ly of manure should not be plowed down wherever the
breaking-plow brings soil to the surface that is deficient in humus. In
the latter case the manure always should be used as a top-dressing, and
should be evenly spread and well mixed with the surface soil. It is
needed there far more than it can be needed farther down. The surface
soil always should have a high content of organic matter.

Heavy Applications.--When the farm supply of manure is small,
applications should be light. The manure should not be the dependence
for plant-food on a part of a field, or a single field of the farm,
under such circumstances. It is more profitable to give a light
dressing to a larger area. The manure is needed to make a fertilizing
crop grow, and a very few tons per acre can assist greatly, when
rightly used. The manure is needed to furnish bacteria to the soil, and
a small amount per acre is useful for this purpose. Always there is
temptation to use all the manure on a field convenient to the barn, and
to concentrate it on a sufficiently small area to make a good yield
sure. The loss to the farm in this method is heavy. The thin spots and
the thin fields have first right to the manure as a top-dressing, and
six tons per acre will bring larger returns per ton than twelve tons
per acre. At the Pennsylvania experiment station the land receiving ten
tons of manure per acre in the common four years' rotation of corn,
oats, wheat, and mixed clover and grass gives added returns of $1.63 a
ton, while an application of eight tons pays $1.85 a ton, and a six-ton
application brings the value per ton up to $2.41. These applications
are made twice in the four years.

Reenforcement with Minerals.--A ton of mixed manure in the stable
contains about ten pounds of nitrogen, five pounds of phosphoric acid,
and ten pounds of potash. This makes the percentage of nitrogen and
potash the same, while the percentage of phosphoric acid is only half
as high. A commercial fertilizer of such percentages would be esteemed
a badly balanced one. Certainly the phosphoric acid should be
relatively high, as this constituent of plant-food runs low in the
soil. If 50 pounds of 14 per cent acid phosphate were added to each ton
of manure while it is being made in the stable, seven pounds of
phosphoric acid would be added, making the percentage in the manure a
little higher than that of the nitrogen and the potash. A better
balance is given to the fertility. There cannot