May 14,1917 Soil Nitrogen and Nutrition of Citrus Plants 191 
Table IV .—Percentage of nitrogen added to Highland, Cal., soils in dried blood and 
green manures recovered as ammonia and nitrates after six weeks’ incubation; also per¬ 
centage gain or loss of r nitrogen added. June 23, IQ14 
[Results expressed as milligrams of nitrogen per ioo gm. of soil] 
PRODUCTIVE SOIL 
Material added. 
Nitrogen 
in ma¬ 
terial 
added. 
Nitro¬ 
gen as 
ammo¬ 
nia re¬ 
covered 
in 6 
weeks. 
Per¬ 
centage 
of nitro¬ 
gen as 
ammo¬ 
nia re¬ 
covered. 
Nitro¬ 
gen as 
nitrate 
recov¬ 
ered in 
6 weeks. 
Per¬ 
centage 
of nitro¬ 
gen as 
nitrate 
recov¬ 
ered. 
Nitro¬ 
gen re¬ 
main¬ 
ing in 
soil 
after 6 
weeks. 
Gain or 
loss in 
nitrogen. 
Percent¬ 
age of 
of nitro¬ 
gen 
gained 
or lost. 
pried blood (i per cent). 
Red clover (i per cent). 
Alfalfa (1 per cent).. 
137- 20 
20.07 
28.60 
33*00 
.00 
•56 
33.33 
• 00 
1.96 
8.96 
11.48 
15*96 
6-53 
57* 20 
55 * 81 
62.90 
30. 70 
39 * 10 
— 74*30 
10.63 
10. 50 
“ 54*15 
52*96 
36* 71 
UNPRODUCTIVE SOIL 
Pried blood (1 per cent). 
Red clover (1 per cent). 
Alfalfa (1 per cent). 
137 * 20 
20. 07 
28.60 
33*88 
• 00 
.84 
24. 69 
.00 
2*94 1 
8.96 
7.00 
18. 76 
6- 53 
34*88 
65. 59 
67 * 50 
• 26.90 
38.10 
—69. 70 
6.83 
9*50 
—50.80 
' 34 * 03 
33* 20 
VIRGIN SOIL 
Dried blood (1 per cent)—... 
Red clover (1 per cent). 
Alfalfa (1 per cent). 
137 * 20 
20. 07 
28. 60 
28.00 1 
.28 
.00 
20.41 
j 1*37 
.00 
19*04 
XI. 48 
13.72 
13*88 
57* 20 
47 * 97 
66.00 
25.00 
35 *oo 
■—71.20 
4 * 93 
6.40 
—SX.89 
24.56 
22- 38 
The addition of 1 per cent of dried blood to these soils caused a rapid 
increase in the ammonia content. At the end of the first seven days the 
ammonia in these three soils varied from 21.28 to 32.2 mgm. per 100 
gm. of soil, and there was little tendency for the ammonia to decrease 
during the latter part of the incubation period. The percentage of 
nitrogen recovered as ammonia, as shown in Table IV, varied from 20.41 
in the virgin soil to 24.69 in the unproductive soil. The increase in 
nitric nitrogen following the addition of 1 per cent of dried blood was 
rather low in these soils. In the productive soil and also in the virgin 
soil the maximum increase in nitrates was secured after 21 days. In 
the unproductive soil there was a slow but steady increase in nitrates 
throughout the incubation period. The percentage of nitrogen recovered 
as nitrates is in all cases less than the percentage recovered as ammonia. 
The loss of nitrogen was very heavy in all of these soils, the average 
for the three soils being above 50 per cent of the nitrogen added. 
When 1 per cent of red clover was added, there was a reduction in the 
ammonia content of the virgin and unproductive soils during the first 
seven days and no increase in the productive soil. At no time during 
the incubation period of six weeks did the increase in ammonia amount 
to more than 0.42 mgm. per 100 gm. of soil. At the conclusion of the 
experiment, none of the nitrogen added in red clover was recovered as 
ammonia in the productive or unproductive soils and only 1.37 per cent 
in the virgin soil. The increase in nitric nitrogen from the addition of 
