io6 



BIOLOGICAL PROBLEMS 



less than 37 million tons of farmyard manure and 

 well over a million tons of artificial fertilizers. Prior 

 to the war the total amounts used each year were: 



When these amounts of artificial fertilizers are 

 divided out per acre of cultivated land, they are seen 

 to be less than is given in Belgium, Luxemburg, or 

 Germany, where the figures are: 



AMOUNTS OF FERTILIZER USED, IN HUNDRED- 

 WEIGHTS PER ACRE, PRE-WAR CONDITIONS 



1 No good estimate can he made of the amount of guano, bones, and other 

 materials used as fertilizers. 



-0.7-0.9, according to the estimate of the International Institute, Rome. 



The potassic fertilizer is reckoned as containing 25 per cent K 2 O. An 

 estimate for British and German consumption, closely agreeing with the above, 



