Randal K. Taylor
Extension Agricultural Engineer

Alfalfa is called the "queen" of forages because it provides high levels of energy, protein and nutrients for livestock. Unfortunately, not all alfalfa is equal in feed value. There are many factors which enter into producing high quality alfalfa. One factor, the harvest process, has a certain amount of risk associated with it. After alfalfa is cut, it dries in the field to a moisture content that is acceptable for packaging. During this time, it is vulnerable to rain damage.

If alfalfa is baled too wet, forage quality is reduced due to heat and mold. On the other hand, if alfalfa is too dry, substantial leaf loss occurs during the harvesting process, which is also detrimental to quality. Since stems and leaves dry at different rates, baling alfalfa within this moisture content range is one of the many challenges of quality alfalfa production. However, mechanically conditioning alfalfa provides a means for meeting this challenge.

The main objective of mechanically conditioning alfalfa is to allow moisture to escape from the stem faster. Properly conditioned alfalfa stems dry at nearly the same rate as leaves, which allows baling to begin sooner. There are three common methods for mechanically conditioning alfalfa: 1) crimping or bending the stem until it breaks; 2) crushing or smashing the stem to break its waxy surface layer, and 3) abrading or rubbing the stem to remove much of the stem's waxy layer. Once the surface layer is opened, moisture will escape.

Types of Conditioners
There are many different conditioners available from hay equipment manufacturers. Most can be grouped into two basic categories: roll type conditioners and impeller or tine type conditioners.

Roll type conditioners consist of two rolls that crimp or crush the stem as it passes between them. Rolls come in a variety of shapes, textures and sizes and are made of polyurethane, steel, rubber or a combination of these.

Some conditioners have a pair of intermeshing rolls, which crimp the stem; others have one smooth roll and one fluted roll, which crush the stem. Intermeshing rubber rolls are the most common type of conditioning rolls (Figure 1).

Tine type conditioners usually consist of steel or rubber fingers swinging from a rotating hub. The free-swinging fingers carry the crop over the hub, against an adjustable conditioning hood (Figure 2). The abrasive action of stems rubbing against the hood and other stems removes the waxy layer from the stem. Fingers on at least one tine type conditioner pass through a comb section to increase conditioning.

There is minimal difference in field curing time between alfalfa conditioned with different types of roll or tine conditioning units. While losses from different types of rolls are similar, tine type conditioners can have higher crop losses than roll type conditioners because of improper conditioner adjustment. Proper machine adjustment has a much greater impact on curing time and harvest losses than conditioner type.

Adjusting Conditioners
The conditioner is the heart of a mower-conditioner and should be treated as such. If properly adjusted and operated, it can speed the drying of alfalfa, which minimizes the chance of rain damage. A recent survey by Oklahoma State University estimated that 72 percent of the state's alfalfa growers use a mower-conditioner; however, only 39 percent of these growers adjusted conditioner rolls annually. Furthermore, 26 percent never adjusted rolls. Similar conditioners are found in Kansas, which raises the question of how well these conditioners are actually performing.

Crop characteristics such as stem diameter and leaf/stem ratio depend on plant maturity and growing conditions and will vary significantly throughout the growing season and from field to field. Conditioning roll adjustment should reflect these changes.

This article is provided by the K-State Research & Extension, Agricultural Library