Bulletin No. 11. New Series June, 1931
T UNG OIL
R1h .- IM LIBRARY
D .DEC 21 1970
Univ. of Florida
STATE OF FLORIDA
DEPARTMENT OF AGRICULTURE
NATHAN MAYO, Commissioner
r I* -
Introduction ------ ----------- 5
Introduction into Florida ---- 5
The Oil and Its Uses ---------- 6
Market Demands .-------------------- 12
The Tree and Its Fruit ------ 13
Acreage and Distribution ------ 15
Soil Considerations --------- 15
Selecting Seed---------- 17
Culture and Fertilization ------- 17
Planting and Maintenance Costs ----- 21
Yields and Profits 21
Pests -- ---- ---- ------- 23
Briefs ---- 23
Producing Tung Oil In Florida
By Ralph Stoutamire
NEW CROP is bidding for a place in Florida's agri-
culture. It is tung oil and it now appears that before
long this new crop will be bringing in an attractive
revenue to growers in those localities of the state adapted to
its growth. The introduction of no plant in recent times has
created such widespread interest as has that of tung oil.
This interest is due, naturally, to the great promise to
America of the production here of a commercial oil which
heretofore has been produced only in the Orient but which
is utilized in both American and European industries in
large and increasing quantities.
Because of the wide consumption and diversified uses of
tung oil, the question of demand or over-supply and market-
ing at this time offer little concern. Methods of oil extrac-
tion having been successfully determined, and the purity,
quality, and superiority of the American product having
been amply tested and demonstrated, the present problems
of tung oil production are mainly cultural. As the tree has
been under cultivation in America but a relatively short
time, much yet has to be learned as to its soil and climatic
adaptability, its varietal differences, and its fertilizer and
other general requirements.
However, enough general information has been gained
that we may say the experimental stage has been passed.
With properly selected plants grown on suitable soil and
with the best known cultural practices, successful and sub-
stantial production is no longer considered a possibility but
an attained reality.
INTRODUCTION INTO FLORIDA
Early in the present century, officials of the United States
Department of Agriculture-notably Dr. David Fairchild,
senior agricultural explorer-realized the importance and
6 DEPARTMENT OF AGRICULTURE
value of tung oil. In 1905 Dr. Fairchild, with the assistance
of L. S. Wilcox, United States counsel general at Hankow,
imported seed for trial planting in America. Those seed
were planted in Chico, California. In 1906 the seedlings
therefrom were distributed to experiment stations and
collaborators in southern and southwestern states. The I
results of this distribution after some twenty years, demon-
strated that plantings in Florida had made the most satis-
factory growth and yields.
A single tree planted near Tallahassee, seems to have
been the only one to survive of those grown from the original
introduction into Florida. It was from seed of this tree that ;
the first tung oil was extracted in America. A later plant-
ing of several trees was made on the grounds of the state
Experiment Station at Gainesville. These early plantings
in northern and north central Florida have, by growth and
yield, given evidence that the climate and certain soil types
here are optimum for the successful growth of tung oil trees.
That evidence has resulted in the present commercial plant-
ings in the state, the first of which was made in Alachua
County in 1924. Since that time plantings have steadily
increased to bring the present acreage in Florida to approxi-
In line with the development of the industry, a modern
and complete oil expressing plant was erected and placed in
operation near Gainesville in 1928. This plant means that
the grower now has a ready cash market for his crop.
THE OIL AND ITS USES
Tung oil, also called wood oil or China wood oil, is that
removed from the seed of the tung oil tree. The oil yield is
about one-third by weight from air-dried seed and about 4
one-fifth by weight from air-dried whole fruits.
Before pressing, the oil in the seed is almost colorless,
the depth of color in the expressed oil depending in part on
the method used in extraction. American oil has a very
light amber or straw color and a very low acid content,
while Chinese oil is much darker and has a high acid content.
Both chemical and mixing tests have demonstrated the
superiority of the American product. Crude hand methods
and hollow-log presses, operated by hand and by an awk-
PRODUCING TUNG OIL IN FLORIDA 7
ward manipulation of wedges, are used in China. It is said
the American method of extracting the oil results in a saving
great enough, over the crude Chinese method, to more than
pay for the cost of our extracting machinery and for the
extracting operation. One man can operate our machine
which does the work-and does it better-of perhaps a
thousand Chinamen. The Chinese method, with its accom-
panying lack of efficiency, and a complicated system of oil
collection, results in an oil varying in degree of purity and
quality. Frequently it is greatly adulterated with inferior
I-ai i ~ ~~
Fig. 1. A young tung oil tree, five years old showing a heavy crop of fruit.
This is typical, If the trees have been properly selected, planted
cultivated and fertilized.
There are three methods of oil extraction-namely, by
volatile solvent, by hydraulic press, ana by screw press or
expeller. By comparative tests the expeller method has
proved best from standpoints of both economy and effi-
ciency. This is the method employed by the plant at Gaines-
ville. The oil-expressing operation is continuous and almost
wholly mechanical. The air-dried whole fruits are decorti-
cated by a combined huller-separator. The seed are then
PRODUCING TUNG OIL IN FLORIDA
conveyed to a grinder which converts them into a coarse
meal. This meal is in turn fed into the expeller which by
pressure extracts the oil. Further treatment of the oil,
other than settling, is not required; it is now ready for
storage or immediate use.
Tung oil has a wide variety of uses. In China it is used
extensively to waterproof paper, cloth and masonry, as well
as a varnish. In America it is used mainly in varnishes,
being combined with rosin to form a combination that has
entirely replaced the imported fossil gums. Further uses-
other than in waterproof varnishes and paints, all of which
require large quantities-are the insulation of electrical
equipment, as wires, cables and motors; the manufacture of
linoleum and oilcloth; leather dressing; sheet packing and
gaskets; and automobile brake linings. Paint and varnish
manufacturers use the oil as a necessary ingredient in an
extremely wide variety of their products, including lacquers,
japans, enamels, fillers, hardeners, insulating and impreg-
nating compounds, finishers, sizings, and numerous others.
They also use tung oil in their many paints and varnishes.
The pomace or seed cake, which is left when the oil is
extracted, contains about 6 percent of ammonia and com-
pares favorably in analysis with castor pomace. This ma-
terial, therefore, has value as a fertilizer. The hulls can be
used to advantage for mulching purposes.
During 1929 over 119,000,000 pounds of tung oil, valued
at about $15,000,000, were imported to supply the demands
of the American markets. This amount was nearly three
times that imported in 1918. The average valuation per
pound in 1929 was 121.' cents. Among chemical importa-
tions into the United States tung oil has attained fourth
place in importance. Europe is also using the oil in large
quantities. Figures showing the remarkable increase in
American imports from 1920 to 1929 are shown on next
10 DEPARTMENT OF AGRICULTURE
Year Pounds Value
1920 45,232,000 not given
1921 27,249,000 $ 2,470,000
1922 79,089,000 7,891,000
1923 87,292,000 13,397,000
1924 81,588,000 11,092,000
1925 101,554,000 11,386,000
1926 83,004,000 9,148,000
1927 89,650,000 11,810,000
1928 109,222,000 13,419,000
1929 119,678,000 14,972,000
Manufacturers, assured of a steady and increasing supply
of American oil, will utilize it in greater quantity and in a
wider variety of products. There is now good reason to
believe that tung oil, when available in sufficient amounts,
will to a degree supplant linseed oil in many ways. That
this will open a wide market is shown by the fact that close
to $60,000,000 worth of linseed oil is imported into this
country every year. The United States produces only about
half of the linseed oil used by its own industries and con-
sumers. From the above figures it is apparent that the
demand for tung oil is already developed and it would
appear that any question of over-production is so far in the
future as not to be considered.
THE TREE AND ITS FRUIT
The tung oil tree belongs to the Spurge family and is
botanically classified as Aleurites fordi, known to the China-
man as Tung-yu-shu.
The mature tung oil tree is about 30 or 35 feet high and
it spreads in all directions equally. It is deciduous, dropping
its leaves in November and leafing out in March or early
April. The blossoms, appearing with or before the leaves,
are of two kinds-staminate and pistillate. Both types of
blossoms are born on the same tree. Therefore, any tree is
In China the tree is said to have a life of from 30 to 50
years. There is no means of knowing how long it will live
in the Florida environment, but there is no reason to believe
that its length of life will be less than in China. Florida's
PRODUCING TUNG OIL IN FLORIDA
first planted tree, despite neglect and damage from fire, has
passed the quarter-century mark and is still producing.
The fruits, commonly but improperly called nuts, ripen
in October and November. When mature they drop from
the tree which obviates the necessity of picking and mark-
Fig. 3. This photograph shows an exaggerated example of the cluster type
of fruit; many individual fruts on one stem.
edly decreases harvesting costs. The appearance and shape
are somewhat like that of a small apple, the diameter being
from two to three inches and the color olive green. The
12 DEPARTMENT OF AGRICULTURE
color becomes brown at maturity. Normally there are five
seed in each fruit. The hull is tough and leathery and be-
comes quite hard when thoroughly air-dried.
There are as yet no named varieties, although several
variations among seedling trees are apparent. These dif-
ferences have to do mainly with the size and shape of the
fruit, variation in leaf shape and blossom color, and the
number of individual fruits born at the twig end. The last
has led to the general designation of two types-single and
cluster. If cluster bearing proves an inherent character-
istic, as now appears to be the case, it will be advantageous
to plant this type so as to secure heaviest yields.
ACREAGE AND DISTRIBUTION
At the end of the 1930-31 planting season the plantings of *
tung oil trees in Florida closely approximated 10,000 acres,
an increase of over 4,000 acres over the previous year's total.
Plantings extend from Polk to Escambia Counties with
the major part of the acreage located in Alachua, Levy,
Clay, Lake and Okaloosa Counties. Alachua leads with
approximately three-fifths of the state's total, or approxi-
mately 6,000 acres. Numerous smaller plantings are to be
found in many other counties.
In addition to field plantings a considerable acreage is
devoted to the growing of nursery stock. Planters who do
not wish to grow their own planting stock or who are
desirous of saving a year's time in planting a grove may buy
it of several nurserymen in the state.
The tung oil's future development will be greatest in
those areas which are best adapted to it by reason of most
suitable soils and climatic conditions. It must be borne in
mind that this tree is more or less sub-tropical in require-
ments and that the region where it may be grown is limited.
It has withstood temperatures as low as 15 degrees Fahren- "
heit without damage, but late spring frosts in the extreme
northern part of the planted area have been known to dam-
age the bloom. From reports of planters themselves it
seems that the tree will not succeed in the southern part
of the state.
PRODUCING TUNG OIL IN FLORIDA
The tree in large degree thrives in ratio to the fertility
of the soils on which it is planted. Usually plantings are
located on the higher soil types but, if adequate drainage is
provided, the lower lands are suitable for tung oil trees.
Many thrifty trees are now growing on such land. How-
ever, an absolute essential to thrifty growth on the lower
soils is a thorough system of drainage which not only
removes excess surface water but also lowers the water-
'ig. 4. View of 1i nursery where rigid seedling selection should be made.
The seed for planting the nursery should first le rigidly selected
from trees that have proved themselves heavy bearers.
table to a point several feet below the soil surface. The
effects of inadequate drainage are not always apparent the
first or second year after planting, but later they appear
through a general lack of vigor, a condition that can be
overcome only by lowering the water-table.
In selecting tung oil land, avoid high, dry, coarse sand
hills. Likewise avoid low, undrained land. There is no
advantage in the former. In the latter there may be plenty
14 DEPARTMENT OF AGRICULTURE
of fertility, but the high water level prevents the roots from
growing downward sufficiently deep.
Plantings have been made on several soil series with
satisfactory growth resulting in each case. These series
include Norfolk, Gainesville, Orangeburg, Greenville, Blan-
ton, Bladen and Leon. Soils with a slight acid reaction are
best suited to the tung oil. It apparently will not thrive in
a soil rich in phosphate and lime.
All soils are not suited to the culture of the tung oil tree
and prospective planters would do well to make rather
exhaustive soil tests and comparisons before investing their
money or planting large acreages.
Seedling trees should be grown in the nursery from seed
selected from prolific parent trees. In the nursery select
the most vigorous trees, those which show a well developed
top and root system. The tung oil tree has been propagated
from seed for thousands of generations. Thus its heredi-
tary qualities are very deeply implanted and an unusually
high percentage of the young are true to their parents.
For this reason it is important to select the seed carefully
and later to select seedlings in the same manner. Then
follow up the trees during future years and when, after a
fair chance, one fails to measure up, eliminate it.
Tree records over a period of years kept at the Florida
Experiment Station (see Bulletin 221 of that station) at
Gainesville show that some trees are almost worthless, inso-
far as yield is concerned, while others consistently bear
heavy crops. At that station the average yield from all its
plantings was greater from the cluster type trees, although
one or two individual trees of the single type were exception-
ally heavy producers.* These differences emphasize the
necessity of rigorous seed selection, whether the type be
single or cluster, in order that future plantings may have
the highest possible proportion of high-yielding trees.
The terms "single" and "cluster" have reference to the number of
fruits produced on the individual twig. The single bears but one fruit while
the cluster, as the name denotes, bears from two to as many as twenty
Fig. 5. Earth removed to show the growth of a tung oil tree's root system. Note the comparative shallow-
ness of the roots; the bulk of the roots are not more than 31/ feet deep. This demonstrates the danger of
16 DEPARTMENT OF AGRICULTURE
CULTURE AND FERTILIZATION
Best results in growth and yield have been secured by
following a cultural system that includes five items of basic
importance. These are:
1. Thorough and complete clearing and preparation of
the land prior to planting.
2. Planting of onlj rigidly selected nursery stock; the
planting to be done during the tree's dormant period (De-
cember through February.)
3. Field cultivate shallow enough to leave the root system
undisturbed, and thorough and often enough to destroy
weed and grass growth which competes with the tree for
moisture and plant food. As the tree grows older and
attains size, less cultivation is needed. Mulching of young
trees on the higher soils with any coarse vegetable material
is advantageous, provided it can be done at little cost.
4. Fertilization adequate to maintain the tree in a vigor-
ous growing condition is essential. It is not sufficient that
the tree only set and mature its crop of fruit any given year;
a strong vegetative growth must appear along with each
fruit crop in order to insure a heavy yield the following sea-
son. It is only on this new shoot growth of this season that
fruit will be produced next season.
5. Maintenance and building up of soil organic content
and fertility by the growing of summer legumes in the row
middles are other requirements.
In China, its country of origin, the tung oil tree is grown
largely around the edges of very small farms and in places
not suited to the growing of regular crops. The average
farmer has from five to fifteen trees. He who has as many
as fifty is regarded as a large producer. Apparently no
effort is made to cultivate or fertilize or to improve the
stock by budding, grafting or seed selection. As a result
a crop of any size is accepted gratefully by the planter.
Under American practices of seed selection and tree ferti-
lization and culture, there is every reason to believe that the
PRODUCING TUNG OIL IN FLORIDA
production of a single Florida acre will be equivalent to
that of many Chinese acres.
Nursery stock is grown best on fertile, fairly moist but
not wet soil. The seed are planted from 3 to 4 inches deep
and from 8 to 12 inches apart in rows from 31,/ to 4 feet
apart. Middle-February planting gives the seedlings the
benefit of the full growing season for development and is
preferred to later planting dates. About 60 days are
required for germination. Little success has followed the
planting of the seed directly in the field where the trees are
to grow. This is due in large degree to the failure to keep
the seedlings free of grass and weeds. Also the young
plants require much moisture, and on a wide acreage mois-
ture variation is great enough that some plants will suffer
and lag in their growth. Nursery stock from 4 to 6 feet in
height, which is of ample size for transplanting, may be
produced in one season. This nursery stock should be care-
fully culled in transplanting; plant only the most promising
On suitable soils and under recommended cultural prac-
tices the value of fertilization is not questioned. The indus-
try is yet too new to give final indications as to the best
fertilizer materials and practices. But in the case of young
trees there is ample evidence to show that a lack of nitrogen
is the determining factor in limiting tree growth. At the
Florida Experiment Station a fertilizer analyzing 5 percent
ammonia, 8 percent phosphoric acid and 4 percent potash,
composed of nitrate of soda, cottonseed meal, sulphate of
ammonia, superphosphate and sulphate of potash, has given
It should be remembered that a soil must be correctly
prepared and contain a reasonable amount of organic ma-
terial, if best results are to be expected from commercial
Very satisfactory results have been secured in some com-
mercial plantings from the use of Peruvian (or bird) guano
supplemented with nitrate of potash. Applications are
generally made twice annually, the first early in the spring
and the last late in June. Quantities applied per year vary
from 1 to 7 or 8 pounds to the tree, the amount depending
on the size of the tree. B. F. Williamson of Gainesville says
22 DEPARTMENT OF AGRICULTURE
he has found Peruvian guano most successful for tung oil
trees, though it should be supplemented by potash and phos-
phate when the trees come into bearing.
Since most soils suited to tung oil trees are deficient in
organic matter, it is generally recommended that a legumin-
ous cover crop be grown between the rows during the sum-
mer months. At present the crotalarias offer the greatest
return for the least outlay. The tonnage produced exceeds
that of other cover crops, the amount of seed required and
seed costs are low, and, if rightly handled, a succession of
volunteer crops for several seasons is possible. Cowpeas,
velvet beans and beggarweed are other admirable legumes,
but the first two of these have the objectionable habit of
climbing the trees. Mr. Williamson, who probably has made
a more extensive study of the tung oil than any private citi-
zen, is a strong advocate of the growing of cover crops. He
finds that cattle may be pastured on the cover crop without
injury to the trees and with advantage to the cattle.
In some cases inter-cropping is employed to some extent,
vegetables and corn being the principal crops grown in the
middles, so far as the writer has noticed. Such a cropping
system possibly is suitable, provided there is not too great
a drain on the soil fertility, and the cultivation given is com-
patible with tung oil tree needs. There is little doubt but
that the growing among the trees of such crops as corn,
sweet potatoes, cotton and vegetables will, if continued,
retard the growth of the trees more than where only le-
guminous cover crops are grown and returned to the soil.
It may prove poor economy to endeavor to secure a tempor-
ary gain from inter-cropping, in that it will likely result in
a loss in vigor and more or less permanent setback to the
PLANTING AND MAINTENANCE COSTS
Values of lands suited to tung oil trees vary considerably,
due to location and size of tracts involved. Clearing costs
also differ greatly and depend almost wholly on the type of
vegetation growing on the land. The number of trees
planted per acre (present plantings range from 48 to 116)
will have a large bearing on nursery stock cost. In the
effort to arrive at expense of planting and maintenance it
must be born in mind that any figures are subject to wide
PRODUCING TUNG OIL IN FLORIDA
variations, because of differences in labor costs, methods
of handling, grass and weed growth, and other unforseen
factors, as well as acreage involved. Usually large acreages
can be maintained at less cost per acre than small plantings.
The first year's expense may be divided approximately
Nursery Stock -- $15.00 to $50.00 per acre
Clearing 8.00 to 40.00 per acre
Plowing, breaking ------ 2.50 to 5.00 per acre
Planting .._--- --------- 4.00 to 6.50 per acre
Cultivation --- 5.00 to 10.00 per acre
Fertilizers and applying 4.00 to 6.00 per acre
No estimate is placed on the cost of the land used, inas-
much as land values vary greatly.
After the first year the fertilizer costs gradually increase,
but as the trees grow cultivation costs in turn gradually
decrease. Since about 10 pounds of fertilizer is the maxi-
mum quantity applied to mature trees, this expense will be
but the cost of 700 to 1,200 pounds per acre, plus the low
cost of application. From $25 to $30 per acre should cover
fertilizer and labor costs on a mature planting.
YIELDS AND PROFITS
Under the crude methods followed in China, yields are
low in that country. From reports of those who have
investigated only from 20 to 30 fruits are yielded by trees
three or four years old. When the tree is six years old it
may produce 150 fruits, and at ten years of age the crop
may run as high as from 200 to 250 fruits per tree.
No acre plantings in this country have reached full ma-
turity. It is, therefore, impossible to give any data as to
yields on groves more than a few years old.
The original planting of 10 trees at the Florida Experi-
ment Station will furnish some indication of possible yields.
These trees, however, were planted but ten feet apart and
up to the time the yield records, as given below, were begun
they had little or no fertilization. Had they not been so
severely crowded, it is quite certain that they would have
24 DEPARTMENT OF AGRICULTURE
produced much more abundantly. Over an eight-year period
(nine to sixteen years) these trees produced an annual
average yield per tree of 22 pounds and 5 ounces of hulled
seed which is equivalent to almost 1 gallon of oil. The trees
are not from selected stock and considerable variation is
apparent. For the period above mentioned five of the trees
produced 339 pounds of seed while the five trees of better
bearing capacity bore 1,443 pounds. This further demon-
strates the value and importance attached to careful seed
selection in growing nursery stock.
Records are available of one small commercial planting
of nearly 200 trees to the acre that produced in its fifth
year (sixth from seed) an average of 3,531 pounds of air-
dried whole fruits or the equivalent of 74 gallons of oil per
acre. B. F. Williamson reports instances where individual
trees have produced over 30 pounds of oil. He adds, "A
small acreage planted in 1925 showed an average yield in
1929 and 1930 of a little less than 700 pounds of oil per acre
per year. Other plantings have shown as high as 500
pounds per acre; these were 1924 and 1925 plantings and
the yield records were for 1929."
The reader may see for himself how impossible it is to
set forth in a publication of this kind definite figures relat-
ing to profits. It is even impossible to say with any degree
of certainty what the average planter should expect by way
of yield from his acres. But as regards profits, figures
compiled by the American Paint Journal show a range in
price of tung oil from January, 1919, through September,
1928, from 35 cents to 9 cents per pound. Naturally these
were the prices for the Chinese oil. American oil brings a
higher price, being of a much higher quality. But with
these import prices as a basis, with perhaps 141/2 cents per
pound a high average, the prospective planter can probably
do his own figuring, inasmuch as he should know his own
situation better than any one else.
No fungus or insect has seriously attacked the tung oil
tree, either in America where it has been grown for 25 years
in test plots or in China where it has been grown for thous-
ands of generations.
PRODUCING TUNG OIL IN FLORIDA 25
This cannot be said of any other commercial tree crop in
Florida. While two or three scale insects have been found
on it in isolated cases, there has been no instance wherein
commercial spraying has been required or even desirable.
In a few instances young nursery stock has been affected by
root-knot, but there is no record of this trouble's affecting
older trees. In order to keep nursery stock free of this
trouble, it is only necessary that the nursery be located on
newly cleared land, rather than on old.
Tung oil or wood oil is expressed from the seed of the
tung oil tree, Aleurites fordi.
Over 119,000,000 pounds of tung oil, valued at nearly
$15,000,000, were imported into the United States in 1929.
The next year the importation increased to over 126,000,000
Tung oil ranks fourth among chemical imports into this
Tung oil is an essential ingredient of waterproof
varnishes and paints and numerous other products of the
paint and varnish industry.
Tung oil is extensively used in waterproofing electrical
Tung oil can, in a large measure, displace linseed oil.
Annual American importations of the latter are valued at
from $50,000,000 to $60,000,000.
Approximately 10,000 acres have been planted to tung oil
trees in Florida. Alachua leads the counties with nearly
America's single and the world's only modern tung oil
expressing plant was placed in operation in Alachua County
American tung oil is superior in color and quality to the
26 DEPARTMENT OF AGRICULTURE
Only the tung oil tree (A. fordi) is commercially planted
The tung oil tree has proved its adaptability to Florida's
soils and climate.
The tung oil tree has no insect enemies or diseases.
Florida's first tung oil tree was planted in 1906 and is
Tung oil weighs 7.82 pounds to the gallon. Commercially
8 pounds is regarded as a gallon.
One-third of the weight of the seed or one-fifth of the
weight of the air-dried fruit is oil.
The author is indebted to Harold Mowry of the Florida
Experiment Station and to B. -F. Williamson of Gainesville
for much of the information contained in this publication
and for much assistance in its preparation. Mr. Williamson
gave a number of photographs which are reproduced here-
with. Several colored illustrations were lent by the Journal
of Chemical Education. The Florida Experiment Station
lent two halftone illustrations.
PRODUCING TUNG OIL IN FLORIDA
WILL CHINESE COMPETITION INTERFERE WITH
Some people have questioned the practicability of produc-
ing tung oil in America in competition with cheap Chinese
labor. Julean Arnold, the American commercial represen-
tative at Pieping, says that Chinese can be employed at 15
cents per day, but one of the American presses will do the
work of 90 to 100 Chinese. Transportation in China, he
states, is on human backs and costs five to seven times as
much as transportation in this country, even with our ex-
pensive labor and high freight rates. Manufacturing in
America will be done with machinery from the time the
nuts are delivered to the press. Cultivation in this country
is also done by machinery. Three small tractors will culti-
vate 100 acres in a single day.
Looking at this matter from every standpoint, it would
appear that here is an industry where over-production is
a long way off, where demand exceeds supply, and where
the product is an essential in an established industry al-
ready developed and rapidly increasing. Assuming that
in the near future the American production of oil will cover
the regular increase in the American demand, then as the
European demand increases it is likely that China may meet
it so long as prices remain high. At the same time it is
certain that there is a limit to the production of tung oil
in China, and there is no indication at present of increased
cultivation in China taking care of the increased demand.
Actually, the trees are not cultivated systematically in
China, for they are hardy, at least when past the seedling
stage, and are commonly found on hillsides or in rocky situ-
ations and on the poorest of soils, unsuitable for ordinary
food crop cultivation.
It has been said that the consumption of tung oil in China
greatly exceeds and may double the total export, but this
reservoir of oil is certainly not available except at good
prices. It is evident that an increasing world demand must
encroach more and more on the stocks of material norm-
ally reserved for domestic use in China with a consequent
upward tendency in price. The disturbed state of the coun-
try can only accelerate this effect since one would expect
supplies to shrink rather than expand. Under the best con-
ditions the difficulties in collecting the nuts, for the tree
is gregarious in habit, expressing the oil by native methods,
28 DEPARTMENT OF AGRICULTURE
and transporting the oil from the interior to the ports, are
many; years of civil war cannot have made these difficulties
In spite of the labor and the large percentage of waste
involved in the operations, tung oil is regarded as a most
profitable crop by the Chinese. In this very fact lies the
strongest argument for presuming that scientific cultiva-
tion of the trees in plantations, with adequate machinery
for crushing and collecting the oil, is bound to succeed. The
systematic cultivation of the tung oil tree may well follow,
though on a smaller scale perhaps, the example of rubber.
Today it is a fact that rubber grown in its true home, the
Amazon basin, although there are countless trees available,
cannot be produced at the cost of plantation rubber, be-
cause the method of ordered, scientific cultivation of the
tree and harvesting the product is more effective than the
casual collection of the jungle product.
DIFFERENCE IN CHINESE AND AMERICAN
Such information as is available on the subject of crush-
ing tung oil seed in China indicates that the husks are first
removed by parching the fruits over a fire in iron pans
(18. in. diam.), or by allowing the husks to ferment away
from the seed, the fruits being piled in heaps for this pur-
pose. The seeds are then ground to a meal in stone mor-
tars (about 3 ft. in diam.), using man or bullock power.
The meal is then heated, mostly by steam, and placed in
wedge presses. The oil is finally strained through silk or
grass cloth. Sun curing the kernels before crushing is said
to produce a light-colored oil, while extreme heat or ex-
cessive fermentation under bad conditions yields a dark
colored oil. It is also usual to press twice, the once pressed
meal being re-heated more strongly than before. The first
cold-pressed oil is said to be mostly exported, and to dry
more rapidly than the second hot-pressed oil which is re-
tained for domestic consumption.
Attempts have been made to establish a tung oil press-
ing centre on European lines at Shanghai, but there has
always been difficulty in obtaining a full supply of seed.
The Chinese much prefer to crush the seed locally, trans-
porting only oil.
PRODUCING TUNG OIL IN FLORIDA
In America the fruit is allowed to fall upon the ground
and may be picked up at any time convenient to the labor
on the groves. They are then delivered in bags to the oil
mill. Power conveyers eliminate all human labor at the mill.
The fruit is delivered direct to decorticators which cut away
the hulls and transfer the seeds to an electrified fanning
machine which shakes them at high speed and eradicates
foreign material. Conveyers then carry the cleaned, hulled
seed in a steady stream to cracking machinery which ham-
mers them just hard enough to to break the shells and pre-
pare the meats for oil expression. The meats are then de-
livered to powerful presses which squeeze out all the oil
that can be expressed.
The first laboratory pressings of American grown seed
were made in 1924, using an Anderson expeller and an
ordinary hydraulic press. It was found that an extremely
light-colored oil could be produced if the seed had been
properly dried, either by the sun or by exposing the seed
upon flat trays in heated rooms. On the other hand, if
seed still contained moisture, a very dark-colored oil re-
sulted. This was found to be due to the high moisture con-
tent of the shells of the seed which resulted in slimy matter
being carried into the oil during pressing. It was also
found that the heating of seed containing moisture con-
tributed to the development of color and to the develop-
ment of acidity through hydrolysis.
Attention is also drawn to the very low acid value of
oil produced from American seed. It is believed that the
high acidity of foreign oil is due to improper storage of
the seed. The development of enzyme action during stor-
age of the seed in moist places, or the hydrolyzing effect of
water in stored oil before shipment and the setting free
of fatty acids would be contributing factors in this direc-
tion. Everything points to the need for effective drying
of the seed before storage and before pressing.
Early in 1928 large scale experiments were undertaken
in hulling, separating and expressing oil from the 1927
crop of fruit. Some 14 tons of fruit were available for these
tests. Decortication was successfully accomplished in a
24. in. disc huller and a separator. In this operation the
whole fruit was delivered to the disc huller which decorti-
cated and discharged the cut seed direct to the shakers of
the separator. In the huller the position of the discs may
DEPARTMENT OF AGRICULTURE
be varied with a tempering screw in order to control the
amount of pellicle to be left on the seed. The separator
does its work through both mechanical and pneumatic ac-
tion. The decorticated seeds from the huller are sifted
onto shaking trays, the loose kernels falling immediately to
the lower tray. The coarse bulk, consisting of outer hulls,
then passes over the upper tray until the mass comes with-
in range of the aspiration chamber where it is lifted by
suction, passed through the fan, and delivered to the cy-
clone collector which may be placed in any convenient loca-
tion. The cyclone collector is part of the apparatus. Be-
fore being discharged from the end of the lower tray, all of
the separated seed is purified by air suction which removes
small particles of hull, etc., which may have passed through
the perforations of the upper tray.
The rate of working was an intake of approximately
3,000 pounds of fruit per hour. The return was 36 per cent
of shelled seed ready for oil-crushing purposes, substan-
tially free from the hard pellicle or skin (which contains
no oil) ; only a sufficient quantity of skin being allowed to
go through with the seed to give a satisfactory "bond" for
proper expelling results.
The Anderson expeller equipment used for the test was
the standard type consuming 15 h. p., costing in all about
$5,000.00. The machine has yielded approximately 50
gallons of oil per hour, with an over-all estimated expense
for crushing of $8.00 per ton of fruit.
In these tests 28,587 pounds of fruit were experimented
with and only 91/2 hours were required for complete hull-
ing of this quantity. The hulling was extremely efficient,
the outer hull being removed and much of the inner hard
pellicle, so that the seed to be crushed was concentrated
down to about 36 per cent of the total fruit. The majority
of this product for crushing was in the form of white meats
without the outer pellicle, and contained over 48 per cent
of oil. As stated heretofore, the seed with the hard pellicle
usually contains only 35 per cent of oil. After crushing
the press cake contained only a little over 5 per cent of oil.
It is evident that the press cake could be produced with
an oil content not exceeding 5 per cent, and special attention
has been directed to its value as a fertilizer on account of
its nitrogen, phosphoric acid and potash contents. It is now
being used experimentally as a fertilizer on the groves of
the American Tung Oil Corporation.
PRODUCING TUNG OIL IN FLORIDA
As an indication of the possible fertilizer value of tung
oil press cake versus guano, it may be stated that the aver-
age analysis of the guano purchased for the groves at $48.00
per ton during the years of 1926 and 1927 showed from 4
to 10 per cent of phosphoric acid, from 5 to 6 per cent of
nitrogen equivalent to ammonia, 1.2 to 1.6 per cent of pot-
ash, and from 8 to 12 per cent of moisture, whereas the
tung oil press, cake showed from 1.7 to 2.7 per cent phos-
phoric acid from 4 to 6 per cent of nitrogen equivalent to
ammonia, about 1.2 per cent potash, and from 5 to 6 per
cent of moisture.
The potash and phosphoric acid contents of tung oil cake
as reported above have been substantially confirmed on
Chinese fruit examined in England. It is generally con-
sidered in America that the fertilizer value of the cake
will offset the cost of crushing. The outer husks removed
from the seed are practically useless even as fertilizer,
containing only about 0.6 per cent of available ammonia,
but their return to the soil would add appreciably to the
humus content, and this would be an important matter on
sandy soil. The outer husks should have a value of $4.50
to $6.00 per ton.
IS THE QUALITY OF AMERICAN GROWN TUNG
OIL SUPERIOR TO THE FOREIGN?
A most important feature in the study of tung oil is the
fact that it has often been liable to heavy adulteration.
Adulteration with soya bean oil, rapeseed oil, tea seed oil,
perilla oil, and sesame oil is still occasionally practiced, ac-
cording to some authorities. One of the most interesting
points of attention about the American production is the
prospect of securing a really pure oil extracted under clean
and proper conditions.
The values in the table (page 32) have been reported for
various samples of oil obtained by laboratory expression
from small lots of American grown seed as early as 1924.
The high gravity, high refractive index, low acidity, low
heat test, and excellent color are noteworthy.
During 1928 the American Tung Oil Corporation distrib-
uted a considerable weight of American grown tung oil to
eighty varnish manufacturers for large-scale varnish-mak-
ing tests. Practically every one of these manufacturers
DEPARTMENT OF AGRICULTURE
reported the American oil to be superior to imported oil.
It is quite clear from the reports of the results obtained
that American oil is entirely satisfactory and generally
superior to imported oil. To quote examples, one maker
reported a slight improvement in color of his finished varn-
ish when made with American grown oil; another reported
that American oil gave a faster bodying action in the kettle,
producing a paler, clearer varnish with a somewhat faster
and harder drying film and with better hot water resist-
ance; another reported that the American oil made tougher
and more elastic varnishes with better water resistance, etc.
There seems no doubt about the fact that American grown
tung oil will be acceptable to the industry. At no time has
a sample of oil been found to give abnormal properties.
pressed Florida pressed pressed
Florida No. 2 Alabama Alabama
No 1 No. 3 No. 5
Appearance and color All pale and clear
Spec. gravity at 15.50 C. 0.9411 0.944 0.942 0.941
Acid number 1 0.5 1.5 1.2 1.36
Saponification number 1193.8 194.4 191.6 191.5
Refractive index 1 1.5191 1.51751 1.51871 1.5188
Iodine number 1166.0 161.0 166.8 166.1
A. S. T. M. heat test 110% 9% 101/: 11
WHAT IS THE COST OF TUNG OIL LAND?
Land suitable for the cultivation of tung oil has been
offered in various regions in Florida, Louisiana and Mis-
sissippi at prices ranging from $5.00 to $10.00 an acre when
in the uncleared state. Some land at slightly higher fig-
ures has been offered when very close to prominent towns
and situated directly upon hard surfaced highways. It
should be stated, however, that the location of the land is
an important consideration, and that a slightly greater
outlay for good land will in the long run prove much more
economical than the purchase of low grade lands because
of a supposed initial saving. The original 200-acre Para-
dise grove of the American Tung Oil Corporation, which
PRODUCING TUNG OIL IN FLORIDA
lies adjacent to a hard paved road, within two or three
miles of Gainesville, was purchased at $20.00 an acre. The
cost of clearing the pine trees from the acreage probably
varied from $40.00 to $60.00 an acre. Difficulty in securing
good drainage added greatly to the cost of preparing some
areas of this land for groves.
Throughout the northern part of the State of Florida
there are thousands of acres of suitable land which have
been cleared and heretofore planted with other crops. Many
of these lands have been idle for years. They could readily
be put in condition for the growing of tung oil. Lands of
this character have apparently been sold at from $20.00 to
$60.00 an acre. It is claimed by some investigators that
new land which is covered with pine trees could hardly be
purchased and cleared for the planting of tung oil at the
WHAT IS THE COST OF CLEARING LAND FOR
TUNG OIL PRODUCTION?
The cost of clearing land will depend upon the kind of
trees to be removed, the density of the stand, the possi-
bility for sale of timber or fire wood, and the quality of
the supervision. For example, scrub oak land can be
cleared at a cost of $12.00 an acre and may run as high
as $35.00 dollars per acre. What might be termed grub-
bing, that is, taking out small groups of trees and brush
from land that is called cleared and has been farmed, will
usually average $5.00 per acre. A dense stand of live oak,
gum and pine may run as high as $75.00 per acre. The
average stand of mixed hardwood and pine will average
$55.00 per acre. The average cost of clearing 560 acres
on the property of the Alachua Tung Oil Co., according to
H. I. Haskins, the Manager of Operations for Benj. Moore
& Co., was $52.00 per acre. The lowest cost was $20.00
per acre and the highest cost was $65.00 per acre. The
experience of the Alachua Tung Oil Co. was that the stump
puller was not a success. The cheapest method found was
to cut the tree roots eighteen inches below the ground,
allowing the tree to fall.
34 DEPARTMENT OF AGRICULTURE
ARE MAN REPLANTS NECESSARY IN THE
TUN GOIL GROVE?
During the first three years of the trees' life in the
groves, there will be some mortality. The number of trees
lost will depend upon climatic conditions, care at time of
planting, and supervision of the grove. The figures ran
from 3 per cent to 22 per cent on one Florida grove, and
a fair average might be 8 per cent. The mortailty after
the third year should drop to a very low figure.
WHAT IS THE COST OF RAISING TUNG OIL
The selling price of tung oil seedlings of the multiple
cluster type has usually ranged from 15 to 40 cents each,
according to the quantity sold and condition of the seed-
lings. Figures obtained from one large producer of tung
oil seedlings are as follows:
Rent of land ----........- ----.. ----
1000 lbs. of seed (fruit) ---.
Hulling seed ....-.- ---------- ----
Fertilizer (to Sept. 1st.) -..
Preparation of land -- ---
Planting ..................------- -----
Cultivation and hoeing ...-...
Application of fertilizer ---....-
.----- ------ $150.00
---... --. 49.55
---- --- 187.50
- --..- 29.70
Supervision (10% on cost exclusive of seed) ------. 86.60
Total cost to Sept. 1st. -..................... -- ----- ..... $1,251.51
Following is the estimated cost to Jan. 1st:
Fertilizer (Sept. application) ....---------- $60.00
Sept. (including fertilizing) -----.--.---.- 50.00
Oct., Nov., Dec. (cultivation only) ..-..--- 90.00
Add cost to Sept. 1st. .... .-~. --------..-- 1,251.51
Total cost of removal from nursery ........----------_--. $1,451.51
The estimate on the number of trees produced by the
above 1,000 Ibs. of fruit, after allowing for throw-outs, was
40,000 trees. This would indicate an actual production
cost of $0.0363 per tree to time of transplanting. To this,
PRODUCING TUNG OIL IN FLORIDA 35
however, there should be added the cost of digging, inspec-
tion, tagging, and loading on trucks for shipping, which
might bring the cost to from 71/t cents to 10 cents per tree.
The cost of delivery on trucks for distances up to 200
miles might be as high as 6 cents per tree, and to the above
there would be added a reasonable figure for general over-
head, advertising, and profit.
Figures from another 30-acre nursery south of Gaines-
ville, which purchased multiple cluster fruit at 30 cents per
pound, indicate a base cost of a little less than 4 cents per
tree for the seed, for hulling the seed, for preparing the
land, planting, cultivating, and fertilizing. The fertilizer
used in this instance was a 5-8-5 bone and phosphate mix-
ture purchased at $46.00 a ton, and this was plowed in the
nursery before the seed was planted. A small amount of
nitrate of soda was later used. To this figure there would
necessarily be added from 3 to 4 cents per tree for digging,
pruning, and other grove expenses.
The above figures do not include the overhead necessary
in the form of payroll for the experts who would be re-
quired to properly grow nursery trees. General overhead,
advertising, and a fair profit might in every instance bring
up the selling price from 15 to 25 cents per tree in large
quantity, according to size.
It should furthermore be stated that when trees are
selected from a nursery, those which caliper from a half
to three-quarters of an inch, and which constitute the best
size for planting, may not run two-thirds of the best trees
in the nursery. The culls and similar trees which must be
left over for the next year may run well over one-third of
the trees in any nursery. Large well formed stock nat-
urally command the highest price.