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 Foreword
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Group Title: New series
Title: Tung oil
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Permanent Link: http://ufdc.ufl.edu/UF00003048/00001
 Material Information
Title: Tung oil one of Florida's greatest potential resources
Series Title: New series
Physical Description: 33 p. : 22 cm. ;
Language: English
Creator: Florida -- Dept. of Agriculture
Publisher: s.n.
Place of Publication: Tallahassee
Publication Date: 1942
 Subjects
Subject: Tung oil -- Florida   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: "Reference information": p. 33.
General Note: Cover-title.
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Bibliographic ID: UF00003048
Volume ID: VID00001
Source Institution: University of Florida
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Resource Identifier: ltqf - AAA3501
ltuf - AME6312
oclc - 41214558
alephbibnum - 002441108
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Table of Contents
    Front Cover
        Page 1
        Page 2
    Foreword
        Page 3
        Page 4
    Main
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
Full Text
DAVID H AIMnriLU


NEW SERI-~E


Tung Oil

One of Florida's Greatest
Potential Resources


1 i' '~'


.ST.\ Tr fP: F 1. )R I I)A
I ) Tp:i'itnwil (of Agricuiltiur
N,'.lh;imi M :Ikt' C vi mirn;' lt)o l'i
"'r,i ~:.,-t->-(i


MAY. 1942









Foreword

We wish to express our appreciation to
B. F. Williamson of Gainesville, national
authority on tung oil, for the material in
this book. We believe its contents will aid
those now producing tung oil and will prove
of great value to prospective growers. The
production of tung oil is so minute com-
pared to the enormous production that
could be absorbed that it offers a lucrative
field. Its expansion would fill a gap in our
present economy.
The Florida Department of Agriculture
offers its facilities to interested parties.
FLORIDA DEPARTMENT OF
AGRICULTURE
NATHAN MAYO, Commissioner.





I)I P.\ hI'T.I ENT 4 .*' .\
Introduction
Among the various economic plants that have been in-
troduced into Florida in recent years probably none has re-
ceived more attention than the tung oil tree (Aleurites fordi,
Hemsl). Owing to the unique uses of its products and the
precarious source of supply it has become vitally necessary to
the paint and varnish industry that tung oil be produced in
commercial quantities in the United States. Florida alone
among the States has a climate suitable for commercial pro-
duction.
Origin
The tung oil tree (Aleurites fordi, Hemsl) is a native of
Central and Western China. While it may be grown in regions
subject to severe frosts, it is killed back very easily by cold,
so that its commercial culture in China is limited to the south-
ern portion of its range. Commercial production is concen-
trated in the valley of the Yang-tze River, over ninety per
cent of the tung oil for export being derived from this region.

Botany
The genus Aleurites belongs to the Spurge family
(Euphorbiaceae). This large polymorphous family is char-
acterized by a milky latex, a spongy mass over the micropyle,
(caruncle), anatropous ovules, and seeds containing an oily
endosperm. Many species of this family are very poisonous.
Most of the economic features of the Euphorbiaceae are due
to the milky latex or to the stored oil in the seeds. Some
genera of this family closely related to Aleurites are Hevea
(H. brasiliensis is the South American Rubber Tree); Mani-
hot (Cassava and the Ceara Rubber Tree); Jatropha (Physic-
nut); Ricinus (Castor Bean).
Sapium (Chinese Tallow Tree); Croton (Croton oil
Plant); and Codiaeum (the so-called ornamental Crotons of
the greenhouse).
Genus Aleurites. Forst. (Greek-farinose or floury).
Euphorbiaceae. Juice milky; leaves alternate, palmately
veined, large, entire or 3-5 lobed, 5-7 veins, long petioles with
two glands at the apex; flowers usually monoecious in lax
terminal panicled cymes; calyx 2-3 lobed; petals 5, longer
than the calyx; stamens 8-20, inserted on a conical receptable,
in 1-4 rows, the inner row monadelphous, the five outer oppo-
site the petals and alternating with the five glands of the
disk; 1 ovule in each cell of the 2-5 celled ovary; style divided
into thick linear branches; fruit drupaceous, with thick
shelled seeds. Five or more species, native to Southeastern
Asia and the adjacent islands of the Pacific Ocean.





6 TUNG OIL

A. fordi. Hemsl. China Wood Oil Tree. Tung Oil Tree,
Tung-yu-shu. Tree up to 30 feet; leaves ovate-cordate, occa-
sionally 3-lobed on young shoots, no stellate pubescence;
flowers appearing before the leaves, in numerous few-
flowered cymose corymbs. 1-11. in. in diameter, white, stained
pink, yellow markings at the base of the petals, central termi-
nal flower of each cyme female, the others male; stamens
8-10; ovary normally 5 celled; fruit smooth, apple-like, about
2 in. long and broad, short-pointed at apex, tapering at base
slightly; seeds 5 compressed, broadly avovoid about an inch
long and broad, slightly ridged and warty on the outside.
China, central provinces from the coast to near the borders
of Eastern Thibet, also the southwestern province of Yunnan.
The Kukui or Candlenut tree (A. moluccana) is a native
of Malaysia but widely distributed throughout the islands of
Polynesia. The Kernels of the seeds contain 60%/ of oil and
have been used since prehistoric times by the islanders, who
skewer the seeds on the rib of a coconut leaflet. Upon light-
ing the rib the chain of seeds burns as a candle, the rib
acting as a wick fed by the oil from the seeds. In Hawaii
the pulverized seeds are roasted and used as a relish with
seaweed. The oil from the seeds is a drying oil and is used
to some extent as a base for varnishes and for making soap.
The Banacalag or Soft Lumbang (A. trisperma) is a na-
tive to the Philippines and is used in much the same manner
as the Candlenut Tree. The seeds yield a valuable drying oil,
used for soaps and paint making. This oil is to a certain
extent similar to that of the wood oil trees.
The Japanese Wood Oil Tree (A. cordata) is a native of
Japan. particularly of the island of Hondo. It is found both
wild and cultivated in Japan. The Oil from its seeds is mark-
edly different from that of the seeds of the other wood oil
trees in that it does not gelatinise when heated. This makes
it unsatisfactory as a substitute for the other wood oils. In
quite a percentage of this oil is used in waterproofing paper
and cloth. By its use paper lanterns and parasols are made
weather resistant. It is also used in soap-making and in
manufacture of paints and varnishes.
The China Wood Oil Tree or Mu-yu-shu (A. montana) is
a native of Southern China, and produces less than ten per
cent of the wood oil of commerce. It is much less hardy than
the tung oil tree, and does not appear to be as desirable for
commercial planting. The oil produced from its seeds is prac-
tically identical with that of the tung oil tree as far as com-
mercial uses are considered; and either oil or mixtures of the
two are exported without any discrimination in favor of
either. The fact that it requires a more tropical climate and





1I__ :1'.\T.1_N'MENT OF AGRICI'TLTItRE __ 7

a more abundant rainfall makes it not as valuable as A. fordi
for commercial exploitation.
The Tung Oil Tree or Tung-yu-shu (A. fordi) is the most
promising of the various species for the commercial develop-
ment of sources of wood oil. It is a native of Central and
Western China, most of the trees which are grown for seed
being found in provinces of Hunan, Szechwan, Hupeh,
Kwangsi, and Kerichow. Over ninety per cent of the com-
mercial wood oil produced in the world is the product of this
tree. The name tung (which means heart) is given to this
tree because of its heart shaped leaves. Because of its wide
distribution and dominating importance in the market it
is the species most generally meant when wood oil is dis-
cussed, and is the only species treated at length in this pub-
lication. Much, however, of the information available on
the tung oil tree is true in regard to the rest of the genus
particularly to A. montana. but as complete studies of A.
montana are not available it is desirable to confine the
subject to the tung oil tree alone. It is the only species re-
ceiving any commercial attention at the present time in the
United States.

History

Wood oil has been used by the Chinese for many centuries.
In a land which has no rubber, where paper has been made
for several thousand years, an oil with the properties of wood
oil is exceptionally valuable, as it increases the life of the
paper and widens its sphere of usefulness. The application
of the oil of a native seed so widely available to the preserva-
tion of wood. and paper seems to have been an early develop-
ment of the ancient Chinese civilization, which was founded
on a different sort of raw material than the Western civiliza-
tions. At the present time wood oil is a particularly im-
portant factor of Chinese life, and a list of the uses to which
the Chinese put it is enormous. It has been stated that the
name wood oil is applied to the oils of the seeds of Aleurites,
because it has been used for many centuries as a wood pre-
servative. This appears doubtful as a further discussion of
its history will show.
Marco Polo says: "They take some lime and chopped
hemp, and these they knead together with a certain wood oil;
and when the three are thoroughly amalgamated they hold
like any glue and with this mixture they pay their ships."
(FOOTNOTE: The Book of Ser Marco Polo, the Venetian;
quoted by E. H. Wilson in The Wood Oil Trees of China and
Japan.) This practice of calking ships with the same mixture
is as common at the present day in China as it was over six
hundred years ago.




























































Above left' is a high branching tree with limbs coming out close
together. Shown next page is a lower branching tree. Some people
have trimmed the trees so as to make them high branching under the
theory that .ou can get closer to them and cultivate them better. As
the feeder roots come very close to the surface any cultivation close
to the trees may inflict damage. The high branching trees have much
less fruiting head area than the Ilo branching trees. Both trees are
not quite three years old. the picture being taken in mid-summer.
Now. where the high branching trees reach the bearing age in six or
seven years with a full crop of fruit, the wind will have the same


Tl'I (; 11,




























































affect as though oln had an umbrella open. whereas the low branching
tree is so close to the ground that the wind has no chance to get
underneath. lWhen the olw br;nching tr-e gts t to be six to ten years
old the shading is such and the roots growth comes so close to the
surface that there is little or no foreign growth under the trees, where-
as the high brancing tree will alhwa.s have more or less foreign growth.
in the way of grass and reeds. and a small hearing surface. This is
shown in practice that the low) branching trees sustain themselves
under heavy winds and have a larger fruiting area, do not break
under heavy yield of fruit. whereas the high branching trees do. and
the best trees are the ones that break.


I)I- '1.\ t .\I.IA N T 1,'> .\ ; Il' 1.T I 1 I;





10 TUNG OIL

The first wood oil to be brought into foreign commerce
was from South China. When the Portuguese began trading
with the Chinese in the sixteenth century, their center of
operations was around Macao and Canton. For three cen-
turies the trade with the West was centered around Canton.
The only species of Aleurites found in the region back of this
port is A. montana. The Chinese name for this tree is mu-
yu-shu, or wood oil tree, given to it probably because of the
hard and woody character of the ripe fruit. In this case, as
in many others in China, the foreign name of the plant at
the treaty port was given to any related plants north and
west when they extended their commerce in those directions.
In consequence, while the Chinese themselves distinguish
sharply between the two species, the trader bought and
handled both of the wood oils under one name and it is only
comparatively recent that the two species have been
separated botanically. Furthermore the pressed oils have
been mixed, handled improperly and adulterated, so that it is
only recently that authoritative samples of pure tung oil
have been obtained for comparison.
While Chinese wood oil has been known for centuries, the
first shipment to the United States was made in 1869. Its
value was not at first appreciated, principally due to the
fact that the various gums available at that time were so
abundant and cheap that there was no apparent need for tung
oil. The gums are mostly found in fossil deposits. and in
consequence are being rapidly worked out. As a result a
closer examination was made of the remaining gums and
substitutes. It was found that varnishes properly made
from wood oil were much more resistant, particularly to
water, than the older expensive copal varnishes. Since the
beginning of the present century the use of wood oil has
become general in paint and varnish manufacture, with a
consequent marked improvement in the quality of these
products. At the present time no substance is known that
could take its place.
China, with its enormous population always close to the
margin of subsistence, is in no position to enlarge its pro-
duction of tung oil. Every acre of land available must be
put in food crops, and at present the trees are only grown
on land which is too poor for food crops. This area is not
large, and cannot be increased without causing starvation to
many Chinese. Furthermore, a large portion of the oil pro-
duced is required for various purposes in China. The abso-
lute dependence of the paint and varnish industry upon this
substance, the lack of power to control and develop tung oil
production in China, the political uncertainty in Chinese af-
fairs, the universal improper handling and adulteration of the
exported oil, all make it essential for the future security of






I)1;P'.A\ I 1 INT (>' .\ l IM('I ,T'i 7I E


- *
- -


-*


of


Showing clusters of fruit on nine (!) year old trees, Lamont Grove.
One of the clusters have 13 well formed fruit.





12 .TUNG OIL

the industry that a certain per cent at least of the production
should be in the United States.

Introduction Into the United States
As stated above the first shipment of wood oil into the
United States was made in 1869, but the paint and varnish
industry did not begin to use it in large quantities until
about the close of the last century. In the annual report of
the Consulate at Hankow in 1899, reference was made to its
value and uses, and many requests were made concerning the
oil and the tree itself. In an endeavor to obtain reliable infor-
mation a questionnaire was sent out by Consul General Wilcox
of Hankow and the information obtained was published in the
Daily Consular Report of March 15, 1905. About the same
time seeds were obtained by the United States Department
of Agriculture. Seedlings grown from these seeds were dis-
tributed by the Department to various collaborators in Cali-
fornia and the Southern States.
The establishment of the tung oil tree in Florida is largely
due to the care and enthusiasm of the late William H. Raynes
of Tallahassee. Five seedling one year old plants were sent
to the Superintendent of the Cemetery at Tallahassee. He,
not interested in them, turned them over to Mr. Raynes,
together with the accompanying descriptive circular. Mr.
Raynes, becoming convinced in their value planted these
trees on the 15th of November, 1906. All but one of them
died. The remaining tree was injured by a severe gale in
1907 and occasionally by frosts, was finally killed by being
moved by the builders of a highway which ran by it. In
1911 Mr. Raynes sent a bushel of the unhulled fruits to
Washington, the first bushel of tung oil fruits produced in
America. In 1913 a bushel of seeds from the original tree
was sent to Mr. L. P. Nemzek, of the Paint Manufacturers'
Association at Gillsboro, New Jersey. From these seeds 2.2
gallons of tung oil was expressed, the first tung oil produced
on the American Continent.
In January of 1912 Mr. Raynes supplied Dr. Tennant
Ronalds of Live Oak Plantation, Tallahassee, with 100
seedling plants. This was the beginning of the first com-
mercial planting in Florida. In 1913 the planting had in-
creased to four acres, and by 1915 it contained forty acres.
These trees were well cared for until 1917 when a severe
freeze destroyed the nursery and many young trees. The
remaining trees were neglected, and many have been badly
damaged by cold, fire, and livestock. At the present time
there are about 900 trees remaining, a few in good condition,
but the majority in poor shape. Proper care and fertilization
should make this planting productive and profitable.





I)IPlIr\'l''.I*X'f 01' AfIIIHCU'I.TUHE~


From seeds sent to Washington by Mr. Raynes and from
imported seeds, the Bureau of Plant Industry grew many
seedlings and sent them out to various collaborators in Cali-
fornia and the Southern States. As a result occasional trees
may be found growing in many localities. In 1912 a few
trees were planted in the trial grounds of the Florida Agri-
cultural Experiment Station at Gainesville. A record of
these trees will be found in Bulletin No. 171 of the Station.
The rapid growth and productiveness of these trees was
brought to the attention of Mr. B. F. Williamson by the late
G. Umlauf, at that time the Assistant Horticulturist of the
Station. A small acreage was planted in the vicinity of
Gainesville as an experiment. Where planted properly under
suitable conditions they did well, and a large nursery was
started, so that it would be possible to develop commercial
production rapidly. Trees for planting the large commercial
acreages about Gainesville have come from this nursery.

Climatic Requirements
As above mentioned the tung oil tree comes from a family
of tropical plants and is easily killed back by cold when it is
in active growth. It is doubtful if commercial plantings can
be recommended where the temperature goes much below 18
or 20 degrees Fahrenheit. A sudden drop to this temperature
may kill young trees, and while mature trees may be able to
stand much lower temperatures, the establishment of a grove
under such conditions is a precarious proposition. Although
in China the tree is grown where the temperature gets much
colder, commercial production in these sections is unimport-
ant, as the tree is killed back to the ground so frequently
that no large crops can be produced.
It seems to be true that the tree when mature is able to
stand extreme heat, but the young tree itself seems to grow
best in partial shade.
According to E. H. Wilson, they will grow anywhere in
Southern China where the rainfall is not less than 28 or 30
inches. In the region where they are grown the maximum
occurs in the summer much as it does in Florida. The
summer in South China is tropical, but the winters are cold,
snow often lying on the ground, although the winter tempera-
ture rarely goes below 28 degrees Fahrenheit in the region
where the tung oil tree is grown.
When well established, the tung oil tree is able to stand
severe temporary drouths without serious injury, but there
is no doubt that the tree will succeed best where there is a
regular supply of moisture and a yearly rainfall of 40 to 50
inches.





14 TUNG OIL

Soils
According to E. H. Wilson: "The tree appears to have no
strong predilection in the matter of soil and grows equally
well on conglomerate, hard limestone, sandstone and sandy
clay." This statement is not entirely true in Florida. The
tree prefers an acid soil, and is severely injured by an
excess of lime in the soil. Further correspondence with Mr.
Wilson has brought out the fact that the limestone under-
lying the trees in certain parts of China is very insoluble
and has little effect on the soil solution. As any soil expert
knows, it is possible to have acid soils overlying limestone,
so that the presence of this hard limestone under some of
the tung oil plantations in China would not justify the plant-
ing of the tung oil tree on soils which are alkaline or which
have soft limestone within reach of the roots of the tree.
There is no doubt that a deep light soil well supplied with
organic matter is suitable to the growth of the tung oil tree.
The average size of the Chinese trees is small and it is proba-
bly true that much of the dwarfing is due to the fact that
the Chinese plant the tree in a type of soil that is too barren
for best results. This is unavoidable in China, where the
only land available for its culture is too poor for the growing
of food crops, but it is unwise to choose such a soil for Florida
Plantings.
While the tree may be grown on flatwoods or rolling up-
lands, one essential must not be overlooked, and that is the
question of drainage. Where the flatwoods type of soil is
selected, it is absolutely necessary to be sure that the drain-
age can be controlled, and any area that cannot be thoroughly
drained should not be selected. If freedom from lime and
proper drainage are assured, there are many acres of land in
Central Florida which are available for successfully growing
tung oil.
Nursery Practice
The young trees for planting are best grown in a nursery
convenient to the area to be planted. While the topworking
of the nursery seedling offers no unusual difficulties, as has
been proven by Mr. Raynes at Tallahassee in 1914, and veri-
fied by Mr. Harold Mowry at the Florida Apricultural Ex-
periment Station, yet the commercial production will depend
for some time to come upon seedlings. The Chinese have
depended entirely on seedlings for commercial production and
by a process of selection have to a large extent eliminated
worthless and unproductive strains, so that our present strain
represents the end-product of a period of selection extending
over many hundreds of years. Recent experiments made in
fruit production show that the major factor affecting produc-








.9~~CPP~ 9 j


9 -~
4-~r,


'. ,
if 4t


Tallest tree in the Lamont grove, the earliest planting was in 1931.
The tree is approximately 37' tall, this is taller than the average.


I)I 'I\IA TM.\ NT 01' .\W ;RT(_ LT -R,,


1l14




16 TI'NG _OIL

tion is the nutrient content of the soil, so that while there
will continue to be variation in the type of tree and fruit,
the actual poundage of seeds is largely within the control of
the grower. In fact, a large percentage of the variation of
yield is accounted for by soil heterogeneity.
The seeds used for planting should have been kept in a
dry place after harvest, and should be of the previous season's
crop. The tung oil seed, like other seeds containing a large
percentage of oil, loses its germinative power very rapidly,
especially when there is a large amount of moisture present.
The seeds should be planted three to four inches deep and
twelve to fifteen inches apart in the nursery row. The rows
should be three to three and one half feet apart in order to
permit frequent cultivation. For best results in the vicinity
of Gainesville, the seeds should be planted between January
15 and February 15; planting much earlier or later will give
poor results. The soil selected for the nursery should con-
tain plenty of organic matter, in fact, new land recently
cleared is best for two reasons; the higher percentage of
organic matter and the greater freedom from weeds.
After the seedlings are up they must be kept well culti-
vated and free from weeds. Later in the spring as the leaves
begin to lose their deep green color, they should be fertilized
again. If the soil of the nursery is of the right type, this
fertilizer should consist only of nitrate of soda and some
readily available source of organic nitrogen. such as guano
or dried blood. If the soils are deficient and worn out, a
commercial fertilizer analyzing 59; nitrogen, 6'; phosphorus,
and 1 to 3'; potash may be used at the rate of 500 pounds
per acre.

Selection of Site for Grove
There are two conditions where the planting of tung oil
trees is promising. The first is on large areas of low-priced
land, where the grove is handled as a factory, with due con-
sideration of the factors which affect efficient production.
The other condition where planting appears to be justified
is where the trees are grown in smaller areas in conjunction
with other crops in a system of general farming. It is be-
lieved that the tung oil tree will become a valuable staple
crop for the sections about Gainesville, West into North
Florida, South Georgia, Alabama, Mississippi and Louisiana.
The repellant and poisonous character of the leaves and
fruit make it possible for the mature trees to be grown in
connection with livestock without serious damage to either
the trees or the stock. An acreage at Tallahasee has been
used for years as a grove and cattle pasture.







Fertilization
The Tung Oil Tree requires, as do most plants in Florida,
Potash, Phosphorus and Nitrogen. We have found that the
source of the Potash and Nitrogen make a tremendous dif-
ference in the growth and development of the trees, particu-
larly as the tree begins to fruit. It is desirable to get a
large percentage of the fertilizer from organic sources and
the use of a fertilizer of about the following mixture has
proven very desirable:
800 lbs. Chillean Nitrate of Potash
700 lbs. 20'; acid Phosphate
400 lbs. Castor Pomace
100 lbs. Goat Manure
When the fruit is in process of development and the oil
cells are forming a top dressing of a high percentage of
Nitrate of Potash is desirable. Too little attention has
been paid to soil organisms that play such a tremendous
part in assisting in plant growth and keeping the soil in a
healthy condition. Too often the things we add under the
name of fertilizer stimulates the plant temporarily but will
produce reactions highly unfavorable to one of the best soil
assets, that is the living organisms. Too little attention is
given to this. In this connection. people say that they have
a good crop one year and a poor crop the next. If the hulls
from the fruit, together with the residue after pressing, are
put back around the trees together with an added amount of
fertilizer to increase the production the only thing that
would prevent a good crop every year is climatic conditions
due to cold or very unseasonable weather. The fertilization
will effect the oil yield. In random trees, near a well fer-
tilized grove, the oil content in the fruit of the well fertilized
grove has shown from three to four per cent more oil than
the fruit from the grove poorly fertilized, or not fertilized
at all. The marked difference in yield is shown by a survey
of the 1940 crop. A grove of 1600 acres. according to
the owners reports produced 2500 pounds of whole dried
fruit per acre. another grove of 1200 acres produced 2000
pounds of whole dried fruit per acre. The properly ferti-
lized grove that averaged about seven years old and was
younger than the other two groves, produced 4166 pounds
per acre of whole dried fruit; this was weighed by an
independent weigher. Preliminary 1941 crop reports show
anywhere from 30'; to 501; less than last year, whereas in
the better fertilized grove an improper change was made in
the fertilizer and too much pruning was done, but even in the
face of these unfavorable actions the 1941 crop will be fully





18 TUNG OIL

70 % of the 1940 crop and the conditions of the trees and the
buds already formed should give a much larger crop than has
grown on this grove.

Cover Crops
Summer Cover Crops can be peas, crotalaria, any one of
three, Striata, Lanceolata, Intermedia; Spectabolis is poison
and will kill your stock. The first three are good cattle food,
practically equal in food value to alfalfa. Winter legumes
are desirable, and here you have vetch and Austrian Winter
Peas. Cattle do well in the grove, while it is desirable not
to allow them among the young trees as they will walk over
them particularly brush against them during fly time in the
summer. Cattle in the grove will add a profit and will con-
sume the cover crop.

Topworking
The trees may be budded or grafted but no advantage has
been demonstrated over the plan of selecting the better
seed from the better trees, using the cluster type and then
culling 25 to 35' of the nursery stock, planting in the grove
only the most vigorous trees. Now, that we have such a
large number of trees to select from that are continuous
heavy bearers and of good shape, were we able to produce
from cuttings from these trees we could reproduce the identi-
cal trees. A few cuttings have been rooted and grown out
but the percentage is small. However, through the work of
Boyce-Thompson Institute, Went of Cal-Tech and some work
now going on at the Dow Chemical Company there is evi-
dence that this method of reproduction can be made suc-
cessful. There are times of the year when results are much
more favorable than others. Some of the people's minds are
working on this problem and should develop practical meth-
ods within the next few years.

Harvesting
Harvesting is simple. The nuts fall on the ground when
they are ripe, they are allowed to lie there until reasonably
dry and then picked up in sacks and put in dry sheds, when
they are dry they are taken to the mill. There is room for
some nice improvements in preparing the nuts for proper dry-
ing and shelling so as to get the best yield of oil at the
press. The best press so far, for removing the oil is the ex-
peller type, commonly spoken of as Cold-Pressing. One of
these presses is made by the V. D. Anderson Company, the
other by The French Company. The nuts must be pressed
before the mid-summer or the oil congeals in the seed and
cannot be removed. This could be avoided by mild refrigera-












f o..'"


-; '


~b -1kL


S.'
-AF


Looking between the rows, nine (9) year ohl trees,
laden with fruit but not visible in the picture.


very heavily


I)i1 '.\I>T) .\i ,.\ T (W1,' .\( A 1('L;t. I i[ I,


.:





24)I T'NG( 011,

tion. The mills usually start in February or March to crush
the nuts grown the previous season. With proper drying
facilities they should start in December.
A very simple way we find of making examination of
the soil is to check inside the ground for the texture and
appearance of the soil. If you take core borings and examine
each core as you go down you will reach a point where the
earth becomes so dense that roots will not penetrate. Where
that condition exists close to the surface your root area is
limited and the tree will suffer in wet or dry weather.
An old pecan grove, perhaps 25 or 30 years old, was
examined and the owners stated that they did not know why
but the grove had never been satisfactory although there
were trees on the same property bearing large quantities of
fruit. It only took a short time to find that those trees
had only about 2' in depth where the roots could penetrate.

Oil Removal
The best method of removing the oil up to now, and the
only successful one has been with an expeller type press.
Hydraulics we have proven are out of the question, tung oil
being in a class by itself. Hydraulics have proven successful
in cotton seed, peanuts and other oils that do not congeal
readily and will sustain reasonably high temperature. where-
as tung oil put through a hydraulic press, accumulates jelled
oil in the pores of the press cloth and in about two pressings
the press cloth is about like a linoleum. The other possible
method of extraction would be with a solvent. To be a suc-
cess. the individual oil cells in the kernels would have to be
broken before the solvent extraction is started. The solvent
extraction method looks extremely simple in the laboratory
and in small units but there are serious hazards that require
constant application of intelligent technically trained help, for
fire, explosions, loss of solvent, destroys efficiency and endan-
gers the help and this all increases the insurance which can
only be modified by properly equipped, entirely fire proof
structure. It is possible with an extraction process to leave
1;, or less, oil in the residue. The oil from a properly equipped
solvent extraction plant has all the qualities of expeller
pressed oil, including the color. In other words, the oil loses
none of its valuable characteristics. As evidence of this I have
on hand a drum of solvent extracted oil that was extracted
in Dearborn, Michigan in 1937 that today is in first class
condiiton.
The real simplicity of operating an expeller plant is a
factor of great importance and if the moisture content in




DEPARTMENT OF AGRICULTURE 21


the material entering into the expeller is the right moisture
content and runs uniform there is little trouble with the
operation.
We must simplify the drying of the nuts. There are al-
ready driers in operation that will do this. So far, the present
Expeller seems to be the process to use. The time required
for pressing these nuts can not be carried into the summer
months of June and July without sustaining a loss of oil
yield from the pressing. There is a break down of the oil
cells as the Summer advances and when this occurs pressing
is difficult and impractical and oxidatiozt takes place so we
should dry the nuts and start the pressing not later than
January first and complete it by the first of June. That is
too short a time to employ highly trained technical help to
operate an extraction plant, so it we turn to extraction we
must first find other oil bearing seed to be used in such a
plant, Castor might fill this place if we could get it and
then it might be possible to operate the year around. This
might also increase the value of the residue if some method
could be developed for treating this residue so it might be
used for food for hogs, such as has been done with cotton-
seed meal.
Another angle which might increase the capacity of the
Expeller plant would be if the residue could be used for cer-
tain purposes, like brake lining. In that case, excess oil left
in the residue might play a part in the brake lining and so
increase the value of the residue, which would off-set the
excess oil left in the residue.

Summary
Best results, thus far, have been obtained by careful seed
selection, planting the seed in the nursery, culling the nursery
trees, planting the vigorous trees in the grove. Trees should
be planted at least 20' apart in the rows, in rows at least
30' apart.
While the plant is free from disease and insects, due to
the fact that its sticky latex is repellent to both insects
and fungus, spraying is never necessary. We are finding some
difficulties due to the absence of some of the rarer elements
in the soil, one particularly being zinc. There has been a
difficulty called bronzing that appears more particularly in
areas where the soil contains an appreciable amount of phos-
phorous or lime. Zinc cures this trouble. There are many
of these rare elements absent in the citrus soils and small
amounts are added effecting the yield.
Cover crops should be grown in between and cattle form
a desirable addition using the grove for that purpose. Trees





TUNG OIL


should not be planted in low areas but elevated so as to get
good air drainage. If the tree is kept in vigorous condition,
and well fed it will sustain much lower temperatures without
damage.
The oil is a necessity, has no substitute, used in paints,
varnishes and certain inks. Our best automobile paints have
a percentage of tung oil. The U. S. consumption has gone
as high as one hundred thirty million pounds of imported oil
a year. The U. S. gets 90 % of the foreign production, which
foreign oil is high in free acid, dark in color, whereas Ameri-
can ull is pracuca tly neutral and light in color. There is
no danger ox overproduction. rne u. S. could use several
hundred million pounds if they could get it. Seventy-five per
cent oi the oil used in surface coatings are imported. Tung
oil is the best of all. The average price over a ten year
period is approximately 14< per pound. The present price is
s6v" per pound.
According to the Government reports, there are approxi-
mately 4,000,000 bearing tung oil trees in the United States,
of which the Lamont Grove contains 51,430, or 1.28% of the
total bearing trees in the United States. The best report we
have been able to get covering the yield of oil from the
1940-41 crop, which is two years, is an average of 4,000,000
pounds of oil, or 8,000,000 pounds for the two years. Taking
our reports of oil produced and shipped from the Lamont
grove there was a total for the two years of 567,859 pounds
of oil, which is 7 ', of the total oil produced in the United
States. An analysis of the nuts on a 10% moisture basis, the
nuts contained 25.88'/, oil and with efficient pressing should
have shown a yield of over 20' There is a check on this;
the B. F. Williamson Guinea Pig Grove, the nuts from which
were pressed by the Alachua Tung Oil Corporation, which also
received and weighed the nuts into the plant, show a yield of
20.68'; filtered oil from the nuts. These nuts were simply
put in a barn in sacks and the drying was a result of the
moisture leaving while in storage, which shows two things.
The nuts from the average grove have shown a yield as low
as 16',; oil. Had the total yield of oil from all the tung oil
groves in the United States been equal to the above figures
there would have resulted a yield of 5,000,000 pounds of oil
instead of 4,000,000 pounds. The other loss, due to oil left
in the cake, residue and the small particles of kernels that are
blown out into the hull pile from the sheller would add more
oil to the reported total oil.
We know we have developed the tree in a production
capacity, in fact, we doubled the original tree, but we can feed
the tree and even under favorable soil conditions produce a




I )Il.\'A HTi'M '' ENT .\( I1CLTI I T RE_] 23

fruit that will show a higher oil content, up to 4/;. We
know the safest area in which to plant from a climatic and
soil standpoint but there is much yet to learn. With these
known factors the planting of tung oil trees should be rapidly
increased until we have reached a production sufficient to
meet the major requirements of our domestic users. This
can be done and done profitably if the present knowledge
is intelligently applied.




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