How to Speed up Hay Drying

June 7, 2019
Hay windrow
Author: Mark Sulc

Author’s note: Most of this article is adapted with permission from an article published in Farm and Dairy on 2nd June 2010. It certainly applies this year.

Many forage producers across Ohio have suffered severe forage stand losses in 2019; however, there are areas where the stands have survived and those are ready for harvest. Unfortunately, rainy weather has slowed harvest progress of the first harvest. Despite the need to harvest as soon as possible for decent quality forage, I strongly urge patience in waiting for soils to firm up before attempting to harvest, because driving equipment on soft soils does long-term damage to future productivity.

Once the soils are firm enough, there are several proven techniques that can speed up the hay drying process to take the most advantage possible with any sunny days we do get.

Haylage vs. Hay

Consider making haylage/silage or balage instead of dry hay. Since haylage is preserved at higher moisture contents, it is a lot easier to get it to a proper dry matter content for safe preservation. Proper dry matter content for chopping haylage can often be achieved within 24 hours or less as compared with 3 to 5 days for dry hay.

Proper dry matter content for silage ranges from 30 to 50% (50 to 70% moisture) depending on the structure used. Wrapped balage should be dried to 40 to 55% dry matter (45 to 60% moisture). Compare that to dry hay that should be baled at 80 to 85% dry matter (15 to 20% moisture), depending on the size of the bale package (see table below). The larger and more dense the dry hay package, the dryer it has to be to avoid spoilage.

Safe moisture ranges for preserving forage


Moisture range

Silage 50 - 70%
Wrapped balage 45 - 60%
Small square dry hay 15 - 20%
Large round dry hay 15 - 18%
Large rectangular dry hay 13 - 15%


You can determine forage moisture by using a hay probe (follow manufacturer's directions carefully), using a microwave oven (click HERE), or a Vortex Forage Dryer (click HERE).

Mechanically condition the forage

Faster drying of cut forage begins with using a well-adjusted mower-conditioner to cause crimping/cracking of the stem (roller conditioners) or abrasion to the stems (impeller conditioners). At least 90% of the stems should be cracked or crimped with roller conditioners or should show some mechanical abrasion when using impeller conditioners.

Some excellent guidelines for adjusting these machines can be found in an article by Dr. Ronald Schuler of the University of Wisconsin, available HERE.

Maximize exposure to sunlight

I once heard someone say "You don’t dry your laundry in a pile, so why do you expect to dry hay that way?" Exposure to the sun is the single most important weather factor to speed drying. The trick is to expose to sunshine as much of the cut forage as possible.

The swath width should be about 70% of the actual cut area. The mowers on the market vary in how wide a windrow they can make, but even those that make narrow windrows have been modified to spread the windrow wider. Details can be found in articles at the Univ. of Wisconsin website mentioned above (see especially “Getting the Most from the Mower Conditioner” by Kevin Shinners).

Another way to spread out and aerate the crop for faster drying is with a tedder. Tedders are especially effective with grass crops but can cause excessive leaf loss in legumes if done when the leaves are dry. Tedders can be a good option when the ground is damp (like this year), because the crop can be mowed into narrow windrows to allow more ground exposure to sunlight for a short time, and then once the soil has dried some the crop can be spread out with the tedder.

When making haylage, if drying conditions are good, rake multiple wide swaths into a windrow just before chopping. For hay, if drying conditions are good, merge or rake multiple wide swaths into a windrow the next morning when the forage is 40 to 60% moisture to avoid excessive leaf loss.

Research studies and experience have proven that drying forage in wide swaths can significantly speed up drying. Faster drying in wide swaths results in less chance of rain damage and studies by the University of Wisconsin showed that wide swaths (72% of the cut width) result in lower NDF and higher energy in the stored forage.

Consider desiccants under good drying conditions

Desiccants are chemicals applied when mowing the crop that increase the drying rate. The most effective desiccants contain potassium carbonate or sodium carbonate. They are more effective on legumes than grasses and most useful for making hay rather than silage or balage. Desiccants work best under good drying conditions, but don't help much when conditions are humid, damp, and cloudy. Consider the weather conditions before applying them. 

Consider a preservative

Sometimes the rain just comes quicker than we have time for making dry hay. As mentioned above, making haylage helps significantly with this. A second option is to use a preservative. The most effective preservatives are based on proprionic acid, which is caustic to equipment, but many buffered proprionic preservatives are available that minimize that problem.

Preservatives inhibit mold growth and allow safe baling at moisture contents a little higher than the normal range for dry hay. Carefully follow the preservative manufacturer’s directions and application rates for the hay moisture content at baling.

Watch wet bales carefully for heating!

If hay is baled at higher moisture contents that are pushing past the safe limits, keep a close watch on them for two to three weeks. Use a hay temperature probe and monitor the internal temperature of the hay during the first three weeks after baling.

Every year someone’s barn burns down because of spontaneous combustion of wet hay. So if hay is on the wetter side, keep it outside or in a well-ventilated area. Don’t stack wet hay, because that prevents the heat and moisture left in the hay from escaping.

It is normal for hay to go through a “sweat” in the few days after baling. Internal temperatures of 110 F in the first five days after baling are quite common in our region and are not a big concern.

Hay bale temperatures of 120 to 130 F will likely result in mold growth and will make the protein in the hay less available to animals. While those temperatures are not high enough to cause hay fires, the concern is if the mold growth continues and pushes temperatures upward into the danger zone.

If the temperature in the hay continues to rise, reaching 160 to 170 F, then there is cause for alarm. At those elevated temperatures, other chemical reactions begin to occur that elevate the temperature much higher, resulting in spontaneous combustion of the hay in a relatively short period of time.

Hay fires can be avoided by careful attention to the management practices outlined above along with cooperation from the sun.

Let’s hope for plenty of sunshine soon!