Oct. 8, 1917 
Nitrate-Nitrogen Accumulation in Soil 
5i 
With a moisture content of 12 c. c. per 100 gm. of soil the medium 
packed gave a greater nitrate accumulation than the loose. The com¬ 
pact, however, showed a somewhat smaller accumulation. In all three 
instances increasing the depth of column increased the nitrate accumula¬ 
tion, indicating no lack of aeration in the lower layers. Even at 16 
inches below the surface in the compact sample the nitrate content was 
much greater than at the surface. 
With a moisture content of 24 c. c. per 100 gm. of soil, the nitrification 
of the added nitrogen was complete, both in loose and medium-packed 
soils, except samples 2 and 3 of the medium. These samples probably 
became puddled on the surface in the course of preparation. The com¬ 
pact samples at this moisture content were saturated; hence, they showed 
no nitrate accumulation except at the surface of No. 4. 
At a moisture content of 36 c. c. per 100 gm. of soil, the nitrification 
was complete in loose samples at all depths. The medium-packed sam¬ 
ples were saturated at this moisture content, and only slight nitrification 
took place, even in surface soil. It was impossible to set up the compact 
sample with this high moisture content. 
The very compact samples 3 and 4, containing 24 c. c. of water per 
100 gm. of soil, and the medium compact samples 2,3, and 4, containing 
36 c. c. water per 100 gm. of soil, all showed heavy gas formation, which 
resulted in the breaking and pushing upward of the columns at different 
places, the former two near the bottom, the latter three near the top. 
It is evident from this that there was little or no gaseous exchange even 
at the high gas pressure necessary to move the tightly packed columns 
of soil. Water stood on top of the medium-packed samples 2, 3, and 4. 
In Table V are reported other experiments in which the moisture con¬ 
tent and degree of compactness were varied. These samples were con¬ 
tained in glass cylinders and incubated in moist chamber at room tem¬ 
perature for 16 days. The period was reduced in order that an analysis 
might be made before nitrification was complete. Nitrification was so 
active, however, that even in this short period it was complete in many 
instances. To all samples 0.5 gm. of calcium carbonate and approximately 
25 mgm. of nitrogen as ammonium sulphate were added per 100 gm. of 
soil. 
The quantity of nitrate nitrogen found in those samples containing 
10 c. c. of water per 100 gm. of soil was too small to be of any significance. 
With a moisture content of 15 c. c. per 100 gm. of soil, compacting slightly 
decreased the nitrate accumulation; however, in all three degrees of 
compactness the nitrate content increased with increasing depth of col¬ 
umn. With 20 c. c. of water per 100 gm. of soil, the nitrification was 
complete in the lower layers of both loose and medium packed, while 
there was an abundance of ammonia in the surface soil of both. In 
the compact sample there was a maximum nitrification at 2 to 4 inches 
deep, below which the accumulation decreased with the increasing depth. 
7766°—17 - 2 
