The Idaho Republican., 1912-02-02

Second. Capillary water or that
which is held in thin film around
each of the soil particles of moist
but not saturated soil. This is the
water used by the plant in its growth.
Third. Microscopic water which is
the water held by the soil but which,
in all probability is not used by the
plant.
Only aqueo or water plants can
grow in soil containing free water.
Hence our problem is confined to the
regulation of the capillary water on
| ly, and to the conditions which gov
ern plant growth There are three
ways by which soil moisture can es-
cape:
First. BY sinking into deep soils
out of reach of the plant roots, and
escaping by under drainage.
Second. BY evaporating from the
surface.
Third. BY passing through the
plant itself in a process known as
Transportation.
Each of these losses can be gov
erned to certain extent. The first
by making lighter applications of
water at each irrigation. The Sec
ond, or surface evaporation, can be
checked by cultivating the surface
sufficient to form dust mulch, thus
closing up the openings of the ca
pillary tubes which form when the
surface soil begins to dry out. And
the third O. Transportation can be
checked by the addition of soil fer
tility or by ordinary cultivation.
Thus, the last two can be governed
by the simple operation of stirring
the surface after an irrigation.
The thought is prevalent among
farmers that a certain amount of
water must be used by a plant in or
der to produce certain weight of
dry matter. AS early as 1899 Wood
ward found that it required less wa-
ter to produce pound of dry matter
in a plant growing in rich soil
where the plant food was evenly
balanced, than in one of opposite ma
ture. Later, in 1878, German in
vestigator found that the yield of
dry matter was greatest where trans
piration was least. He also found
that the enriching of the soil ena-
bled the plant to produce dry matter
with less water.
Now the question may arise in
your minds: Why should cultivation
decrease the amount of water actual
ly used by the plant? Cultivation
permits thenair and sunshine to enter
the soil more readily, causing con-
sequent liberation of plant food,
which is equivalent in effect to the
addition of the food artificially.
That cultivation actually decreases
the amount of water used. by the
plant is shown in the results of ex-
periments conducted at the Utah ex-
pertinent station in the vegetation
house. Certain tanks were planted
to corn. An equal number of tanks
containing the same kinds of soil
were left bare for a check on the
evaporation from the surface. For
ty-eight hours after each irrigation
and then every week, half the sur
faces were cultivated while the other
half were left bare. Table No. l
shows the results.
TABLE No. l.
Cultivation VS.. Transportation
Average for three years
Pounds water used by
Soil Plant to produce l
College Loan lb dry matter
IA hours after irrigation 252
Then Weekly
None 603
Sample Clay
48 hours after irrigation ,42S
Then Weekly
None 535
Clay
4S hours after irrigation 5S2
Then Weekly
None 755
AS the soil in each set of tanks
was exactly alike, and as all other
conditions except the cultivation
were identical it necessarily follows
that the reduced amount of water
required to, produce pound of dry
matter in the cultivated pot was due
to the cultivation and it's effects.
There is, then, double reason for
cUltivating 70 crops. You not only
hold the moisture in the soil by pre-
venting evaporation from it's surface
but you make it possible for the
moisture retained to produce in some
instances more than twice as much
plant growth. This means that by
the practice of cultivation you can
make your irrigation water cover
twice as much ground.
There is marked variation in the
amounts of water required for diff
!ferent varieties of plants For ex-
ample, all other conditions being
equal, the potato plant requires more
than two and one-half times the wa
ter to produce pound of dry matter
that the corn plant requires.
Further experiments at the Utah
experiment station give us these re-
suits:
TABLE No. 2.
Relative amounts of water required
by different crops to produce
one pound of dry matter
To produce l lb. lbs. water