132 
INVESTIGATIONS ON KOTHAMSTED SOILS. 
i 11 tz,* downward of the nitrates could not have occurred to anything 
like so great an extent as in 1881. On the other hand, the moisture 
after harvest, as in 1881, must have aided aufeumn nitrification, though 
not to so great an extent. 
The result of the difference between the two seasons is that, on the 
whole, Ave find in October, in 1893, a much larger quantity of nitrates 
than in the same month in 1881. For example, if we take the con- 
tinuously dunged plat, 2b, we find in the three depths (27 inches) 
about 68 pounds of nitric nitrogen per acre in 1893, as against about 
51 pounds in 1881. So, also, in the rape-cake plat we find over 60 
pounds per acre in 1893 and only about 34 pounds in 1881. On the 
unmanured plats, 3 and 4, and on plat 5, which is manured with min- 
erals only, we find but little difference, the production of nitrates on 
these plats being, it will be remembered, at a minimum, there being 
no manurial nitrogen to yield nitrates, but only the natural-soil nitro- 
gen reenforced by meager crop residues. It may be noticed, however, 
that while plats 3 and 1, under the conditions of the 1893 season, 
showed in 27 inches only about the same quantity of nitric nitrogen as 
plat 5, yet the last named plat in 1881 showed considerably more than 
the two unmanured plats, indicating, in the more favorable nitrifying 
conditions, the effects of its greater stock of crop residues owing to 
its greater average fertility. 
Plats 9a and 9b receive sodium nitrate yearly — in the case of 9a 
with full minerals in addition, but in the case of 9b without them. 
In 1881 the quantity of sodium nitrate applied was 550 pounds per 
acre per an mini, but in 1893 it was only 275 pounds. Nevertheless, 
in 1881, after the heavy rain, the total quantity of nitric nitrogen 
found on both plats down to 27 inches was less than in 1893 after the 
much Lighter dressing. In both years, however, we find that in the 
second and third depths the quantity of nitrate left is much less on 
plat 9a, which receives mineral dressings and gives larger crops, than 
on plat 9b, which, gelling the same quantity of sodium nitrate but no 
minerals, gives a smaller annual produce. 
Plats L0, 11, 12, L3, and 14, all dressed alike in both years with 
ammonium salts, with and without various mineral additions, all 
showed in the total 27 inches much less nitric nitrogen in L881 than in 
L893, again indicating that the washing down of the nitrates formed 
from the ammonium salts was in 1SS1 much more complete than in 
the season of IS!):}. 
A very marked difference will be noticed in the nitrogen found at the 
two different periods on plat 16. Plat 16, in 27 inches, showed only 
30 pounds of nitric nitrogen per acre per annum in 1881, as against 
77 pounds in L893; hut in L881 this plat was, and had been for nine- 
teen years, unmanured, while in 1 893 it had for ten years been receiv- 
ing a full mineral dressing, including 550 pounds per acre per annum 
of sodium nitrate. The difference is mainly shown in the second and 
t hird depl lis. 
