organic matter; and, vice versa, the percentage of nitrogen is an
approximate measure of the organic matter, because nitrogen is a
regular constituent of the organic matter normally contained in
soils. Consequently if the organic matter of a soil is reduced the
supply of nitrogen is also reduced.

In the most depleted soils nitrogen is usually the most deficient
element, although it may not be the only deficiency. Thus in the
depleted "Leonardtown loam," which occupies such extensive areas of
land in Southern Maryland, near the District of Columbia, and which
has been to a large extent agriculturally abandoned after one or two
centuries of farming, only 900 pounds of nitrogen are found in the
plowed soil of an acre--that is, in 2,000,000 pounds of surface
soil, corresponding to about 6-2/3 inches an acre. This total amount
if made available would be sufficient for only six such crops of
corn as are actually produced on our best land in good seasons, and
yet it is four times as much as is contained in an equal weight of
the subsoil.

The average prairie land of the Corn Belt contains only 5000 pounds
of nitrogen in the plowed soil of an acre 6-2/3 inches deep, whereas
a 100-bushel crop of corn removes 150 pounds of nitrogen from the
soil. A simple computation shows the supply in the plowed soil to be
sufficient for only 33 such crops. Even the 100-bushel crop of corn
per acre is known to have been produced in many places on
exceptionally rich land, and yet the ten-year average yield in the
United States is only 25 bushels to the acre.

200 Per Cent for Nitrogen