be any loss in this
purchased plant-food, if the stable floor is tight. Fermentation cannot
drive it off, and when applied to the soil it is tightly held.
Practically no phosphoric acid is found in drainage waters. Eight tons
of manure thus reenforced would contain the same amount of plant-food
as a ton of fertilizer having 4 per cent nitrogen, 5 per cent
phosphoric acid, and 4 per cent potash. The addition of the 50 pounds
of acid phosphate per ton does not bring the phosphoric acid content up
as high relatively as in most commercial fertilizers, but it helps. The
total amount in the eight tons manure may be sufficient, and the
greater part of the total has sufficiently immediate availability,
while the manure must undergo decomposition, and some of the nitrogen
and potash does not become available within the year.

Durability of Manure.--Tests of the durability of manure in the soil
involve some uncertain factors, but we are interested only in the
effects of applications. These effects may continue for a long term of
years, and an example will illustrate. Land may be too infertile to
make a good clover sod. If a good dressing of manure be given half the
land, affording proper conditions for making a sod, the result will be
a heavy growth of clover, while the seeding on the unmanured half will
be nearly a failure. If no manure or fertilizer be used in the
crop-rotation, the probability is the manured portion of the field will
again make a fairly good sod. How much this success may be due to the
remains of the manure, and how much is attributable to the effect of
the clover and to better bacterial life introduced and favored by the
manure, no one knows. Probably the greater part of the benefit comes
only indirectly from the manure applied three or four years previously.
Half of the field may thus be lifted out of a helpless state and remain
out of it for a long term of years, while the other half grows only
poorer. A probable illustration of this lasting indirect effect may be
seen in one of the plats in the soil fertility experiments on the
Pennsylvania experiment station farm.

Experiments at the Rothamstead station, England, show some lasting
results from applications of manure. Director Hall cites the case of
one plat of grass land which was highly manured each year from 1856 to
1863, and has since been left unmanured. In 1864 this plat gave double
the yield of an adjoining plat which had been left unmanured durin