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Equal to ammonia:
[A] I. Clover twice mown } 4,050 2,275 1,600
[B] II. Clover seeded } 5,725 4,050 2,700

Lbs.
I. Nitrogen in roots of clover twice mown } 24-1/2
II. Nitrogen in clover, once mown, and grown }
for seed afterwards } 51-1/2
I. Weight of dry roots per acre from Soil I } 1,493-1/2
II. Weight of dry roots per acre from Soil II } 3,622
Total amount of nitrogen in 1 acre, 12 inches }
deep of Soil I[A] } 5,249-1/4
Total amount of nitrogen in 1 acre, 12 inches }
deep of Soil II[B] } 8,126-1/4
Excess of nitrogen in an acre of soil 12 }
inches deep, calculated as ammonia in part }
of field, mown once and then seeded } 3,592-1/2
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[A] Equal to ammonia } 6,374-1/2
[B] Equal to ammonia } 9,867

"It will be seen that not only was the amount of large clover-roots
greater in the part where clover was grown for seed, but that likewise
the different layers of soil were in every instance richer in nitrogen
after clover-seed, than after clover mown twice for hay.

"Reasons are given in the beginning of this paper which it is hoped will
have convinced the reader, that the fertility of land is not so much
measured by the amount of ash constituents of plants which it contains,
as by the amount of nitrogen, which, together with an excess of such ash
constituents, it contains in an available form. It has been shown
likewise, that the removal from the soil of a large amount of mineral
matter in a good clover-crop, in conformity with many direct field
experiments, is not likely in any degree to affect the wheat-crop, and
that the yield of wheat on soils under ordinary cultivation, according
to the experience of many farmers, and the direct and numerous
experiments of Messrs. Lawes and Gilbert, rises or falls, other
circumstances being equal, with the supply of available nitrogenous food
which is given to the wheat. This being the case, we can not doubt that
the benefits arising from the growth of clover to the succeeding wheat,
are mainly due to the fact that an immense amount of nitrogenous food
accumulates in the soil during the growth of clover.