Iron County record. [volume] (Cedar City, Utah) 1893-1982, 1914-01-30


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 7.2 acre inches-S16 tons
per acre. may be denoted the effective
BOIL 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 q 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 a meager yield even IL the
entire quantity were utilized. In ordi-
nary farming the water Is not fully
conserved and applied to plant growth.
so that practically the 7.2 acre inches
of effective soil fluid growth would not
suffice to produce a crop or even per-
init 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. II 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
" 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 Slant 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. It 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 dora varies with the
rainfall from sparsely distributed cact
and other desert plants to luxuriant
forests, and as lands are brought IN
| der cultivation the crop yields vary
.sYszl to place antif stsisscnn- %
season with the rainfall or with the |
water supplied by irrigation Gener- |
ally throughout the United States the |
actual yield per unit Of water Is con-
siderably less than the ratio OF dry
matter to water determined by plant |
exhalation. A fair to good crop from
an acre q. e., an acre FOOT of fertile |
soil supplied with four acre feet of |
water during the year may be put at |
ton Of grain and three tons Of stover |
and stubble. or four tons in all-equiv- |
alent to 1880 Of the weight of the |
water. With lessening Of the aggre-
gate water supply (whl,h of course |
Includes rainfall, accumulated ground |
water, subsurface how and irrigauon) |
the yield diminishes more rapidly than |
the quantity Of water, virtually ceas.
ing when the supply falls below an
acre foot, while with augmented SUD-
ply the yield increases more rapidly |
than the water 80 long as the tillage
and character Of crop are adapted to
full use of the entire supply.
With present knowledge the ratio "a
Of course, but rough approximation.
Measurements a-e vague and experl.
ences variable, soils differ both In com.
position and in the texture controlling
circulation, and the yield OF succuent
vegetables or Of juicy fruits or fresh
forage may be several times that Of
grain, nuts or dry forage, 50 that n
will probably be found needful in time
/ w WIN Out tubOs lOi crOD9
just as It is now convenient to reckon
yields per acre In different averages for
the several crops.
In the course of his work on irripa.
ton Powell recognized the necessy
for determining ''the amount Of water
which is needed to serve an acre Of
land" and spoke of this service as the
duty" Of water measurable In acr,
feet, and irrigators have frequently an
piled the phrase to the measure Of the
water rather than OF the service Der.
formed by the water-a service sus
cepuble of useful measurement only M
terms OF what the water does In tina,
production which furnishes food for
man and forms the foundation for In
man Industries and institutions. So
| pending more precise determinations
the agricultural duty OF water NAV he
defined as the production of one one.
thousandth part Of its weight in aver.
age plant crop or one four-thousandth
Of Its weight In grain.
Naturally the coefficient for plant
yield will not apply to general farm
production. including crops Of NEST
eggs, wool hides, ETC., for not only AZ
animals drink many times their weight
in water annually, but they consum,