The Yale expositor., 1901-08-16
Notes on soil Nltrnren.

the most advanced investigators In the
domain of agricultural science. Lit
tie by little the puzzles have been made
plain, but the progress has been sur
prisingly slow. generation of think
ers makes but little Roadway. The ag-
gregateis, however, large. Nitrogen has
so many forms and so many changes
that it has proved a most difficult ele-
ment to bind and analyze. To follow its
transformations and learn the causes
OF those transformations have proven
still more difficult. The experimenters
start out to prove one thing relative
to soil nitrate, and find, before they
finish their tests, that they have proved
a part of something else. A vast
amount of experimenting along these
lines remains to be done, even to reach
a few certain conclusions.
For years the Wisconsin station has
been carrying on experiments having
in view the determining of a number
Of things relative to nitric nitrogen in
the soil. Among the things to be
found out were ~ the varia5leness
OF nitric nitrogen in the soil during
the growing season; co the difference
in amounts of nitric nitrogen in fal!ow
soil and soil in crops; (3) the infu-
ence of cultivation on the formation
OF this element; "a the influence OF
nitrates on the thrifty versus The yell
low and withered plants; 90 the va
riableness of the nitric supply N and
between rows of corn; CO. the differ
ence in supply of nitrogen in soil and
well water; % the discovery of an
accurate method Of determining the
nitric nitrogen in soils.
A few of the conclusions reached
may be summarized as follows: In
dividing the soil into foot layers to a
depth of four feet, the greatest changes
were found in the foot next the sur
fact. In this top layer the supply of
nitric nitrogen varied greatly through
out the growing season. The amount
in the spring was small, but increased
rapidly during the first three months
of growth, reaching their maximum
amount in June or July, according to
the kind of crop being grown upon
the fields. During July, when crops
are growing most vigorously, the nitric
nitrogen rapidly decreases till the first
part of August, after which it remains
quite constant in the surface layer.
In the other layers little change is
observed.
The value of frequent cultivation is
apparently in the more rapid accumu-
lation of nitric nitrogen rather than in
the mere conservation of moisture. 1t
was found that stirring the soil once
per week, as compared with the STIR
ring of it once in two weeks, left the
soil stirred, after 81 days, with OSLO
as compared with 5301 pounds of nj.
trio nitrogen per million of dry soil.
In the second series of experiments
which covered 25S days the soil stirred
once per week had acquired a mean
of 225.41 parts and that once in two
weeks 1879 parts per million of dry
soil showing the largest gains with the
more frequent cultivation. 1t was
found that stirring the soil to depths
of one inch two inches, three inches
and four inches during an interval of
25S days resulted in an increasing
amount of nitric nitrogen until the
three inch depth was passed, but that
cultivation four inches deep gave
smaller nitrifcation than the three
inch depth did. Thus in a soil stirred
once a week the action of the forces
that create nitric nitrogen is stimulated
exceedingly. The increase of these nj
trates results in a decided increase in
growth of plants. all of which has
fn
ton of the water supply.
The amount of available nitrates af-
fects the thrift and color of the leaves. |
From the experiments referred to we
draw the conclusion that leaves turn
sere because the supply of nitrates Is
virtually cut off; and this lessened sup
ply Of nitrates is provision of ma
ture to assist in the elaboration OF |
seed. The amount Of nitric nitrogen
left In the surface foot of soil before
crops begin to turn yellow for lack
of available nitrogen becomes very
small, the amount found being .213
parts per million where oats were yet
green, and .025 parts per million where
they were turning yellow. In corn it
was found as low as .95 parts where
corn was green. and 10 parts per mil
lion where 1t was strongly yellow. The |
rapid growth of stalks just before ma
turity apparently has the result of TAX
ing out of the soil about nine-tenths |
of the nitrates available in the sur
face soil.
The amounts of nitric nitrogen were
found greatest between the rows of
corn, as they were coming into tassel, |
and least directly beneath hills, except
in the surface six inches, and in the |
fourth foot where the relations were
slightly reversed. The amounts of nj |
trio nitrogen are less in the deeper
ground water wells of this vicinity |
than in the soil, moisture of the fourth |
foot, the nitric nitrogen being only
about one-third of the amount. Obser- |
vations indicate that when the textural |
equilibrium of soils is destroyed IN
the presence of salts in solution, |
re1occulation and reorganization of the |
coil NAV falxe mt of colution a norfior /