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i Agricultural Experiment Station,
E. V. WILCOX, Special Agent in Charge.
PRESS BULLETIN NO. 29.
Management of Pineapple Soils
I,- FL 'EST BY
The cultivation of pineapples in Hawaii has deve.ejr .j-
ing the past fifteen years into one of the important agricihtjj
industries of the islands. This crop for the most part has been
grown on virgin soils, which produced large yields of excellent
fruit, and this naturally encouraged a rapid expansion of the
industry. While a small part of the land is owned by the grower,
by far the greater part of the crop is grown on leased land.
From the beginning the pineapple growers have been controlled
largely by the idea of getting out of the land maximum crops at
a minimum of cost, and with little forethought for the perma-
nence of the industry or the maintenance of the soil. Pineapples
constitute practically the only crop that is cultivated on these
lands. The contixiuous growing of any one crop on the same soil
is likely to be attended with certain difficulties and can hardly
be said to belong to a system of permanent agriculture. The
more especially is this true when it is applied to soils contain-
ing large percentages of finely divided ferric hydrate and small
amounts of humus; soils that under the prevailing conditions
naturally require.the most intelligent management. There need
be little cause for surprise, therefore, that conditions have arisen
which at the outset were unsuspected and which are hindrances
to the continued welfare of the industry.
A large part of the pineapple crop is grown on the upland
plains of Oahu, principally in the Wahiawa and adjacent dis-
tricts. The discussion in the following pages has been drawn
largely from observations and a study of the conditions and soils
in the Wahiawa district, although the deductions apply equally
well to similar soils throughout the islands.
As pointed out in previous Annual* Reports of this Station,
q flnea~ le soils have been the subject of investigation at the
S-' EMperi 4 t Station for more than two years. In 1909 a pre-
limina&yeportt was issued in which it was pointed out that
the pineapppl soils of Oahu may be divided into two classes as
regular cohor-viz., black and red soils. In this report some of
the pecolarities of the black soils were emphasized. Since then
each bf. tese classes of soil has been under continued investiga-
Stion, which has resulted in the bringing together of a large
amount of scientific data. In the present bulletin it is purposed
to present the more practical phase of this work in so far as it
relates to the management of the red soils. What follows,
therefore, has no reference to the black manganiferous soils.
The failure of pineapples there is due to altogether different
THE CONDITIONS IN THE FIELDS.
For some time the growers have realized that in some way
not definitely understood by them, their soils after a few years
of cultivation begin to show indications of exhaustion. In gen-
eral the first crop and the one or more rattoons following it are
For the chemical composition of these soils, see Hawaii Sta. An.
t Hawaii Sta. Press Bul. No. 23.
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quite satisfactory, but subsequent plantings result in .dimin-
ished harvests. As already pointed out, pineapples constitute
practically the only crop that is cultivated on these soils. Before
replanting a field it is customary to haul off and remove all of
the old plants, thus taking from the land every vestige of plant
residue produced thereon. From 15 to 24 months being
required for the production of the first harvest, followed by one,
two or three rattoon crops of one year each, makes necessary the
continued cultivation of the land for three or four years. Gen-
erally the virgin soil is porous and naturally absorbs and drains
away excessive rains before the water becomes stagnant in the
soil, and brings about a water-logged condition. After the virgin
soil has undergone the necessary preparation to insure good
tilth, it is granular and porous. It has what the farmer calls
a shotty texture.
After a few years cultivation, however, there is brought
about a noticeable difference in the appearance of the soil. It
loses its granular texture, tillage becomes more difficult and nat-
ural drainage is retarded. Following a heavy rain the soil
becomes compact, and dries out into a hard mass which, unless
it is cultivated before thoroughly drying out, becomes almost
solid. The same condition may be brought about even during
the early growth of the first crop by an overflow of the ditches
during excessive rains, which frequently cause the pineapples to
show a stunted growth from which they rarely recover. Usually
the second planting even on soils that produced abundant har-
vests, results in greatly reduced yields.
LACK OF DRAINAGE.
The reduction of the pineapple-producing power of these
soils has called for inquiry, both by the farmer and by the Sta-
tion. Various expedients such as fertilizers, lime, manure, etc.,
have been tried, and often with indifferent success. Without
excluding other possible factors it has been recognized for some
time that. the fundamental difficulty is associated with inade-
quate .drainage, that under the existing conditions the water- '
holding power of the soil becomes greatly increased, that perco-
lation and consequently drainage is hindered by the methods
employed. In the old fields there are generally isolated plants
or small areas that are more thrifty than the surrounding plants.
Close examination has shown that the more thrifty plants are
found on slight elevations such as a back furrow or ridge made
by throwing together two furrows, etc. Upon pulling up the
unthrifty plants the roots are often found to be dead, except
perhaps one or two small roots near the surface. Sometimes
only one root barely beneath the surface of the soil is the only
living subaereal part of the plant. The underground part of
such plants is frequently undergoing putrefactive decay, and
even several days after rains they may be surrounded by a wet
soil containing stagnant water.
The pineapple, like all cultivated plants, requires free circu-
lating air around its roots; it demands oxygen just as animal
life requires it. Probably nothing is more effective in prevent-
ing proper aeration in soils than stagnant water, or a water-
logged condition in which the inter-spaces or pores of the soil
are more or less completely filled with water. Air is. then
largely excluded, the necessary oxygen is shut out and condi-
tions unfavorable to plant growth ensue. Under such condi-
tions the soil bacteria can not perform the functions so neces-
sary in the preparation of plant food, and fertilizers can not do
their normal duty. Evidently the- development of roots near
the surface of the soil, above referred to, is an effort by the plant
to secure oxygen through its absorptive organs.
The introduction of surface ditches has usually been bene-
ficial, but rarely of itself restores the soil to its original fertility,
and not even when used in conjunction with liberal quantities of
high-grade commercial fertilizers. It has been suggested that
under the influence of a tropical sun, continuous cultivation
would bring about an oxidation of the soil organic matter.
Humus, as is well known, has the property of making heavy
soils more porous and thus aiding drainage, and if the humus
should become decomposed it would materially affect these lands.
Experiments have shown, however, that a slow decomposition
of the humus takes place, but that it goes on at such a slow rate
as largely to preclude it as the principal factor. Likewise the
lack of available plant food, important as it may be, is not at
the bottom of the difficulty, for literally hundreds of experi-
ments by the growers and the Station as well, where all sorts
of commercial fertilizers in every kind of mixture have been
applied in various quantities, have not in themselves restored the
land. It is true the nitrifying power of the soil becomes greatly
reduced, but the application of commercial forms of nitrogen
has not proven effective.
Mechanical analyses of the virgin and cultivated soils show
that the ultimate particles that constitute the soil have not been
materially altered, which they could not be reasonably supposed
to be. The ordinary operations of cultivation are not of such
nature as to pulverize and grind to powder the coarser particles
of the soil. The mechanical analysis shows, however, that when
reduced to its ultimate particles these soils contain a very small
percentage of grit or coarse material, and a relatively high per-
centage of clay and fine silt. They are what would be classified
as heavy clay soils, although the so-called clay is of a different
nature from true clay in a chemical sense, and while possessing
some of the same properties, behaves in other senses vastly dif-
ferent. The word clay in this bulletin is used in a physical
sense only, and has reference to the size of the soil particles.
THE CAUSE OF FAILURE.
While the percentages of clay or other constituents are not
materially different in the new and old soils, the degree of gran-
ulation of the clay is greatly modified. The virgin soil when
shaken with a column of water, will soon settle out, leaving
practically a clear solution above it, whereas the older cultivated
soils when so treated give rise to a turbid solution which will
not settle out for weeks.
In the state of nature where good tilth is attained, the par-
ticles that constitute the clay content of a soil, particles which
when separated are extremely small and will remain in suspen-
sion in water almost indefinitely, are collected into aggregates
or granules, which granules act as units and impart to the soil
properties in every way similar to those brought about by ulti-
mate particles of a much larger size than clay. The bringing
about of such conditions in the soil is variously styled grauula-
tion, flocculation, coagulation, etc. It is an important function
of cultivation to aid nature in cementing the clay particles into
granules, and is accomplished by admitting sunlight and air,
and subjecting the soil to different degrees of moisture, carbonic'
These soils are frequently cultivated and usually well pre-
pared, but instead of an open granular structure being main-
tained by this operation, the soil steadily becomes more difficult
to till, drainage is hindered, and deflocculation results. The
soil is simply puddled. What are the causes of this phenome-
non? The principal causes are cultivation, tramping over and
otherwise disturbing the soil when it is wet. It is a principle
known by farmers for centuries that the cultivation of clay soils
when they are wet injures the land and brings about conditions
which it may take years to overcome. The intelligent farmer in
older agricultural regions will only as a last resort allow the
cultivation of his clay soils when they are wet. In the cultiva-
tion of wet clay soils the loosely-bound granules become broken
up and separated into their component particles, and when once
the bonds of union are severed, it is by no means easy to reunite
them. We need no better illustration of the effects of tillage
on wet soils than is to be found right here among the rice-
growers, who deliberately puddle the soil by working it when it
is wet in order the better to prevent loss of irrigation water
through seepage and drainage.
It is a common practice in the pineapple sections of the
islands to cultivate when the soil is practically saturated. At
certain times heavy rains thoroughly wet the land and these
are often followed by strong winds and a hot sun, which brings
about a rapid drying of the surface. Frequently the cultivators
are sent into the fields when the surface seems dry enough to
cultivate, but the soil two or three inches below the surface is
wet almost to saturation. The mere trampling of the soil at
such times when continued through a period of years tends to
bring about deflocculation of the clay and, therefore, puddle the
soil, so that effective drainage is hindered.
Puddled soils hold water tenaciously and under such condi-
tions denitrification instead of nitrification may take place;
effective aeration is made impossible and a condition unfavor-
able for pineapple growth follows. The application of fertilizers
to such soils is almost sure to result in disappointment, because
the fundamental difficulty is not a lack of plant food. Good
tilth, a good mechanical condition in the soil, is just as impor-
tant as available plant food, and in its absence fertilizers can
not perform their normal function and bring about the desired
results. In some instances under such conditions fertilizers may
even prove injurious. Nitrates in water-logged soils may be
reduced to nitrites. Such changes actually take place in some
Hawaiian soils, and nitrites are active plant poisons.
Furthermore, soils that contain such large quantities of
finely-divided ferric hydrates under the influence of putrefactive
decay may be reduced to ferrous carbonate and sulphate, either
of which are poisonous to many plants.
It has been shown in other countries and here that the con-
tinued use of nitrate of soda on clay soils* also tends to bring
about a deflocculation of the soil, and where it has been so used
the land remains wet longer after rains. The same condition
may arise from the continued use of certain other fertilizers. In
At the Rothamsted Expt. Sta., where nitrate of soda has been in
continued use for 60 years, a deflocculation of the soil has resulted.
See Jour. Royal Agr. Soc., Vol. 70, 1909, pp. 12-35.
the pineapple sections, however, such fertilizers have not come
into general use. In fact, no fertilizer has been used in many
instances where the soil has assumed a bad condition. It has
been found, however, that on some of these soils the application
of nitrate of soda tends to aggravate the already existing troubles
and, therefore, injures rather than benefits the growth of pine-
The bringing back of these soils into a condition favorable
for pineapple growth can not be accomplished in a day and is
far easier to prevent than to overcome once it is brought about.
With the virgin soils the farmer should by all means strive to
prevent such conditions. No heavy clay soils should ever be
cultivated when they are wet. If the fields demand attention
through the rapid growth of weeds, during rainy seasons, it
will be far better to pull out the weeds by hand or cut them off
near the surface with hand hoes. The results of cultivating wet
clay soils aside from that of checking and destroying grass and
weeds, are positively injurious and in fact really hinders one of
the very objects of tillage, that is aeration.
Air and sunshine in time will bring about granulation of the
soil and by thoroughly stirring it at intervals when fairly dry,
nature may be aided in restoring tilth. This should always be
accompanied by the best possible drainage that can be provided.
When this has been done fertilizers will no doubt prove effective
and can be used profitably. Barnyard manure will also aid
nature in restoring these soils, by making them more porous and
allowing a freer circulation of air, but should be applied some
months before the land is to be planted. Lime is also generally
recommended for heavy clay soils as a means of making them
more friable and improving their tilth, but the application of
lime to the pineapple soils of Wahiawa has at least failed to
show any advantage to be derived from it. Some of the growers
maintain that lime makes the cultivation of the soil more diffi-
cult, causes it to remain wet longer after rains and brings about
poorer drainage. This subject is now under investigation but
it is too soon to draw conclusions. It should be borne in mind,
however, that while these are called heavy clay soils, the clay
in them is of an altogether different nature from the clay in
most countries, and it is not inconceivable that lime will react
in a manner likewise different. If lime is to be added as a
means of correcting acidity or for other reasons, beach sand is
It will be far easier to maintain "condition" in these soils
under a system of rotation of crops. In fact, some of the
Wahiawa soils are almost sure to get into a bad mechanical con-
dition if continuously cultivated in the same crop. It is doubt-
ful whether any crop can be most successfully grown without
rotation on soils similar to these. With the vast majority of
cultivated crops, it is far better and more permanent to grow
them in a system of rotation. Whatever rotation is employed
it should include some leguminous crop which is plowed under.
This will tend to improve the tilth of the soil and at the same
time add nitrogen, an important and deficient element in these
SUMMARY AND CONCLUSIONS.
The continued cultivation of pineapples on the same land
has already brought about conditions unfavorable to the growth
of the crop. The use of fertilizers, lime and manure have"not
restored this soil to its -original productivity. The mechanical
condition of the soil becomes greatly affected and poor drainage
While only a slight change has taken place in the humus,
the clay has become deflocculated, thus reducing the size of the
pores in the soil and effectually hindering drainage. This con-
dition in these soils is brought about and really caused by culti-
vating the soil when it is wet. In some instances, however, it
has been caused by beating rains, accompanied by overflows. In
such puddled soils proper aeration is impossible and bad physi-
cal, biological and chemical conditions prevail.
The best remedy is that of prevention; these soils should
not be cultivated when wet, for damage is sure to result. Sun-
shine and air aided by thorough tillage when the soil is in proper
moisture conditions will assist nature in restoring tilth. The
best possible drainage should be provided by introducing ditches
at short distances apart. Manure, especially if accompanied
with ample aeration, will tend to make the soil more porous and,
therefore, aid drainage. And finally, the continued cultivation
of the land in pineapples should give way to an intelligent system
suchpudledsois prperaertio is mposibe ad ba phsi- .':.I,;
Sabooia n hmclcniin rvi.,""!!
UNIVERSITY OF FLORIDA
S 3 1262 08929 1172
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