148 
Journal of Agricultural Research 
Vol. IX, No. s 
Table IX .—Effect of time on the fixation of ammonia by soils 
Time ammonia was allowed to remain in contact 
with the soil. 
Nitrogen 
in am¬ 
monium 
sulphate 
added per 
100 gm. 
of soil. 
Nitrogen recovered. 
Riverside soil. 
Lordsburg soil. 
Hours. 
Mgm. 
Mgm . 
Per cent. 
Mgm. 
Per cent. 
x . 
50.00 
20. 82 
41. 64 
10. IO 
20 . 20 
50.OO 
26. 50 
53-oo 
9. 90 
I9. 80 
50.00 
25. 46 
50. 92 
9. IO 
l 8 . 20 
8 . 
50.00 
24. 02 
48. 04 
7. 90 
15. 80 
50.00 
23.OO 
46. OO 
7. 70 
15. 40 
24. 
50. OO 
22. 57 
45- U 
7 - 75 
T 5 - 50 
48. 
50. OO 
21. 84 
43.68 
7. 80 
15. 60 
72. 
50. OO 
21. 26 
42.52 
7. 60 
15. 20 
96.. 
50. OO 
20. 97 
41. 94 
6. 60 
13. 20 
Heating a soil to high temperatures caused marked changes in the 
chemical and physical nature of the soil, as shown in Table X. A 
temperature of 200° C. or less for six hours seems to have had very 
little effect, but 250° caused a marked reduction in the ammonia-fixing 
power of the soil, and a temperature of 300° reduced the fixation 
in the Riverside soil to 10 per cent and in the Lordsburg soil to 12.8 
per cent. 
Table X .—Effect of heating the soil in a hot-air oven for six hours previous to the addition 
of ammonia 
Temperature. 
Nitrogen 
added 
per 
100 gm. 
of soil. 
Nitrogen recovered. 
Ammonium sulphate. 
Ammonium chlorid. 
Riverside soil. 
Lordsburg soil. 
Riverside soil. 
°C. 
Mgm. 
Mgm. 
Per cent. 
Mgm. 
Per cent . 
Mgm. 
Per cent. 
100 . 
50. 00 
25. 76 
5 1 * 52 
10. 40 
20. 80 
25.76 
5 1 - 52 
150-. 
50.00 
25. 76 
5i- 5 2 
10-35 
20. 70 
25.76 
SI- 5 2 
200 .. 
50.00 
26. 88 
S3- 76 
10. 60 
21 . 20 
26. 60 
53- 20 
250. 
50.00 
37- 24 
74.48 
33- 10 
66. 20 
37-19 
74- 38 
275. 
50. OO 
42. 92 
85.84 
39. 20 
78. 40 
42. 64 
85. 28 
300. 
50. OO 
45. 00 
90. OO 
43.60 
87. 20 
45-00 
90. OO 
An examination of Table XI shows that the percentage of nitrogen 
as ammonia recovered remained constant until the amount of nitrogen 
added was greater than 25 mgm. per 100 gm. of Riverside soil. After 
this point the percentage fixation decreased, but the absolute fixation 
increased until about 23 mgm. per 100 gm. of soil were fixed, after which 
no further increase was secured. The percentage fixation in the Lords- 
burg soil remained constant until the nitrogen added amounted to more 
than 50 mgm. per 100 gm. of soil. When amounts of nitrogen greater 
