• Nov 01, 2022

Importance of Rapid Drying Immediately After Cutting

Dr. Dan Undersander
Forage Professor Emeritus, University of Wisconsin
chopper cutting alfalfa at sunset
From the time forage is cut until it’s fed, the goal is to minimize forage yield quality loss. While some loss is inevitable after cutting, the amount of decline is largely determined by management practices.

An often-overlooked source of these losses is respiration after mowing. Respiration is the breaking down of starch and sugars to produce energy and carbon dioxide. The process occurs in growing plants and continues after mowing, even in baleage and silage.

Respiration and Dry Matter

Data suggests that 2-8% of dry matter may be lost due to respiration. Losses are greatest in the West where forage is often cut with a large cutter bar and put into a windrow that fits between the swather tires. This hay typically takes 5-7 days to dry for baling, while some farmers of the same region put forage into a wide swath and bale it in two days. Not only does the faster drying time result in less dry matter loss but getting the hay off the field faster results in less wheel traffic damage to regrowth and higher yield potential for the next cutting.

Respiration and Forage Quality

Respiration also impacts forage quality since the starch and sugar lost are 100% digestible, increasing the content of remaining components. For example, a 4% starch/sugar loss would increase NDF slightly over 3%. That equates to a drop in RFQ of almost 20 points. If the alfalfa had been cut at just below 40% NDF, however, and lost 4% sugar/starch, the harvested quality would be above 40% NDF.

Minimizing Respiration Losses

Hay needs to reach 60% moisture or less as quickly as possible or at least by the end of the day it is cut to minimize respiration impacts. An effective way to speed up drying time is by spreading cut hay into a wide swath and driving over it rather than making a windrow that fits between the wheels. This allows more sunlight to be intercepted and helps stomates – breathing holes in the leaves – stay open, leading to more rapid drying of the leaves. Hay put immediately into windrows dries slowly and has high respiration rates for an extended time.

If you must put hay into a windrow, adjust for the respiration losses of sugar and starch by cutting the forage earlier at 40% NDF (150 RFQ). Cutting earlier will allow for the respiration losses but will lead to a 10% yield loss or more and greater stress on the stand.

Another way to reduce respiration losses is by packing haylage in a pile, bunker or plastic bale wraps. Respiration requires oxygen. If packed tightly, the forage respiration will quickly use up the oxygen and respiration will stop. This practice is most effective if combined with the practices outlined above: putting forage into a wide swath at cutting, drying it down to 60% moisture quickly and then ensiling or wrapping it in a bale.

Reducing the unseen losses of respiration will help increase yield and forage quality potential. Plus, getting hay off the field faster will help increase yield potential of the next cutting. For more information on alfalfa harvest practices, contact your local NEXGROW® dealer.
© 2023 Forage Genetics International, LLC. NEXGROW® is a registered trademark of Forage Genetics International, LLC.

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Do you really know the quality of your alfalfa?
Article • Agronomic Information

Do you really know the quality of your alfalfa?