Nashville union and American. [volume] (Nashville, Tenn.) 1868-1875, 1874-06-04
RECENT RESEARCHES ON EVAPOR-
ALTON FROM PLANTS.


The present dry weather In Davidson
county leads us to notice somewhat in
detail, recent researches of Mr.. E.
Risler on the evaporation from several
agricultural plants. The quantity of
water that escapes from leaves Of corn,
grass and clover, is not diminished
when the surrounding air is saturated
with aqueous vapor. One might sup
pose, if not contradicted by direct ex-
experiment, that a dry atmosphere
would augment the escape of moisture
IN plant life. No continuous absorp-
ton Of vapor in the air has been OBJ
served. Plants in general evaporate
but very little during the nighttime.
All plants evaporate more in the sun
than N the shade.
Lucerne evaporated nearly four times
more in tie sun than in tue shade, even
where the difference in temperature is
notvery considerable. With Indian corn
the difference is still greater, showing
very clearly the reason why, if the soil
near tree were equally fertile, its shade
would dwarf corn by greatly reducing
the circulation through the plant from
root to leaf.
Independently of heat, bright solar
light is an important force in the or
ganization of our great staples, corn
and cotton. 1t may be, and from some
observations we think it probably is,
different with tobacco. We do not
know that Risler experimental with
that plant.
In the remarkable difference found
in the leaves and green surface of
plants to evaporate water in the shade
and sunshine, Mr.. Risler finds reasons
why some grow much better than
Others in woods, and under the shade
OF trees and other plants. A current
of air exerts no applicable influence on
evaporation, although the approach Of
a storm increased it even when heat
and light have not increased.
The moisture Of the soil is of the
greatest Importance. After rain or
watering, the evaporation increases.
With continued dryness, plants wilt,
as all the world knows; but clouds and
shade check the excess of evaporation,
and Wiltcd plants may recover.
When large volume of soil is ac-
cessible toa plant the supply of moist
ure is more regular and larger. Hence
the conclusion that the thicker one
plants his corn or cotton, the more
rain, or water from irrigation, he
needs to make his crop. Weeds and
grass will pump water out of the
ground near the roots that supply
moisture to ones bread-corn or money
staple, to his serious injury. The bet
ter soil is manured, the more hygro-
SCOPE it becomes, and the lessit suffers
from droutb. A given surface ofyoung
leaves evaporates less than of matured
leaves, and especially when seed or
fruit is forming.
Plants in our Southern climate gen.
orally evaporate much more water in
summer and the first two months of
autumn than falls in rain, the excess
being in the soil and subsoil. Forests
evaporate considerably less water than
cultivated land. Risler estimates the
quantity at about half of all that falls;
the other half may serve as a reservoir
of water for agricultural purposes. He
says that it is by no means proved that
woods increase the precipitation of
water from the atmosphere. The
leaves, roots and fallen trunks of trees
check the outflow of surface water, and
shade checks evaporation and develops
many springs, which cease to flow when
Il.