The San Juan islander. [volume] (Friday Harbor, Wash.) 1898-1914, 1902-09-11
WINTER IRRIGATION.
arizona Experience Containing "A
Hint For the Humid Ro-,o

mint For the Humid Regions.
FRUITS can be successfully grown in
the valleys of southern Arizona only
by the aid of irrigation. Until within
recent years it has been the common
practice of fruit growers in that SEQ.
tlon to irrigate orchards once or twice
month from February until October.
Inc summer supply of water for this
purpose is often Inadequate. for while
the heaviest rainfall occurs during
midsummer, the amount of water
available for crops is only about one
third of that available i'm winter In
1898 experiments were begun bv a I
McClatchie of the Arizona station for
the purpose of determining to what
extent summer irrigation of the de-
clduous orchard fruit trees might be
rendered unnecessary by the liberal
application OF water during the winter.
When the supply was comparatively
abundant. The advantage of winter
irrigation and the reasons for the good
effects obtained in these and succeed
ing experiments are stated as follows:
During the winter the lower temper
atures and the higher relative humid
lty cause evaporation to be much low
er than during the remainder of the
year. In applying water, therefore,
comparatively little escapes into the
atmosphere. The supply of water, be-
greatest Of
makes it possible to apply large
amounts at short intervals, thus avoid
ing the loss that occurs II small
amounts are applied at greater inter
walls. Then, too, the trees are dormant
and roots need little air. hence no in
jury is done them by keeping the soil
supermoistened or by letting the sur
face bake to some extent. Consequent
ly cultivation after each irrigation is
not necessary, much time thus being
saved.
Trees make use Of and consequently
need water much earlier than is COM
monty supposed. An examination made
Feb. 20, 1900. revealed that at the
depth of ten to sixteen feet even young
roots three to six inches long had al
ready grown. At this date there were
few above ground indications Of
growth, and it would not have been
supposed by making a casual Observa-
ton that the trees would make use of
any water that might be applied.
While the air above ground is still too
tn n ri nf 10
buds, the roots far beneath the surface
are making a growth that prepares the
tree for the demand for water that the
leaves will make later. Thus if the
trees have an abundance of water dur
ing the winter the early root growth
that will be made will enable them to
make rapid growth as soon as the air
above ground is warm enough to per-
nit it. These facts account for the
rapid and vigorous growth that the
winter irrigated orchard made in early
spring compared with those that had
not been thus irrigated.
While the lessons taught by these eX
periments apply specifically to Arizona
conditions, they have a much wider
applicat ton and value, for conditions
similar to those of Arizona prevail eX-
tensively in other parts of the arid re-
gion where agriculture is dependent
upon irrigation. Moreover, they en-
phaSiZe the Importance even for humid
regions of keeping the soil in such con-
dition that it will store UP in time of
abundant rainfall sufficient supply Of
water to carry crops safely over pc
riod Of drought.