May i4, 1917 
Soil Nitrogen and Nutrition of Citrus Plants 
229 
soil between the furrows. Soil B never received any fertilizer and, 
as shown in figure 1, it lies adjacent to soil A, which received 145.8 
pounds of nitrogen per acre each year. On comparing the amount of 
nitric nitrogen found in plot B with that in plot A, it is seen that soil A 
contained about 18 times as much nitric nitrogen as soil B in the upper 3 
inches. At a depth of 3 to 6 inches soil B contained only 0.21 mgm., as 
compared with 1.33 mgm. at the same depth in soil A. Soil B also con¬ 
tained a much smaller nitrate content from 6 to 12 inches than did soil A, 
thus showing that the fertilizer applied to soil A very greatly increased 
the nitrate content of the surface layers of the soil. 
In the upper 3 inches of soil G the variation in nitrate content was from 
043 mgm. in boring 1 to 35.01 mgm. in boring 5. The column of aver¬ 
ages shows that a very high percentage of the nitrates found in the first 
foot of this soil was confined in the upper 6 inches, which are above 
the feeding roots of the tree. 
The results secured with the soil in plot L were similar to those obtained 
in soils A and G, although the highest nitrate content was not always mid¬ 
way between the furrows, indicating that the lateral movement of the irri¬ 
gation water took place more rapidly from one furrow than from the other. 
The amount of nitrates found in the soil of plot M, like that of plot B, 
was low. However, the distribution of the nitrates was quite variable. 
The highest amounts are always found at some distance from the furrows; 
but, as in soil T, the maximum quantity found is not always midway 
between the furrows. Although no fertilizer was applied to this soil, there 
was a tendency for the nitrates to accumulate in the upper 3 inches, 
where the average amount was 1.46 mgm., as compared with 0.38 mgm. 
at a depth of 3 to 6 inches. 
On September 12 and 13 samples were drawn from five plots in the 
Citrus Experiment Station grove at Arlington. The distribution of ni¬ 
trates in these soils is given in Table XXII. 
Plot 13 has received 22 pounds and 14 ounces of blood per tree each 
year for two years. The nitrate in the upper 3 inches on September 12, 
1916, is shown in Table XXII. The soil removed in borings 2 and 6, 
which are near the furrows, contains only 3.37 and 2.28 mgm., respec¬ 
tively, while the soil removed in boring 4, which is farthest from the 
furrows, contains 40.78 mgm. A study of the column of averages is 
interesting, as it indicates that about 50 per cent of the nitric nitrogen 
found in the first 4 feet of soil is located in the upper 3 inches, which is 
well above the feeding roots of the tree. It also appears that the lowest 
nitrate supply is from 6 to 24 inches, at which depths the largest number 
of feeding roots are probably located. 
Plot 14 lies immediately adjacent to plot 13 and was conducted as a 
control. The character of the soil was quite similar, and, as the sam¬ 
ples in both plots were taken between furrows 28 inches apart, it 
would seem that the difference in nitrate content may be attributed to 
