192 DRY FARMING 



trol of weeds, suggests the need for them in any good 

 rotation. Unfortunately, under dry conditions these 

 crops are often so low in yield that in the drier prairie 

 areas men will not grow them until forced to do so by 

 drifting soil or by weeds. 



(4) The lack of a suitable legume is a hindrance to 

 good rotations in many parts. Alfalfas hardy enough to 



Fig. 74. Oats on Irrigated Alfalfa Sod. 

 Courtesy Department of Interior. 



withstand the prairie winter are now available for all 

 except the higher altitudes. But the crop is so expensive 

 to get under way, and yields so little in dry years and is 

 so difficult to break up that it is not a good rotation 

 crop. Peas do well in the more moist regions but suf- 

 fer from drought in the dry belt and from fall frosts in 

 the north. Red clover is not hardy enough for com- 

 mercial use, except in favored areas and in mixtures of 

 grass. Sweet clover seems now to offer the greatest 

 promise as a rotation legume for the prairies. Hardy 

 strains of red clover may be found satisfactory in the 



