REPORT

ON

FERTILIZATION

BY

Charles F. Eckart |

CHAIRMAN OF COMMITTEE

SUBMITTED TO THE

Hawaiian Sugar Planters’ Association

NOVEMBER, I90!.

———

HONOLULU:
HAWAIIAN GAZETTE CO.

—_ 7 1901 |

Ryel Oi aee

ON

PERVILIZATION

BY

Charles F. Eckart

CHAIRMAN OF COMMITTEE

SUBMITTED TO THE

Hawalian Sugar Planters’ Association
NOMgEDMRERs 1901.
try! %

HONOLULU:
HAWAIJAN GAZETTE CO.
{QOI

Committee on Fertilization
CG. Eo -ECKART,
C. M. WALutroNn,
Jet CRAw un.
Goro. Ross,

JOHN WATT.

rea 8 1916

REPORT

ON

FERTILIZATION

(C. F. ECKART, Chairman of Committee)

Honouuuu, H. T., November 18th, 1901.

To THE PRESIDENT. TRUSTEES, AND MEMBERS of THE HAWAIIAN
SuGAR PLANTERS’ ASSOCIATION,
Honolilie ire

GENTLEMEN :—During the past vear, no less than twenty-five
thousand tons of commercial fertilizers have been added to
our Hawaiian soils to satisfy the demands of the sugar in-
dustry.

The initial cost of this large quantity of fertilizing materia},
added to the cost of LSE TIUTD, and application, makes the
subject of fertilization from an economic standpoint one of
great importance and? worthy of{close consideration. The
comparative cost of the different manurial compounds, their
relative efficacy in meeting the requirements of the cane crop,
their proportional liability to waste under given climatic con-
ditions, combined with a knowledge of the soil to which they
are to be applied, must constitute the only basis from which
any rational and economical system of fertilization can be
derived.

The earliest method in use for determining the ability of a
soil to furnish the requisite amount of plant food for a given

crop, involved practical tests with small field plats. On a
small area, without fertilization, but with due observance of
proper tilth and cultivation, a crop was started for purposes
of comparison. At the same time other plats were laid off
in the same field and received allotments of nitrogen, phos-
phoric acid, lime, potash, etce., and the effect of each one of
these applied elements was carefully noted as regards any in-
crease of the given crop over and above that on the unfertil-
ized area. Not only were these fertilizers added separately on
some plats, but in mixtures of varying proportions on others,
and valuable conclusions were reached as te the demands of
the plant. These practical tests are still carried on to a large
extent in some agricultural communities, and results are
reached of sufficient value to more than compensate the farm-
er for time and labor expended.

These plat experiments, however, are found to be open to
the following objection: The time necessary to determine the
proper quantity and the best balanced proportion of fertiliz-
ing ingredients to be added for maximum yields, covers per-
iods of considerable length.

The chemist has endeavored to overcome this objection, and
to reach in the laboratory results that have taken the agricul-
turist months to learn from observation in the field. By an
examination of the ash of the particular plant to be grown,
he learned the quantities and proportions of the various min-
eral elements that had been removed from the soil, and used
in the development and elaWoratfon of the plant and its pro-
ducts. He digested a small quantity of the soil in hydro-
chlorie acid of a certain specific gravity, and noted the per-
centages of the different elements in the resulting soil extract.
From these analyses, conclusions were drawn as to the fertil-
ity of the land in question, and the supply of plant food, from
which the crop could draw as needed, was supposed to have
been measured,

Unfortunately, discrepancies soon begin to arise between
field results with the growing crop and the conclusions
reached from chemical analyses, and the chemist found that

his: shorter method was not without palpable defects. If an
element was lacking in the soil or was present in very small
quantity, he felt safe in recommending the application of that
element in fertilization, but where an ingredient was present
in large amounts, he sometimes found that that self-same
element was one to be added in manurial mixtures for satis-
factory results. In other words elements can be present in
large amounts in the soil, but in a state which renders them
unavailable to the plant. Regarding the ordinary agricultural
method for determining soil deficiencies, this may be said in
its favor: That in some instances it serves as a valuable guide
in fertilizer recommendations, when the chemical analysis is
supplemented with reliable data as regards the physical con-
dition of the soil, combined with a knowledge of the climatic
conditions of the locality from which the sample has been ob-
tained.

In view of the objection which has been mentioned regard-
ing the agricultural method, investigators have endeavored to
find an acid more suitable for soil digestion than hydrochloric,
and one whose solvent action would be more comparable with
the acids of the plant roots. Organic acids were substituted
for mineral acids in the experiments, and a long stride was
taken towards the solution of this important problem.

Aspartic Actp Meruop.—This method of determining the
availibility of the plant food in the soil, is the one at present
in use at the Experiment Station, and a few words may be
said in regard to its practicability for Hawaiian conditions.
The credit for this system of soil investigation belongs to Dr.
Walter Maxwell, the former director of the Experiment St-
tion, and Mr. J. T. Crawley, and is the result of a close and
scientific study of conditions obtaining on these islands. A
detailed account of the work along this line and the logical
conclusions drawn from the same, may be found in an article
on ‘Lavas and Soils of the Hawaiians Islands,” published by
Dr. Maxwell in 1898, and in this report only a brief reference
to the deductions will be made.

The amount of mineral matter being carried into the sea

4

by waters of discharge from the land was determined with
the following results:

Hawaiian Waters.

1 Dh RRR Fr in TRE A eda re eek i er ae a ak MR 0.0013 Per cent
gE 2 Re] OBR pn emt tah Alen tn a i es Aa RA A a ea 0.0005 Per cent
Phosphoric acid —— =... Poe ena CRN wena ec ges ose 0.0001 Per cent

These figures represent the average mineral content of Ha-
Wallan waters collected at many places considered suitable
for such observations.

An analysis was made of upland cropped and corresponding
virgin soils, the average results being as follows:

UPLANDS.
Elements | Virgin Cropped Loss
pa | Per cent. Per cent Per cent,
DE siTas Sg a as S i r 0.415 ().248 40.20
1 ECGs (=) ON Near Cee ae come el | 0 324 0.270 16.60
Phosphoric Acid_ es 0 248 ().248 2.02

The term cropping as applied to the above table is used in a
very general sense. It includes the action of rain, cultivation,
and growing crops in removing plant food from the soil.

Data were obtained which showed that in one case where
7,000 Ibs. of lime were removed per acre, only about 15 per
cent of this amount had been utilized by the crop itself, and
in respect to potash the crop took only one-half of the amount
removed by total cropping. “These data show that any sys-
tem of judging of the depletion or of restoring the fertility of
soils, that is based upon a mere calculation of the amounts of
the elements that are carried away from the land in crops, is
devoid of any approach to the actual facts of the matter.”
The reason that upland virgin and cropped soils were taken
for this comparison, was on account of the washing action of
the rains. The makai soil receives a large part of the wash
from the mauka lands, and in some instances cropped soils
on the lower lands show a higher proportion of given elements
than the virgin. The amount of lime removed by cropping is

5
4().2 per cent, and if this is taken as a standard, applying it also
as a basis for the waters of discharge, the relations existing
between it and the other elements may be tabulated as below:

Elements Removed from the Soil in Elements Removed from the Soil by
Water. Cropping.
ee = posers a
‘ Phosphoric : | Phosphori
Lime Potash Ped Lime Votash A Acad je
Per cent. Per cent. Per cent, Per cent Per cent. Per cent,
40 2 15.1 2.80 40 2 16 6 2 02

As Dr. Maxwell has pointed out, these results do not appear
so remarkable, when it is considered that the great bulk of
matter removed by total cropping is found in the waters of
discharge.

With these data at hand, the next step was to find some
acid whose solvent action on the soil would remove the essen-
tial elements in proportions approximating those of cropping.
Many organic acids of different strengths were allowed to act
on the soil for varying lengths of time, and it was found that
an one per cent solution of aspartic acid, when shaken with
the soil at intervais during twenty-four hours, apparently met
all requirements. The amounts and proportions of the ele-
ments, removed by this acid during twenty-four hours, were
approximately the same as were removed by total cropping
during a period estimated at twenty years. Dr. Maxwell's
conclusions were stated as follows: “An one per cent solu-
tion of aspartic acid takes out of Hawaiian soils in twenty-
four hours, the saine amounts of lime, potash, and prosphoric
acid, that are removed during the production of ten crops of
cane. Therefore one-tenth of these amounts may be taken as
the proportions of iime, potash, and phosphoric acid that are
available for the inmediate crop of cane.” The Aspartic Acid
Methed, although not perfect, offers a fairly reliable means for
determining the amount of available plant food in the soil,
and is in fact a better guide in the matter of fertilization on
these islands than any other known method, as in its concep-
tion, Hawaiian conditions influenced every consideration.

6

3efore considering the subject of fertilization in its more re-
stricted sense, i. e. the application of different manurial com-
pounds to the soil, probably a few words on the average avail-
ability of the essential elements in question might prove of
interest.

AVAILABILIVY OF ELEMENTS.—Considerable data are at hand
to give an adequate idea of the amounts of lime, potash, phos-
phorie acid and nitrogen that are present in the soils of the
respective islands, the subjoined table representing average
results of about one hundred analyses.

Phosphoric |

ISLAND | Lime Potash Acid Nitrogen
abu a sacs hee | 0 380 0.342 0 207 0 176
Rae Poets tourette (0) 418 0.309 02187: | 0.227
Minis Stich oxen 0.395 0 357 Os270 ae 0.388
Hawait Py Ne eosin 0.185 0.346 | 0.513) eam

These results were obtained by the ordinary agricultural
method, which was in use at the Experiment Station prior to
the adoption of aspartic acid as a soil solvent, and althongh
an absolute analysis would give somewhat larger results,
these are comparative to a large extent as showing the pro-
portions of lime, potash, phosphoric acid, and nitrogen present
in the island soils.

The amounts of the mineral ingredients which are found to
be available are as follows:

ISLAND Lime Potash Phosphoric Acid

| Per cent. Per cent. Per cent.
Oahu. Aas Pea ail .01568 .00256 .00012
Rauiany sehen RT| .01367 | 00249 00013
Maui PG Wet IR Re near 01764 | 00312 .00012
Pawaii it) 3 se Soe 00789} 00156 00014

or reducing these percentages to a more tangible form, we
have:

oa |

ISLAND ~ 2 Lime Potash lpiteshorte Acid
(OMIT 3. SS Ree eee 549 lbs. 89 lbs. 4 2 lbs.
LECT EAT, “ee Fo ea en ATS" Si Ca
IYTIS\TEL. S215 ORORe eae Oe a aaron Ug Oki OG yy ee
1S DAV 2 eae A ae eae ned MIke Us | AS | AVS) SS

which quantities represent the amounts of the essential min-
eral elements, in one acre of soil to a depth of one foot, that
are in a condition to be removed through the several actions
of total cropping, during the growth of one crop.

It is interesting to note that Kauai stands highest in lime,
Maui in potash, and Hawaii in phosphoric acid. The smallest
percentage of lime is on Hawaii, while Kauai is lowest in
potash and phosphoric acid.

If, however, we consider the availability of these elements
instead of the actual amounts in the soil, a somewhat modi-
fied order presents itself: Maui and Oahu are both higher in
available lime than Kauai, Oahu standing first. Maui with
the highest total content of potash has also more of that
element in an available ferm than the other islands. The
amounts of available phosphoric acid show little variation,
notwithstanding a difference between .187 per cent total phos-
phoric acid on Kauai, and .513 per cent on Hawaii. This
latter ingredient is so closely bound up in iron and aluminic
compounds as to be practically insoluble; on Hawaii nine tons
of the element per acre scarcely yvieid five pounds in an assim-
ilable form.

Having considered the method in use for gauging the avail-
ability of the minera! elements in question, and having noted
the amounts in which they are present in the soils of the
respective islands, we will next consider the demands of the
crop.

ELEMENTS REMOVED BY 'THE Crop.—In the report of the
Experiment Station for 190, it was pointed out that where
29,610 lbs. of sugar were produced per acre by Lahaina cane,
6,606 lbs. of mineral matter were extracted from the soil,
while with Rose Bamboo, 30,475 Ibs. of sugar required 7,662

8

Ibs. of mineral matter. The following table shows the
amounts of the various elements including nitrogen, which
were required to produce one ton of sugar by the respective
varieties:

Varieties | Nitrogen Eboennese Potash Lime
tbs] = — — ——,
Paha i200 Se ioeiden |POlO sa OR: 16.0 Ibs. | 89.5 Ibs. 28.7 lbs.
Rose Bamboo ....|_ 405“ 13.6 “4-1 114-2) eee

If we should take five tons of sugar per acre, as the average
production for the Hawaiian Islands, and consider for our pur-
pose that the amounts of the essential elements required by
the crop for such a yield would be the same as at the Experi-
ment Station, we have:

Nitrogen, Phosphoric Acid, Potash, and Nitrogen Required
by the Cane to Produce Five Tons of Sugar

Varieties Nitrogen EOE ROE Potash Lime
Mahainatosere sk 127.0 lbs. 80 Ibs. 447 5 Ibs. | 148 5 Ibs.
Kese Bamboo........ | 202.5 deta 571.0 “ 74.0 *

As it is our present purpose to consider crop requirements
in general, and net the special demands made by particular
varieties, we will take the mean of the figures presented
above, as representing Lahaina and Rose Bamboo needs, and
for future consideration say, that a crop to produce five tons
of sugar, would require per acre, about:

164.7 Ibs. of nitrogen.

74.0 Ibs. of phosphoric acid.
509.2 Ibs. of potash.

158.7 Ibs. of lime.

We will next compare the amounts of available elements in
the soils of the respective islands, with the amounts of these
elements that would be required by a crop producing five tons
of sugar. The nitrogen contents of the lands are not given,

as at the present time we have no reliable method for deter-
mining its availability.

|

e Phospho-'..
: : Lime | Potash | Phospho- 7. \*,;, Nitrogen
ISLAND ee required poe required | ric Acid mart uy required
s by crop by crop | in soil 1 by crop

by crop

Pounds | Pounds |} Pounds Pounds | Pounds Pounds | Pounds

Osha s..: . 549 = 89 a 4.2
Kauai. >... 478 <i 87 = 4.5 H os
PUAN 7. 5... 617 = 109 2. 42 a &
Hawialii..5| ~ 276. | 54 4.9

It will be noticed from the above figures that lime is the
only one of the elements that would appear to be present in
sufficient quantity for the needs of the crop. But when we
consider the statement previously made, concerning the small
proportion of lime that is taken up by the crop on some up-
land soils as compared with the proportion removed by the
other factors involved in total cropping, we may see that the
average lime content is not so large but what we must con-
sider it very carefully. Maui stands highest in available lime,
having 617 Ibs. on an average to the acre, but if only 15% of
that amount could be utilized by the crop, as in the instance
above referred to (which was most likely an extreme case),
only 92.55 would go to the crop where 164.7 lbs. were needed.
Even if the cane gets on an average 30 per cent of the lime
removed, but small margin would be left on Maui, above
actual crop requirements, while on Oahu there would be just
enough, and on Kauai and Hawaii a marked deficiency.

The potash is found to be very much too low on all the
islands for supplying the wants of the cane, and it is readily
seen why it was found necessary, during recent years to in-
crease the proportion of that element in fertilizers applied.

Concerning phosphoric acid, the dearth of this element in
available quantities in our island soils is very apparent, but
we are almost convinced that the aspartic acid method for soil
analysis would indicate this ingredient to be lower in avail
ability than it really is.

In the consideration of the amount of plant food taken from

10

the soil by the growing crop, in order to produce one ton of
sugar, we took an average of the quantities removed by
Lahaina and Rose Bamboo varieties, as giving a fair idea of
the large demands made by the cane upon the soil. However
these proportions and amounts are not to be taken as repre-
senting the exact requirements of the cane in any locality or
under any conditions. At the Experiment Station, the figures
in question were reached in a comparative test of thirteen
varieties of cane, grown under similar conditions as regards
soil, fertilization, and climate, one of the objects being to note
their respective drafts on the soil as compared with their
value as producers of sugar.

MiInERAL Marrer RETURNED TO THE SOIL IN CANE REFUSE.

The last table, although it gives an idea of the amount of
plant food that would be required for a crop of such size as
was under consideration, does not show the quantities of lime,
phosphoric acid, potash and nitrogen, that are taken away
from the field. If it did, the application of artificial manures
from crop to crop would reach much larger proportions than
it really does. As a matter of fact, after the cane is cut for
the mill, and the trash and dead canes, etc., are burned, as is
most generally the case on plantations, a much larger amount
of mineral matter is returned to the soil than is generally
supposed. By burning, of course, all the nitrogen is lost with
its corresponding manurial value, but the other essential
elements remain on the field to be used largely by the succeed-
ing crop.
The following figures indicate the relative amounts of the
elements found in the tops, etc., and in the cane, per ton of
sugar grown at the Experiment Station.
ELEMENTS REMOVED FROM SOIL PER TON OF SUGAR

ie PRODUCED.

<7 PUPNT In tops, leaves, and :

ELEMENT | dendtcaned. In cane
7 ao ~~] — wu ae
Taine ge ee ies yee tn os Tear | 27.9 Ibs. 3.7 Ibs.
Phosphoric Acid.....,.......| Gof | Orne
PotashPerces hee a ene | Gores Bee
INiSrOBENY Oe skeen se ee ee ; PA RO} at erie F:

1]

These results show the lime in the tops, ete., to be over
seven times that in the cane; the phosphoric acid is more
evenly balanced; while the tops, ete., have nearly twice as
much potash as the cane. It is thus seen that if only one-
half of the mineral matter in the refuse of the field is con-
served, a manurial mixture is added to the soil of particular
value, which would lessen to a large extent the amount to be
applied during regular fertilization.

In regard to the comparative availability of those elements
returned to the soil through the burning of the trash, and the
same added in ordinary fertilization, there is some difference
in favor of the latter. The potash in the ash is chiefly in the
form of chloride, with a smaller amount as carbonate and
silicate, and the chloride is as assimilable as any that could
be added in manurial mixtures. The phosphoric acid is re-
turned to the land as iron and aluminic phosphates with a
much smaller amount as phosphate of lime, and phosphate of
magnesia. These phosphates are more insoluble than those
generally added in fertilizers and are not immediately avail-
able to the plant. The lime in the ash is most likely com-
bined with silica, phosphoric acid, and sulphuric acid and is
only slightly soluble.

Forms IN wHicH FEertinizinc INGREDIENTS ARE APPLIED.—
The amount of available plant food in the soil and the proba-
ble requirements of the crop to be grown are important fac-
tors to be considered in any estimation of manurial needs.
However, unless these data are supplemented by a knowledge
of climatic conditions, and a proper regard shown for their
several influences, analytical investigations in respect to the
pature of the soil are often of little value.

To the action of the heavy rains of the uplands in washing
away the more soluble ingredients of the soil we have already
referred. These rains not only leach out material which is
eradually being rendered available for plant needs, but also
that which is artificially applied in the form of fertilizers.
The erosive action on the natural material of the land cannot
be controlled, but with a due consideration of the physical and

chemical properties of applied ingredients, we can place in the
soil those substances required by the plant, and in a form
least liable to waste.

We now come to a consideration of the elements themselves,
the relative efficacy of their various combinations, and the
conditions that influence their selection as component parts of
manurial compounds for different locations.

NirrROGEN.—This element is applied to the land in three
forms, namely as nitrate of soda, sulphate of ammonia, and
organic substances.

Nitrate of soda is the most soluble of these three forms and
besides holds its nitrogen in the most assimilable condition.
Solubility and availability are not necessarily synonomous
expressions as regards nitrogen compounds, although the lat-
ter condition is greatly influenced by the former. The solu-
bility of nitrate of soda is influenced by the temperature of the
solvent, at 78° Fahr., 100 parts of water dissolve 90.33 parts of
nitrate. Added to this extreme solubility is an unfortunate
disinclination of the acid part of the salt to become fixed in
the soil, which causes its use on some lands to be attended by
considerable risk on account of the leaching action of the
rains,

A test was conducted at the Experiment Station in 1898 to
determine the relative liabilities to waste of nitrogen in the
form of nitrate of soda, and the same element in the form of
sulphate of ammonia. In one instance 200 grams of nitrogen
as nitrate of soda and in another the same amount as sulphate
of ammonia were added to corresponding soils draining into
a lysimeter. Forty-eight hours after the application of these
compounds, a copious irrigation was allowed to over-saturate
the soil, and the excess of water was collected in a receiver
and analyzed. The loss in nitrogen is seen by the following
table:

13

Nitrogen lost in water

Forms Nitrogen Applied| - —- —
As Nitrate As Ammonia
Nitrate of Soda.......... | 200 grams 72.56 grams 0.00 grams
Sulphate of Ammonia.... 200“ S08.) = | OM

The loss of nitrogen from nitrate is very large. Of the
nitrogen from sulphate of animonia only a minute proportion
was found in the receiver, the major part of this small quan-
tity being in the form of nitrate, into which state it had been
converted by the nitrifying organisms of the soil.

Mr. J. T. Crawley, of the Committee on Fertilization, con-
ducted a number of interesting experiments during the first
part of this year, for the purpose of obtaining data as regards
the retentive power of “sandy soils” for fertilizers and water,
and his results are of particular value in a consideration of
the subject in hand. Four soils varying in their proportions
of lime carbonate from 71.25 per cent to 91.07 per cent were
placed in iron pipes two feet six inches long and one inch in
diameter, the pipes being filléd to within six inches of the top.
One gram each of ammonium sulphate, nitrate of soda, and
muriate of potash were dissolved in a liter of water and 500
cubic centimeters of this solution holding one-half gram each
of the salts mentioned were poured upon the soils and allowed
to drain through. It was found in regard to the nitrate of
soda that practically none was retained by any of the soils,
while the other compounds were fixed in an inverse proportion
to the lime carbonate content of the medium through which
they filtered. In a consideration of the action of sulphate of
ammonia and sulphate and muriate of potash when applied to
the soil, we shall have occasion to again refer to Mr. Craw-
ley’s interesting experiments.

The readiness with which nitrate of soda may be taken up
by excessive rains or irrigation and carried from the land is
readily seen, but bound up with this question is another of
almost equal importance. When the nitrate is lost from the

14

land through the over-saturation of its soil, not only so much
nitrogen is lost, but likewise a large amount of lime. ‘The
nitric acid of the nitrate on coming in contact with the lime
of the soil, forms lime nitrate, which is almost as easily solu-
ble and as readily washed out as the nitrate of soda.

To observe this action of nitrate on lime, as well as the rel-
ative action of different salts in the same particular, tests
were made at the Experiment Station in connection with
other lysimeter investigations. Nitrate of soda, chloride of
potash, ammonium sulphate and sulphate of potash were ap-
plied to the rows of cane growing over the lysimeter drains,
and forty-eight hours later these rows were irrigated with
102 gallons of water. of which quantity 33 gallons leached out
and was analyzed.

Drain | Salt applied Lime Lost
Nokia? oe ceen INOTES eetareree eee eerie eerie tine 1.72 grams
NOB 2 eee a INIbrate lol SOddeaeeek oats. woes 2GEO2E yee
IN@kton nee oan eae Chloride‘of Potash) 203.222... Bret) St
IN Oat pe tenes Sulphate of Ammonia. ......... Da Omics
NOL saan citys SulphatevoteRotasivess. «ose 21S eee

The lime taken out through the influence of nitrate is seen
to be extremely high.

We have spoken at some length concerning the unfavorable
characteristics of nitrate of soda when applied to lands of
heavy and uncertain rainfall, particularly when such lands
are deficient in lime. However, notwithstanding these several
draw-backs to its general use in all localities, nitrate of soda
has sufficient superior qualities when applied in proper quan-
tities and under suitable conditions to render its use of the
highest advantage.

When applied in large amounts and under such conditions
as to allow of the fullest effects, nitrate has been observed in
many instances to induce an abnormal and undesirable
growth, which retarded the ripening of the cane, and resulted
in juices of low purity and low sugar content. On the other

15

hand this self-same stimulating property has been of the
greatest service to yellow and “nitrogen-hungry” cane, and
with the application of small amounts of this material, won-
dertul tonic effects have been produced in an extremely short
space of time.

In regard to the influence of nitrate on tasseling, Mr. Geo.
Renton of Ewa Plantation writes: “My experience in one
case with a late application in September of nitrate of soda
was that it materially effected tasseling. About one-third
only of the stalks flowered. As the application in this instance
was made for the express purpose of preventing the tasseling
of the cane, these results were gratifying.” Mr. Renton fur-
ther says: “It is my opinion that either excessive or late ap-
plications of nitrate of soda will lower the juice purity. The
best juice obtained at this mill was from canes upon which
nitrate was put on not later than the latter part of April.”
The experience of Mr. Olding at Kohala has been that
“nitrates prevent tasseling in a very marked degree.” It was
observed last year at the Experiment Station that nitrogenous
fertilizers in general prevented tasseling during the flowering
period, whereas, unfertilized plats, and plats receiving merely
potassic and phosphoric acid fertilizers flowered without ex-
ception. On account of the readily available condition of
nitrate of soda we should expect small applications of this
material to exert a more potent influence in preventing tas-
seling than would be the case with either suiphate of am-
monia, or organic nitrogen.

Some difference of opinion exists as to the amount of nitrate
that can be judiciously added to the soil, and reference will be
made to that subject later on.

Attention has been called to the fact that where nitrate of
soda and chloride of potash are applied to the same land, a
chemical reaction might ensue to the detriment of the soil.
This supposition is based on the fact that the solinm of the
nitrate of soda has a strong affinity for chlorine, which forms
a part of the chloride of potash, and that the two elements
might combine with each other to form common salt. <Al-

16

though this reaction is within the realm of probability we are
without the necessary data for a confirmation of this view.
However it is better to be on the safe side, and on account of
this probable interchange of elements to use potassium sul-
phate instead of potassium chloride, where nitrate of soda is
being used on the land.

Sulphate of ammonia on account of its ready solubility, and
small liability to waste as compared with nitrate of soda, is
held in much fayor as an economical nitrogenous compound,
At 15° ©. 1.3 parts of water dissolve one part of sulphate of
ammonia and it is seen that little difference exists between its
solubility and that of nitrate of soda, rendering its diffusion
throughout the soil almost as compiete as in the case with the
latter substance. However it has one very strong advantage
over the nitrate of soda, in its ready ability to become fixed
in the soil, and on that account alone, its particular suitability
for some locations is very apparent. If we refer to the results
previously given as to the comparative waste of the two fer-
tilizers under similar conditions, a striking contrast is noted.
Of 200 erams of this material added to the land in the lysi-
meter tests: only 3.52 grams of its nitrogen was lost in drain-
age waters, as compared with 72.56 grams of nitrogen lost
from an equal amount of nitrate of soda. Of this small loss,
3.08 grams were in the form of nitrate, into which condition
it had been converted by the nitrifying bacteria of the soil as
previously mentioned. Only .44 gram of nitrogen escaped in
the form of sulphate of ammonia.

To show Mr. Crawley’s experience with this salt on “sandy
soils,” we will give his determinations in full, the conditions
of his experiments having been described on page 15.

] 2 3. 4

Amount of mcisture in

the original soils... . Nor acie mo: Oop. Chali USspweus 0.61 p. ct.
Carbonate of lime in

UTR BOUNS Asse ate! Ge lbipact pio lapeCintoleconp Cosme Ole Oijnpecb.
Weight of soil taken. . 365 grs. 407 grs. | 362 ers. 374 ers.
Time required to pene-

trate two feet. . .. 55 min. 19 min. 12 min, 8 min.
Total water passing

UOT O NE ed Oe Roe ee 320 ee. 342 ec. 345 ce. 355 Ce.
Time required for the

above water to pass |

Phouetion sane 335 min. , 180 min. 95 min. 95 min,
Water holding power |

OL bhe:soils; 2s... 5 49 p. ct. | 39 p. ct. | 43 p. ct.| 38 p. ct.
Moisture in soils after

HENUGAY Ss -<ss0 c= a 31.5) Pach. 20ke pact.) 18eo pp. ct: | 1626" pre.
Sulphate of ammonia

HOBO Css, See AL Sed Mies p. ct. | 42 p. ct. | 59 p. ct.| 86 p. et.
Muriate of potash lost None. 44 ». ct | 56 p- ct. | 65 p. ct,

Sulphate of potash
NOS tea version satu. es

None. 8 Deeb 0 D, Ct.) 29 p. ct.

“Nitrate of soda practically all was lost, there being little
difference in the various soils.” It will be seen that where
the lime carbonate of the soil amounts to 71.157 only &¢% of
the sulphate of ammonia was lost, but the loss increased rap-
idly in proportion as the content of lime carbonate became
larger, a soil of 91.07% of lime carbonate only retaining 147
of the ammonium sulphate applied. These are unusual soils,
however, and the proper conditions for holding the salt in
question are notably lacking; but they afford us a proper
realization of the superior power held by ammonium sulphate
to become fixed under the most adverse circumstances, In
the last column it is seen that one soil is composed almost
entirely of coral or lime-stone, and that other ingredients must
be present in very small quantities. As the double silicates in
the land are most probably responsible for the fixing of the
ammonia radical, it may be easily understood why the co-
efficient of fixation will be reduced in proportion as the bulk
of the soil is taken up with carbonate of lime, and the silicates

excluded.

18

As regards the action of ammonium sulphate as compared
with nitrate of soda on the lime of the soil, there is a marked
difference in favor of the former. In the lysimeter tests to
determine this point, it was found that whereas 26.52 grams
of lime were lost through the action of the nitrate of soda ap-
plied, only 5.49 grams were removed through the influence
of the sulphate of ammonia. In making these comparisons,
attention should be drawn to the amount of lime that was
carried from the soil by the application of water alone with-
out the addition of the various salts. This amount was 1.72
grams, and should be subtracted from the weights of lime re-
moved, as given in the table on page 14, in order to reach the
actual amounts of this soil element that were lost through the
influence of the several agencies.

The action of ammonium sulphate in the soil in furnishing
nitrogen to the cane, is considerably different from that of the
nitrate. The latter substance is in a suitable condition to be
absorbed by the plant roots immediately on going into solu-
tion in soil water, or in coming in contact with the plant root
acids. The ammonia of the ammonium sulphate on the other
hand has to be oxidized by soil bacteria and changed into
nitric acid before it reaches an assimilable state for the cane.
This difference in the immediate availability of the two com-
pounds will explain to a large extent the several differences
displayed in their effects upon the crop. The nitrogen as
nitrate is so readily absorbed when applied to the land as to
act like a stimulant, while the more slowly acting nitrogen
of ammonium sulphate is yielded more gradually as a plant
food, and forms a longer lasting supply of this material, per
given weight of ammonium sulphate added than that from the
nitrate of soda.

We now come to a consideration of nitrogen as supplied
from organic sources. The chief nitrogenous substances of
this order as applied to Hawaiian soils, are dried blood, tank-
age, and fish scrap or ‘fish-guano.” Of these materials dried
blood unquestionably ranks first, both in its high content of
nitrogen and the ease with which it is rendered available by

19

the micro-organisms of the soil. In a perfectly dry state it
has been known to run as high as 14 per cent of nitrogen.
The samples of this material received at the Experiment Sta-
tion would indicate an average of about 12 per cent., with a
small amount of water.

Tankage, though containing less nitrogen than the blood,
is an organic source of nitrogen of no little value. It is com-
posed of scraps and fragments of flesh which have been dried
and ground, after the removal of fats by steaming. Tankages
have been received at the Experiment Station for analysis
which were found to have as high as 10 per cent phosphoric
acid in addition to their liberal content of nitrogen, which
gives them added value as fertilizing compounds.

Fish scrap, on the average, contains about 8 per cent of
nitrogen and 7 per cent of phosphoric acid. It constitutes the
ground residue of fish from which the fats and oils have been
largely removed, and varies considerably in its value as a
manurial substance. Occasionally samples are met with
which contain a large amount of fatty matter, and these fats
and oils when present in considerable quantity cause the other
organic matter to decompose with great difficulty in the soil.
Some years ago a sample was received at the Experiment
Station laboratory which was found on analysis to contailr
over 24 per cent of total fats.

In the consideration of organic substances as a source of
nitrogen, a distinct difference is manifested between them and
the soluble chemical salts which have just been discussed.
Nitrate of soda and sulphate of ammonia, on account of their
solubility in water, may be readily taken up by that medium
and distributed throughout the mass of the soil. The organic
material on the other hand can only be applied to the land in
spots and needs slight covering to depths varying with the
nature of the soil and of the substance used, in order that
the most suitable conditions will be reached for thorough de-
composition and nitrification.

Nitrification is believed by many authorities to be accom-
plished through the agency of three kinds of soil bacteria.

20

One kind changes the nitrogenous material into ammonium
compounds, another converts the latter into nitrous acid, and
stil! another completes the work by a conversion from nitrous
into nitric acid. These processes are slow and in the course
of their operation a gradual distribution of soluble ammon-
ium compounds and nitrates throughout the entire soil very
probably takes place.” For instance as the ammonia is formed
it may be taken up by the water of the soil and carried some
little distance before it becomes fixed, and on being oxidized
into nitric acid a further dissemination most likely results.
The extent of this gradual distribution cannot be measured,
but that available nitrogen is carried to parts of the soil
remote from the point of contact of the original substance is
unquestionable.

PorasH.—This element is usually present as sulphate of
potash in Hawaiian fertilizers, although the muriate is also
used to some extent. The sulphate on account of its very
small effect upon the lime of the soil is favored more than
the muriate, and as littie difference exists between the prices
of the two compounds, the former proves very often the more
economical in some localities.

Owing to the rapidity in which potash becomes fixed in
loams or soils of a clayey nature, Dr. Stubbs of the Louisiana
Experiment Station believes that, in some instances, the more
proper time for application would be before planting, in order
that the repeated plowing and harrowing might thoroughly
distribute the element throughout the soil; otherwise if used
asa top dressing it might become entirely fixed in places con-
tingent with the point of application. However, on account
of the basic nature of Hawaiian soils, and their smaller con-
tent of double silicates as compared with American soils as a
rule, potassic fertilizers are much more readily disseminated
throughout the soil mass by means of rain or irrigation water.
In fact, in the lvsimeter tests conducted at the Experiment
Station, it was shown that potash was found in the drainage
waters where excessive irrigation was followed, and in
amounts sufficient to indicate a loss of the potassic fertilizers

21

which had been applied to the soil. Data are lacking to indi-
cate the relative fixing power of potash in the two salts under
consideration, but figures may be found in the table on page
14 to show the intluence exerted by each form in removing
lime from the land. It is seen that nearly nine times as much
lime was removed from the land where muriate was added,
than resulted from the application of sulphate. The influence
of potassium chloride is evidently almost as potent as that of
the nitrate of soda in its depleting action on the lime content.

In Mr. Crawley’s investigations with the “sandy soils” pre-
viously referred to, some very surprising results were reached
as regards the disposition of the respective potassic com-
pounds to become fixed under similar conditions in soils of a
highly calcareous nature. By referring to the tabulated re-
sults on page 17 it will be noticed that none of the chloride or
sulphate of potash was lost in the soil containing the least
amount of lime carbonate. In the soil with the highest per-
centage of lime carbonate, 65 per cent of the chloride was lost
and 28 per cent of the sulphate. The absorption of potash by
these peculiar soils is intluenced chiefly by their content of
lime carbonate for several reasons. The higher the percent-
age of lime carbonate the lower must be that of the double
silicates in the respective soils, as was pointed out before in
considering sulphate of ammonia, and these silicates are par-
ticularly instrumental in holding potash. The mechanical
condition of the soils is influenced to a large degree by the
quantities of lime carbonate that they contain, and as the
mechanical condition varies so will the rapidity with which
a solution may filter through them. The time that the solu-
tions of potash were in contact with the earth in the pipes i2-
fluenced in great measure the extent of the resulting chemical
changes.

In the early reports of the Experiment Station it was point-
ed out that in adding chloride of potash to lands bordering on
the sea and which are sometimes abnormally high in salt,
there is a liability of increasing the proportion of this deleter-

99
a

ious substance, and on that account sulphate of potash was
advised as the proper form under such conditions.
PuHosrHoric Actb.—This element exists in fertilizers in
many combinations with varying degrees of solubility. It is
usually classed as water-soluble, citrate-soluble, or insoluble.
In considering the availability of what have been called the
essential elements of the soil, it was noticed that although the
lands of the Hawaiian Isiands are usually very high in phos-
phoric acid, that very little of it is rendered assimilable dur-
ing the growth of the crop. On that account it would seem
most natural to apply this element in its most soluble form.
The water-soluble phosphoric acid in the form of super or
double super-phosphate is readily taken up by rain or irriga-
tion water and distributed more or less throughout the sur-
rounding soil and is rather thoroughly fixed. This fixation is
brought about by the carbonate of lime and by the hydrated
ferric oxide and alumina present. In the first case, a more or
less insoluble phosphate of calcium, and in the second case
a basic phosphate of iron or alumina is produced. Althongh
there are Hawaiian soils with no inconsiderable amount of
lime carbonate, the great bulk are either lacking in that com-
pound or else contain it only in very small proportions, The
predominating bases are those of iron and alumina, and with
them the phosphoric acid is rather quickly united; even where
calcic phosphate is formed the indications are that the phos-
phoric acid of this substance is gradually vielded to form com-
binations with the former. As nearly all the phosphoric acid
in the island soils is already a component part of these basic
phosphates, it would seem on first consideration that little or
no improvement could be effected by a further addition to
these insoluble compounds. However, when the soluble phos-
phoric acid is taken up by the water in the soil it is distrib-
uted thoroughly and coming in contact with the minute part-
icles of iron and alumina, results in compounds which on ac-
count of their existence in extremely small grains, and on
account of their thorough dissemination throughout the soil

23
mass, are in a much more available condition than the natural
basic phosphates of the land.

Citrate-soluble, or di-calcic phosphate, although insoluble
in water, is soluble in a solution of citrate of ammonia, and is
readily absorbed by the acids of the plant roots. Owing to its
insolubility in water, however, it cannot be so thoroughly in-
corporated with the soil, as the form previously described and
is of corresponding less value.

Ry insoluble or tri-calcic phosphate is meant that form
which exists in natural or untreated phosphate, and is in-
soluble in water or citrate of ammonia. In the soil it is ren-
dered slowly available through the processes of decay or de-
composition, which action is influenced by the amount of
organic matter with which it is associated, the fineness of its
mechanical division, and also by the moisture content, depth,
and temperature of the soil in which it lies. Dr. Maxwell
has pointed out that the acidity of a soil also assists material-
ly in this decomposing action, and attributes the greater effect
of bone meal on some of the uplands to the higher moisture
and acid content of those soils as compared with the lands of
a lower elevation.

Limn.—This element is present in nearly all fertilizers con-
taining phosphoric acid, and as calcium phosphate is added in
large quantities to Hawaiian soils. In addition to the lime as
phosphate a considerable quantity is also present as sulphate
or gypsum in treated phosphates such as the form designated
as water-soluble or citrate-soluble, and on account of its fine
mechanical and chemical condition is of high value as a fer-
tilizing ingredient.

Ground coral and coral sand are also good as well as cheap
sources of this element and are used to a considerable extent
on these islands, especially where the content of organic mat-
ter is low as well as the lime. The percentages of lime in the
various compounds are approximately as follows:

SUSU ree sone ne eae 32 per cent of lime.
Ground coral... ee sees: 45 per cent of lime.

Corabesand? Jor ees 49 per cent of lime.

24

The difference in lime content between coral sand and
eround coral is due to the admixture of shells in the former,
which are composed of almost pure lime carbonate. Slaked
as well as quick lime are used in some localities, but owing to
the readiness with which these forms of lime attack the nitro-
genous material of the soil, they are unsuitable for many
lands.

Ferrinizers Usep oN tHe DirrerEeNtT ISLANDS.—The amount
of fertilizer to be added to any land involves a consideration
of the available constituents of the soil, and the demands of
cropping. The form in which its ingredients should exist is
influenced by a consideration of their respective properties
and the existing climatic conditions of the localities in which
they are to be applied.

On the Island of Oahu, the average mixed fertilizer con-
tains its phosphoric acid in the water-soluble and citrate
soluble forms; the potash is in the form of sulphate; and the
nitrogen is applied in three forms, as nitrate of soda, sulphate
of ammonia and organic material.

On Maui, fertilizers are applied to a large extent in the
same forms as on Oahu, the water-soluble and the insoluble
phosphoric acid being somewhat lower. The three forms of
nitrogen are generally used in the same fertilizer, although
nitrogen as ammonium sulphate is in excess of the organic
and nitric. The total nitrogen is 0.6 per cent higher than on
Oahu.

On Hawaii on account of the diversity of conditions, fertil-
izers are naturally found to vary more in their composition
than on the other islands. In the Hilo district owing to the
heavy rains, nitrate of soda cannot be used without liability
to waste, and potash in the form of chloride is in disfavor
owing to its depleting action on the lime content of the soils —
which are already low in that element. Most of the nitrogen
ased in the district is derived from organic sources and also
in some measure from sulphate of ammonia, although some
few fertilizers used during the past vear contained nitrate.
In Hamakua phosphoric acid is applied mostly in soluble

forms, the nitrogen as a rule beine derived from ammonium
sulphate and the potash from sulphate.

On Kauai, nitrate of soda and sulphate of ammonia are fay-
ored as sources of nitrogen for mixed fertilizers, very little
of this element being applied in an organic form. According
to the analyses of the Experiment Station laboratory, Kauai
fertilizers are higher in nitrogen as a rule than those from
any other island.

On account of the wide variations in the composition of fer-
tilizers and the limited number at hand for forming an esti-
mate, it would be impossible to give average formulas for the
different islands which would be reliable for purposes of com-
parison. The following table will give an idea of the wide dif-
ferences between the lowest and highest percentages of each
element applied in mixed fertilizers of which we have data.

ag |
Potash. Phosphoric Acid. Nitrogen.

=

|
|
ISLAND. t.

Lowest | Highest.| Lowest. | Highest,| Lowest. | Highest.

|Per Cent.|Per Cent |Per Cent |Per Cent,.Per Cent.| Per Cent.

INIT evel ees ae .| 4.13 17 . 24 5.10 | 14.26 5.04 9.70
IMM ie ee se ote Cao 10.10 5.68 | 9,39 6.66 9,91
EFawalliniy ae sect. sr | 4.03 99.54 5.29 |

14.61 3.25 | 10.42
| 4.70 7.10

8.50 | 14.66 | 7.01 | 15.00

Theoretically the various
elements should be added to the land in such proportions and
at such times as the crop requires them. This would neces-

Trin AND MrtrHops or APPLYING.

sitate repeated applications of small quantities of mixed fer-
tilizers with their respective ingredients in ever varying pro-
portions, due consideration being given to their individual
inclinations to waste. It would mean the feeding of the plant
according to the needs of its fluctuating growth and develop-
ment, and the multitudinous changes involved in the elabora-
tion of its products. Agricultural science has not advanced
so far as to make such nice calculations possible, and if it
had, the cost of labor would not permit the close application
of such theoretical doctrines.

26

Most plantations make two applications of mixed fertilizers
during the growth of the crop and the times of these applica-
tions vary on different plantations. Some incorporate fertil-
izing material with the soil of the seed bed before planting
and others make the first application when the cane is six to
eight weeks old or after suckering has actually commenced.
Where two applications are made, the first is usually at the
end of the suckering period and the second in the fall or in
the following spring, depending on the time of the planting
season.

The methods followed in applying fertilizers depends large-
ly upon the kind used. Where the ingredients are in soluble
forms, on account of labor considerations the practice on
many plantations is to merely drop the material in the fur-
row beside the cane stalks, without covering. This method
should give satisfactory results with any but fertilizers con-
taining organic and insoluble forms such as blood, tankage,
etc., which latter substances require a slight depth in the soil
to meet the proper conditions for nitrification and satisfactory
decomposition.

Dr. W. ©. Stubbs, (“Sugar Cane,” Vol. 1) says, in speaking
of practices in Louisiana: ‘Nitrates and salts of ammonia
are always best used as a top dressing—at short intervals, in
small quantities. Dried blood requires but little depth, pro-
vided moisture necessary for conversion into available plaut
food be present. Tankage, bones, and fish scrap must be sunk
to deeper depths to obtain fermentation necessary to their
conversion into soluble plant food. None of the above should
be turned too low, especially in stiff soils, since air, moisture,
and heat are the factors needed in decomposition.”

It was pointed out in the report of the Experiment Station
for 1896, that considerable risk is entailed by applying soluble
fertilizers in the furrow under the seed where irrigation is
practiced. Under such conditions there is a likelihood of the
material being washed down and out of the soil before the
young cane is in a condition to appropriate any of it. This
would not apply, however, to organic sources of nitrogen or

27

phosphoric acid which are so gradually decomposed, and we
understand that such material is giving good results in one
locality when applied in such manner.

Mr. Geo. Ross, member of the Committee on Fertilization,
writes a very interesting letter on the practices followed ou
Hakalau Plantation. He says: “At Hakalau I am using al-
most exclusively a high grade fertilizer of the following aver-
age composition. Nitrogen (from sulphate of ammonia and
organic ammonia of dissolved bones) 5 to 6¢; Phosphoric acid
(available) 9 to 10 ¢: Potash in the form of sulphate of potash,
9 to 10¢. This is applied to the plant cane at the rate of 900
Ibs per acre in two applications, the first at time of planting
and at the rate of 300 Ibs. per acre, scattered by hand in the
bottom of the furrow, or seed bed, followed by a cultivator wo
stir it up with the soil. The second application is at the rate
of 600 Ibs. per acre and just prior to ‘hilling up,’ or when the
cane is too high for further cultivation by mule or horse im-
plements. At this time it is scattered, also by hand, on both
sides of the cane row and covered up by small plows which
throw the soil in towards the cane, which is afterwards
trimmed up by the hoe.

The same grade of fertilizer is applied to all ratoon cane,
but usually in one application of about 500 lbs. per acre. It
is applied to both sides of the row as is done in the case of
the second application to plant cane, and is covered over in
the same way by small one horse plows. The usual practice is
to apply it to the ratoons as early as possible after the tirst
hoeing.

We have used a fertilizer of this general composition for
several years, and although I have experimented to some ex-
tent with such special fertilizers as tankage, fish scrap, and
bone meal, I have had no results to warrant their continuance.
Nitrate of soda on account of its solubility is not adapted to
this district, where in the past we have been subject to sch
heavy rainfall whereby this salt is liable to be lost before be-
ing taken up by the plant. Lime always gives satisfactory

NO
28

results and this is true of all soils in this district. Filter-press
cake when passed through a disintegrator and applied in lib-
eral quantity gives excellent and lasting results. The same,
of course, is true of stable manure. I might state that the
percentage of potash in the mixed fertilizer, above referred to
was increased from 5 to 6¢ up to its present strength about
three years ago, and with marked results. This was suggest-
ed to me from observing the luxuriant growth produced by
ashes from timber burnt in forest clearing.”

On some plantations a most commendable system is fol-
lowed of modifying the composition of fertilizers to suit the
requirements of the different fields. Mr. D. C. Lindsay, of
aia Plantation says: “Our regular plant cane mixture is
composed of superphosphate, sulphate of potash, nitrate of
soda and sulphate of ammonia. We have each field we plant
analyzed and vary the proportions of the above ingredients to
suit the analysis, so that as a rule every field has a different
fertilizer to suit its requirements.

We sometimes use as a special fertilizer a mixture of nitrate
of soda and coral lime in equal quantities and apply about 400
to 500 Ibs. per acre. We apply this as late as July and
August in the same manner as plant cane mixture.

The difference between our plant cane and ratoon mixture,
is, that in the latter we increase the proportion of nitrate of
soda and decrease the phosphoric ingredient.”

Mr. John Watt of the Committee on Fertilization, in wiit-
ine concerning the practices followed at Honokaa, says that
it is customary to apply from 500 to 800 pounds of mixed ter-
tilizer per acre for the crop. “On poor upper lands we give
two applications, on lower lands where soil is rich we give
only one. With only one application we distribute the fer-
tilizer in the furrow before the seed is put in, mixing with the
soil by a subsoiler or small plow. Where we give two appli-
cations the first is given as above and second is given when
the cane has about two months’ growth, sometimes a little
later depending upon the condition of the cane, by distribue-

29

ing the fertilizer along side of the stool and either hoeing it
in or running a cultivator along the furrows.”
This year the general composition of mixed fertilizer ap-

plied at Honokaa has been as follows:

I—107 Phosphoric acid.
S¢ Ammonia from sulphate.
o¢ Potash from sulphate.

Mr. Watt savs: “The above is the fertilizer which we have
used this vear and the weather has been so that we cannot
tell what results we may have from it. Last vear we used a
different mixture on the upper lands with very good results,
the analysis of which was as follows:

15” Potash from sulphate.
o¢ Ammonia from sulphate.
10—12¢ Phosphoric acid.

“With the above fertilizer the cane came up very well and
maintained a vigorous growth until it was checked by the
very dry weather during the past five months. When we
planted this cane we gave it an application of T00 pounds of
the above fertilizer with the seed and about four months later
we gave it 700 pounds per acre more.”

For some years past Mr. Watt kas been'very careful in
regard to the preserving of all stable manure, which is liber-
ally treated with a dressing of superphosphate to prevent loss
of ammonia. Both with this compound and with mud-press
cakes which have been passed through a disintegrator he has
obtained splendid results.

We are in receipt of a very interesting letter from Mr. J. T.
Crawley. who writes of a method in vogue at Kihei Plantatiou
for the distribution of nitrate of soda. On account of its bear-
ing so strongly on the question of labor economy the letter
is given in full.

30
Honouutu, T. H., Sept. 24, 1901.

CHas. F. Eck4rt,
Chairman, Committee on Fertilization.

Dear Str:—I wish to include in the report on fertilization
a method of applying nitrate of soda devised and used by
Manager W. F. Pogue of Kihei Plantation, and communicated
to me in a letter from him dated July 26. Mr. Pogue says:
“Lacking labor sufficient to apply nitrate of soda with ground
coral, I have just finished fertilizing some 600 odd acres with
nitrate dissolved in water and applied in the irrigation, The
form of application was as follows: Dilute one bag of nitrate
of soda in one barrel containing 50 gallons of water, one paii
of this solution is added to 4 pails of water, or in that pro-
portion; in another barrel a hose bibb in the bottom of the
last barrel discharges the diluted solution into a tub which is
kept filled to a given mark, from the tub the mixture flows
in an exact amount all day into the main irrigation ditch. The
outlet of the tub is fixed, and cannot be opened or closed by
the laborer doing the work. Strainers are used on the tub
and diluting barrel. In this way one man can easily apply
100 lbs. per acre of nitrate to 60 acres in six days, two men
will do three or four times as much. In applying I have put
on 75 lbs. of nitrate to an irrigation, then skip one or two
irrigations and apply the same amount again.

The fields thus treated have started from short joint sticks
to very long joint sticks which means a very rank growth.

It seems to me that any soluble fertilizers can be applied
much more evenly and certainly very much cheaper than in
the ordinary method.

It also seems to me that if the applications could be made
in small doses as the cane needs it, it would be the correct
method, exactly as we would feed a horse or a cow.”

Again in a letter of Sept. 20, Mr. Pogue says that he is
applying 50 pounds nitrate per acre. To quote his words:
“We have with my method applied 50 pounds to the acre with

one ordinary Jap to as high as 26 acres in one day, that is,
5,250 pounds were applied to 105 acres (one field) in four days
by one Jap. The cane began showing the effects on the fifth
day, by the seventh day after application, the cane roots had
fully gotten hold of the stimulant, from a greenish yellow the
leaves were turned a dark green.

We apply 50 Ibs. nitrate every other irrigation, or say every
18 days. Cane shows the want of stimulant in from 20 to 30
days, according to nature of soil, after first application, and
30 to 40 days after the second application with this amount
of 50 Ibs. per acre. Later on, I can give you results of further
experiments on these same lines.”

The idea of dissolving the nitrate of soda in the water of
irrigation was suggested by the scarcity of labor, and My.
Pogue saw the added advantage of applying this very soluble
fertilizer in very small quantities and frequently, rather than
in one or two large doses. The only objection that I can see
to this method is that there will be loss in the ditches through
which the water passes before it reaches the rows of cane, and
this loss will depend upon the nature of the soil that compose
the bottoms and sides of the ditches. Mr. Pogue states that
in the red soils where he is using the method the loss of water
is very small. Again, if the part of the row where the water
is entering takes up more water than the far end it will like-
wise take up more nitrate of soda.

The main advantage, aside from the labor question, to my
mind is the advantage of applying only so much nitrate as the
cane needs at the time, and to be able to apply it in small and
frequent doses.

With as fugitive a substance as nitrate of soda this is a
ereat consideration indeed. Whatever of this substance as is
not taken up by the cane, can be washed away either by a
heavy rain or by a heavy irrigation, and the least amount that
is in the soil at any one time the less is the danger of loss.

Very truly yours,

J. T, CRAWLEY.

32

This method for the distribution of nitrate of soda, as
adopted by Mr. Pogue, apparently has much to commend it,
both as regards the saving of labor and the added advantage
of being able to apply small quantities of the material as the
cane seems to demand it. As the barrel from which the
nitrate solution is discharged into the main ditch is kept at
a constant level, an even pressure and discharge is obtained
which would guarantee a regular and unchanging admixture
of nitrate solution and irrigation water. Mr. Crawley’s obser-
vation as regards probable loss of nitrate during the passage
of the water through the irrigation ditches is well taken,
though this loss may probably be small and of little conse-
quence as compared with the saving of labor and other ad-
vantages to be derived from a following of this method. How-
ever this loss is a factor which will be considered later on in a
special reference to the use of nitrate on plantations.

A curious point manifests itself in this method of applying
nitrate of soda, which would be particularly striking where
the cane is planted in long rows receiving their water direct
from the main ditch, and less so in proportion as lateral
trenches are used and the cane rows shortened. In the former
instance the ends of the rows next to the ditch necessarily re-
ceive more water than the other extremities and consequently
they will receive more nitrate. When this material is dis-
tributed in the usual way by hand, each part of the field has
approximately the same amount applied to it, and loses it in
proportion to the amount of water added providing a point
above saturation is reached. At the ditch end of the furrow,
according to Mr. Pogue’s method a larger quantity of nitrate
comes in contact with the cane roots, while in the ordinary
method that point is marked by the greatest loss.

Mr. Pogue speaks of the probable advisability of applying
all soluble fertilizers in this way on irrigating plantations and
the plan certainly presents many favorable points for consid-
eration. However, the question would arise whether the say-
ing of labor and the advantage of small and frequent applica-
tiens would off-set the loss of soluble high grade fertilizers

aS
in the irrigation ditches, which is influenced by the area and
nature of the exposed soil. This is a point which must be
studied out very carefully before any radical change in the
system of applying fertilizers is introduced, and I believe this
point may be fully determined by a method which will shortly
be presented for consideration.

It has been pointed out that the ends of the furrows next
the ditches receive more water than other points along the
cane row. Under ordinary conditions the soil at these furrow
ends, where long rows are the rule, will soon become. sat-
urated and lose a larger quantity of their available plant food
than other points, through the leaching action of the excess
of water. With that water will go a certain percentage of the
fertilizer in solution it is true, but the dissolved elements
which leave the irrigation water to become fixed in the soil,
would doubtless be more than sufficient to replace the same
elements that had been removed from the soil itself. In other
words the largest amount of fertilizing material would be
added to the points suffering most from ordinary irrigation,
on account of the resultant leaching action.

NITRATE OF SODA.

Owing to the differences of opinion held by plantation man-
agers concerning the efficacy of this substance as a fertilizing
compound, I wish to give a consideration of this subject some
prominence in this report on fertilization, as I believe that the
reasons for this difference of opinion can be largely explained,

In the early reports of the Experiment Station, the readi-
ness with which nitrate of soda is taken up by the cane and
its corresponding stimulating action on the plant were re-
ferred to at some length. We may quote from the Report of
1895, page 29, where Dr. Maxwell says: ‘Excepting in loca-
tions where the water supply is so small as to retard its quick
operation, nitrate of soda is not a safe and normal. fertilizer—
it is not a good ordinary diet for comparatively slow growing
plants. Under the average conditions of moisture and
warmth, the plant takes it too greedily, and the result often is

34

abnormal growth. The results of this abnormal growth in
cane are bulk, which includes an excess of water and un-
elaborated products of assimilation, and comparatively less
sugar, with low purity of the juice. In wheat and oats the
result is lots of straw and little grain. In one case where the
manager of a plantation called my attention to a piece of
cane, which he called ‘very coarse and rank, and would never
get real ripe, I found that 350 pounds of nitrate had been
added all at once, and the weather had been such as to allow
of the fullest effects. I do not advise nitrate of soda as a reg:
ular diet in any situations excepting those of extremely small
water supply. I advise nitrate of soda only as a tonic and
immediate source of nitrogen in a crisis of a crop, and only in
locations of moderate or small rainfall, but never where the
rainfall is constant or heavy.”

The views of Dr. Maxwell on this subject are clearly set
forth, and the advices of the Experiment Station in regard to
the use of this material have been largely influenced by his
practical observations of field effects following the application
of nitrate on plantations.

During the last few months, my attention has been called to
the fact that a number of plantations are applying nitrate far
in excess of amounts considered safe by the Experiment Sta-
tion for the normal growth and development of the cane, and
reports from these plantations indicate that the cane is doing
well. These cases certainly need careful consideration, and a
study of the conditions under which nitrate is applied in these
instances must necessarily throw considerable light on this
important and apparently perplexing problem. Reference has
been made to a case where 350 pounds of nitrate, per applica-
tion per acre, were seen to produce a rank and frothy growth
on one plantation where conditions allowed its complete ap-
propriation by the cane. In other instances of more recent
observation it is found that 500 pounds, per application per
acre, leaves nothing to be desired, the cane presenting not
only a vigorous, but a perfectly sound and healthy growth.
This apparent inconsistency, I believe may be fully explained,

35
and the explanation will involve a factor of greater econom-
ical significance than the nitrate itself, namely that of water
supply.

The properties of nitrate of soda have already been dis-
cussed, and its ready solubility and disinclination to become
fixed in the soil have received special attention. It was noted
in the lysimeter tests referred to on page 13 that the loss of
nitrate of soda from over-irrigation reached extremely large
proportions aid those data will now be of particular value in
considering the subject in hand. If a plantation were to use
say 500 or 600 Ibs. of nitrate, per application per acre, also
applying more water to the fields than the soil will hold, the
excess of water which drains off is necessarily going to carry
from the land, a large percentage of the nitrate of soda, and
the nitrate remaining in the soil after irrigation is concluded
might be easily reduced to such a quantity that a harmful in-
finence could not be exerted on the crop. In other words the
cane would not get all of the nitrate applied and a large per-
centage of this material together with a large amount of
water would be going to waste.

It is seen that such a condition of affairs is possible, and
“with the light of further data it will be seen to be probable.
Where a plantation is using large amounts of nitrate without
any signs of an injurious action, and where the water of irri-
gation is practically free from salt, a view that over-irrigation
is practiced can only be based on the non-deleterious action of
the nitrate of soda; at the present time sufficient data for a
thorough confirmation of this opinion are lacking. But if we
take a plantation that is using nitrate of soda in large quan-
tities and is irrigating with water of high salt content, suffi-
cient evidence is at hand to show that a large part of that
nitrate is being wasted. and in proportion to the amount of
water used over and above what is necessary to saturate the
soil. This leads us into a consideration of the salt content of
irrigation water and of Hawaiian soils, which subject has a
particular bearing on the question before us.

In Bulletin No. 90, U. S. Department of Agriculture, en-

36

titled “Irrigation in Hawaii,” is given a table showing the
percentages of salt that have been found in Hawaiian soils,
and the resulting condition of cane growing on those lands.
The tabulated results are given in full.

SALT FOUND IN HAWAIIAN SUGAR LANDS, AND ITS EFFECT
UPON SUGAR CANE.

Sample Salt in

of Location. Soil. Condition of Cane.

Soil Per Cent.

Denes SAaphlands cies hein .061 Normal.

Diiaied SAI sit Ha ReMANO Se Oas .063 Normal.

BHA Paina ote ee kta aea ty .050 Normal.

4 ..} PANN ose coer eS TAENR At cs .059 Normal.

a ieyroee bel Bo id Er 0s 1s besa at al 129 Not wholly healthy.

Git Sag aie ose ARIS RR . 130 Not wholly healthy.

thee i Fen UES oe a i 155 Quite healthy and normal.

Sa Fp muy Cea A fee rh 181 Yellow in color.

eae rh Pipette na a eR .181 Yellow in color.
Osea] SIMCHA PRR ES edPane tye .460 Small, yellow, stunted.
let OF REN ASE uN .832 (ane white and dying.
12 Eee Sea vb lutinlan dee pean or A228 Leaves bleached, cane small.

Another table gives the effect of salt upon the growth of
cane, on “three parts of one field which contained different
amounts of salt in the soil, the soil in other respects being —
identical.”

Yield of-

!

Salt in
mis sugar
pete Per Cent. | Per acre.
| Ons
AB Lys i 07s Wa AURA Mien Sra EM eae SIR ba ACAI mA CERN Ms Ve 0.10 | 6.0
SeconGs parti wees ay ee eS MOGs apa ainien ce: WRU RE 0.45 1.5
MI raat be eres kc trem aay ieee we mane y eet ee Shady closers el sO apnea Che CO

It is noticed from the first table that where the salt content
of the soil reaches over 0.1 per cent an injurious effect is pro-
duced on the cane, soil sample No. 7 with 0.155 per cent being
an exception.

We will now consider the amount of salt that is found in
some of our irrigation waters and take for an example, the

aT

water of a plantation which is using 1,000 pounds of nitrate
of soda per acre, making two applications of 500 pounds each.
The manager of this plantation estimates that he is using
about 2,500,000 gallons of water per acre for the crop, and this
water is found on analysis to contain over 125 grains of salt
per U.S. gallon. If 2,500,000 gallons of water are being ap-
plied to the acre, with it go 44,642 pounds of salt, during the
growth of one crop. If the land in question were not irrigated
to a point above saturation practically none of this water
would drain off and the salt would remain in the soil. The
weight of an acre of soil to a depth of 12 inches is approxi-
mately 3,500,000 pounds, and 44,642 Ibs. of salt are practical-
ly 1.27 per cent of this amount. This would mean that at the
end of five or six irrigations the cane would likely sicken and
turn yellow. A certain amount of salt is taken up by the
cane itself without apparent bad effects, and the percentage
remaining in the soil would consequently be lessened but only
to a very small degree and not enough to alter these figures
to any appreciable extent.

However the cane on this plantation is doing well and the
salty water is having no apparent effect, which would indicate
that the salt from the water is not reaching a harmful accu-
mulation in the soil. An undue concentration of salt could
only have been prevented by an occassional very heavy rain
or by an excessive amount of water used in irrigation. For
instance let us say that only so much water was added during
five irrigations as the soil would take up and hold. Then this
water would evaporate from the surface of the soil and be dis-
sipated into the air through the leaves of the cane, leaving
the salt behind, and in quantities sufficient to weaken the
erowth of the cane. If, however, for the sixth irrigation,
double the amount should be used as was applied during any
of the previous irrigations, the accumulation of salt would
be dissolved up and removed in large measure in the drainage
from the land.

The soil would then be freed from its injurious amount of

38

salt and again be suitable for the growth of the cane. This
occasional flushing of the land to such an extent is not likely
to occur, however, on an irrigating plantation; the chances.
are in favor of an excess being applied at each watering, and
that the amount that drains off from the land during every
irrigation is what keeps the salt down below a harmful pro-
portion. The manager of this plantation did not feel that he
was using an excess of water, because if he decreased the
amount applied, the cane soon showed it. Now on cutting
that water down did the cane suffer from too little water or
too much salt?) To my mind it was more likely the salt which
produced the sickening of the cane, because conditions were
then made more favorable for an accumulation of that ma-
terial.

If a soil were irrigated with saline water below a point of
saturation, for a number of times, it has been pointed out that
the salt solution in the soil necessarily becomes more concen-
trated and contains a higher percentage of salt than the irri-
gation water. Providing that the drainage from the land is
good and an excess of water can find an outlet through under-
ground or other channels, the more water that is put on in
excess of the amount that the soil will hold, the more dilute
will become the salt solution in the soil, until a point is
reached in which the solution in the soil is practically of the
same density as the irrigation water. The more dilute this
salt solution is rendered, naturally the more suitable it is for
the growth of the cane. But as soils have a high absorptive
power for water varying on these islands between 30 and 87
per cent., it is readily seen that after any irrigation where
there is much salt in the water, a considerable quantity of
that material must necessarily be left behind in the land no
matter how much water is applied. When the next applica-
tion of water is made, the concentrated solution of the soil is
added in large measure to the irrigation applied, and the salt
percentage of the latter is increased as it passes into the soil,
until an amount is added sufficient to leach through the soil
and drain off, when the dilution will set in according to the

excess of water applied after that point is reached. It can
readily be seen what may happen when the irrigation is cut
down in some instances and particularly when it is cut down
to such a degree as to allow of no drain from the land what-
ever. If the supply of water were decreased gradually it is
not too much to suppose that before a point is reached at
which the cane will suffer from too little water, it will suffer
from too much salt.

It has been established as a principle in soil physics that if
a continuous and rather heavy rain falls evenly upon the sur-
face of a homogeneous soil, a column of water is formed in
the soil which will as it descends displace a salty solution
without mixing with it to an appreciable extent. If the drain.
age of the land were good, the salt solution would be forced
out of the soil into the natural outlet. In irrigation as prac-
ticed on these islands, however, I believe that the diffusive or
diluting action of the applied water would be a more potent
factor in removing salt from the land, if the soil were deep
and of high absorptive power, than that of mere presstre.
This is caused by the water having to be distributed through-
out the soil from fewer points of application as compared with
rain water, and also by the fact that the salt or salt solution
in the hills between the furrows where it is carried by capil-
larity, could not be forced out by any column of water
descending from the cane furrow. However, the question of
pressure cannot be omitted entirely in a consideratiun of the
manner in which salt is removed from the lands of irrigating
plantations, as its importance will increase with the shaliow-
‘ness of the soil and its inability to hold much water.

We have now seen that a plantation which is using very
salty water for irrigation purposes must have a well drained
soil, and irrigate quite frequently above saturation, in order
that the cane may produce a healthy and normal growth, and
we now come to the point upon which this question of irriga-
tion bears from a fertilizing standpoint. Under such condi-
tions what becomes of the nitrate of soda that is applied in
such large quantities to the land? <As nitrate of soda is an

4()

extremely soluble material and is but slightly fixed in the
soil, large amounts must be leached from the land and lost
through the excess of irrigation water used under the existing
conditions, and it is not unreasonable to suppose that the
amount of nitrate remaining in the soil is decreased to such
an extent, that the effects of this material on the crop do not
correspond with the effects of the same material added in like
quantities, but under conditions where the cane may appro-
priate the full amount.

These points in regard to the use of salty water on our
cane lands open up a new field for investigation along the line
of irrigation, but a consideration of that matter must neces-
sarily be left out of a report of this nature.

On a plantation where nitrate of soda is being added to the
land in considerable quantities at each application, and where
the irrigation water contains in solution only a very smail
amount of salt, we cannot say positively that over-irrigation
is practiced, as at the present time data are lacking to sub-
stantiate such a view. The fact that such land is able to
stand more nitrate than other lands where irrigation is not
practiced, but where the full effects of the nitrate are unques-
tionably obtained, points to the conclusion that an excess of
water may in large measure account for this apparent incon-
sistency. The original nitrogen content of the soils and the
size of the crop are naturally factors to be taken into consid-
eration, but they are not sufficient to account for such varia-
tions in the behavior of nitrate as we have found in some
instances. Unfortunately over-irrigation is not always man-
ifested in a visible drainage from the land. An excess of
water in some instances can sink down into a deep soil below
a point from which capillarity can raise it, and find an outlet
into an underground reservoir, or along impervious strata
into the sea.

The necessity of determining the probable loss of nitrate on
a plantation such as we have just described would seem to be
of more importance than in the case which has already been
considered. Not only is there a likelihood of so much nitrate

41

being lost, but with it is bound up the question of water
which, economically, is a matter of greater concern. Where
irrigation with brackish water is practiced, more water would
necessarily have to be used, than would be the case if the
water were “sweet,” as an occasional over-irrigation is re-
quired. However, in both instances a loss of nitrate and a
corresponding loss of water are conditions capable of amel-
ioration, although the degree of conservation of brackish
water would vary with its percentage of salt.

On one plantation where nitrate is used in large amounts,
the manager informs me that directions are always given to
use less water for the first irrigation following an application
of nitrate of soda, and this certainly is a good precaution to
observe, as in a measure it constitutes a safe guard against
the immediate loss of the nitrate. But if we look into this
matter more closely, it can be seen that this practice does not
insure completely against a considerable loss of this soluble
material, although a certain saving would take place, provid-
ing of course, that we assume that over-irrigation is the rule,
which still remains to be proven. For instance, let us say that
500 pounds of nitrate are applied, and one-half of the water
ordinarily used, is applied at the first irrigation following.
Then we may feel reasonably certain that none of the nitrate
is lost from the land during that irrigation; but the question
arises: Can the cane appropriate all of that 500 pounds of
nitrate between the time it is applied and the second irrigation
following? Such a period we might say would probably cover
ten or twelve days at the most, and we may feel sure that ail
the nitrate could not possibly be assimilated by the cane in
that time. What is not assimilated is then liable to waste
during the second irrigation and those following.

Although this report is concerned primarily with fertiliza-
tion, owing to the manner in which soluble fertilizing material
may be washed out of the land and lost, the question of over-
irrigation must needs be bound up quite closely in an eco-
nomic consideration of this subject. Through the examina-
tion of many soils from various plantations, a wide variation

42

was found to exist as regards their capacities to take up and
hold water. and consequently irrigation requirements were
seen to vary within very wide limits in different localities. A
comparison of the amounts of water used per pound of sugar
produced at the Experiment Station and on several planta-
tions, Showed a variation between 859 Ibs. at the Experiment
Station and five and six times this amount on the plantations
(‘Irrigation in Hawaii,” Maxwell). Such results would seem
to indicate that a superfluous amount of water had been used
and probably still is being used on many plantations. This
question from an economic standpoint is certainly one of the
highest importance, and although at the present time we have
data that point quite significantly to the fact that there must
be a waste in many instances, the amount of irrigation water
that can be applied to Hawaiian soils, without waste, has
never been determined. The importance of the subject would
require that a definite conclusion be reached in every case
where the conservation of water is a vital consideration, and
I believe that this may be accomplished in a practical man-
ner and on the field to which the water is being applied.

In a deep soil where the drainage is evidently through some
underground and invisible outlet, any method for the determ-
ination of loss of water must be based on the water absorptive
power of the soil. If on such a land we can trace the down-
ward movement of the water, and show that a penetration is
reached below a point from which capillarity can raise it, the
question of loss is fully solved. When water is applied to the
land, it is only when the minute capillary pores of the surface
are filled, that those immediately below can take up water,
and on becoming saturated allow the water to proceed to
depths below them. The downward movement of water in a
soil is then characterized by an increasing layer of saturated
soil which graduaily extends toward the lower levels until
an outlet is reached and percolation ensues from hydrostatic
pressure. Now if we can follow the extension of this saturat-
ed layer and note the time in which it comes in contact with
a stratum or suitable medium for drainage, we can say pos-

43

itively that any water applied after such time is bound to
waste from the land.

oy the adaptation of an electrical instrument, termed a soil
hygrometer, devised by the Division of Soils, U. S. Department
of Agriculture, for determining the moisture content of soils,
I believe the point referred to above may be fully determined.
In describing this soil hygrometer we will quote from an
article of Lyman J. Briggs, Department of Agriculture. ‘‘This
method depends upon the principle that the resistance offered
to the passage of an electric current from one carbon plate to
another buried in the soil depends upon the amount of mois-
ture present in the soil between the carbon plates and elec-
trodes. This resistance is measured by a suitable instrument
designed for this purpose.

The electrical resistance of the soil between the carbon
electrodes depends not only upon the amount of water present
in the soil, but also upon the quantity of soluble salts dis-
solved in the water, and upon the temperature. For soils iu
which the amount of water soluble material is not sufficiently
great to interfere with plant development, field experiments
appear to show that for any given water content, the amount
of salts in solution remains very approximately the same in
any given soil. The determinations made by this method rest
consequently upon the assumption that the salt content does
not change independently of the maisture content. Wherever
we have a translocation of salts due to excessive evaporation
or seepage, this assumption will not hold. In such cases the
fact that a translocation of salts has taken place is shown by
gravimetric moisture determinations which should be occa-
sionally made for this purpose; and if the departure from the
previous conditions is not great, the error may be easily cor-
rected.

The effect of the change in the soil resistance due to tem-
perature is eliminated by comparing the soil resistance with
the resistance of a small cell containing a solution whose elec-
trical resistance changes with temperature at exactly the same

44

rate as the soil resistance, and which is buried in the soil near
the electrode so as to possess always the same temperature as
the soil.

The comparison of these resistances is made by an instru-
ment which is a modified form of the well-known Wheatstone
bridge method of measuring electrical resistance. The soil
resistance and the temperature cell resistance occupy adjacent
arms of the bridge, and any change in temperature affects
both resistances to the same extent, and so does not change
the reading of the instrument.”

“The moisture record obtained, consequently deals with the
variation in moisture content of the same portion of the soil.
This is one of the advantages of the method since it has been
shown that the moisture content of a seemingly uniform soil
may vary as much as 4 per cent within an area of one square
rod. Consequently in order to obtain a consistent record of
the change in water content, it is necessary to deal with the
same sample of soil, which can only be done by this electrical
method.”

“We thus see that the electrical method has the advantage
of working always with the same portion of soil and furnishes
a direct and rapid method of determining the water content
after having once been installed.”

From the above description an idea may be gained as to the
principle of this method for making moisture determinations
of the soil in place. In adapting it to meet the requirements
of an investigation in respect to the loss of water from the
land, these electrodes can be sunk to varying depths in the
soil and the movement of water can be traced.

I believe that a number of extremely important facts may
be learned from its use on Hawaiian plantations which could
not be learned in any other practical way. For instance the
amount of water that is lost in irrigation ditches might be de-
termined by noting the depth of soil saturation and the extent
of the exposed area. The amount of nitrate of soda that
would be held by this amount of water, where that material

45

is applied as at Kihei, could be calculated with fairly reliable
results.

Where irrigation with long rows is the rule, the amount of
water that is taken up at the ditch end could be measured and
compared with the amount absorbed at the other extremity of
the furrow.

The amount of salt dissolved in waters may also be de-
termined by this method and an insight gained as to the move-
ments of common salt where brackish water is used in irri-
gation.

In fact, this method would seem to present a means of solyv-
ing many problems that have heretofore been the subject of
much theoretical speculation, but of which our exact knowl-
edge has been rather limited. In conclusion I will say that
the Experiment Station is about to procure one of these soil
hygrometers and after a thorough trial in the Experiment Sta-
tion field I would suggest that investigations be conducted on
the cane fields of various plantations where conditions would
warrant the expectation that valuable results might be ob-
tained.

Respectfully submitted
C. F. Eckart,

Chairman of Committee.

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