14 
Bulletin 99. 
slightly branching, but able, in our soils to attain to a depth of from 
9 to 12 feet, even through soil so firm that a pick is necessary in or¬ 
der to remove it. The largest, most branching portion of this root 
system is at the point of its greatest depth or nearly so. This sys¬ 
tem is marvelously free from fibrous roots, though under special 
but easily explained conditions there may be a fair abundance of 
what may be termed fibrous roots. For our present purpose we 
may waive the question of the relative ability of these two plants, 
the wheat and the alfalfa, to obtain food from sources which may 
yield it slowly or with great reluctance, and simply consider the 
amount of soil which they respectively lay under tribute, consider¬ 
ing that the whole of the soil from the surface to the maximum 
depth attained by the respective root systems is involved. Using 
this assumption as our basis, we see that no part of the soil would 
be laid under a relatively heavier tax by the alfalfa than by the 
wheat, because the alfalfa feeds to a depth at least three times as 
great as the wheat plant. Our assumption, however, is not jus¬ 
tified by what we know of the roots of the alfalfa, which form a 
cone-shaped system whose base is from 9 to 12 feet from the sur¬ 
face. The first few feet of the root may consist of a single tap root 
and cannot possibly come in contact with more than a small fraction 
of the soil reached by the smaller roots of the deeper portion of the 
system. The larger portion of the tap root near the surface, even 
if it is as active in gathering food as any other portion of the root 
system, can only gather a comparatively small portion of the food 
used by the plant. This justifies us in using the term so frequently 
heard, characterizing the alfalfa as a deep feeding plant. These 
considerations also justify the popular expression that the alfalfa 
rests the land, meaning, of course, that portion of the soil pre¬ 
viously exhausted by the wheat. The correctness of this assertion 
is not in the least affected by the apparently contradictory fact, that 
a four ton crop of alfalfa hay removes from the soil a trifle over 
three times as much plant food as a fifty bushel crop of wheat, in¬ 
cluding the straw. 
There are some interesting facts relative to this question, and 
while certain reservations ought to be made, we can still, with a fair 
degree of accuracy, state that the alfalfa obtains its food very 
largely below the depth to which the wheat root can penetrate. This 
explanation may not be a complete one, but it answers two ques¬ 
tions which are frequently asked: First, Is alfalfa a heavy feeder? 
To which the answer is, yes. Second, How does it rest the soil? 
To this we offer the following answer: By feeding below the 
depth had in mind by the questioner. 
EFFECTS OF ALFALFA DUE TO OTHER CAUSES. 
We will now turn to some other facts which cannot be omitted 
