Soil Changes Produced By Micro-organisms. 
21 
Colorado; apple orchard; clay loam; niter 3541 1328 
Colorado; apple orchard; sandy loam; 
niter. 3629 2656 
Colorado; apple orchard ; clay; niter.. 3665 5081 
Georgia; pine forest; gravelly loam. 13 22 
Oklahoma; cotton field; sandy loam. 89 841 
Washington; apple orchard; loam.. 133 841 
Ohio; corn field; clay loam..,. 266 620 
California; vineyard; clay loam.. 513 loss 
Virginia; apple orchard; heavy clay.. 620 1107 
Kansas; sugar beet field; sandy loam. 2833 3098 
Duration of the experiment was six weeks at 28 degrees C. 
Denitrification. 
Denitrification may be defined as the partial or complete re¬ 
duction of nitrates. It is the reverse of nitrification, and from an 
economic standpoint, is to be regarded as undesirable, since there 
is an actual loss of valuable nitrate. Whereas in nitrification, 
oxygen is added to ammonia and nitrites to form nitrite- and 
nitrates respectively, in denitrification, the oxygen is taken away 
from the nitrates and they are reduced to nitrites, ammonia, and 
even to a point where free nitrogen is liberated, and oxides of 
nitrogen are formed. I11 a strictly scientific sense, denitrification 
applies only to the complete reduction of nitrates to gaseous 
nitrogen. The list of micro-organisms that can produce this phe¬ 
nomenon is a long one, and includes both bacteria and molds. 
In soil and manure, most of these develop readily in the pres¬ 
ence of air (aerobic), however, in the role of denitrifiers, they 
appear to be favored by the partial exclusion of air. A fine grained, 
close, compact soil, in other words a heavy soil, to which excessive 
quantities of fresh, strawy manure (50 to 60 tons per acre) have 
been added, presents the optimum conditions for bacterial denitrifi¬ 
cation. The free circulation of air is interfered with seriously in a 
soil of this character, and the growth of the denitrifying organisms 
is favored by the large amount of readily decomposable organic 
matter. Under such conditions, there may be a loss of nitrogen 
both from the soil and from the manure, since the bacteria, in all 
probability, will draw upon the nitrate for the necessary oxygen 
with which to liberate energy from the organic compounds. In this 
manure, the nitrates which we have been striving to restore to the 
land, and maintain there, .may be changed from valuable plant 
food into an inert gas. On the whole, the danger from denitrifica¬ 
tion under field conditions has been greatly over-estimated, and 
