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Kuhn North America, Inc: - Hay in a Day
Hay-in-a-Day: A Wide Swath More Important Than Conditioning
By Karen Topel
The concept of producing haylage in just one day, of the called 塗ay-in-a-day, is well-liked by anyone who痴 waited three days for their crop to dry to the point where they can chop it and then watched it get rained on only to start over again while knowing how much lower the quality will be once it is finally pulled off the field.
It痴 been found that by using a wider swath in the field the hay will dry more quickly and evenly. Naturally, it is due to the fact that more of the swath is exposed to the sun, yet the latest research has provided a greater understanding of a plant痴 drying process and brought about the question to condition or not condition?
Dan Undersander, University of Wisconsin forage specialist, states, 的f 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.
Depending on the growing conditions, when forage is cut it has a moisture content of 75 to 80 percent. This 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.
的n 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 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 into a wide swath it maximizes the amount of forage exposed to the sunlight thus keeping the maximum amount of stomates open.
適eeping the stomates open is crucial at this stage because plant respiration continues after the plant is cut, Undersander says. The plant痴 natural respiration rate is highest when the plant is first cut and gradually declines until plant moisture has fallen below 60 percent. This rapid initial drying to remove the first 15 percent moisture from the plant will reduce loss of starches and sugars and preserve 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% moisture continued drying occurs from 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 to break the stems is critical to enhance drying during this phase. It allows more opportunity for water loss from the stem.
填nderstanding these principles will allow us to develop management practices in the field that maximize drying rate and TDN of the harvested forage, Undersander says.
He continues, 典he first concept is that a wide swath immediately after cutting is the single most important factor maximizing initial drying rate and preserving of starches and sugars.
In a trial at UW 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.
The importance of wide swaths was also backed up by drying measurements that Undersander took at the 2002 Wisconsin Farm Technology Days where different mower-conditioners mowed and conditioned strips of alfalfa and put the cut forage in windrow widths of the operator痴 choice. The moisture content was measured 5.5 hours after mowing and across all mower types and designs, the most significant factor in drying rate was the width of the windrow.
Wide swaths have also proven 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 NDF and 1.8 percent more NFC. The NFC difference in both quality and yield was to respiration where starch is changed to carbon dioxide and lost to the air, Undersander says.
The haylage from wide swaths had almost 1 percent more TDN and 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.
He 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. For dry hay when drying conditions are good, rake multiple swaths into a windrow the next morning when forage is at 40 to 60 percent moisture to avoid leaf loss.
Lastly, he says, 殿 wide swath may be more important than conditioning for haylage.
For another perspective we talked to Chris Horton, Product Manager for Kuhn Farm Machinery. He notes that for the last 20 to 30 years hay has been cut into four or five foot windrows and research is now showing this is not the best practice . The hay on top dries quickly taking in sunlight, but all the crop underneath essentially goes into respiration as photosyntheses stops. The plant starts using up it痴 own internal energy supplies trying to stay alive. A wide swath exposes a far greater amount of hay to the sun allowing photosyntheses and the production of energy to continue until the point where lack of moisture shuts down the plant. You are increasing the amount of time that photosynthesis takes place and decreasing the time that respiration takes place
Horton cites Tom Kilcer痴 research as an Extension agent for Cornell, which echoes Undersander痴 in saying wide swaths allow the plant to dry down faster to the 60-65 percent moisture at which point the drying process slows down . 鉄lowing down the drying rate at this point is also good for ensiled hay because you don稚 want the moisture level to go down too far, Horton says.
If you look at the hay in narrow swaths the hay on the bottom is not dead, it痴 just dormant and continues to respire using up it痴 own nutrients. Whereas a wide swath is still alive producing energy until it dies at the point of chopping. Thus providing more energy to a balanced ration and requiring 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.
Kilcer states, 典he greatest change that occurs in drying is the respiration loss of carbohydrates (Nel). This loss of readily digestible material makes even smaller respiratory losses important, representing 14 percent of the total dry matter losses for wilted silage. In wet and humid conditions the respiratory losses may be as high as 16 to 30 percent of initial dry matter.
*dding insult to injury, Kilcer says, 鍍he better the forage quality the greater the respiration losses.
He adds that crushing the plant didn稚 help, but actually increased the respiration rate of alfalfa 15 percent higher than uncrushed or conditioned stems.
Thus current research shows that 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 or by using tedding or other methods.
的t痴 important when discussing the concept of 塗ay-in-a-day to differentiate between haylage and dry hay, Horton notes. Dry hay also benefits from being placed into wide swaths, otherwise the top 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.
