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Louisiana State UniversityLSU Digital Commons
LSU Agricultural Experiment Station Reports LSU AgCenter
1935
Artificial curing of forage cropsHarold Thomas Barr
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Recommended CitationBarr, Harold Thomas, "Artificial curing of forage crops" (1935). LSU Agricultural Experiment Station Reports. 522.http://digitalcommons.lsu.edu/agexp/522
r 36 7
MAY. 1935 LOUISIANA BULLETIN No. 261
Artificial Curing of Forage Crops
By
Harold T. Barr
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LOUISIANA STATE UNIVERSITY
AND
AGRICULTURAL AND MECHANICAL COLLEGE
AGRICULTURAL EXPERIMENT STATIONS
C. T. Dowell, Director
Artificial Curing of Forage CropsBy
HAROLD T. BARR
The drying of some agricultural crops by the use of artificial heat has received
increasing attention during the past few years. However, it is not a new process.
The first reference to artificial drying seems to be that recounted in "Horse-
Hoeing Husbandry," by Jethro Tull, published in 1829.1
Artifiicial heat was used in
this case in order to reduce the moisture content in wheat, so as to store it for long
periods of time, in order to sell when the price was high. One of the earliest at-
tempts at artificial drying in the United States was for drying prunes about 1880,
and then a few years later for the drying of walnuts.
The first10 work in artificial curing of forage crops was carried on by the United
States Department of Agriculture from 1910 through 1912, at Hayti, Missouri. In
1911, Arthur J. Mason built an experimental drier at West Point, Mississippi. Hemoved to the vicinity of Chicago three years later, where he continued his work.
The Bayley Blower Company of Milwaukee, Wisconsin, in 1915, built a dehydrator
for the McCracken Land Company of Houston, Texas.
The Louisville Drying Machinery Company, of Louisville, Kentucky, started
experimental work about 1915. From 1915 to 1925, there seemed to be little interest
along this line, with about the only work going forward being that of Mason and the
Louisville Company, each of whom was making improvements on his dryers.
During 1925, the interest in artificial drying gained momentum, and has been get-
ting greater each year. The United States Department of Agriculture, state agri-
cultural experiment stations, commercial companies, and various individuals have
each put forth considerable sums of money, time, and effort in bringing about this
development.
The importance of the hay crop in the United States is best shown by referring
to the yearbook of the United States Department of Agriculture for 1934. A total of
all crops harvested for 1933 is 327,324,000 acres, with 66,144,000 acres, or 20.20 per
cent, devoted to hays. In Louisiana, in 1933, the total hay acreage was 202,000
with a farm value of $1,577,000. In the humid area of the Gulf States, the average
monthly rainfall for the summer months is 4.56 inches. With this heavy rainfall,
the production of the best quality of hay is an uncommon occurrence. It is not
uncommon to have the quality of from 30 to 60 per cent of the hays in the Gulf
States lowered one or two grades, or completely lost from rain damage.
Throughout the Gulf States there are large acreages which will produce heavy
crops of hays, but they have only been partially developed because of the difficulty
encountered in producing hay of good quality.
Artificial drying gives a better color, a more uniform product, higher protein
content, and slightly higher percentage of leaves.3
Artificially cured
Field cured
Color %67
60
Leaves %52
48
Protein %20.4
19.5
2
The leaf loss and lower protein content are doubtless due to mechanical losses in
the process of field curing. With alfalfa hay, Kisselback and Anderson4 found that
from 68 to 75 per cent of the total protein was contained in the leaves, varying some
according to the stage of maturity, while work at the Louisiana Agricultural Experi-
ment Station on soybean hays, carefully cured, shows the leaves to make up 59.7
per cent of the plant and the stems, 40.3 per cent of the plant. The leaves at the
same time contained 4.78 times more crude protein than the stems.
With clear hot weather alfalfa or soybeans dried in the swath to a moisture
content satisfactory for barn storage were badly bleached. In this condition, few
leaves were lost if picked up by hand forks and loaded onto wagons; when raked
into windrows, the ground in several cases was covered with leaves and fine stems.
Where hay is grown as a cash crop or commercial enterprise, a suggestion by
Hurst and Kisselback7
is that the value of the hay should be determined by com-
parison with the actual prices paid for the various grades at the terminal markets.
They found that "a greater part of the alfalfa hay sold on the Kansas City market
falls within No. 2 and No. 3 grades." In 1927 and 1928 the average price of
U. S. No. 1 Extra Leafy Alfalfa was $8.01 higher than U. S. No. 2 on the Kansas
City market. For the period of 1922-1932, according to the United States Depart-
ment of Agriculture yearbook of 1933, the average price of U. S. No. 1 alfalfa
was $4.12 higher than U. S. No. 2 at the Kansas City market.
With reasonable care, and allowing from two to four hours wilting in the swath
before delivery to the drier, the hay from an artificial drier will grade U. S. No. 1,
Extra Leafy.
Workers at other stations have found artificially cured hays to have several
times as much vitamin A and vitamin E as similar hays cured in the sun. Vitamin
D is lowered somewhat, perhaps due to the shorter period of exposure to the sun
after cutting. In order to test out the effect of the curing process alone on the feed-
ing value of soybean hay, two adjacent "cuts" of Biloxi soybeans of the same
age and stage of maturity were cut. One-half was dried in the field, and the other
half put through the artificial drier.
In order to be able to answer the questions as to the feeding value of the
artificially dried hay, the Animal Industry Department8of the Louisiana Agricultural
Experiment Station made a very careful study. "Four lots of calves were used in
the test. Lot I was fed long soybean hay as it is normally fed. Lot II was fed
field cured soybean hay cut or chopped the same as it is chopped for artificial drying.
Lot III was fed the same amount of artificially dried hay as Lot II. Lot IV was
fed artificially dried hay just as the calves would consume it." Their results were
as follows: "1. One hundred pounds of artificially dried soybean hay was equivalent
to 162 pounds of uncut field cured soybean hay in producing gains on calves.
2. Artificially dried soybean hay produced from 10 to 11 per cent more gains on
calves and steers than cut or chopped field cured soybean hay. Two years' results
showed artificially dried hay to be from 10 to 15 per cent more efficient in producing
gains than field cured chopped soybean hay of the same quality. 3. Cutting or
chopping reduced the waste of soybean hay about 40 per cent, probably because
the steers eating the long hay consumed more leaves and refused more stems.
4. Artificially dried hay was more palatable than field cured hay."
During five years' work in artificial drying, most of the experimenting was
with soybeans, as this has proved the hardest crop to cure successfully, and is a
widely used hay crop throughout the Southern States. Other hay crops and pos-
sible hay crops were cured artificially, and their relative feeding values given in Fig. I.
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The principal hay crops are relatively high in moisture content when ready for
cutting, and if brought direct to the drying plant necessitate the hauling of large
amounts of moisture and at the drying plant reduce the total amount of dry hay
that may be produced per hour. Each pound of water in the hay requires a definite
amount of heat to raise its temperature from the temperature as delivered to the drier
up to 212 degrees, and then evaporate this moisture. Each drier is built with a
furnace capable of delivering a predetermined quantity of heat at maximum capacity.
Hence, the dried hay capacity of the drier is normally this maximum heat, divided by
the amount required to raise the temperature of, and evaporate, the moisture in green
hay above that of the dried hay.
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hours; then the rate of moisture loss slows up, as shown in Fig. II. Jones and Palmer9
found similar results on Johnson grass and soybeans, but on alfalfa they found that
the rapid loss continued from 7 to 8 hours. In curing a 250-pound sample (in the sun)
of soybeans, it was necessary to leave the beans in the field four and one-half days
in order to reduce the moisture content from 82 per cent to 17 per cent, with an
average daily temperature of 88° F. by 10:30 a. m. With analyses from five
years' work, the initial moisture content of green soybeans cut for hay ranged from
64 to 83 per cent, with an average of 74 per cent moisture. With a moisture con-
tent of 83 per cent, it is necessary to evaporate 8,353 pounds of water to leave one
ton of 12 per cent hay, or requires hauling 10,353 pounds of green hay from field
5
to drier. With 74 per cent initial moisture, 4,769 pounds of water must be driven
off, and 6,769 pounds of green hay is needed. While with 64 per cent initial mois-
ture, 2,888 pounds of water must be driven off, and 4,888 pounds of green hay is
used (Fig. III).
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By leaving the soybeans in the field from two to four hours after cutting, the
moisture was reduced from 60-45 per cent, depending upon the time left in the sun and
the stage of maturity. This is the practice as recommended for use in artificial dry-
ing of forage crops.
In order to remove artificially the excess moisture in the forage, heat must be
supplied in rather large quantities. To evaporate one pound of water from 80° F.
(temperature of hay delivered to drier) into steam at 212° F. requires 1,102 British
Thermal Units. With forage in which there is an initial moisture content of 74
per cent, there is a necessary removal of 4,769 pounds of water to produce one ton
of 12 per cent hay. This would require 4,769 X 1,102, or 5,255,438 British Thermal
Units. With forage of 64 per cent initial moisture content, and the necessary re-
moval of 2,888 pounds of water to produce one ton of 12 per cent hay, this would
require 2,888 X 1,102, or 3,182,576 British Thermal Units.
With fuel oil containing 19,000 British Thermal Units per pound, and coal
containing 14,000 British Thermal Units per pound and a theoretical efficiency of 100
per cent, the first case would require 276.6 pounds of oil, or 375.3 pounds of coal,
while the second would require 167.5 pounds of oil or 227.3 pounds of coal to pro-
duce one ton of dried hay. Fourteen tests made on artificial driers in operation
gave fuel efficiencies varying from 28 to 78 per cent. Leaving out two extremely
low tests and one extremely high test, the average efficiency obtained was 63 per
cent (Fig. IV).
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In 1927, work was started at this station by Messrs. C. L. Osterberger and J. J.
Munson on artificial drying. Upon Mr. Munson's resignation, Mr. Carl Nadler worked
for one year on the problem. Mr. Osterberger and Mr. Nadler resigned in 1929,
and Mr. William Whipple and Harold T. Barr filled their places. The first drier
was essentially a rectangular box, four by eight by forty feet high, on a framework
of angle irons. The green material was chopped and blown to the top of the tower,
where a set of baffles distributed it evenly over the top, allowing the material to
fall off by gravity through a rising stream of hot furnace gases which entered the
tower near the bottom. A given batch of hay was recirculated until the moisture
was lowered sufficiently. Considerable trouble was encountered when the hay
reached moisture contents just above the desired condition. It was hard to get the
hay to travel against the stream of gases. Very low fuel efficiencies were also
obtained.
In 192S. a single rotary drum drier three feet in diameter by twenty-eight feet
long was tested out with very good results, but lacked capacity. From these results,
a large drier was built in 1929.
The present drier which has been used successfully for three seasons is shown
in Fig. V. The green forage is delivered to the ensilage cutter, chopped into short
lengths (cutter set for 3/16-inch cut), elevated into the cyclone feeder, and fed by
gravity into the high temperature end of the revolving drum. At this point, the
green material comes in direct contact with furnace gases at a temperature of from
1600° F. to 1800° F.
An exhaust fan draws out the gases after they have been cooled by furnishing
heat for the evaporation of the excess moisture at a temperature of 225° F. and main-
tained in the drum a current of air (400 F. P. M.) sufficient to carry out of the
high temperature zone the particles of low density and therefore low moisture con-
tent. Repeated tests have been run which show the best temperature at the furnace
end to be from 1600° F. to 1800° F., with an exhaust temperature of from 225° F. to
240° F. As soon as the drier is thoroughly warmed up the oil burners are set to give
a heat of from 1600° F. to 1800° F. with complete combustion of the fuel.
Then the exhaust temperature is maintained or varied by the amount of green
material (or moisture to be evaporated) fed into the high temperature end of the
drum. This gives a very simple and practical method of controlling the moisture
in the dried hay. The velocity of the flue gases carries the lighter portions through
the drum in a few seconds while the heavier stems are picked up and dropped
through the path of the hot gases until they lose their moisture. The entire drum is
under a vacuum of about H" static water pressure maintained by the exhaust fan
which helps to keep down the maximum temperature of the material as well as to
reduce the amount of heat required for evaporation. At the entrance to the drum the
chopped hay receives considerable heat by radiation from the flame and the in-
candescent brick work, so that the temperature of the material would be higher than
the wet bulb temperature of the flue gases, and the rate of vaporization is increased
above what it would be if shielded from direct radiation. The heat which must be
supplied to the drying material can enter only through the surface, and cutting the
hay into short lengths increases the ratio of dry to wetted surface and thus speeds
up the rate of drying by exposing a greater possible surface to the hot gases. The
high velocity of the gases past the wet surface of the material and the high mean
temperature difference between the hot gases and green forage tends to speed up
the drying process and give high evaporative capacity to this type of drier.
8
The drier as shown in Fig. V gave an average capacity of evaporating of 3,800
pounds of water per hour for two seasons. One test run of two hours evaporated
4,110 pounds of water per hour and a second test of one hour gave 4,400 pounds
of water per hour.
The dried hay leaves the drier at an average temperature of 168° F., with
exhaust gas temperatures of 230° F. with 10,030 pounds of dried hay in sacks
stacked in a storage building the temperature in the hay reduced from 168° F. to
85° F. in twenty-four hours, with an outside temperature of 83° F. in the shade at
the same time the final temperature reading was made in the hay. As the hay is
discharged from the drier it can be sacked, baled, blown into a storage building,
or conveyed direct to the mixer and the necessary molasses or other ingredients
added to make a mixed feed.
With an average evaporating capacity of 3,800 pounds of water per hour an
average efficiency of 55 per cent was obtained. This in turn required 41 gallons of
fuel oil.
In producing one ton of dry hay from 74 per cent or freshly cut hay with a
required evaporation of 4,769 pounds of water, 51.5 gallons of fuel oil was required
and 134 hours to produce 1 ton of dry hay. When hay is left in the swath from
three to five hours and is reduced to 64 per cent moisture and a required evaporation
of 2,888 pounds of water, only 31.16 gallons of fuel oil are required and 1.3 tons of
dry hay are produced per hour.
The amount of labor required to operate the drier will depend upon whether
the hay is baled, sacked, or blown into a storage building. Successful operation
has been obtained with three common and one semi-skilled laborers, when produc-
ing and sacking one ton of dry hay per hour.
The power required to operate the drier is distributed as follows: 10 horse-
power to drive the ensilage cutter, 5 horsepower on the burner fan, 2 horsepower to
revolve the drum, 1 horsepower on the oil pump, 1 horsepower for the conveyor
screw, and 5 horsepower on the exhaust fan. If an elevating fan is used to store
the dry hay, an additional 5 horsepower will be needed. For experimental work,
individual electric motors were used, but for a permanent installation, a line shaft
running lengthwise of the drum would be preferable, and one 30 horsepower electric
motor, a 35 horsepower engine, or a tractor with 35 horsepower on the belt should
be used.
A standard 16-inch ensilage cutter was used, but in order to secure a cut shorter
than y2 ", an increased capacity, and a lower horsepower requirement, the following
changes were made: To obtain a shorter cut (3/16-inch) a jack shaft was installed
between the counter shaft and the lower feed roller shaft. Then for each 3/16-inch
advance of the feed table, one knife passes the shear bar. To compensate for the
slow feed table travel, the cutter was speeded up to 650 r.p.m. from a recommended
500 r.p.m. This increased speed gave a large increase in horsepower required, and
to reduce this, 3 of the 6 fans were removed. The cutter thus modified was operated
by a 10 horsepower motor and handled the material easily, as the maximum eleva-
tion is 12 feet.
In order to arrive at the cost of operation per ton of dry hay, the moisture in
the green hay will be considered at the average for freshly cut hay. And thus the
fuel required will be at the upper limit. With careful management and field wilting
for 3 to 5 hours the fuel and power can each be lowered somewhat below the follow-
ing figures. With any expensive piece of machinery in order to reduce the over-
9
head cost per hour or ton of material, sufficient work must be available before buy-
ing the equipment. The following table is based on 500 tons of dry hay per season:
Drier depreciation, $3,500— 10 -years.. - - - -$ 350.00
Interest, $3,500—$350 @ 6 per cent 94.50
2
Fuel, 51 gal. per ton @ 2J^c X 500 637.50
Power, 22 K.W. @ 2c X 500 220.00
Labor—3 common @ 10c 150.00
1 semi-skilled @ 25c 125.00
Repairs 2 per cent of original investment 70.00
Total cost of drying 500 tons '.. $1,647.00
Total cost per ton of dry hay...._ 3.29
FIELD OPERATIONS:To get the complete cost of artificially cured soybean hay, records were kept
for two years on all operations. An upright-growing Biloxi soybean has proven the
best bean to grow for the drier in this locality. Drilling in rows 42 inches and 22
inches apart were each tried. The yield in each case was about equal; but the 22-
inch rows gave smaller main stems and thus a slightly better grade hay. The average
yield of dry hay was two tons per acre. Part of the field was operated with mule
power and the remainder with tractor power as shown in the following table:
FIELD LABOR AND POWER SUMMARYFig. VI
Disking Planting Cultivating Mowing Loading Hauling Unloading
T M T Mule M T Mule M T Mule M Mule Men **
2-Mule .35 .38 1.24 .68 3.4 1.87 1.80 1.0 6.3 12.6 9.5 4.75 3.78 1.90
.35 .38 3.1 1.70
General Purpose 35 .38 .72 .79
.50 1.10* .70 .77 .63 12.6 9.5 4.75 3.78 1.90
Tractor 35 .38 .435 .48
Cutting with a power-driven corn binder increased the tractor work .30 hours
per acre, and decreased the man hours 3.15 in loading and unloading. The bundled
beans also decreased the labor in feeding the cutter; however, the bundled beans do
not wilt down evenly, and the increased amount of fuel to evaporate this increased
moisture will more than offset the gain from using the binder. Dump wagons or
slings for unloading at the drier are recommended time savers.
TYPES OF DRIERS:Driers in general may be classified briefly as follows:
1. Rotary drum (Louisiana State University, Ardrier)
2. Conveyor (Mason, Bayley, Fulmer)
3. Multiple Fan (Koon)
4. Tray driers
5. Tower driers
6. Stack driers
The first two types have proven the most successful with installations of each
type scattered in various parts of the United States.
'Two men with 4-row 22-inch planter.
**Hauling 1 miles and returning to field.
10
12
The Ardrier (Fig. VI) employs the same general principles as the Louisiana
State drier, of air flotation, parallel passage of material and hot gases. The one
difference is that it has three drums, one inside the other, which allows for a some-
what more compact unit. The characteristics of this type drier have already been
covered in this bulletin.
Conveyor Driers: The first drier of any record in the United States was a
conveyor drier, built and tried for three seasons, 1910 to 1912, at Hayti, Missouri.
Later conveyor driers were built by Arthur J. Mason, Bayley Blower Company,
and J. H. Fulmer. These driers consisted in the main of an endless apron for con-
veying the material to be dried through a tunnel where the green material is sub-
jected to the hot drying gases. In this drier, the driest hay comes in contact with
the hottest gases. They produce an excellent quality product, require a rather high
horsepower, cost of drier is relatively high, and because of slow speed of conveyor,
are difficult to adjust. If the material is drying too much or not enough, it is dif-
ficult to adjust quickly.
'Multiple Fan: This type of drier was developed by A. W. Koon, of New
Orleans, Louisiana. It consists of a series of fans, pipes, cyclone separators, and
furnace. The green material and hot gases are mixed at the fan and blown up into
a cyclone separator. Six fan and cyclone separator circuits comprise the travel of
the hay. Most of the gases are recirculated through the furnace. Each drier has
been built differently from the former, and he now has a modified portable drier.
Tray, Tower, and Stack Driers: Each of these has been built with compara-
tively little success. The tray type is a batch process, having a relatively low
capacity, and high labor requirement. The tower driers have employed gravity or
conveyors to carry the material to be dried down through the drier over various
baffles or shelves. Low capacity, low fuel efficiency, and in some cases recirculation
to get the necessary moisture reduction have characterized this type drier. Stack
drying has been used where a portable furnace and fan have supplied heat for drying
material stacked around a central perforated pipe in the field. This type has given
moderate success where only a small amount of moisture is to be removed.
ACKNOWLEDGMENT
The author wishes to acknowledge the work of C. L. Osterberger, Carl Nadler
and J. J. Munson in beginning and carrying on the first two years of this work.
To William Whipple, for his valuable assistance during three years of active tests
as a co-worker, and to the Chemical Laboratory, Louisiana Agricultural Experiment
Station, for all chemical analyses, thanks are also due.
SUMMARY
Artificial drying of hay crops is an economical and practical operation in the
humid area.
Many acres now idle in the humid area can be used for hay crops by the use
of artificial curing.
By artificial curing, a hay may be produced which is uniform as to color, odor,
and food value, regardless of weather conditions.
Feeding trials with beef cattle gave faster gains on machine-dried soybean hay
as compared to chopped field cured soybean hay.
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Feeding trials have shown 2,000 pounds of artificially cured hay to be equivalent
to 3,237 pounds of long field cured soybean hay for beef cattle.
Dairy cattle gave favorable results on artificially cured hays for each of the
three years' tests.
REFERENCES
1. Artificial Drying of Agricultural Products, by R. B. Gray, W. M. Hurst and
E. D. Gordon. Agricultural Engineering, Vol. 13, No. 10. October, 1932.
2. The Nutritive Value of Mechanically Dried Hay as Affected by High Tempera-
tures in the Presence of Air. The Pennsylvania Agricultural Experiment Sta-
tion, 44th Annual Report. Bulletin 266. July, 1931.
3. The Artificial Curing of Alfalfa Hay, by H. B. McClure. United States Depart-
ment of Agriculture. Circular 116. March 8, 1913.
4. Quality of Alfalfa Hay in Relation to Curing Practices, by T. A. Kiesselbach
and Arthur Anderson. U. S. D. A. Technical Bulletin 235. April, 1931.
5. Chopping Hay for Livestock and Steaming or Pre-Digesting Foods, by G. Boh-
stedt, B. H. Roche, I. W. Rupel, J. G. Fuller and F. W. Duffee. Wisconsin
Agricultural Experiment Station, Research Bulletin 102. December, 1930.
6. Chemical Problems in Connection with Artificial Drying of Hay, by Henry
Atterson, Ph.D. Paper presented at annual joint meeting of American Asso-
ciation of Medical Milk Commissions and Certified Milk Producers' Association
of America. June 23, 1930.
7. Drying Alfalfa Hay by Forced Draft with Heated Air, by W. M. Hurst and
T. A. Kiesselbach. Transactions of the American Society of Agricultural En-
gineers, Vol. 23, pp. 19-21, 1929.
8. Machine Dried Soybean Hay for Fattening Calves, by M. G. Snell. Louisiana
Agricultural Experiment Station, Bulletin 257. August, 1934.
9. Hay Curing III: Relation of Engineering Principles and Physiological Factors,
by T. H. Jones and L. O. Palmer. Agricultural Engineering, Vol. 15, No. 6.
June, 1934.
10. Pasture Fertilizer Results, by R. H. Lush and J. L. Fletcher. Journal of Dairy
Science, Vol. 17, No. 11, pp. 733-735. November, 1934.
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