Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1915-04-20
Water Supply for Crop Growth.
AMOUNTS NEEDED FOR PRINCIPAL CROPS
AND HOW PRODUCED.

Il
| AND HOW PRODUCED.
/ Harold 8. Osler, Assistant Professor Of Agron
| omy, at Farmers Week.
| The ability of plant machinery to do
work depends largely upon four factors;
namely, heat, light, food and water.
Too much plant food may result in de-
veloping an unbalanced or unsymmetri
cal plant and reduce its resistance to dis
ease. Potatoes with large growthy tops
are more susceptible 10 blight. A soil
saturated with water is not conducive to
good root development which is Deces-
sary for good production. The farmer
may not be able to control heat and and
blight but be can modify the water hold
ing capacity Of the soil by tile drains in
wet land or Incorporating organic matter
to retain moisture in dry land.
Compared on the hundred pound ba-
sis of green material, fresh meadow
grass contains 60 to so pounds of water.
Red clover may contain as high as So
pounds. Plants of field corn from two
to three feet high contain 80 pounds and
at roasting ear stage, so pounds, and at
weight can be given because of the vari-
alton Of the water content OF the plant
from the time of termination to maturi-
ty. The percent of water in the grain or
seeds of plants will also vary, but usual
ly is about equally proportioned to the
water in the air-dred plant. Wheat and
rye are about IA percent each, and corn
about l2 percent. In the grains, low
water content insures better germina-
ton and allows the seeds to remain dor
mant for longer time.
In experiments it has been found that
for the addition of every pound of dry
substance, there passes off 80 parts of
water. An acre of grass which produces
2 tons of hay has approximately 3400
pounds of dry substance. II the hay ia
ID percent water, 527 tons Of water per
acre is evsporated from the growing
plants. An average crop of wheat
would be 900 pounds of grain and 1850
pounds of straw. In its production 296
tons of water would pass off. Other
grain crops will lose water by evapora-
ton in about the same proportion, other
things being equal. There is produced
from 1000 to 5000 pounds Of dry sub
stance in a so bushel per acre yield of
corn and in the production of'this crop,
there would evsporste from the leaves
one thousand to twelve hundred tons of
water, or about 20 tons per bushe of
grain produced.
An inch of rainfall per acre equals
about one hundred tons of water. Hence
the hay crop evaporates 5 IA inches.
wheat 3-5 inches, and corn 10 to II
inches of rainfall. This is only an aver
age. The amount lost through the foil.
age varies () with the kind of crop.
whether large or small leaf surface; (2)
with the character Of the plant; (3) the
size Of the crop; (4) the amount of moist
ure supplied. In very moist times, the
crop will lose less in proportion to the
amount of dry substance produced and
in very dry times, more. 1t should be
understood that the amount of water
mentioned is not sufficient supply for a
crop, but under all field conditions al
lowance must be made for some run-off
and evaporation from the surface of the
soil as we'll as the part used in the plant
structure itself.
The water is absorbed from the soil by
the very fine root hairs Of the plant
The composition and texture of the soil
influence its water holding capacity. The
roots develop best when the water sup
ply approximates q certain amount, vari-
ations being allowed for the different
plants, soil, temperature, etc. Plants
will not root deeply in wet soil and con-
sequently they suffer when the latter
dries out and the deep. rooted plants will
nn - l;ya lnpo Is tho pnil hooornoo axoosc
lively wet. A proper amount Of moisture
not only produces the greatest yield Of
both straw and grain but the growth
will be influenced so as to give maxi
mum yield Of grain with minimum
amount of straw.
When the water content of the soil is
so percent or more, or so percent or less,
of its water holding capacity, it is detr-
mental to the growth of the plant.
Ordinarily plants develop best in
soil retaining water amounting to 40 to
60 percent of its water holding capacity.
This water is held in spaces between the
soil grains 80 that the amount of water
depends upon the total amount of space
which in turn depends upon the size of
the particles. A cubic foot of sandy
soil contains about 40 percent by volume
of air space and when all this space is
filled with water, the sand will contain
% pounds of water. A cubic foot of
good wheat soil completely filled has
been found to contain "a pounds OF
water and the amount most favorable to
growth is 40 to 60 percent of 81 1-2
pounds, or IS II to 20 pounds. A cubic
foot of clay soil completely saturated
holds about 80 pounds of water so that
the most favorable condition for plant
to 21 pounds.
The character Of the soil, cultivation,
and distribution of the rainfall through
out the growing season, have their effect
upon the necessary supply.