Wide Swath Drying for Haylage and/or Dry Hay

Relentless spring rains aren't only a challenge for corn and soybean planting, as anyone needing to make quality forages knows well. Wide swath cutting and/or manipulation not only speeds up drying, it also preserves some of the TDN (Total Digestible Nutrients) of the forage.

Solar radiation is the most important factor in drying hay by evaporating and moving moisture out of the plant. Drying of hay requires the removal of about 3 tons of moisture for every ton of hay produced, requiring the energy equal to about 70 gallons of fuel oil! Cutting in the morning and using wide swaths to take advantage of sunlight is key to both fast wilting and preserving digestible dry matter as well as improving fermentation in haylage. Obviously, warm air temperatures and low humidity also aid in drying.

When forage is cut, it has 75-80% moisture which must be lowered down to 60-65% moisture content for haylage and down to 14 to 18 percent moisture content for hay (lower figures for larger bales.) In the first phase of drying, moisture is lost from the leaves through the stomates. Cut forage laid in a wide swath (covering >70% of cut area) maximizes the amount of forage exposed to sunlight. Respiration (and photosynthesis) continues after the forage is cut and declines until plant moisture has fallen below 60% (and the death of cells). Rapid initial drying to lose the first 15% moisture will reduce loss of sugars and starches, preserving more total digestible nutrients in the harvested forage.

The second phase of drying is moisture loss from the leaves (stomata have closed) and from the stem. At this stage conditioning can help increase the drying rate, especially as the forage becomes drier.

The final stage of drying is the loss of tightly held water, particularly from the stems. Conditioning is critical to enhance the drying during this phase. Broken stems every few inches or scraping off the stem's waxy cuticle will increase water loss through the stems. Many producers still mow into (narrow) windrows because they thought since they conditioned, they didn't need wide swaths (like they used to before conditioners.) Remember, conditioning dries stems and wide swaths dry leaves. We need both to make high quality hay.

The basic concept of the three phases of drying forage helps us understand how to best get the job done.  Wide swaths maximize initial drying rates and preserve starches and sugars. A wide swath may be more important than conditioning for haylage.

Remember that narrow windrows are very high humidity with little drying. Most producers have checked a windrow made the previous day only to find very little drying has occurred. The plants have respired all night losing sugars, carbohydrates, CO₂, and dry matter (from the 100% available nutrients), resulting in forage quality losses.

Strategies for wilting silage are quite different than dry hay making, but wide swaths are advantageous for both. The best recommendation is to dry forages rapidly. Mechanical conditioning should be used, and high yielding crops should be spread in wide swaths. Tedding may be useful in drying grass crops, but it should be avoided with alfalfa, particularly after the crop has partially dried.

Recommendations

1. Cut at the proper height of 2 to 4 inches for grass and grass/legume mixtures. This results in early regrowth and sooner subsequent cuttings, improved persistence, and stubble that elevates the wide swath for aeration and rapid wilting/drying. Improper cutting height can increase the ash content of the forage from a natural level of 6% to 16-18%.
2. Adjust conditioners properly (1-5% of leaves showing some bruising). May not be needed for haylage.
3. Lay hay in a wide swath covering 70% or more of the cut area (with mower or tedder).
4. Rake/merge ahead of chopping or at a moisture that minimizes leaf loss (40-60% moisture – often not reached until about 24 hours or more after mowing into narrow windrows.)

Finally, I have "borrowed liberally" from articles by various forage experts, especially Undersander, Rotz, and Kilcer. I acknowledge and refer to their work.