of the field, and 4,725
lbs. on the other half; and it is not at all surprising that on the
latter half there should be a greater growth of clover and clover-roots.
To suppose that during the six or seven weeks while the clover was
maturing its seed, the clover-plants could accumulate 1,375 lbs. of
nitrogen, is absurd."

"But Dr. Voelcker," said the Deacon, "states, and states truly, that
'more leaves fall on the ground when clover is grown for seed, than when
it is mown for hay; and, consequently, more nitrogen is left after
clover-seed than after hay, which accounts for wheat yielding a better
crop after clover-seed than after hay.'"

"This is all true," said the Doctor, "but we can not accept Dr.
Voelcker's analyses as proving it. To account in this way for the 1,375
lbs. of nitrogen, we should have to suppose that the clover-plants, in
going to seed, shed _one hundred tons_ of dry clover-leaves per acre!
The truth of the matter seems to be, that the part of the field on which
the clover was allowed to go to seed, was naturally much richer than the
other part, and consequently produced a greater growth of clover and
clover-roots."

We can not find anything in these experiments tending to show that we
can make land rich by growing clover and selling the crop. The analyses
of the soil show that in the first eighteen inches of the surface-soil,
there was 6,550 lbs. of nitrogen per acre, on one part of the field, and
10,300 lbs. on the other part. The clover did not create this nitrogen,
or bring it from the atmosphere. The wheat with which the clover was
seeded down, yielded 40 bushels per acre. If the field had been sown to
wheat again, it probably would not have yielded over 25 bushels per
acre--and that for want of available nitrogen. And yet the clover got
nitrogen enough for over four tons of clover-hay; or as much nitrogen as
a crop of wheat of 125 bushels per acre, and 7-1/2 tons of straw would
remove from the land.

Now what does this prove? There was, in 18 inches of the soil on the
poorest part of the field, 6,550 lbs. of nitrogen per acre. A crop of
wheat of 50 bushels per acre, and twice that weight of straw, would
require about 92 lbs. of nitrogen. But the wheat can not get this amount
from the soil, while the clover can get _double the quantity_. And the
only explanation I can give, is, that the clover-roots can take up
nitrogen from a weaker solution in the soil than wheat-roots can.

"These expe