Oct. 8, 1917 
Nitrate-Nitrogen Accumulation in Soil 
63 
the exchange of gases between the two must take place very rapidly. 
This is true under practically all conditions and to such depths for 
which data are available. 
So far as the writers are aware, there are no data available invali¬ 
dating the assumption that the results reported by Schloesing (12) are 
applicable to soils in general. If this be true, it would certainly seem 
with the experimental data now available, that conditions are rarely ever 
met with where there is not sufficient oxygen potentially available to 
insure maximum nitrification. Furthermore, Stoklasa (13) mentions 2 
per cent of porosity as the point below which anaerobic processes become 
active, 3.8 percent is the lowest found recorded for field conditions, and 
seldom does it fall below 15 to 20 per cent. The writers have shown 
that in a tightly compact soil with a moisture content of 15 c. c. per 100 
gm. of soil 6.33 per cent of porosity were sufficient for maximum nitrate 
accumulation at considerable depths below the surface. Therefore these 
experimental data and theoretical considerations from an entirely differ¬ 
ent point of view all tend to the same conclusions as do the original 
experimental data herein reported. 
SUMMARY 
In the experimental data submitted in this paper it has been shown 
that: 
(1) As the moisture content of a soil decreases, increasing the com¬ 
pactness from a very loose condition will increase the accumulation of 
nitrate nitrogen. 
(2) With any degree of compactness tested the optimum moisture 
content will be reached when the soil contains approximately two-thirds 
the total amount of moisture it will retain. 
(3) Aeration will be sufficient to the depth of 1 foot with any degree 
of compactness, provided the moisture content does not exceed the 
above relation. 
(4) Increasing the depth of column up to 2 feet does not, as far as 
tested, alter the above relations. In fact, the accumulation of nitrate 
nitrogen increases with increasing depth down to 2 feet, so long as the 
moisture does not exceed approximately two-thirds saturation. 
(5) Nitrate nitrogen accumulates more rapidly in unbroken soil 
columns than in pulverized soil. Aeration in a column of soil uncul¬ 
tivated for seven years is far in excess of that required to maintain 
aerobic conditions. 
It has also been pointed out that such experimental data as is avail¬ 
able, regarding oxygen relations in normal field soils, indicate that 
obligate aerobic conditions almost universally exists within the first 
foot of surface. Therefore such beneficial effect as cultivating may have 
upon biological activity can not be attributed to increased aeration. 
