CROP ROTATION AND IRRIGATION 115 



has been the custom in Argentina. Sixty per cent of t'he wheat 

 is raised under the renting system. The colonist owns nothing 

 which grim necessity does not compel him to own, and he prac- 

 tices his ruinous methods of farming until the land is com- 

 pletely exhausted. Then he fastens the bullocks and horses 

 to the carts, packed with his many children and his few mis- 

 erable pots, boxes, beds and implements, and travels until he 

 finds new fields. Mixed farming as known in the United States 

 is little understood or practiced in Argentina, and the farmer 

 is generally either a wheat grower or a maize grower. There 

 Is complaint of the methods of farming in all parts of the Re- 

 public, however, and a practice of rotating crops is already be- 

 ginning, by alternating wheat and maize, or by planting the 

 land with alfalfa after three or four years of wheat cropping. 1 

 For the best crops of wheat in Egypt, it is sown every fifth 

 year, the rotation being (1) cotton; (2) "birsen" (clover) or 

 "full" (beans); (3) wheat; (4) dura (maize); (5) "birsen." 

 A commercial success has been made of growing wheat and 

 alfalfa together on the dry uplands of North Africa. In Al- 

 geria two rows of wheat are sown 4 inches apart. A space of 

 40 inches is left between the double rows, and in this space 

 the alfalfa is sown. Wheat is sown only every other year. 

 This is of interest, as alfalfa is now the greatest American 

 fodder crop, especially in the arid southwest where durum 

 wheat is being more extensively grown. 



Experiments with Mixed Crops have been made, chiefly in 

 Canada and North Dakota. Results seem to be in favor of un- 

 mixed grain, although wheat and flax have an advantage under 

 certain conditions, as when wheat is apt to lodge, or when there 

 is a superabundance of moisture. In the latter case flax has 

 increased the yield of wheat as much as 6.5 bushels per acre, 

 in addition to giving 1.2 bushels of flax per acre. 



IRRIGATION. 



Historical. Irrigation is of prehistoric origin. Water, as 

 was shown in a former chapter, is one of the greatest essen- 

 tials of all plant growth, and it is also one of the most variable 

 quantities involved. Since the effects of these variations upon 

 vegetation appear quickly, they must have been noticed at an 

 1 U. S. Dept. Ar., Bu. of Statistics, Bui. 27 (1904), pp. 41-42, 



