BARN MOW HAYDRYING IN CALIFORNIA John B. Dobie CALIFORNIA AGRICULTURAL EXTENSION SERVICE • CIRCULAR 149 • FEBRUARY 1949 THE COLLEGE OF AGRICULTURE • UNIVERSITY OF CALIFORNIA • BERKELEY 8arn Mow ttaydrying is a method of drying wet hay in the mow by forcing air through it. Barn haydrying is particularly useful in areas where wet weather makes complete field curing difficult. It is also of value wherever haying must be done quickly. It Has These Advantages: It produces better quality hay than field curing. It greatly reduces danger of loss by spontaneous heating and fire. It may often save a hay crop which otherwise would be ruined. It Has These limitations: It does not completely replace sun-drying. It must be done quickly to prevent mold growth. It can result in spoilage by bacterial action, if interrupted for too long a time. This publication is the nineteenth in a series reporting investigations conducted by the California Agricultural Experiment Station in co- operation with the California Committee on the Relation of Electricity to Agriculture. BARN MOW HAYDRYING IN CALIFORNIA John B. Dobie Associate in Agricultural Engineering in the Experiment Station Barn mow drying of hay is a new prac- tice in California. It is already being widely used in sections where damp weather often prevents complete field curing. In the drier parts of the state mow driers are useful for curing early and late cuttings, and for speeding up hay re- moval from a field which is to be ir- rigated for another crop. A barn mow haydrier consists of a sys- tem of channels or ducts, generally made of wood, through which air is blown by a fan. Hay is piled on the ducts so that the moving air passes through it and dries it. Driers are usually located in the barn mow, but similar units can be used for open stacks. Drying by this method is progressive, taking place first in a thin layer near the ducts and then advancing in a drying layer toward the outside of the hay mass. Below this layer, the hay is dry ; above it the hay remains moist until it becomes a part of the drying layer. This layer moves outward slowly, usually at the rate of one- half to one foot per day, depending on the speed, temperature, and humidity of the air forced through it, and on the in- itial moisture content of the hay. A mow of hay will dry to a safe storage level (20 per cent) in from seven to fifteen days, depending on the above factors, the depth of hay, and the rate of loading. ADVANTAGES There are three main advantages of barn mow haydrying over field curing. A haydrier can often save a hay crop which otherwise would be a total loss. When wet weather prevents complete field curing, the hay can be dried in the mow to a safe moisture con- tent for storage. This method greatly reduces danger of loss by spontaneous heating, because the hay is kept cool until curing is complete. When stored hay is too moist, the heat it pro- duces may cause it to burst into flame. Even if fire does not break out, there may be enough heating within the stack to destroy much of the hay's nutrient value to livestock. In barn drying, the air cir- culated through the hay keeps it cool while drying. With comparable weather and harvesting practices, barn mow haydrying should always produce better quality hay than field curing. Most green forage crops contain 75 per cent or more moisture when cut and. under good conditions, can be sun-dried to 50 or 40 per cent moisture in one day. From this point on, however, field drying is much slower. Bleaching and leaf shat- tering may then cause considerable loss before the hay reaches a safe moisture content for storage. Barn drying takes advantage of the first day of quick sun- drying, but removes the hay from the field before such loss takes place. In an experiment with an alfalfa-clover mixture, the U. S. Department of Agri- culture 1 found that the dry matter yield 1 Hodgson, R. E., J. B. Shepherd, W. H. Hes- terman, L. G. Shoenleber, H. M. Tysdal, and R. E. Wagner, Comparative Efficiency of Ensiling, Barn Curing, and Field Curing Forage Crops. Agricultural Engineering. 28(4) : 154-56. 1947. [3] for feeding was 5.9 per cent greater for barn curing than for field curing, produc- ing 8.1 per cent more milk per acre of hay. Barn curing saved 74 per cent of the protein of the original crop, while field curing saved 68 per cent. Barn-cured hay averaged about twice as high in carotene (vitamin A) as field-cured hay. Later ex- periments in less favorable weather showed greater differences in favor of barn-cured hay. LIMITATIONS Barn mow haydrying does not solve all the problems of haymaking. It is still limited in the following ways. Barn drying is not completely in- dependent of the weather. To be successfully dried in the mow, long hay should have less than 50 per cent mois- ture content, chopped and baled hay 35 per cent or less. It must therefore still be sun-dried for one or two days before it is taken to the barn. To prevent mold growth, barn drying must be done rapidly. Molds flourish throughout the normal range of temperature and moisture content found in mow drying. In tests using hay of 40 to 67 per cent moisture, Jennings 2 found that hay should be dried to a 10 per cent moisture average in less than seven days to prevent mold. It is not always possible in seven days to dry all of the hay to a moisture content which will not support mold growth. Unless the hay is put on in layers of less than five feet, a light dusty mold may form in the top of the hay. Such damage usually would be much worse if the hay were being field-cured during the same drying period. Bacteria may cause spoilage if air circulation is interrupted too long. Spoilage may occur whenever the fan is shut off so long that the tempera- ture of the hay rises above the outside air temperature. Continuous blowing will 2 Jennings, B. A., 1945, Progress Report on Mow Curing of Hay, No. 824, Cornell University. keep the temperature low enough to check bacterial action. Mow drying, particularly of baled hay, may not always be successful because of these limitations. The more closely you follow the recommendations given in this circular, the greater will be your chances for successful haydrying in the mow. POINTERS TO REMEMBER To house a haydrying system, a barn should have: A good roof to protect the hay from rain A sound, relatively airtight floor under the hay storage area Ventilation good enough to carry away the damp air as it leaves the hay and prevent recirculation to the fan A strong and well-supported hay track for long hay, able to carry the added weight of moist hay. To barn-dry successfully, long hay must go into the mow with less than 50 per cent moisture content, chopped or baled hay less than 35. A method for checking the moisture content of hay in the field is given on page 15. To obtain even drying through- out the stack, spread hay evenly over the drier in layers, with as little packing as possible. Hay which is tightly packed will have a higher resistance to the air flow, and will receive less air and dry more slowly than loosely packed hay. To get the most out of your drier, load the hay in small quantities at fre- quent intervals, so that the top layer of moist hay is never more than 3 or 4 feet deep. Each layer will then be dried soon after it is placed on the drier, giving mold growth less chance, and static pressure will be kept at a minimum. Avoid the common mistake of loading too much hay on the drier too quickly. To prevent loss of air sideways through channels in the hay, lateral ducts should be at least 6 feet from the [4] LATERALS-4 TO 5 FEET APART AIR OUTLET ' BOARD^ COVER n l! II i I 1 n n 1 1 ii n 1 1 II II U u_ u_ y u u Fig. 1 . Central main duct drier. edge of the hay. Channels are easily formed between layers of hay on the drier, and offer less resistance to the flow of air than the mass of wet hay above. This tendency of the air to move hori- zontally rather than vertically limits the depth to which hay may be dried, and reduces the efficiency of the drier during the final stage of drying. To raise the temperature of the air at the intake, if possible locate your blower inlet on the south side of the barn, or where incoming air will be warmed by passing over objects heated by the sun. Warm air dries hay more rapidly. If the fan is powered by a gaso- line engine, it may be possible to direct incoming air so that it is warmed by the engine's heat. A temperature rise of 3 to 4 degrees Fahrenheit may thus be obtained. To avoid clogging the system with dust, do not operate the fan when a large amount of dust is in the air. When dry hay is being chopped near the fan, or when dry field-chopped hay is being placed on top of or near hay being mow dried, turn the fan off until the air is fairly clear. Do not locate your fan near a chopped hay mixing or feeding chute where fine material may be picked up. THE DUCT SYSTEM You must have even air distribution to prevent spoilage, and to obtain quick, uniform drying at low power consump- tion and blowing cost. Air distribution depends on the duct system and the way hay is spread over it. The duct system is made up of two parts— a main duct and, connected to it, a series of smaller ducts or a slatted floor. The main duct is a large tunnel, usually airtight, which also acts as a pressure chamber to aid in even air distribution. It is sealed against leakage except at the smaller duct openings. It may be either tapered or uniform cross section, and is extended at the large end to receive air from the fan. The size of the main duct de- pends on the quantity of air required for the given mow area, and on the air ve- locity, which should be about 1,000 feet per minute. A door should be provided to permit entry into the main duct after it is covered with hay. The air in the main duct is spread out under the hay by means of small lateral [5] ducts or a slatted floor. Laterals are in- verted troughs, open at one end to receive air from the main duct, and closed at the other end. They are usually wider than they are high, and are supported 2 or 3 inches above the floor to provide space for passage of air to the hay. They should not be more than 25 feet long. The closed end of the laterals or slatted floor should be 6 feet from the closest barn wall for long or chopped hay, and the laterals should be spaced on centers 4 to 5 feet apart. A slatted floor for baled hay may be 4 or 5 feet from the sidewalls, or even closer if the walls are airtight. Types of Duct System Duct systems fall into one of the follow- ing general classifications. The central main duct drier has the main duct down the center of the barn floor with laterals at right angles on each side. Air may also be admitted to the hay through baffled openings in the top of the main duct. The main duct must be well supported, since it usually is directly under the hay track and must support the wet hay being dropped on it. The main duct should be kept as small as possible by gradually decreasing its height toward the closed end. This system is used mainly in barns 30 feet or more wide. For barns less than 20 feet wide a high, narrow, slatted central main duct without laterals can be used. Other variations include an A-frame central main duct, either slatted or airtight with regulated openings and a vertical duct system for use with chopped hay. A slatted main duct should not be used except where the first hay put on the drier will cover the duct sufficiently to permit blowing without excessive loss of air. The side main duct system has the main duct located along one wall with laterals extending at right angles from it. Since the main duct is along the wall, or even outside the wall, size and strength are not so important. The duct does not have to be tapered, thus simplifying de- sign and construction, and providing a large pressure chamber. Use of this sys- Fig. 2. Side main duct drier. [6] SLATTED FLOOR _^ ?<__ ^— 6'— ► AIR OUTL BOARD COVEF * p.' ^ i i i l i i J. I I i_ j n i ii n 1 1 1 1 n ii u r r < D *" 6 . SIDE VIEW v ( j? - 5 .. - — n. — =^ Fig. 3. Slatted floor drier. tern is limited to barns 36 feet wide, since the length of the laterals should not ex- ceed 25 feet. The slatted floor drier is a more recent design which is useful for long or baled hay. It may have either the side or central main duct, but instead of indi- vidual laterals, has a slatted floor held off the solid floor by spacers to permit the flow of air under and through it. The opening for air delivery from the main duct under a slatted floor is continuous throughout the length of the main duct. The slatted floor should be built in mov- able sections to permit cleaning. In this type of drier the air moves more slowly when it enters the hay, and is distributed more evenly. Designing Your Drier The basic design of any haydrying sys- tem is simple, but planning details for your particular barn may be complicated by several factors. To decide which type of drier is best for your barn, you must consider the shape of the mow, the depth to which hay may be piled, any obstruc- tions in the hay storage area, placement of fan, feeding arrangements, and har- vesting practices. For example, suppose your barn is 24 x 36 feet and your crop is chopped hay. Its dimensions suggest a side main duct with laterals. However, there are feeding chutes along the sides, so that the main duct should be placed in the center of the barn. If you intend to put in more than 10 feet of hay, a high narrow center main duct should be used to admit air as far up in the stack as is practical. Keeping all these factors in mind, study the descriptions of the three main types of system above, and choose the type which best fills your needs. Table 1 gives figures from which you can estimate the dimensions of a drier for any size barn; tables 2, 3, and 4 give dimensions already worked out for several sizes of barn mow with long, chopped, and baled hay. To find the size your main duct should be, you should know the total air require- ment for your barn mow and type of crop. Multiply the area of your barn mow by the figure under item 2 of table 1 [7] MAIN DUCT Fig. 4. Schematic drawing of the various types of barn mow haydriers, showing construction details. Left, side or central main duct with laterals fitted to flared transition pieces; center, side or central main duct with straight laterals; right, slatted floor drier. PERMANENT SECTION MOVABLE SECTION UNIFORM CROSS SECTION LATERAL Table 1 — RECOMMENDED VALUES FOR FIGURING HAYDRYING INSTALLATIONS Long hay Chopped hay Baled hay 1. Type of unit 2. Amount of air (cubic feet per minute per square foot of mow area) 3. Pressure at fan discharge 4. Maximum depth of hay, settled . . 5. Maximum moisture content of hay when placed on drier 6. Space between laterals 7. Minimum space between laterals and walls Slatted floor or laterals 16 2 A inch water 10-1 2 feet 50% 4-5 feet 6 feet Laterals or slatted floor 20 1.00-1 .25 inch water 8-10 feet 35% 4-5 feet 6 feet Slatted floor side main duct 25 1.25-1 .50 inch water 7 layers 35% Slatted floor 5 feet (2 feet with tight sidewalls) Table 2 — DESIGN DATA FOR HAYDRIERS — LONG HAY Capacity for 12-foot depth (tons! Air Main duct Laterals Size of mow floor* (ft.) required (cfm) required at %" water Size of cross section (sq. ft.) Length (ft.) Number Inside cross section (sq. in.) Length (ft.) 20x2411 14 7,680 1.5 8 18 4 288 12 20 x 32 If 19 10,240 3.0 10 26 6 240 12 20x36 11 22 11,520 3.0 12 30 7 247 11 20x48H 29 15,360 5.0 15 42 10 216 11 24x32t 23 12,288 3.0 12 26 6 288 15 24x48f 35 18,432 5.0 18 42 10 259 15 28x36f 30 16,128 5.0 16 30 7 329 18 28 x 48 1 40 21,504 5.0 20 42 10 288 18 32x48$ 46 24,576 7.5 24 42 20 173 7 32x601: 58 30,720 10.0 30 54 26 166 7 36x48t 52 27,648 10.0 28 42 20 202 8H 36x601: 65 34,560 10.0 35 54 26 194 8V2 * Type of main duct recommended according to size of barn only. U Slatted center main duct without laterals may be used. t Side main duct. t Center main duct, tapered. [10] Table 3 — DESIGN DATA FOR HAYDRIERS — CHOPPED HAY Main duct Laterals Size of mow floor* (ft.) Capacity for 10-foot depth (tons) Air required (cfm) Horsepower required at 1" water Size of cross section (sq. ft.) Length (ft.) Number inside cross section (sq. in.) Length (ft.) 20x24 11 24 9,600 3.0 10 18 4 378 12 20x321f 32 12,800 5.0 12 26 6 288 12 20x36 11 36 14,400 5.0 15 30 7 247 11 20x48f 48 19,200 5.0 20 42 10 288 11 24x32| 38 15,360 5.0 16 26 6 384 15 24x48f 58 23,040 7.5 24 42 10 288 15 28x36| 50 20,160 7.5 20 30 7 411 18 28x48f 67 26,880 10.0 27 42 10 346 18 32x48| 77 30,720 10.0 30 42 20 216 7 * Type of main duct recommended according to size of barn only. fl Slatted center main duct without laterals may be used. t Side main duct. t Center main duct, tapered. which is correct for the type of crop you will dry. Divide this figure, which is your total air requirement, by 1,000, which is the number of feet per minute air should travel through the duct system. This will give you the cross-sectional area of your main duct in square feet. For example, if your barn mow floor is 24 x 40 feet, or 960 square feet, your total air requirement for long hay will be 960 x 16, or 15,360 cubic feet per minute. The area of your main duct should there- fore be 15,360 divided by 1,000 or 15.4 square feet, and its dimensions should be about 4x4 feet. Since its closed end should be 6 feet from the wall, your main duct would be 40 minus 6, or 34 feet long. Laterals should be spaced so that there are 4 or 5 feet from the center of one lateral to the center of the next, and they should be 6 feet from the barn wall at both sides and closed ends. For a side main duct in the barn described above, you could plan 7 laterals spaced 4' 8" on centers. Since your main duct will be 4 feet wide, the laterals would be 24 minus 4 minus 6, or 14 feet long. The total cross-sectional area of all the laterals must be equal to the cross- sectional area of the main duct at its larg- est point, so that an equal amount of air will reach all laterals. In this example the main duct area is 15.4 square feet, so the 7 ducts would each be 15.4 divided by 7, or 2.2 square feet in area. You could therefore design laterals to have inside dimensions of 19 x 16% inches, includ- ing a 3-inch air space along the floor of the mow. (The laterals may be tapered, preferably by maintaining a constant width while reducing the height. At their openings into the main duct, tapered laterals will have the same dimensions as straight laterals.) Openings in the top of a central main duct should be planned for any part of the main duct 4 feet or more wide, and their total area must be added to the total area of the laterals. The sum of both should be equal to the cross-sectional area [11] of the main duct. Such top openings are usually 1- to 2-inch cracks covered with an elevated baffle board. They are placed in the top of the section of main duct be- tween laterals, rather than immediately above lateral openings. If the main duct is to be tapered, de- crease its cross section gradually so that it is always equal to or larger than the combined areas of the laterals remaining between that point and the small end of the main. In the slatted floor drier, the height of the continuous air delivery opening is equal to the area of the main duct di- vided by the length of the opening. In the above mow this would be 15.4 divided by 34, or 5.4 inches for a side main duct. A 5%- to 6-inch opening would be satis- factory. FANS The fan is located at the inlet end of the main duct, preferably inside the barn to protect it from the weather. If inside the barn, the air opening on the suction side of the fan should be twice as large as that on the blowing side. To find out what size fan you will need, you must know the maximum air requirement for your mow, and the static pressure at which this amount of air must be delivered. As described above, multiplying your barn mow area by the proper factor in item 2, table 1, will give you the air requirement of your drier. Table 1 also gives you the recommended static pressure for each type of hay. Take these two figures— air requirement and static pressure— to your dealer when you shop for your fan. Types of Fans Three types of fans are suitable for haydrying: the centrifugal, both forward- curved and backward-curved blade fans ; the high-speed propeller; and the vane- axial. Their characteristics are sum- marized in table 5. The backward-curved blade cen- trifugal fan is relatively expensive, and for this reason is seldom used for hay- Table 4- -DESIGN DATA FOR HAYDRIERS — BALED HAY Size of mow floor* (ft.) Capacity for 7-layer depth (tons) Air required (cfm) Horsepower required at 1.25" water Main duct Slatted floor Size of cross section (sq. ft.) Length (ft.) Height above solid floor (inches) 20x24 20 12,000 5 12 19 8 20x32 27 16,000 7.5 16 27 8 20x36 30 18,000 7.5 18 31 8 20x48 41 24,000 10.0 24 43 8 24x32 33 19,200 10.0 19 27 10 24x48 49 28,800 10.0 28 43 8 28x36 43 25,200 10.0 25 31 10 28x48 57 33,600 15.0 33 43 10 32x48 65 38,400 15.0 38 43 12 * All side ma n ducts, prefer ably outside mow. [12] Table 5 — FANS FOR HAYDRIERS Fan Price Noise Efficiency Installation and operation Backward-curved High Little High For greatest capacity, must be blade centrifugal equipped for changes in speed Forward-curved Medium Little Fair When static pressure is low, blade centrifugal will overload motor unless air flow is dampered or fan speed changed High-speed propeller Low Much Good Simple Vaneaxial High Medium High Simple drying. It is made in a satisfactory range of sizes, and is suitable for any volume or pressure desired. For greatest capacity, it must be equipped so that its speed can be changed. This fan protects the motor from overload at low static pressure, an advantage often overemphasized, since it may be impractical to run at the same speed under all conditions. This fan has relatively high efficiency, and is quiet in operation. The forward-curved blade cen- trifugal fan is less expensive, but not so efficient as the backward-curved, nor is its range of efficiency so wide. If selected to require 5 horsepower at one inch static pressure, it will overload the motor at % inch. This effect must be corrected, either by dampering the air flow to con- trol static pressure, or by changing the speed of the fan. This fan is lighter weight, but somewhat noisier than the backward-curved blade fan. The high-speed propeller fan is widely used for haydriers, because it is comparatively inexpensive, light in weight, usually non-overloading, and easy to install. This type is quite efficient for static pressures up to 2 inches of water, and is primarily adapted to constant- speed operation. Its power requirements vary little with changes in static pressure or volume. Propeller fans are noisy be- cause of their high tip speed. The vaneaxial fan is probably the best all-around fan for haydrying, but is high in first cost. It consists of a disk- type fan mounted within a cylinder. Sta- tionary vanes guide the air through the inlet, and also act as supports for the motor. This fan can be built to give any desired volume of air, or any pressure. It has the same power requirements as the propeller fan, but greater efficiency. It maintains good volume throughout a wide range of pressure at constant speed. It is noisier than the centrifugal, but quieter than the propeller fan. POWER UNIT Wherever electricity is available, a 3- phase electric motor usually powers the fan of a haydrier. It is easy to protect against overload, easy to start, adaptable to time-clock controls for off-and-on op- eration, and gives good, trouble-free service with no fueling problem. An elec- tric motor should be connected through a magnetic starting switch for motor pro- tection. [ 13 ] The fan may be powered with a gaso- line engine, which also has certain ad- vantages : its speed may be easily changed to vary the fan output, and heat from the engine may be used to raise the tempera- ture of the air stream and thus increase its moisture-carrying capacity. COSTS Based on 1948 prices, the total cost of a barn haydrier should range from 60 to 80 cents per square foot of mow area. The fan, motor, and switch assembly will usually amount to more than one half the total cost of the installation, with lumber and labor making up the balance. Oper- ating an electrically driven fan costs about one dollar per ton of dry hay. FIELD CURING The hay should be cut after all surface moisture from rain or dew has dried off the plants. Let it lie in the swath until the top of the swath is nearly dry enough to shatter; then windrow, preferably with a side delivery rake. Leave the hay in the windrow until the average moisture con- tent is reduced to a satisfactory point for barn drying. If hay is to be dried in the mow, you must be certain that its mois- ture content is low enough. When it enters the mow, long hay should not have more than 50 per cent moisture. Chopped and baled hay must have 35 per cent or less. A method for testing moisture con- tent of hay is given at the back of this circular. The time required for field curing will vary with the weather, crop yield, ma- turity, and method of handling. In very good drying weather, hay cut in the morning may be put on the drier that afternoon. Hay which is to be chopped or baled will have to be left in the field one- half to one day longer than if handled as long hay. HANDLING THE HAY The usual methods of handling, such as hayloader and wagon, transport buck- rake, field chopper and wagon, and field baler, will all operate satisfactorily with damp hay. Capacity of some machines may be reduced because of the heavier hay, and heavy-duty equipment is recom- mended. In handling long hay with a track and carrier, smaller loads of the heavier hay should be hoisted to prevent breakage. Blower pipes for handling chopped moist hay must be 6-inch or larger and in good condition to prevent clogging. Baling chamber tension should be reduced when baling moist hay for drying. OPERATING A HAYDRIER Loading of the drier should be started when the hay has been field-dried to the recommended moisture content. Chopped or baled hay should be loaded in the morning to prevent shattering of the dry surface leaves. Spread the hay in hori- zontal layers over the entire system, keep- ing the depth nearly uniform at all times. Place baled hay on the drier in horizontal layers, staggering the rows so that the cracks between bales in one layer will not be directly over the cracks in the next lower layer. As soon as enough hay has been placed in the barn to cover the ducts to a depth of 2 feet, the blower should be started. Where a slatted central main duct is used, the first layer of hay should be rounded over this duct uniformly be- fore blowing. Continuous operation of the drier is necessary for chopped or baled hay to prevent spoilage. Long hay, however, may be dried by either continuous or inter- mittent blowing. On many farms, con- tinuous operation is preferred for all types of hay, because mold and bacterial action are kept down. Those who use this plan say that it takes advantage of all conditions in which drying can be ob- tained, with a minimum of attention. Some people argue that continuous blowing for long hay uses more power and may actually add moisture to the hay during damp or foggy weather, such as [14] Fig. 5. Materials needed for calcium carbide method of checking moisture content in hay. may occur in the early morning hours. They prefer to run the blower from 7 or 8 a.m. to sundown on good days, and turn it off for any foggy or rainy weather dur- ing the day. However, while the fan is not operating the hay may heat. Tempera- tures of 120° to 130° F. have been re- corded in hay that has not been blown during the night. In such cases, when blowing is resumed, the moisture in the warm wet air leaving the hay may con- dense when it comes into contact with cool outside air, and spoil much of the surface hay. To prevent such spoilage during inter- mittent operation, turn the blower on for a cooling period every 4 or 5 hours. A timer may be set to turn the blower on for an hour at one or two predetermined periods during the night. Automatic con- trol by thermostat or humidistat is not recommended. There is no hard and fast method of determining when the hay is dry. The most practical is to turn off the blower when the drying seems to be complete and allow the hay a chance to heat one or two days. Then the blower is started, and the top of the stack is immediately in- spected for warm air or steam. If any is found, blowing is continued for two days more, after which the procedure is re- peated. No appreciable spoilage should occur from this method, because the hay should be dry or nearly so before the blower is turned off. A METHOD FOR CHECKING MOISTURE CONTENT IN HAY To determine the moisture content of hay in the field, the calcium carbide method is quick and reasonably accurate. To avoid error due to sampling, test 2 or 3 samples which will give a fair average of the hay in the field. For this test you will need: One set of scales or balances, capacity 300 grams, accurate to 0.1 gram Calcium carbide, finely ground if possi- ble (14 N.D. or finer) One teaspoon One pair heavy scissors, or other device for cutting hay [15] Three cans for test samples The 16-ounce soil sample cans have a suitable size, shape, and capacity. They are seamless, so that samples may be completely removed without washing. They measure about 3% inches in diameter and 2Vfe inches deep. The lid fits snugly. Any similar can will do. Prepare the lids of the cans as follows: 1. Drill six holes, % inch in diameter, in each lid (see fig. 5). 2. Glue a filter paper on the inside of the lid with a good grade of glue or liquid cement. The filter paper will keep carbide dust in the can but allow vapor to escape. To test hay sample: 1 . Set scales level and balance. 2. Obtain a large handful of hay of representative moisture content for each test. 3. Remove lid and place can and lid on scale as shown in fig. 5. 4. Cut hay in %- to %-inch lengths with scissors and weigh 30 grams of hay into the can. 5. Weigh 81 grams of calcium carbide into the lid, using a teaspoon to handle the carbide. 6. Note carefully the total weight of the can, hay, lid, and carbide and record the weight. 7. Sprinkle the carbide over the hay sample, place the lid tightly on the can, and shake the contents until heating is noted. Allow to stand until cool, then shake can again. Re- Acknowledgment is made to Dr. R. Q. Parks, Assistant Head of Division of Soil Management and Irrigation, U. S. Department of Agriculture, Beltsville, Md. (formerly Assistant in Agronomy at the Ohio Agricultural Experiment Station, Columbus, Ohio) for use of material from his paper "A Rapid and Simple Method for Deter- mining Moisture in Forage and Grains," pub- lished in the Journal of the American Society of Agronomy, and to the Ohio State University Research Foundation, which holds all patent rights on the process (U. S. patents 2358877 and 2362396). (Letter 5/13/48.) peat this process until the can no longer becomes hot when shaken. Occasional shaking even when can has not cooled will speed this proc- ess. For very wet samples, after first shaking, lid should be removed from can to allow excess vapor to escape. (Caution: The can may be- come very hot, and you may need gloves or some other protection for your hands.) 8. Weigh the can and contents, again recording the weight. 9. Subtract this weight (8) from the initial weight (6) to obtain the loss in weight. 1 0. Determine the original moisture content of the hay from table 6. 1 1 . Dump contents of can into a safe receptacle where livestock cannot reach it. Brush or wipe cans out, but do not wash unless carbide be- comes pasted to inside of can. Table 6 — MOISTURE CONTENT OF 30-GRAM SAMPLE If the loss in The per cent moisture in weight is: the hay sample was: 2 grams 14 3 grams 18 4 grams 22 5 grams 27 6 grams 31 7 grams 35 8 grams 40 9 grams 44 10 grams 49 1 1 grams 53 12 grams 58 13 grams 62 14 grams 66 15 grams 70 16 grams 74 17 grams 79 18 grams 33 I5m-2,'49(B1122) [16]