56 
Journal of Agricultural Research 
Vol. XI, No. a 
It will be observed that nitrification was much more vigorous in un¬ 
broken soil in natural position down to a depth of 8 inches than in the 
sieved soil. Below this depth there was a decrease, indicating insufficient 
aeration. This did not occur in sieved soil. It should be remembered, 
though, that this soil at such a depth has never been cultivated and also 
that the percentage of organic matter is low and the percentage of clay 
high. These factors, coupled with the fact that the soil contained 28 c. c. 
of water per 100 gm. of soil, produced practically saturated conditions 
in the lower layers. When the column was inverted, air could not 
penetrate the lower layers in sufficient quantity to prevent denitrification 
a few inches below the surface. It will also be observed that the sieved 
soil column when inverted gave a higher nitrate accumulation than it 
did in its normal position. All these facts are in accord with the ex- 
periments already given. 
In addition to the experiments just mentioned, others have been 
carried out upon a soil that has not been cultivated for seven years. 
Columns of soil 5 inches in diameter and 7 inches long were taken by 
driving a sharp edged cylinder into the soil. These were easily trans¬ 
ferred, without even cracking, to anaerobic jars through which a current 
of moist air could be drawn. At the same time 100 gm. samples of the 
same soil were incubated under as favorable conditions as possible. 
The quantities of nitrate nitrogen accumulating under such conditions 
are, of course, small, because of the absence of added nitrogen. Neverthe¬ 
less the gains were greater in the unbroken column in every instance. 
In addition, in order to see whether oxygen could diffuse through such 
soil columns in excess of that required by the normal activities of the 
organisms in the* column, the following experiments were planned and 
carried out. Below an unbroken column 5 inches long were placed 
2 inches of sieved soil containing ammonium sulphate and calcium 
carbonate. The column was then pressed down upon the loose soil 
and the space surrounding it filled with melted paraffin. 1 This ran into 
all cracks, etc., made in transferring the column from field to jar, thus 
making conditions such that all oxygen reaching the loose soil below had 
to pass through the column. Another 7-inch-long column was well 
moistened over the bottom and lower sides with a solution of ammonium 
sulphate and then dusted with calcium carbonate. The column was 
then placed in a jar and melted paraffin poured around to fill all space 
at bottom and sides. In this instance there was no method of controlling 
the concentration of ammonium sulphate in the outer layers of soil, 
and it is possible that it was sufficient to retard nitrification. In 
both instances the gain in nitrate was far in excess of that in untreated 
1 Since these experiments were carried out, the senior writer has called attention to the danger of the 
use of paraffin in such experiments. (Gainey, P. L. effect of paraffin on the accumulation of 
ammonia and nitrates in the son,. In Jour. Agr. Research, v. io, no. 7, P- 355-364* Literature cited, p. 
363-364. 1917.) In these experiments, however, the paraffin would probably tend to eliminate rather 
than to accentuate the differences to which attention is called. 
