54 
Journal of Agricultural Research 
Vol. XI, No. a 
The writers can offer no satisfactory reason as to why compacting 
increases the nitrate accumulation, but suggest the explanation that 
bringing the soil particles into closer contact increases the thickness of the 
moisture films by pressing the moisture out of those areas actually in 
contact, and thus reducing the area to be covered by film. Also by 
transforming the films surrounding individual soil grains into films sur¬ 
rounding clusters the area to be covered by the film is decreased. The 
same factors operating in increasing nitrification in compact soil probably 
operate in increasing nitrification in lower layers. Nitrates accumulate 
faster in the lower laters of a column, even if evaporation from the surface 
be stopped. 
• The question will very naturally arise as to whether the oxygen utilized 
in the lower depths of such samples as are here reported actually diffused 
there, or was not already contained in the freshly aerated soil. From the 
data given above it is very easy to calculate the maximum amount of 
nitrogen that could be oxidized to N 0 3 condition, provided all the 
inclosed oxygen was utilized in this process. If the soil is saturated, only 
that oxygen actually dissolved in the water or adsorbed by the soil itself 
would be available. As is well known, this is insufficient for a measurable 
accumulation of nitrate nitrogen; and it can therefore be eliminated from 
consideration. In the very compact soil, with a moisture content of 
15 c. c. per 100 gm. of soil, the air content could not exceed approxi¬ 
mately 5 c. c., the oxygen content of which could not form more than 
approximately 1.85 mgm. of N 0 3 . In Tables IV and Vit will be observed 
that under such conditions the NO s formation was more than 10 times 
this amount. With 20 c. c., in which there must have been a negligible 
quantity of air, the N 0 3 accumulation was in some instances more than 
20 times that calculated for 15 c. c. of moisture. Similar calculations 
can be made for the other degrees of compactness, and in all instances it 
will be found that the N 0 3 formed was many times in excess of that pos¬ 
sible from the inclosed oxygen. 
The above calculations have been verified experimentally, in that 
controls have been run with each experiment to show that the nitrate 
gains could not be due to the oxygen contained in the soil when the 
experiment was set up. The results reported in Table VI are typical. 
Here is given, in parallel columns, the quantity of N 0 3 accumulation in 
open and stoppered bottles when both were filled with soil. With low 
moisture content and loose conditions nitrification, to a limited extent, is 
possible in absence of aeration. However, with a very compact soil even 
containing low quantities of water or with a high moisture content even 
in loose condition, the quantity of inclosed oxygen is insufficient to 
prevent decreases in N 0 3 , In no instance does the quantity formed 
tinder inclosed conditions equal that when aeration was possible. 
