The risk of rain damage to curing hay is substantial, points out J.W. Schroeder, North Dakota State University Extension dairy specialist. An inch of rain on swathed hay can reduce yield by greater than 5%, total digestible nutrients by 5-6 % and dry-matter intake by 8-9%, he says.

In areas where humidity is a problem, as has been the case in North Dakota, drying hay to a moisture level safe for storage (15-16% for large round or big square bales, 17-18% for small square bales) may take more than five days.

“Unfortunately, the chances have been high that a significant rain event will occur during any given five-day stretch,” says Schroeder. “To make matters worse, the high humidity and the condensation of dew actually can cause the moisture of the partially cured hay to increase overnight. Consequently, drying hay as quickly as possible is critical.”

He offers these suggestions:

  • Take full advantage of good drying conditions. Begin cutting the crop early in the day (immediately before or soon after the dew is off) to fully utilize days known to provide good drying conditions. By waiting to the end of the day to cut, the drying time is pushed back by a full day or more, exposing the curing hay to more risk of weather damage.
  • Use a conditioner on the mowing implement. A conditioning mower will aid crop drying greatly. Studies have shown the drying rate of a hay crop is 15-25% better when a conditioner is used.
  • Use the right conditioner for the crop being harvested. Impeller conditioners generally are better for fine-stemmed grass hay crops, such as bermudagrass and tall fescue, while roller-crimper conditioners are better for thick-stemmed species like pearl millet, sorghum-sudangrass hybrids and legumes. Avoid using an impeller conditioner on alfalfa or expect another 7% leaf loss during the harvesting process. Leaf loss using a roller-crimper conditioner is minimal.
  • Spread the harvested swath widely. The hay producer’s best friend is sunshine. When the drying plant material intercepts sunlight, the energy of the light heats the plant and speeds drying. Therefore, using every square inch of the field to intercept the sunlight is important. For alfalfa and other legumes, however, wheel traffic over the top of the swath may increase leaf loss. In that case, laying the forage in a narrow swath at first and then using a tedder to spread it out may be best.
  • Use a tedder wisely. A hay tedder inverts, stirs and spreads out the crop. Proper use of a tedder can increase the drying rate by 15-30%, and it’s a relatively economical tool. Using a tedder the morning after the crop was cut usually is best. Running it after the dew has completely dried or when the forage is too dry can lead to excessive leaf shatter and losses. Try to complete all tedding operations before late morning.