Durability Of Manure
Categories:
CROP-ROTATIONS
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, whi
e 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 during the
eight years. In 1865 the plat, last manured in 1863, gave over double
the yield of the unmanured. In the following ten years its yield was a
half more than that of the unmanured. In the next ten years the yield
was a quarter more. In the next ten years it fell to 6 per cent more
than the plat that had received no manure in the beginning of the
experiment. In the following ten years it rose to 15 per cent. Here is
a lasting effect of manure for over forty years where grass was grown
continuously.