62 QUEENSLAND AGRICULTURAL JOURNAL. [1 Jan., 1898. 
NITRIFICATION OF INERT NITROGENOUS SUBSTANCES. 
This process has been known for a considerable time, and until compara- 
tively recent times this process was made use of in the artificial preparation of 
saltpetre on the so-called nitre beds. These beds were formed out of certain 
earthy matters—loam, marls,ashes—mixed with dung; they were kept moist with 
urine, and turned over frequently. Periodically they were washed out with 
water to obtain the nitrates formed. The heaps had to be kept loose to promote 
free circulation of air, as a plentiful supply of oxygen is necessary for this 
process of oxidation. A similar process takes place in the soil, and is due to 
the activity of micro-organisms. 
DENITRIFICATION OF NITROGENOUS SUBSTANCES. 
The discovery made by Wagner and Maercker, which at present startles 
all agriculturists, is the fact that dung contains bacteria which are able to 
destroy nitrogenous substances under liberation of free nitrogen, which, of 
course, escapes to the air. 
Dung contains nitrogen in the various forms already mentioned ; the chief 
part, however, about 80 to 90 per cent., is in the inert albuminoid form very. 
slowly, if at all, assimilated by plants. The remainder of the nitrogen is in the 
form of ammonia, nitric acid, and the easily decomposed amides, which are all 
available to plants at once. The nitrogen contained in liquid farmyard manure, 
chiefly urine, is principally in the form of urea, which is also readily decom- 
posed and easily available. 
Maercker showed this great difference in the assimilability of the nitrogen 
by experimenting with plants grown in pots filled with soil which contained an 
abundance of phosphoric acid and potash. Oats grown in this soil without 
nitrogen being added yielded 44-82 grammes of grain and straw. Another pot, 
with an addition of 1°5 grammes of nitrogen in the form of nitrate of soda, pro- 
duced 12837 grammes, corresponding to an increase of 186 per cent. By 
supplying 2°25 grammes of nitrogen to soil in the form of two different samples 
of horse-dung, one of cow-dung, and one of ox-dung, the respective yield of 
grain and straw was 85°91, 23°38, 41°65, 46-80 grammes. In the first three 
cases, the yield was reduced—in one instance as much as 48 per cent. The 
ox-dung produced an increase of only 4 per cent. Experiments with white 
mustard gave similar results. 
Wagner experimented also with white mustard, and, like Maercker, repeated 
each experiment three times, and all the results agreed very closely. The yield 
of mustard was 1:6 grammes in soil without nitrogen, and 35°6 grammes in soil 
supplied with 2 grammes of nitrogen in the form of nitrate of soda. When 
supplying the same amount of nitrogen. to the soils in the form of cow-dung 
and horse-dung, the yield was only ‘5 and ‘4 grammes respectively, corresponding 
to the heavy drop in the yield of 69 and 75 per cent. Analyses of the plant 
showed that the crops had appropriated absolutely no nitrogen from the dung, 
and the plants contained even less nitrogen than the plants grown without any 
added nitrogen, thus showing that even the ammoniacal and amide nitrogen, 
which is always present in small quantities in the dung, was not used up by 
the plants, but was made inoperative. 
Further experiments made by Maercker showed that -75 gramme of 
nitrogen, added in the form of nitrate of soda or urea, more than doubled the 
yield when applied to soils containing no dung; the yield, however, was very 
much reduced if applied to soils containing also dung. The larger the amount 
of dung contained in the soils, the greater the loss of nitrogen. 
Wagner found that by using nitrade of soda in soils containing no horse- 
dung as much as 60 per cent. of the nitrogen applied was recovered in the 
increased crop of mustard, whereas with a light dressing of horse-dung only 
80 per cent. of the nitrogen applied was recovered. Horse-dung similarly 
affected the nitrogen added in the form of ureaand chopped lucerne. In other 
extensive pot experiments with oats, various nitrogenous manures were applied,. 
