f 



THE CARBOHYDRATES PRODUCED IN CROPS 119 



the same land without change, but the best yields arc obtained 

 on virgin lands, or under systems of mixed farming with 

 rotation. The yields per acre in the British Isles, and in 

 Canada, are generally about 30 bushels, but the yield in 

 some other parts of the world does not amount to more 

 than about one-quarter of that figure (see p. 206). The 

 use of nitrogenous manures for wheat is important. The 

 desirability of top dressing with such a manure as sulphate 

 of ammonia has been alluded to in Part I., Section I. 

 As a rule, wheat is not used for the industrial manufacture 

 of starch, because wheat commands too high a price. 



Maize. — Three-quarters of the world's supply of 

 maize is grown in North America, but the advantages of 

 maize are gradually becoming more and more recognized 

 in the warmer parts of the globe. It is better suited to 

 higher temperatures than wheat, and though much benefited 

 by a sufficient rainfall, is capable of developing in drier 

 situations than wheat. The actual amoimt of maize 

 yielded is, howevei, not dissimilar to that of wheat, and 

 in mediumly warm districts the two cereals compete with 

 one another. In cooler climates maize does not ripen 

 satisfactorily, though the crop is often used as green fodder. 

 The growth of maize is ver}^ rapid, four months being not 

 infrequently sufficient. As a rule, it is best grown under 

 some system of rotation, needs fairly deep and thorough 

 cultivation, and is improved by fair dressings of farm- 

 yard manure, lime, phosphates, potash, and sulphate of 

 ammonia. On the large scale it is often planted in heaps 

 three or four feet apart, so as to allow of cultivation in 

 between. The plant grows from about five to twelve feet 

 high. Much of the crop is fed to stock, a large fraction 

 husked in the field and sold for manufacturing purposes. 

 Maize is admirably suited for the manufacture of starch, 

 and in the United States of America forms the chief source 

 of all forms of that article. The composition of maize is 

 very constant at about 70 per cent, carbohydrates, mostly 

 starch, and about 4 to 5 per cent. oil. Maize germ meal, the 

 germ after extracting the oil, is used as cattle food. Gluten 



