. 
The data reported in Table IV were secured from the same soil, but 
the variations in the quantity of basic material added were much greater. 
Here again 15,000 pounds of calcium, magnesium, or sodium carbonate 
failed to reduce the acidity to Ph 6.0 or to make conditions favorable 
for the existence of Azotohacter. The Ph where 15,000 pounds of cal¬ 
cium carbonate were added was 5.3. Where 30,000 pounds, the next larg¬ 
est quantity, were added the Ph was 6.5 and the sample contained Azo- 
tobacter at all subsequent analyses. 
Soil G with a reaction very close to Ph 5-8 (colorimetrically) was used in 
the experiments reported in Table V. The quantity of calcium, sodium, 
or magnesium carbonate necessary to reduce the acidity to Ph 6.0, or less, 
was not as great as was required by soil B. Two months after incubation 
started all samples except No. 12 (Table V) contained Azotohacter. In 
this particular case the high concentration of magnesium carbonate had 
apparently destroyed all organisms of this group. At the next analyses, 
seven weeks later, Azotohacter had disappeared from all samples more 
acid than Ph 6.0 and still remained in all those with a less high hydrogen- 
ion concentration, except when apparently destroyed by the high con¬ 
centration of magnesium and sodium carbonate. 
\^en excessive quantities of sodium and magnesium carbonate were 
added they apparently became toxic to the Azotohacter. The quantity 
necessary to produce such a condition was greater in soil G than in soil B. 
Lipman ® has reported a toxic effect upon Azotohacter from both sodium 
and magnesium carbonate. 
« Lipman, Charles B., and Sharp, L. T. toxic iepfects of “alkali salts” in soils on soil bacteria. 
m, nitrogen fixation. In Centbl. Bakt. [etc.], Abt. 2, Bd. 35, p. 647-655, i ng. 1912. 
Lipman, Charles B., and Burgess, Paul S. the protective action, against Mgcos of cacos for 
A. CHROOCOCCUM. In jour. Agr. Sci., v. 6 , p. 484-498. 1914- Bibliographical footnotes. 
