As an auxiliary manurial agent of definite, well-proven value in this
Archipelago, I will briefly recite some of the benefits that may be
expected to follow occasional irrigation during the dry season.
It strongly accelerates growth and early maturity. A few irrigated
trees, reputed to be under five years from seed and already bearing
fruit, were shown the writer on the Island of Joló. The growth was
remarkably strong and vigorous, notwithstanding that the water of
irrigation had been applied in such a way that the tree could only
hope to derive a minimum of benefit from its application. It had merely
been turned on from a convenient ditch whenever the soil seemed baked
and dry, at intervals of one to three weeks, as circumstances seemed
to require.
Irrigation, but always in connection with subsequent cultivation,
may be considered equal to a crop guaranty that is not afforded so
effectually by any purely cultural system.
Rarely has a better opportunity occurred to demonstrate the
unquestioned benefits that have inured to these few Joló trees from
the use of irrigating waters than the present season of 1902-3. From
many sources reports come to this Bureau of trees failing, or dying
outright, from lack of moisture. While it is true that the present
dry season has had no parallel since 1885-86, and that the rainfall
during the dry season has been less than half the normal, yet it
should not be forgotten that, during the eight months from October to
May, inclusive, the average precipitation on the west coast, at the
latitude of Manila, is only about 460 mm. and that, when the amount
falls below this, the cocoanut is bound to suffer.
Though it is true that the evil effects of drought may be modified,
if not altogether controlled, by cultivation, the assistance of
irrigation places the cultivator in an impregnable position. If
evidence in support of this statement were called for, it might be
found to-day in the deplorable condition of those groves that have
been permitted to run to pasture, as compared with those in which some
attempts have been made to bolo out the encroaching weeds and grasses.
It is probably true that, except on very sandy soils, continued surface
irrigation would aggravate the superficial root-developing tendency
of the tree; and to what extent, if any, occasional laceration by
deep shovel tooth cultivation would injure the tree remains to be
seen. There are, however, few economic plants that so quickly repair
root damage as the Palmæ, and, unless the seat of injury extends over
a very large area, it is probable that the resulting injury would be
of no consequence, as compared with the general benefits that would
result from irrigation.