Round bale silage is a relatively new method of preserving forage. It is a combination of hay and silage making and has certain advantages and disadvantages over other forage preservation systems. Round bale silage is simply forage of a relatively high moisture content that is baled with a round baler and then stored in a sealed container, usually a plastic bag. Both grasses and legumes can be preserved as round bale silage if proper techniques are followed. It is much easier to make good hay crop silage in silos than in large round bales.
Baled silage is more likely to spoil as compared to silage in traditional silos because (1) fermentation is less complete and (2) opportunity is great for damage to the plastic covering, resulting in the harmful introduction of oxygen. Some people think that baled silage is best adapted for use late in the growing season, with bales fed as early as possible that fall or winter. Fall also is a difficult time to dry hay in the field.
Cut and mechanically condition the forage as normal for haymaking. Forage for round bale silage should be baled at 40-60% moisture. Baling at the proper moisture content is the single most important variable in round bale silage making. Baling silage with too much moisture reduces the amount of dry matter stored per bag which greatly increases storage cost. Baling silage with inadequate moisture reduces fermentation which greatly increases storage losses. Forage should not be baled for round bale silage if it contains less than 40% moisture.
The type of baler does not appear to affect results, but comparative data are lacking. Chain-type balers might be slightly better than belt-type since belts might start slipping due to the wetness of the forage. Regardless of the type of baler used, it is important to remember that bales containing 40-60% moisture will weigh about two times more than will normal hay bales of the same size. Therefore, bales for round bale silage should be smaller than for dry hay so that the final weight of the bale is about 1500-2000 lbs. Bales much heavier than this are very difficult to move and handle. The size of bales that weigh 1500 - 2000 lbs will depend upon moisture content, type of baler and type of forage, but bales 4 to 5 feet in diameter containing 50% dry matter forage should weigh about one ton. Bales should be put in bags or wrapped as soon as possible after baling for maximum preservation. Quality of the silage decreases rapidly as the length of time between baling and bagging or wrapping increases beyond 1-2 hours. The size of bag should be slightly bigger than the bale. Bales should be elevated using a bale probe mounted on a tractor and then the bag is pulled carefully over the bale. After placing the bale in the bag the end should be tightly closed and double tied with good quality twine. Immediately after bagging or wrapping, inspect the plastic for holes, and patch if necessary. All holes, regardless of their size must be patched to minimize storage losses. Bales should be stored in a well drained site that is free of vegetation and trash. A clean site reduces the potential for rodent damage to the bags. Do not move the bales until feeding to avoid damaging the plastic. Plastic should be inspected at least weekly and holes patched as soon as they are found.
In theory, round bale silage should not spoil as long as the plastic remains intact. Many people, however, suggest that round bale silage should be fed within a few months of bagging to avoid excess spoilage. The risk of damaging the plastic is proportional to the length of time round bale silage is stored. If bags are inspected and repaired frequently, then storage life should be relatively long. Storage life is also a function of the quality of the bag. High quality bags are formulated to resist damage caused by exposure to sunlight, and retain the ability to prevent oxygen infiltration for long periods of time. Lower quality bags allow more oxygen to infiltrate; therefore, round bale silage stored in these bags probably should be fed within a few months.
Reusing bags increases the risk of spoilage, but reduces storage costs. Reusing bags, even high quality bags, can reduce the safe storage time. Prior to reusing, bags should be inspected and all holes patched. A good way to inspect bags is inflate the bags using a fan or the wind in a brightly lit area (e.g. a sunny, windy day). Then from inside the bag look for light shinning through small holes. Bags that contain many holes probably should not be reused. Between use, bags should be stored in a dry place, protected from sun and excessive heat.
Round bale silage has three distinct advantages over haymaking or conventional silage making. Harvesting forage as round bale silage has the potential of minimizing harvest losses. Round bale silage requires a relatively low initial investment of capital. Round bale silage also is an extremely flexible system.
Many different losses of nutrients can occur between cutting a forage crop and harvesting the crop. Certain losses, such as respiration are unavoidable and largely independent of the type of harvesting system used. Other losses such as mechanical shattering and rain damage can be avoided or greatly reduced depending upon how the forage is harvested. Haymaking generally causes the greatest field losses because forage is dry when it is mechanically handled. Estimates of dry matter losses when forage is baled with large round balers range from 5 to 20% of the crop. Losses caused by small square balers generally range from 5-10%. The amount of loss is directly proportional to the dry matter content of the forage when handled. Forage containing more than 40% moisture resist mechanical shattering (average loss is about 3%), but as forages become drier than 40% moisture, shatter losses increase rapidly. Another potential loss during haymaking is rain damage. In Ohio, hay generally needs to cure about three days before it is dry enough to bale. The longer a forage crop lays in the field the greater the risk of rain. Silage (round bale or conventional) usually has to wilt about one day prior to harvest; therefore, the risk of rain is much less than for haymaking. Round bale silage is similar to conventional silage making with less risk for rain damage and decreased nutrient losses due to mechanical shattering as compared to haymaking.
Conventional silage-making reduces field losses as compared to haymaking, but has large capital costs. Conventional silage making requires a forage chopper, silage wagons, silage blower, a silo, and unloader plus forage cutting equipment. Haymaking requires the same forage cutting equipment plus a baler, some hay wagons, and a storage barn. Capital costs for conventional silage making range from 2 to 3 times more than haymaking. Round bale silage making requires less capital cost than haymaking because a hay barn is not required. If bales are wrapped instead of bagged a bale wrapper is needed that will increase capital outlay. Round bale silage, however, has many additional short term costs which will be discussed later.
Round bale silage is a very flexible system because of its low capital costs. Depending upon weather and labor factors, a producer can choose to either make large round bale hay or round bale silage. If a producer owns conventional silage making equipment, the high capital investment in equipment almost mandates that forage be stored as silage. With round bale silage, a major portion of the cost is in bags or wrapping. Therefore, if a producer chooses not to make round bale silage, he simply does not purchase any bags or plastic wrapping. His haymaking equipment, however, is still productive.
Round bale silage has some serious problems that must be considered prior to using this system. Major disadvantages with round bale silage include potentially large storage losses, high short term costs, high short term labor requirements, and increased pollution.
Hay crops ensiled with 40-60% moisture (the recommended moisture range for round bale silage) do not ferment extensively. The pH of wilted silage, including round bale silage, is rarely less than 4.5. A pH of 5 is common for round bale silage. Silages with pH values of 4.5 to 5 are considered unstable and must be maintained in an oxygen-free (anaerobic) environment to prevent spoiling by molds, yeast, and heat. Low moisture silage is usually contained in a sealed silo which prevents infiltration of oxygen. With round bale silage, a plastic bag or wrapping is used to maintain an anaerobic environment for the silage. Plastic is much more susceptible to damage than is a concrete or steel silo, so the likelihood of maintaining an oxygen-free environment is much less for round bale silage than conventional silos. Research has found that between 15 and 25% of round bale silage can spoil during storage. This is considerably higher than the 5% storage losses associated with traditional silos.
The second disadvantage with round bale silage is cost. Round bale silage must be kept in an oxygen-free environment; therefore, high quality plastic must be used. Quality bags range from $6-10 each and are recommended. Each bag can hold 700-1000 lbs. of forage dry matter; thus, if bags are used only once, the storage cost would be about $18/ton of dry matter. The average bag is used less than twice so an average storage cost is might be about $12/ton. The plastic for wrapping costs between $1-2/bale but the cost of buying or renting the wrapper must be considered. In comparison, a large concrete silo (400 tons of dry matter capacity) with a life of 20 years has a storage cost of about $6/ton (this figure does not include interest, maintenance and other factors, but is based solely on capital cost).
A third disadvantage of round bale silage over round bale hay is increased labor requirement. At least one extra person is needed to put the bales in the bags. Bagging must occur shortly after baling so additional labor must be available at that time. Bale wrappers eliminate the need for the extra person but again, the cost of the machine must be factored into the decision. Making round bale silage, however, requires less skilled labor than conventional silage making.
The fourth major disadvantage of round bale silage is the potential for pollution. Wrapping or bagging individual bales requires considerable amounts of plastic. Certain types of bags will not burn and many communities have laws restricting outside burning. Laws regarding solid waste and burning will probably become more restrictive as society becomes more concerned about environmental issues. This may influence the decision about using round bale silage.
Round bale silage is a flexible, low capital cost method of preserving forage; however, variable costs and spoilage losses can be high. This system of storing forage might be most practical for smaller farms that can not justify the high investment needed for conventional silage storage. Also, it may be appropriate for occasional use by forage producers, preferably late in the growing season. If proper techniques are followed, acceptable quality silage can be produced. Higher storage costs and proper disposal of used plastic must be considered when making the decision to use round bale silage.
Assistant Professor, Dept. of Dairy Science
District Specialist Emeritus, Agronomy
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-6181