USES OF LAND 



163 



It has been pointed out above that an increase in the crop yields 

 per acre relieves the tax upon the area of productive land. The 

 following table shows that improvements have recently taken place 

 in the yields throughout the world of the two more important 

 cereals not available directly for food animals. 



AVERAGE PRODUCTION OF WHEAT AND OF OATS IN BUSHELS PER 

 ACRE FOR THE YEARS 1905-9 AND THE YEARS 1910-14 

 IN THE WORLD AND IN SOME OF THE LEADING 



COUNTRIES. 1 



In the onward march of cereal cultivation in the leading countries, 

 including especially those of Central and Eastern Europe, striking 

 changes have taken place in the character of the animal industries. 

 As will be shown later, it is the nomad sheep that has suffered most 

 inUhe process. 



(c) POTATOES. 



The world's total area under potato crops, which are grown 

 chiefly in Europe and North America, has increased considerably 

 in recent years, having risen from about 34 million acres in 1905 

 to over 37 million acres in 1912, for which year the total production 

 has been estimated at nearly 100 million tons. From the present 

 point of view, the interest in potato cultivation lies especially in 

 the extent to which the crop is fed to food-animals in various 

 countries. In human diet potatoes act largely as a substitute 

 for other starchy foods, of which they produce on an average a 

 considerably greater quantity per acre cultivated than cereals do. 3 



1 The figures are those published by the Internat. Agric. Inst., converted 

 from quintals per hectare to bushels per acre. 



2 Decrease due to droughts and crop failure in 1910 and 1911. 



8 The weight of the potato crop per acre is normally at least seven times 

 that of the wheat (exclusive of straw) produced under the same conditions, but 

 the former contain more water. The percentage of dry matter in wheat 

 is at least four times as great by weight as that in potatoes, and the dry matter 

 in the former has a higher nutrition value per unit. 



In earlier times the masses of the European population lived mainly upon 

 coarse whole-meal bread. The modern practice of refining flour so as to retain 

 the starchy elements only, or of using potatoes partly in l^eu of bread, neces- 



