Evening star. [volume] (Washington, D.C.) 1854-1972, 1901-03-07
Results Of Irrigation in the Island Of
1911
Hawaii.
:@X1l
THE REGIONS MaSAALL RAINFALL
Physical Laws Underlying Applica-
ton of Water to Crops.
VIEWS OF CHEMIST MAXWELL

prepared n.y. waiter. MAX Well, Ql-
rector and chief chemist of the Hawaiian
experiment station, and issued by author
ity of the Secretary of Agriculture. Mr..
Maxwell discusses the china tic soil and
other conditions as affecting Irrigation in
Hawaii, and gives the results of expert
ments carried on by him for a. number Of
years. He brings out some of the most in
teresting phases of irrigation problems in
that territory, and lays basis for -urther
investigations of this subject there.
1.-THE precipitation of atmospheric mois-
ture," writes Mr.. Maxwell, lis very un-
even and irregular over the surface Of the
earth. There are zones that are marked
by annual deluges. and there arc vast areas
upon which rain rarely falls. These rain
less areas are not confined to conditions
peculiar to specific ATTITUDES, but are found
In the tropical regions Of India and Africa,
over the wide plateaus of North America
and In other localities having widely vary
ing climatic conditions.
1.-THE regions of small rainfall are very
generally distinguished by lands Of great
natural fertility. This Is due largely on the
one hand, to the absence of great rains that
leach out the elements that feed plants,
and. on the other. to the relative absence
of crops. which results from lack of rain.
Among the most productive tracts upon the
earth today are regions that were naturally
arid, but which have been rendered pruduc-
Punjab and other vast districts of India.
the great basin of the.-Ni1e in Africa, and
large semi-arid areas that have more re-
Gently been brought under cultivation in
the middle and western United States.
Lack of Rainfall.
s'The failure of the natural rainfall to
produce crops may be due to the INSULT
cheney OF the total precipitation, as in re-
gions in India, Africa and other lands,
81 ton
year. or 1t may be due to the seasonal dis
tributon as in other parts of India and
Africa in northern Queensland and some
of the Pacific islands, where a heavy and
almost the whole precipitation takes place
within two three months.
IN some localities in northern Queens
land the annual rainfall reaches and ex-
ceedS 100 inches, yet the sugar-cane crop
has to Hnger throughsan annual arid pc
riod which greatly reduces the yield, while
upon the Pacific islands Of Hawaii, despite
the winter rains, many Of the most fertile
lands would be useless without the pre-
yailing practice of. irrigation. Irrigation
consequently, is playing an increasingly
important part in modern intensive agri-
culture. z,gr.y
1.-THE history of irrigation covers methods
Of applying water to crops. including the
crudest efforts of the peasant and the great
systems executed by governments or cor
porationS. such as are IN operation in India,
the United States and in the valley of the
Il,
and have been instituted under the pressure
of meeting great emergencies. Today India
is using irrigation upon a. stupendous scale
in graphing with the calamity of famine
Economic irrigation REQUIRES the consid-
Grafton of physical laws. which were UNI
known to the authors Of primitive meth
DDS, and which have not. been generally OBJ
served in establishing the huge systems of
irrigation already mentioned.'' ~t.r a'''s.s-
Application of water to Crops.
Tn mo ~ fl,o nh, Low
which underHe the application of water to
crops and the evaporation Of moisture
from water and soil surfaces Mr.. Maxwell
says: --.-i : r--,
10 1.-The movement of moisture Is constantly
going on: The simplest evidence of this
movement is seen in rainfall and in the
evaporation from water and soil surfaces
1.-The factors that have been given the
greatest prominence exercising a control
ling action upon evaporation from soil and
from the surface of water are the tenn
perature and the relative humidity of the
air. This view is amply sustained if the
examination Is confined to the action of
these factors during the extreme seasons of
the year. There is no question concerning
the greater evaporation of moisture from
soils and waters during, the months Of sum-
mer, when temperatures are high, and the
amount Of atmospheric moisture is also
relatively small as compared with the be-
havior of these factors in the cold season.
This Is demonstrated In many localities by
the excess of water that accumulates with
IN apd upon the soil in winter, and the
droughts that obtain In the summer. There
are localities and regions, however, that are
so fortunate as to have the greatest rain
rail- during the season of greatest eVapora-
ton and consequently of greatest plant
growth. Setting aside the differences con-
current with the seasons and combining OBJ
servations to the relative actions of the
several factors during the months of SUM-
mer, 1t is then found that the temperature
of the air and the amount of moisture that
1t contains are not the most dominant fac
tors in the control of evaporation. AS al
ready said, they. are factors, but their
combined effects do not compare with the
effects of wind. Not only in the matter Of
irrigation. but also in the location and ex-
posture OF reservoirs this fact is of lead
Ing Importance
Result of Experiments.
The bulletin contains an account of a
series of evaporation experiments. Under
the heading of Transportation of Moisture
by Vegetation the bulletin recites:
1.-THE volume of water evaporated from
the soil and the volume transpfred by the
plant during it's growth are the controlling
factors In determining the total water re-
quired In the production of a crop and
therefore the quantity of water to be sup
piled by irrigation.
water enters very largely into the struc-
ture of all living organisms. 1t is not only
the agent which makes possible the mobility
of other constituents of the plant, convey
ing them from one location to another. but
1t enters in large proportion into the struc-
ture of the organism itself. Consequently
plants and trees at all times hold great
volume of water. the@supply of which Is
constantly replenishea by%o the water taken
up by the roots and as constantly depleted
by the moisture given off into the air by
means of transpiraHnn.' 1t Is these quanti-
ties that we require 4to know something
definite about.
Experiments withyahe,sugar; cane to de-
termfne these quantitfesGhave been carried
on by the writer att thesHawaiian expert
| ment station. The specific purpose was to
determine the Volume Of water required by
the cane at differents stages of its growth
ton The experiment awas carried out as
follows: Two tubs. Hereoused, having per-
| forated bottoms. overfwfHch pieces of linen
were laid to prevens- thob soil from going
through or filling upethe perfOrations. One
hundred and twenty fire mounds OF similar