ROTATION IN DRY AREAS 401 



to furnish humus and nitrogen in addition in all parts 

 of the dry area. 



But few objections can be offered to this rotation. 

 When the virgin lands of the prairie are first broken up 

 the grass roots are present in the soil to the extent of 

 hindering production. The hindrance is felt in the slow 

 decay of the vegetable matter. This means that in a 

 dry year less production will be obtained from such 

 lands than from the same when the original grasses have 

 reached a more advanced stage of decay. Because of this 

 it may be wise, arid usually it is wise, to try to secure 

 several crops of small grain from these lands before they 

 are laid down to grass in any form. The objection that 

 introducing grasses involves the introduction of fencing, 

 is not well taken, for live stock cannot be so well kept in 

 the arid country, or indeed in any country, in the absence 

 of a certain amount of fencing. 



Rotation that should not be followed. The discus- 

 sion of this question will consider: (1) growing small 

 grains in succession; (2) growing pastures for many 

 successive years ; (3) growing alfalfa for many succes- 

 sive years, and (4) growing small grains in any rotation 

 which does not bring them after a cultivated crop. 



The mistake of growing small grains in succession 

 in dry areas should be avoided. This does not mean that 

 the method of growing them thus will not succeed in 

 some instances, as when the precipitation is unusually 

 large. But an abnormally large precipitation can never 

 be forecasted. The Montana Experiment Station has 

 shown conclusively that a good crop is never assured 

 under such conditions of growth, and that a limited term 

 of years of such cropping will result in the production 

 of crops that are not worth harvesting. Adherence to 

 this method of crop production, especially along the 

 eastern side of the semi-arid belt, has unquestionably 



