Hay-in-a-Day: A Wide Swath More Important Than Conditioning
By Karen Lee
The concept of producing haylage in just one day, commonly called “hay-in-a-day,” is catching on among producers who want to quickly harvest their crop and ensure that it retains the highest nutrient content.
Previous research has shown that using a wider swath in the field dries hay more quickly and evenly. Naturally, this is due to the fact that more of the swath is exposed to the sun. The latest research has provided an even greater understanding of a plant’s drying process and leads to an important question: to condition or not condition?
Dan Undersander, University of Wisconsin forage specialist, states, “If we understand and use the biology and physics of forage drying properly, not only does the hay dry faster and have less chance of being rained on, but the total digestible nutrients (TDN) of the harvested forages are higher. As mowing and conditioning equipment has evolved, some of the basic drying principles of forage have slipped by the wayside and we need to review them.”
When forage is cut it usually has a moisture content of 75 to 80 percent, but may vary some depending on the growing conditions. The freshly cut forage needs to be dried down to 60 to 65 percent moisture for haylage or 14 to 18 percent for dry hay and an even lower number for larger bales.
“In the first phase of drying, the initial moisture loss occurs from the leaves through the stomates, which are the openings in the leaf surface that allow moisture loss to the air to cool the plant and allow carbon dioxide uptake while the plant is growing,” Undersander explains. In order for this first 10 to 15 percent moisture loss to occur rapidly, the stomates must remain open. Stomates open in daylight and close in the dark. By laying forage in a wide swath the amount of forage exposed to the sunlight is maximized thus keeping the maximum amount of stomates open.
“This is crucial at this stage because plant respiration continues after the plant is cut,” says Undersander. The plant’s natural respiration rate is highest when the plant is first cut and gradually declines until plant moisture has fallen below 60 percent. Therefore, rapid initial drying to remove the first 15 percent of moisture from the plant reduces the loss of starches and sugars (due to respiration) and preserves more total digestible nutrients in the harvested forage.
According to Undersander, this initial moisture loss is not affected by conditioning.
Once the stomates close at around 60 percent moisture, continued drying occurs from both the leaf surface and the plant stem. This second phase of drying is where conditioning can help increase the drying rate, especially at the lower end of the phase.
The third phase of drying is the loss of more tightly-held water, mostly in the stems. Conditioning, which breaks the stems, is critical to enhance drying during this phase, thereby allowing more opportunity for water loss.
“Understanding these principles will allow us to develop management practices in the field that maximize drying rate and TDN of the harvested forage,” says Undersander.
He continues, “The first concept is that laying out a wide swath immediately after cutting is the single most important factor maximizing initial drying rate and preservation of starches and sugars."
In a trial at UW-Madison's Arlington Research Station, alfalfa put in a wide swath reached 65 percent dry matter in 10 hours and was ready to harvest that same day. The same forage in the same fields put in narrow windrows was not ready for harvest until later the next day.
Wide swaths have also been shown to improve the quality of alfalfa haylage compared to narrow windrows. In the study at Arlington, alfalfa was mowed and conditioned and forage was sampled two months after ensiling in tubes. The wide swath alfalfa had 2.3 percent less neutral detergent fiber (NDF) and 1.8 percent more nonfiber carbohydrate (NFC). The NFC difference in both quality and yield was due to respiration where starch is changed to carbon dioxide and lost to the air, says Undersander.
The haylage from wide swaths had almost one percent more TDN, as well as more lactic and acetic acid. According to Undersander, the higher acid content would indicate less rapid spoilage on feed out and the overall improved forage quality would be expected to result in 300 pounds more milk per acre.
Undersander recommends putting cut forage into a wide swath at cutting that covers approximately 70 percent of the cut area. For haylage, when drying conditions are good, rake multiple swaths into a windrow just before chopping, usually five to seven hours later. Lastly, he says, “for haylage, a wide swath may be more important than conditioning.”
“It’s important when discussing the concept of ‘hay-in-a-day’ to differentiate between haylage and dry hay,” says Ryan Pearcy, product manager for Kuhn North America. “Dry hay also benefits from being placed into wide swaths, otherwise the top of a narrow windrow will be overexposed while waiting for the hay on the bottom to dry. Yet, for dry hay, you still need to condition the crop in order to continue the drying process to the point where you can bale.”
If you look at the hay in narrow swaths, the hay on the bottom is dormant and continues to respire, using up its own nutrients. However, hay in a wide swath is still producing energy until it dies at the point of chopping or for baleage. This provides more energy to a balanced ration and requires the farm to purchase less replacement energy feedstuffs.
By not conditioning the crop, Horton says, it stands to reason that the leaves of the plant are able to pull moisture out of the stems and the hay will dry quicker to 65 percent moisture. If the plant is conditioned and the stems are cracked and broken this natural process is stopped.
Another advantage of skipping conditioning has to do with machinery. “By using a mower without conditioning, a producer will lower the power requirement by approximately 50 percent,” says Horton. “When using a 10-foot mower, this equates to a fuel savings of three and a half gallons of diesel an hour.” In addition, as opposed to a mower conditioner, a mower costs less up front and typically has less maintenance since it is a less complicated machine.
“Some producers may be reluctant to try ‘hay-in-a-day’,” says Pearcy. “Some say they do not want to drive on the hay. I would encourage them to give the technique a try. If they harvest some of their hay the traditional way and the ‘hay-in-a-day’ way, they can then take samples of the hay to determine which method yields higher TDN. I think producers will find that it’s worth it to do ‘hay-in-a-day’ because of the increased value of feed. In addition, tedding the crop while it is still in a high moisture state will lead to even quicker drydown in most conditions, while retaining leaves."
As the current research shows, conditioning the crop when producing haylage does not appear to be as important or as necessary as the ability to create a wide swath behind the mower by adjusting the swath boards, tedding, or other methods. Kuhn North America’s wide range of mowers and tedders ensure producers can find the machine that will best fit the needs of their “hay-in-a-day” operations.