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THE FIXATION OF ATMOSPHERIC NITROGEN. 
The Fixation of Atmospheric Nitrogen. 
By F. H. CAMPBELL, D.Sc. 
(Member of the Special Committee on the Nitrogen Requirements of Australia.) 
Like oxygen, the other main constituent of the atmosphere, nitrogen 
is essential to animal and vegetable organisms. Unlike oxygen in the 
uncombined condition, nitrogen is available to them in special cases 
only. 
Until the end of last century the requirements of the agriculturist 
were met without difficulty by the suppliers of nitrogenous an‘mal 
wastes, of ammonium sulphate, and Chilian sodium nitrate. But, as 
was pointed out by Crookes and others, the world was living on its 
capital, and with the exhaustion of the Chilian fields, which now yield 
58 per cent. of the fixed nitrogen produced,.the demand for nitrogenous 
fertilizers would far exceed the supply. Since that time several develop- 
ments have occurred, which have postponed the day when the world will 
depend solely upon chemically-fixed nitrogen. The proportion of the 
world’s coke made in by-product recovery ovens has much increased, 
and the discovery of new deposits and improved methods for treating 
low grade caliche have caused a revision of the estimate of the probable 
life of the nitrate deposits; it has been increased from 20 to, at least, 
100 years. The position, however, is unaltered fundamentally, and the 
time is approaching when it will become imperative to draw upon the 
atmosphere for our supplies of nitrogenous fertilizers. 
Apart from peace demands, which depend to a great extent on 
prices, the future of the industry is assured. No great Power, with 
the possible exception of Great Britain, will now venture to depend 
solely on overseas raw material of nitric acid and the explosives derived 
from it. Had it not been for their faith in the capability of synthetic 
processes to replace imported nitrate it is unlikely that the Germans 
would have brought about war when they did. They hoped for and 
expected speedy victory, but caleulated on a long war. 
Under normal conditions, plants obtain the nitrogen required by 
them as a result of a series of changes caused by bacteria. The protein - 
matter contained in animal or vegetable remains is converted into 
ammonia, the ammonia into nitrites, and these into nitrates, in which 
form the nitrogen in the soil solution is absorbed through the rootlets 
and built up into proteins by the plant. Animals using the plants for 
food still further change the material, and animal proteins result. 
Carnivorous animals obtain their nitrogen from plants at second hand. 
With the exception of one genus—the leguminose—all plants depend 
for their nitrogen on the cycle of changes described. Healthy peas, 
beans, wattles, &¢., have growing upon their roots saprophytic 
organisms, which are capable of working up atmospheric nitrogen into 
a form assimilable by their hosts. This fact is at the basis of the long 
established custom of growing and ploughing in a green crop of some 
legume. As far as is known at present, there is no other natural 
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