CULTIVATION OF WHEAT 59 



number of variations survive. In cultivation itself, as above 

 defined, there is no selection. 



The principal effect of cultivation on the growth of wheat is 

 through its influence upon the physical condition of the soil, to 

 which great importance is attached. By physical condition, is 

 meant friability or openness, capacity for absorbing and retain- 

 ing water and heat, and permeability to roots. Air, which 

 is necessary to the roots, is excluded by hard, water-soaked, 

 baked or puddled soils, and such soils are also impermeable to 

 roots. Stirring or cultivating the soil enables the air to cir- 

 culate and the roots to penetrate through it. Tillage has been 

 known to increase the yield of wheat over eight bushels per 

 acre. 1 Richardson claimed that it increased the nitrogen con- 

 tent of wheat. Generally about 50 per cent of the volume of 

 soils is empty space. That is, in one cubic foot of soil there is 

 about a half a cubic foot of space into which air and water can 

 enter. 



The Motor Power first utilized was the muscular energy of 

 man himself. Its application requires the least intelligence. 

 The abundance of human labor, and hence its cheapness, 

 coupled with a lack of intelligence to utilize other forces, are 

 conditions still existing in vast regions of the earth where it is 

 impossible for any other motor power to compete successfully 

 with man himself. India, largely using human labor, often 

 at a cost of but 4 to 8 cents per day, has been so successful in 

 competing with more civilized nations using other forms of 

 power as to assume fourth rank among the wheat raising na- 

 tions, and to be able to undersell many of them in the world 

 markets. Hand labor is used almost exclusively in raising wheat 

 in China, Japan, Siam, Syria and Colombia, and very exten- 

 sively in Egypt and parts of Greece, Spain, Mexico, and some 

 of the South American republics. 2 4 



Animal Power. The first one of the forces of nature which 

 man subdued and utilized in relieving himself of . some of the 

 drudgeries incidental to agriculture was that of the domesti- 

 cated beast. There are no marked periods of progress in this. 

 Animal power is by far the most universally used in agricul- 

 tural operations. As a rule, oxen are found in communities 



1 s. c. Bui. 56, p. 12. 



2 U. S. Daily Consular Repts., Oct. to Dec., 1903. 



