A hay conditioner is an agricultural implement designed to accelerate the field drying process of newly cut forage crops. By physically treating the plant material immediately after cutting, the machine ensures the hay reaches a safe moisture level for baling. This mechanical treatment is a standard feature on most modern mower-conditioner units, combining cutting and drying preparation into a single pass.
The Problem with Drying Hay
The challenge in haymaking lies in the structural difference between the plant’s leaves and its thick, waxy stems. Leaves are thin and have stomata, or pores, that allow moisture to escape quickly once the plant is cut. In contrast, the stems are covered in a protective, waxy cuticle that retains water.
This disparity means the leaves dry out and become brittle quickly while the stems still hold excessive moisture. Waiting for the stems to dry causes brittle leaves to shatter and fall off during baling, resulting in the loss of the most nutritious part of the plant. Baling too early risks mold growth, spoilage, or spontaneous combustion due to high internal moisture. Proper conditioning solves this problem by forcing the stems to dry at a rate closer to that of the leaves.
Mechanical Conditioning Explained
Conditioning works by physically damaging the stem’s protective barrier to create avenues for water vapor to escape. This mechanical action compromises the water-retaining cuticle layer, allowing internal moisture to evaporate rapidly. The process involves a combination of crimping, crushing, or scuffing the stem along its length.
For the treatment to be effective, this physical damage must be applied at frequent intervals along the stem. The goal is often to create a break or crimp roughly every three to four inches of the stem’s length. This destruction of the water-holding structure ensures that the entire plant dries uniformly.
Applying this treatment can reduce the overall field curing time by 30 to 50 percent, allowing the hay to be baled in two or three days instead of four to seven. Rapid drying minimizes the time the cut forage is exposed to rain damage and reduces the loss of digestible carbohydrates that occurs as the plant continues to respire after cutting. The increased drying rate is most beneficial after the initial surface moisture has evaporated and the leaf stomata have closed.
Two Main Conditioner Styles
The conditioning process uses one of two mechanical designs, each suited to different forage types. Roller conditioners use intermeshing rubber or steel rolls to crush or crimp the hay. This action breaks the stem’s structure without damaging the leaves, making rollers the preferred choice for delicate, leafy crops like alfalfa and clover (legumes) where leaf retention is important.
The alternative is the impeller or flail conditioner, which employs a high-speed rotor equipped with pivoting metal or plastic tines. The rotor spins rapidly, using the tines to beat or scuff the cut forage against a stationary hood. This scuffing action abrades the waxy cuticle of the stem, accelerating moisture loss in coarser, tougher-stemmed forages.
Impeller conditioners are the optimal choice for grasses, such as timothy, Bermuda grass, or orchardgrass, which benefit from aggressive abrasion. While both systems can condition any forage, the roller type is gentler on legumes. The impeller system is more aggressive and can lead to higher leaf loss in alfalfa, so the choice depends on the specific type of hay being grown.