106 The Nitrogen Problem in Crop Production 
There is clearly no deficiency of nitrogen compounds in 
any of the above soils, but unfortunately only a small pro- 
portion of these compounds is of any value as plant food. 
One of the great problems of the future is to discover a 
means of converting the useless compounds into valuable 
material, but for the present they must be left out of account ; 
in most cases the farmer cannot get enough nitrogen out of the 
soil itself for profitable farming. 
2. Purchased manures . — The simplest of these, sulphate of 
ammonia, obtained from coal, and nitrate of soda, found in 
South America, are in such demand that many attempts have 
been made to obtain them, or similar bodies, at cheaper cost 
than at present. Enormous quantities of nitrogen exist in the 
air around us — a cubic yard of air contains enough to make 
10 lb. of nitrate of soda — and the difficulties of conversion are 
now to a large extent overcome. At least two manures are at 
present being made from the nitrogen of the air. The so-called 
“ nitrate of lime,” a basic calcium nitrate, closely resembles 
nitrate of soda in speed of action and effectiveness, while it 
promises to be better adapted to stiff soils, since it does not 
render them sticky and unkindly. The second manure, calcium 
cyanamide, which has unfortunately received the name “ lime 
nitrogen,” is more like ammonium sulphate in general action, 
though it still remains to be seen whether it will prove as 
useful on potatoes. The fact that these manures can be made 
on a commercial scale definitely dispels any fear of the 
“nitrogen famine” about which gloomy apprehensions have at 
times been entertained. 
Certain bye-products from manufacturing processes are 
also available as manure, and the amount tends to increase by 
reason of the economies necessitated by modern manufacturing 
conditions. As an instance : the great demand for vegetable 
011 has led to a number of oil seeds being brought into com- 
merce, the residues from which after extraction of the oil are 
available as manure if they cannot be used for food ; rape and 
castor meals are familiar examples. Again, the woollen fac- 
tories of the West Riding of Yorkshire turn out quantities of 
waste material which can no longer be worked up into cloth, 
and is therefore sold as shoddy, wool waste, &c.,for manure. 
Even the importation of immense amounts of foreign meat is 
not altogether bad, in this respect, for the agriculturist, since 
a certain amount is condemned and converted into manure. 
Other sources of nitrogen have not yet been fully exploited, 
e.g ., sea-weed, inedible fish, peat, &c., and, finally, immense 
amounts of nitrogen compounds, which ought to fertilise our 
soils if only the way could be discovered, are annually de- 
stroyed in our sewage works. 
