Yorkville enquirer. [volume] (Yorkville, S.C.) 1855-2006, 1909-02-19

The leaves are not entirely helpless
at such a time, however. On each side
of the tiny pores on the underside OF
the leaf Is a cell known as q guard
cell When the supply Of moisture be-
gins to fail, these guard cells shrink
up and in doing so close the openings,
thus checking evaporation. In some
plants, like corn, the leaves curl up at
such a time, thus still further lessen
ing the rate Of evaporation. OF course
when a leaf is wilted in this manner
the work Of building up plant tissues
Is seriously checked. This often hap
pens during the dry weather OF July
and August, when the soil becomes so
dry that the roots have difficulty IN
obtaining. the needed moisture. The
checking Of development which results
often reduces the yield Of corn as
much as twenty to thirty bushels per
acre and that Of other crops in pro-
portion. For every pound Of dry mat
ter in a mature plant from 300 to 800
pounds Of water have been brought
up by the roots and evaporated from
the leaves. One Of the most impor-
tant factors in the production OF a
maximum crop is the maintenance OF
a plentiful water supply within easy
reach Of the roots.
There are three classes OF water IN
the soil. The first Is known as ground
water and is that water which COL
lects in a hole dug in a wet soil or
runs off through the tile in drained
land. The second is the capillary
water and is that which is left be-
tween the soil particles after the
ground water has been drawn on.
The ground water is affected by grav-
itation, while the capillary water Is
not.
If a sample Of soil that looks per-
fectly dry is placed in an oven and
heated for some time 1t will be found
that it has lost considerably in weight,
owing to moisture being driven off.
This is the third class, or microscopic
moisture. This, Of course, Is OF no
value to the plant, since the roots
cannot extract moisture from an air
dry SOIL Neither can they use the
ground water. This Is really a dam
age in the upper two or three feet OF
soil, since it so fills the spaces that
the roots cannot get enough air.
During the rain the ground water
passing through the soil draws con-
siderable air with 1t. AS soon as the
soil becomes saturated, however, so
that the water Is no longer moving,
the air soon becomes used up, and the
crop will turn yellow and cease to
grow. The remedy, Of course, Is to-
provide drains to remove the ground
water quickly.
The only kind Of water which the
roots can use is the capillary water.
When this is present In the right
amount, it fills about half of the
spaces between the soil particles. The
rest are filled with air. The water
easily dissolves plant food from the
soil grains which it surrounds. Thus
the two essentials for rapid root de-
velopment, air and plant food, are
present in the proper amounts and IN
a readily available form. AS fast as
the water Is taken up by the roots
more is brought up by capillarity from
the supply in the subsoil in the man.
ner noted in article No. 2
The place where the capillary water
joins the ground water Is called the
water table. If this water table Is
too high, the feeding ground of the
roots is greatly restricted, since they
cannot go below it. If, on the other
hand, the water table is too deep,
capillarity cannot bring the water up
as fast as it is used by the roots.
In dry weather the water table low
ers rapidly, but the roots are also
growing downward at the same time.
The greatest damage from drought
comes when a sudden dry period fol-
lows a few weeks Of excessive rain
fall The abundance Of moisture dur
ing the early part of the season has
kept the plants from sending their
roots down very deep. When dry
weather does come, the soil bakes and
cracks and evaporation goes on very
rapidly. This, together with the de-
mands made by the plants, lowers the
water table so rapidly that root growth
cannot keep pace with it. AS result
the capillary moisture within reach of
the roots is not replaced as fast as 1t
is used, and the growth of the plants
is seriously checked.
Fields with a clay subsoil withstand
dry weather much better than those