What moisture should dry hay be?

Right Hay Moisture Content

Of the different kinds of hay bales, small square bales tend to have the highest tolerance for moisture. According to research cited by the Alberta Agriculture and Rural Development site, a small square bale’s moisture content can be between 18 and 20 percent and be safe.

Part of the reason for this is because small square bales tend to be much less densely packed than larger hay bales. For example, at 5.5 cubic foot of volume with a weight of 60 lbs. or less, there is less than 11 pounds of matter per cubic foot of space in a small square hay bale (60 ÷ 5.5 = 10.9090). Compare this to a large rectangular bale, which packs 1,800 lbs. of material into 112 cubic feet of space, which means there is roughly 16 pounds of matter per cubic foot of space, nearly half again as much as the small square bale.

The biggest challenge when dealing with small square bales is that processing so many smaller bales is inefficient when compared to simply making one huge bale. To recall the previous example, for a small square baler to match the output of the large square baler, it has to make thirty bales, which means stopping for the baler to finish thirty times to other unit’s single stop.

Large Square Hay Bales

Being more densely packed than small square bales, large square bales have a much lower tolerance for moisture. For a large square bale, the allowable range for moisture content is often between 12 and 16 percent, with 12 being more desirable for long-term storage and warmer climates.

With their very low moisture tolerance, square bales can be much more finicky to get dry enough for storage or transport, but they do have their advantages, such as:

As we mentioned before, using a large square baler is often faster and more convenient than using a small one.

Large square bales are easier to load onto flatbeds for transport than other bale types. With a higher density than small square bales, large square bales are more efficient on space per pound, and are much easier to stack and transport than round bales.

For a hay grower who is looking to deliver large quantities of hay over long distances, large square bales are often the best choice.

Round Hay Bales

Many newer baling machines render hay into barrel-shaped round bales instead of the traditional compacted square shapes. While the density at which these bales will still differ depending on overall size, the moisture tolerance of round-shaped bales holds fairly steady at 15 percent.

The Consequences of High Moisture Content in Hay Bales

When the %MC in a hay bale is too high, the hay will undergo a process called thermal expansion. To put it simply, hay bales will become hot as the moisture inside the bale attempts to bleed out.

During this process, bacteria and mold in the moisture trapped in the bale may multiply, using the nutrients in the bale to fuel their growth. In the best case scenario, this may merely strip the bale of useful nutrients and make it inedible to livestock. In a worst-case scenario, the hay will continue to become hotter from the growth of these microscopic organisms until the heat and pressure causes the bale to spontaneously combust.

The higher the moisture content of the hay, the larger the risk will be.

When Hay Doesn’t Have Enough Moisture

Of course, if hay’s moisture content is too low, then different problems will occur. While hay with exceptionally low moisture might not be at risk of growing mold and bacteria, that’s because much of that hay’s nutritional value is already gone.

Measuring Moisture before Baling

Because of the incredibly challenging demands of growing top-quality hay, many farmers are up before the crack of dawn to start collection so that they can get the most hay that they can before it becomes too dry.

Using a hay moisture meter with extended-length probes, these professionals check moisture levels in the windrow before activating their balers so that they know that their hay is ready to be baled. During the baling process, many hay experts attach special baler-mounted moisture meters to their baling machines to continuously check the %MC of their hay throughout the day so that they know right away when their hay is getting too dry to continue baling.

Hay Baling with Moisture

It’s springtime in Central Texas and while you might still be trying to cut and/or bale those first hay cuttings of the year, you should consider the moisture content. The moisture content during baling and storage can considerably effect to the nutritive value of the hay. Hay baled with high moisture content levels can have negative impacts such as hay spoilage, barn fires, and decreased nutrition.

A natural event, commonly referred to as “heating,” occurs when growing forages are cut and continue to give off heat due to respiration. Plant and mold respiration generates lots of heat; providing proper growing conditions for bacteria. If wet hay is baled while it is too wet, microbe populations will flourish and intensify the heating process. This results in hay that is lower in nutritive value and dry matter availability.

Allowing cut hay to dry (or cure) will slow down the respiration process. Respiration slows down as moisture content decreases but will not completely stop until plant moisture reaches 20 percent or less. Moisture levels above 20 percent allow the respiration process to continue and mold to develop, which then produces heat.

If the internal temperature of a bale of hay exceeds 130 degrees F, a chemical reaction occurs within the bales that release flammable gases that can ignite. So when harvesting, the most effective way to reduce the potential of spontaneous combustion in hay bales is to make sure the cut has dried sufficiently prior to baling. Consider the weather conditions because this greatly influences the rate at which hay dries. Cut hay that has been rained on or is slightly wet should be mechanically teddered, or fluffed, to speed up the drying process.

Moisture levels for safe storage vary with the size and density of the bale and the type of hay. Hay in small square bales should be baled between 15 and 22 percent moisture to minimize leaf shattering, molding and heating. Larger round bales or the large square bales are larger in size and weight. So obviously these will retain core moisture, thus internal heat longer than the small square bales. These larger bales should not be baled with a moisture content level in excess of 18 percent. If you are deciding to bale your large bales while the moisture content is in excess of 22 percent, you should not stack the bales for at least 30 days and consider this when feeding.

Large bales stored outside will suffer variable losses, depending upon the moisture of the hay at baling, the extent of exposure to precipitation, soil drainage characteristics where the bales are stored, the amount of space between the bales and the type of hay. Properly-baled hay should be stored in well-drained areas, with a minimum of three feet between bale rows, away from trees or shade, and all facing the same direction as prevailing winds (ends facing north and south). Check newly stacked hay for possible heating, especially for hay that has been rained on. It is not unusual for hay to heat to 100 degrees F within the first couple of weeks after it is baled.

For more information, please contact Chelsea Dorward at the Texas A&M AgriLife Extension Service – Bosque County Office at 254-435-2331

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Tips about moisture measurement in hay

How to use a hay moisture meter in the windrow, in bales, in the bale chamber or during storage

Hay that contains too much moisture is fertile ground for fungus. As those micro-organisms accumulate during storage, they can raise the temperature of the hay. When the temperature rises, protein begins to degrade and the hay may be become indigestible. When temperatures reach 80 ° Celsius ( 180° F), there is a risk of spontaneous combustion.

Appropriate Moisture Levels for Hay

Moisture measurement in hay should be measured in terms of ranges and not specific points. Generally, round bales requires a slightly lower moisture level than square bales. The challenge in either form is the variability of both the electrical properties of hay, as well as its non-uniformity, making it difficult to accurately represent anything but an “average” moisture level for one or more hay varieties.

Traditionally, the recommended moisture content for baling hay without a preservative is between 18-20%.

If using a preservative, follow the instructions provided by each particular preservative manufacturer. Smart use of a moisture tester in combination with preservatives and drying agents allows hay to be baled at higher than traditionally recommended moisture levels.

In either case, do not attempt to bale hay before it is at an acceptable moisture level, even when using a preservative.

Using a Moisture Tester for Hay in the Windrow

As with baled hay, multiple tests are required in order to obtain an accurate reading. After taking the first reading, the operator should mix the hay, re-pack it and test again several times, then average the readings. A secondary test involves choosing several large, slow-drying stems from the same area of the windrow and lying them one at a time across two adjacent points on a multi-prong electrode. These readings will typically be a few points higher than the actual moisture level.

Repeat these steps in different parts of the field and pay special attention to the areas where the hay is heaviest. Your decision to start baling should consider the amount of variation found among windrow readings as well as the average stem moisture.

Using a Moisture Tester for Hay in Bales

A firm, uniform contact will yield more accurate results, so the prod should be driven across bale slices.

On-the-Go Moisture Testing in the Bale Chamber

The hay producer can install a micro-controller based moisture meter in the tractor cab and connect it to a sensor in the bale chamber to produce on the go moisture monitoring while baling, without leaving the cab. The microcomputer collects and processes eight readings that are accumulated every four seconds. The meter then displays the average and highest reading. This cycle is repeated every four seconds.

A microprocessor-based continuous monitor is an easy and reliable way to give the operator clear guidelines and a little less to worry about. Even though this method provides reliable information, we recommend that you take readings in several bales, especially at the beginning of baling, and as you see conditions change. The FX-2000 can be used for on-the-go moisture monitoring or as a portable meter.

Additional Safety Precautions — Temperature

Whether hay in the windrow or bale is tested, the number of tests made should be increased whenever the initial readings show considerable variations.
Ensuring that hay is not baled at moisture levels above 20% is a significant step toward safe storage. However, moisture may be inconsistent and readings may be impacted by humidity levels in the air and other factors. Checking the temperature of stored hay, whether stored indoor or out and—especially during the risky period that lasts from two to six weeks after storage—is an important additional safeguard.

View online video for further information: F-6/6-30 , F-2000 , FX-2000

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