Licking Valley courier. [volume] (West Liberty, Ky.) 19??-current, 1913-05-29

mean moisture when plant growth
ceases by reason of exhaustion of the
soil fluid is probably less than 10 per
cent, and the difference measures the
store of water additional to the cur
rent rainfall on which the plants may
draw. This difference Q5 per cent Of
four feet, or To acre inches-S16 tons
per acre. may be denoted the effective
soil fluid of average soil.
The rate of soil plant circulation and
the quantity Of water passing through
soil and plants during the growing
season are indicated by the exhalation
from growing plants. A grass plant
will in the course Of hot day exhale
its own weight of water, and a young
leaf of wheat or rye exposed to the sun
may even exhale its own weight In an
! hour.
The maintenance Of the soil plant cir
culation required for crop production
generally involves repeated additions
of water during the growing season,
| for the effective soil fluid within four
feet of the surface would at the OBJ
served rate Of plant Transportation suf-
fee for but meager yield even II the
entire quantity were utilized. In ordi-
nary farming the water is not fully
conserved and applied to plant growth.
80 that practically the 7.2 acre inches
of effective soil fluid growth would not
suffice to produce crop or even per-
NIT any yield whatever from most
types of soil, though under certain
conditions water may be drawn from
greater depths in the subsoil than four
feet. If properly cultivated and wa
tered the average acre foot Of soil,
weighing some 1000 tons Qncluding
the contained water), retains efficiency
for centuries, but to be even moderate
ly productive this soil must convey to
the crop plants fully 1.5 acre feet Of
water, or an amount equivalent to its
own weight, during each growing sea-
son.
To become effective In plant growth
water must enter the soil body, take
up both mineral salts and organic sub
stances in solution and pass thence
into the plants and on into the air.
This is the normal course of soil plant
circulation, and the relative quantities
Of the solid and fluid parts of the soil
involved in plant growth probably cor
respond fairly with the strength OF
the solution, or one to several hundred
Pending precise determinations, 1t may
be assumed that the strength Of the
solution forming the soil fluid and the
ratio of the solid and fluid parts requir
ed to maintain efficiency are about
equal and something like to 1000. =
In nature the fora varies with the
rainfall from sparsely distributed cact
and other desert plants to luxuriant
forests, and as lands are brought un
der cultivation the crop yields vary
from place to place and from season tc
season with the rainfall or with the
water supplied by irrigation. Gener
ally throughout the United States th'
actual yield per unit Of water is COP
slderably less than the ratio Of dry
matter 10 water determined by plan
exhalatlon. A fair to good crop from
an acre q. e., an acre FOOT Of fertile
soil supplied with four acre feet O.
water during the year may be put a
n ton of grain and three tons Of stove
and stubble, or four tons in all-equiv
alent to 1890 Of the weight Of tn
water. With lessening Of the aggre
gate water supply (whl,h Of cours
includes rainfall, accumulated groun,
water, subsurface flow and irrigation
the yield diminlshes more rapidly thal
the quantity Of water, virtually ceas
Ing when the supply falls below a
acre foot, while with augmented sur
ply the yield Increases more rapid
than the water so long as the tillag
and character Of crop are adapted I
full use Of the entire supply.
With present knowledge the ratio 4
Of course. but a rough approximation
Measurements are vague and exper
ences variable, soils differ both In con
, position and In the texture controlllu
! circulation, and the yield Of succuleI
vegetables or Of juicy fruits or fres
forage may be several times that
| grain, nuts or dry forage, so that
Will probably be found needful in tin
to work out ratios for particular crop
/ Just as It is now convenient to reckC
: yields per acre In different averages {,
, the several crops.
In the course of his work on irrlg
= ton Powell recognized the necessit
for determining "the amount Of wat,
+ which is needed to serve an acre
land" and spoke Of this service as Il
r duty" Of water measurable In ac
r feet, and irrigators have frequently a
) piled the phrase to the measure OF Il
!, water rather than OF the service pc
, formed by the water-a service su
. ceptible Of useful measurement only
0 terms Of what the water does In th
production which furnishes food Z
r man and forms the foundation for b
!. man industries and institutions.
pending more precise determination
Q the agricultural duty Of water may
I defined as the production of one on
3 thousandth part Of Its weight In ave
J, age plant crop or one four-thousand
y of its weight In grain.
I Naturally the coeflclent for pla
/. yield will not apply to general far
: production, including crops OF met
!. eggs, wool, hides. etc, for not only
animals drink many times their weig
i In water annually, but they consur
Q indirectly In their feed the equivale
Q Of that much larger quantity requir
/ for the growth Of the vegetal tissue
which the feed consists. The hum
l. consumption Is still larger. The 800
L 100000 acre feet Tor, 2l5,O00,0 ,000 000,0
s cubic feet constituting the total year
Il water supply of mainland Unit