Hermanner Volksblatt. [volume] (Hermann, Mo.) 1875-1928, 1914-02-13

soil fluid is probably less than 10 per
sire of water additional to the cur
rent rainfall on which the plants may
draw. This difference Q5 per cent Of
four feet, or 20 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 exhulation
from growing plants. A grass plant
will in the course of a 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 a meager yield even If the
entire quantity were utilized. In ordi-
nary farming the water is not fully
conserved and applied to plant growth.
so that practically the 10 acre inches
of effective soil fluid growth would not
suffice to produce n 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. IL properly cultivated and wa
tered the average. acre foot of soil.
weighing some 1000 tons Including
| 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
I'D 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 Il 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 cactl
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 tho
water supplied by irrigation. Gener'
ally throughout the United States the
actual yield per unit of water Is con
siderably less thar the ratio of dry
matter to water determined by plant
exhalation. A fair to good crop from
an acre ii. e., an acre FOOT OF fertile
soil supplied with four acre feet OF
water during the year may be put al
a ton of grain and three tons of stovei
and stubble, or -four tons in all-equiv'
alent to 1880 of the weight of the
wafer. With lessening Of the aggre'
gate water supply (whi of course
includes rainfall. accumulated ground
water, %subsurface flow and irrigation
the yield diminishes more rapidly thar
the quantity of water, virtually ceas
ing when the supply falls below an
acre foot. while with augmented sup
ply the yield increases more rapidly
than the water SO long as the tillagt
and character of crop are adapted tc
full use of the entire supply.
With present knowledge the ratio is
of course, but a rough approximation
Measurements are vague and expert
epces variable, soils differ both in com
position and in the texture controlling
circulation. and the yield of succulen
vegetables or of juicy fruits or fresl
forage may be several times that o
grain, nuts or dry forage, 50 that ]
will probably be found needful in time
to work out ratios for particular crops
Just as it is now convenient to reckon
yields per acre in different averages TO
the several crops.
In the curse of his work on irriga
ton Powell recognized the %necessit.
for determining 'the amount Of waite
which is needed to serve an acre o
land'' and spoke of this service as tn
duty" of water measurable in acr'
feet, and irrigators have frequently ap
piled the phrase to the measure of tn
water rather than of the service per
formed by the water-a service sus
ceptible of useful measurement only II
terms of what the water does in tina
production which furnishes food 70
man and forms the foundation for hu
mar industries and institutions. Sc
pending more precise determinations
the agricultural duty Of water may b
defined as the production of n one
th%ousandth part of its weight in I've
age plant crop or one four-thousandtI
of its weight in grain. q
Naturally the coeiticient for plan
yield will not apply to general farm