May 14, 1917 
Soil Nitrogen and Nutrition of Citrus Plants 
213 
Table XVIII .—Average ammonia content of Citrus Experiment Station soils. Septerti' 
ber, 1914, to August , 1915, inclusive 
[Results expressed as milligrams of nitrogen per .100 gm. of soil] 
Treatment and depth in inches. 
Sept. 
Oct. 
Nov. 
Dec. 
Jan. 
Feb. 
Mar. 
Apr. 
June. 
July. 
Aug. 
Seven plots receiving 145 pounds 
of nitrogen per acre in commer¬ 
cial fertilizers: 
0-6 .. 
x.02 
o -99 
1.05 
0.90 
0.80 
©•47 
c. 78 
0.58 
0.74 
©• 55 
6-18. 
.61 
.62 
• 35 
• 45 
• 47 
.29 
• 44 
• 3 © 
.27 
.18 
_ iSr-30...... 
.42 
.46 
.18 
•23 
•34 
•09 
•31 
•23 
.14 
.18 
.09 
Two plots receiving approxi¬ 
mately 145 pounds of nitrogen 
per acre as barnyard manure: 
0-6 . 
.88 
x. 00 
.70 
.76 
.90 
•57 
.66 
•49 
•57 
•63 
■54 
6-18.. 
. 60 
.66 
•25 
.46 
•45 
. 22 
•37 
.38 
. *25 
• 3 © 
. 16 
_ 18-30.v... 
• 53 
.46 
.14 
•39 
•34 
. xo 
•34 
.19 
•13 
•23 
.03 
Four plots receiving 48.60 pounds 
of nitrogen per acre in commer¬ 
cial fertilizer: 
0-6. 
.85 
.78 
.71 
.82 
•74 
• 5 i 
•77 
•75 
.65 
•56 
.41 
6-18.. 
•56 
•49 
•47 
•58 
•50 
.28 
•47 
•33 
• 3 © 
.28 
.18 
1&-30. 
.46 
.42 
.17 
•30 
•30 
. XI 
•25 
.18 
.19 
. x6 
•©5 
Seven plots receiving no nitrog¬ 
enous fertilizers: 
0-6. 
•74 
• 7 i 
• 7 i 
.76 
•73 
• 52 
.67 
•53 
•56 
•49 
•36 
6-18. 
.60 
•49 
•47 
•43 
.48 
• 32 
.41 
.42 
.28 
• 3 © 
. 16 
18-30. 
•44 
.41 
.30 
. 26 
•30 
. II 
.28 
•25 
•17 
. 12 
.04 
On comparing the quantity of nitric nitrogen in the surface 6 inches 
before and after irrigation in Table XIX, it is observed that the amount 
found in the second set of samples is less in every plot. The average 
reduction for the 10 plots amounts to a little less than 30 per cent. There 
is also a consistent reduction at a depth of 6 to 18 inches, which amounts 
to nearly 40 per cent. The average nitrate content of the plots before 
irrigation at a depth of 18 to 30 inches is 0.471 mgm.; after the irrigation 
the average for the 10 plots was only 0.272 mgm. At a depth of *30 to 
42 inches the nitrate content is still somewhat lower after irrigation. 
The averages for all plots indicate that some movement of nitrates may 
have taken place at a depth of 42 to 54 inches. Below a depth of 54 
inches the difference between the two sets of samples would seem to indi¬ 
cate that the irrigation had had little or no effect upon the distribution 
of the nitrates. Certainly there is no indication that the nitrates in the 
surface layers have been carried down into the deeper layers by the 
irrigation. 
Since the determination of nitric nitrogen in the samples drawn 9 
inches from the furrows before and after the June irrigation had shown 
a reduction in nitrates in the surface layers without any apparent increase 
in the deeper layers, it was believed that the irrigation must have caused 
a lateral movement, which would result in an increase in the nitrate 
content of the surface soil at some point farther from the furrows, pre¬ 
sumably about midway between the furrows, as the water moving 
laterally from adjacent furrows would be most likely to meet near this 
point. As the furrows were run about 36 inches apart, samples were 
drawn from each of eight plots 9 inches from the furrows and 18 inches 
