INOCULATION AND NITROGEN. 235 



conclude, however, that alfalfa used in any way is 

 a soil builder. There is reason to suspect that al- 

 falfa is one of the most energetic searchers after 

 potash and phosphoric acid known to the soil. The 

 roots go deeper, penetrate more, dissolve more than 

 those of most plants. 



Thus if the alfalfa is all sold off from the farm 

 it may become steadilj' poorer and poorer. It is 

 certain that it would be poorer in mineral elements. 

 There have been instances under the writer's ob- 

 servation where the land has grown alfalfa continu- 

 ously for some years and nothing returned, where 

 after a time it would not grow alfalfa any longer, 

 nor anything else very well. Exhaustion of avail- 

 able phosphorus would seem to be the most rea- 

 sonable explanation of this phenomenon. In some 

 instances where alfalfa has grown well for some 

 years and then failed it has been impossible to re- 

 establish it on the same land. This has occurred 

 where hay has been sold off and nothing returned 

 to the soil. 



Alfalfa is a vigorous soil enricher, provided the 

 forage is fed on the farm and the manure religiously 

 returned to the land, not necessarily to the very field 

 where the alfalfa grew, but to some adjoining field. 

 Thus the one field builds another, the two may be 

 set in alfalfa after a time and they will build a third 

 and in this way through the magic of alfalfa roots 

 a whole farm may be redeemed from the scourge of 

 poverty and barrenness. ' Thus may vast stores of 

 nitrogen be gathered. One may need to buy phos- 



