792 
Supplement to the "Tropical Agriculturist." [May 2, 1904. 
out these bacteria everything would have come 
to a staudstill long ago, for unless decay takes 
place and the decomposed elements are re- 
arranged into deflnice nitrogenous salts no plant 
is able to use them. Thus it will be seen that 
certain bacteria in the soil play as important 
a part in the food supply of the earth as do 
the animals and larger plants upon which we 
•think we are so dependent. 
It is hardly necessary to refer to the vast waste 
of nitrogenous material that is involved in modern 
sewerage methods. Millions of dollars' worth of 
nitrogen which would naturally return to the 
soil under the action of nitrifying bacteria is 
every year carried off in various waterways and 
ultimately reaches the ocean, where, of course, 
it is of no benefit to man. More than fifty 
years ago Liebig said on this subject: — 
" Nothing will more certainly consummate the 
ruin of England than the scarcity of fertilizers. 
It means the scarcity of food. It is impossible 
that such a sinful violation of the divine laws 
of nature should forever remain unpunished, 
and the time will probably come for England, 
sooner than for any other country, when with 
all of her wealth in gold, iron, and coal she 
will be unable to buy the one-thousandth part 
of the food which she has during hundreds of 
years thrown recklessly away," 
A third great source of nitrogen lo^s is through 
the action of a group of bacteria which have 
the power of breaking down nitrate?, depriv- 
ing them of oxygen, and reducing them to 
ammonia or nitrogen gas, when they are, of 
course, unavailable for plant food. This process 
of denitriflcation, while very useful in the septic 
tank, which is the most sanitary method of 
sewage disposal, is the source of considerable 
loss to the farmer, and manures may dften be 
rendered practically worthless by the action of 
these bacteria. 
Other means by which nitrogen is lost so far 
as plant foods are concerned, are the washing 
out of nitrogen salts from the soil and the 
burning of explosives which are largely composed 
of some nitric salt that would be directly valuable 
to the vegetable kingdom. Tl;e action of nitrate 
of soda, or saltpeter, has been studied experi- 
mentally, and it is known that up to a certain 
maximum about 23 pounds of nitrate of soda 
will yield an increase of one bushel of wheat 
per acre. Thus, when hundreds of thousands 
of tons of explosives are used in wnging war, 
every battle liberating nitrogen which, if applied 
to the soil, would increase the yield of wheat 
by thousands of bushels, the actual cost of war 
should be estimated at considerably more than 
is usually calculated ; and if there is soon to 
be a nitrogen famine, war becomes more serious 
than ever before. 
With all of these destructive forces at woik 
and nitrogen being liberated on every hand, it 
is no wonder that thinking men have become 
alarmed at the prospect, and have endeavoured 
in e^ery way possible to discover some means 
of increasing the world's supply of this most 
necessary element. 
The most valuable compound containing suffi 
cient fixed nitrogen to be used in any quantity 
as a nitrogenous fertilizer is the nitrate of soda, 
already referred to as the basis of so many 
explosives. This salt occurs naturally in certain 
regions of Chili and Peru, where for countless 
centuries the continuous fixation of atmospheric 
nitrogen has been carried on by bacteria. Un- 
fortunately, however, like any other mineral 
supply in the earth, the quantity is limited, 
and although it is difficult to get accurate 
estimates of the amount of nitrate remaining 
in the beds, authorities seem to agree that at 
the present rate of exi,ort the raw material will 
all be exhausted within from forty to fifty 
years. To show how much more rapidly this 
supply is being exhausted than was thought 
possible forty years ago, it is only necessary to 
state that iu 1860 all estimates showed that the 
amount of nitrate of soda theu known would last 
for nearly fifteen hundred years. The demand 
has rapidly increased, however, and although 
the output is controlled, there is annually con- 
sumed in the world's markets nearly 1^ million 
tons of nitrate of sodn, representing a value of 
about 1100,000,000. Of this amount, the United 
States requires about 15 per cent., and it is 
by far the most expensive fertilizer that is iu 
use by the farmer. 
In addition to the nitrate of soda beds there 
have also been large deposits of guano, which 
have served as one of the principal sources of 
nitrogen. The greater part of the guano beds 
are now- completely exhausted, however, and 
although new deposits are occasionally discovered 
they are of such limited area, or of such a low 
percentage of nitrogen, as to have practically 
no effect upon the available nitrate supply. 
There are certain other chemical salts which 
furnish a limited amount of nitrogen, such as 
the product which remains from the distillation 
of coal in the process of gas making, but all 
of them are obtained in such comparatively 
small quantities that they are not worth takinc 
into consideration when one realizes the enor- 
mous amount of nitrogenous fertilizer necessary 
to replace the combined nitrogen which is ainiually 
removed from the soil in one way or another. 
Ever since the importance of increasing the 
combined nitrogen supply has been realised, men 
of science have naturally turned to the atmo- 
sphere as being the most promising field for 
experiment aud the one most likely to even- 
tually solve the whole problem. When it is 
remembered that nearly eight-tenths of the air 
about us is nitrogen, and the plants are able 
to obtain their entire source of carbon from a 
gas which is present in the comparatively small 
production of one-tenth of one per cent,, it 
seems almost incredible that there should be 
any more difBculty about a plant's nitrogenous 
food than about its supply of carbon dioxid. 
Since it seemed so well settled, however, that 
plants could not use nitrogen as a gas, the 
chemists and physicists have made every effort 
to devise some mechanical means of making 
this elenjent available in a combined form. It 
