INOCULATION AND NITROGEN. 935 
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 steadily 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 thas 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- 
