228 FertUuers

A gain cf fertility by the rotation system.
Assuming that the increased yield of com is 20
bushels^ with accompanying stalks, of wheat 10 bushels
per acre, of oats 15 bushels, of clover § ton and of
timothy § ton, the amounts applied will be practically
sufficient to furnish all of the potash contained in this
increase, and more than sufficient to meet the demands
for phosphoric acid. That is, by this system there has
been applied in the materials 30 pounds of nitrogen, 64
of phosphoric acid and 80 of potash. While, if this in*
creased crop was secured, the following amounts would
be required: 71 pounds of nitrogen, 31 of phosphoric
acid and 79 of potash. The considerable amounts of
plant-food contained in the yard manure, and the gain
from the roots and stubble of the clover, serve to supply
the balance of nitrogen required, and to provide a store
of unused residue for future crops.
The method, if adopted, would be more rational, and
likely to result in more satisfactory returns than the
one now generally practiced, namely, to purchase with-
out particular regard to the character of the materials
furnishing the constituents, or their proportions, and
to apply, on the average, even less per acre than is
here recommended. Assuming that 200 pounds to the
acre of the average corn fertilizer, showing a composi-
tion of 2.5 per cent nitrogen, 8 of phosphoric acid and
5 of potash, were applied only to the crops com, oats
and wheat, omitting both clover and timothy, there
would have been added 15 pounds of nitrogen, 48 of
phosphoric acid and 30 of potash, amounts of each too
small to provide for a large increase in crop, provided all
were needed.
