74 
INVESTIGATIONS ON ROTHAMSTED SOILS. 
on plat 16, yet we find less nitrates in the subsoil. It is true that 
under the unusual influences of the dry summer of 1893 the crop of 
plat 9a was exceptionally small, being less than that of plat 7. The 
difference in nitrogen assimilation, however, does not account for the 
discrepancy. It may be that the complete nitrification )f the ammo- 
nium salts is not always as rapid as we know it to be sometimes, and 
that some of the ammonia supplied in the spring is still held in some 
form of temporary combination in the soil. The drainage waters 
show that ammonium salts are not removed, as such, in solution. 
Their nitrification might be thus protracted, and their passage down- 
wards as nitrate be more distributed over the year than is the down- 
ward passage of the nitrogen applied as sodium nitrate. 
The spring and summer of 1893 were excessively dry, and not 
favorable to the rapid nitrification of ammonium salts. If the exam- 
ination of the soils was carried out in another season we might find 
relatively more nitrate in the subsoils of the ammonia-dressed plats. 
There is no evidence of permanent accumulation of ammonium salts, 
as such, in the soils; but there may be temporary accumulation. If 
the large unused excess is not wholly converted into nitrates we 
should seem to be driven to suppose that some of it is lost by decom- 
position into free nitrogen — of which decomposition, however, there 
is no evidence, except where there is a large excess of organic matter 
like dung. 
COMPARISON OF PLATS RECEIVING LIKE DRESSINGS OF AMMONIUM 
SALTS BUT WITH VARYING MINERAL TREATMENT. 
We will now turn to the series of plats all receiving the same dress- 
ing per acre of ammonium salts, but differing as to mineral treat- 
ment. The nitric nitrogen results for these plats are shown in the 
following table : 
T.\ ble 38.—Broadbalk wheat soils, plats 3, 10a, 10b, 11, 12, IS, and 14— Nitrogen 
as nitrates ("nitric" nitrogen) in samples collected October, 1893. 
Depth. 
Plat 3, 
unma- 
nured 
50 
years. 
Receiving anually 400 pounds ammonium salts contain- 
ing 8(5 pounds nitrogen per acre. 
Plat 10a, 
with no 
mineral 
manure 
since 
1844. 
Plat 10b, 
with no 
mineral 
manure 
since 
1850. 
Plat 11, 
with su- 
perphos- 
phate. 
Plat 12, 
with su- 
perphos- 
phate 
and 
sodium 
salts. 
Plat 13, 
with su- 
perphos- 
phate 
and 
potas- 
sium 
salts. 
Plat 14, 
with su- 
perphos- 
phate 
and 
mag- 
nesium 
salts. 
First i» inches 
Second 9 inches. 
Pounds. 
«.».»; 1 
9.22 
2.74 
l'<i innls. 
12. 52 
25. 43 
11.25 
/'on nils. 
51.41 
2!». (Hi 
18. 99 
Pounds. 
LI. 67 
24. 58 
14.88 
j 1 . c,t; 
S. til) 
5.02 
4.48 
8.11 
, 51.18 
35. 87 
87.00 
I '0 101 ( Is. 
II L6 
25. 48 
L2. 1 1 
7. 46 
5. 85 
5.06 
5. 38 
5.31 
51.78 
29. 08 
80. hi 
Pounds. 
L3.92 
2(5. 15 
9. 44 
4.68 
3.52 
3. 80 
3. 54 
3. 56 
4!». 51 
L9, L0 
68.61 
1', hi nils. 
13.38 
30.99 
11.78 
6.85 
6. hi 
5. 39 
5.62 
6.80 
56. 15 
30. 76 
86.91 
Fifth '.) iiH-hos 
Sixth \\ inches 
Sc\ cut ii !t Inches 
Ki^hth :i inches 
1 to 87 inches 
21. 60 
10.20 
52. 49 
1 to 72 Inches 
