The process of making hay aims to preserve forage crops, such as grasses or legumes, for animal feed when fresh pasture is unavailable. Hay is forage that has been cut and dried to a low moisture content so it can be safely stored without spoiling. Baling creates a compact package for efficient transportation and preserves the nutritional value of the forage. The entire operation relies on carefully managing moisture levels to prevent mold growth and the risk of spontaneous combustion in storage.
Preparing the Field and Cutting the Crop
Selecting the proper moment for cutting the crop is the first step toward producing high-quality hay, balancing the plant’s maturity with its nutrient content. For maximum nutrition, the forage should be cut when it is mature but before its stems become too coarse or its leaves begin to drop. The initial cut is highly dependent on weather, requiring a forecast of several consecutive days of clear, dry conditions to allow for adequate field drying.
Most modern operations use a mower-conditioner, which simultaneously cuts the crop and mechanically processes the stems. The conditioning component crimps or crushes the stems to break their waxy outer layer, allowing moisture to escape faster. This significantly speeds up the drying process, which is beneficial for thicker-stemmed crops like alfalfa. Setting the cutting height correctly, usually leaving a few inches of stubble, keeps the cut material elevated off the damp ground, promoting better airflow and quicker drying.
Curing the Hay and Forming Windrows
Curing is the process of reducing the forage’s moisture content from its initial level, typically 75 to 80 percent when standing, down to a safe range for baling. This reduction is accomplished by spreading the cut material across the field in a wide swath to maximize its exposure to the sun and air. The goal is to reach a moisture content of approximately 15 to 20 percent for dry hay, with the specific target varying based on the final bale size and density.
To promote uniform drying, the material is often disturbed or “fluffed” using a tedder, which gently spreads the hay and turns it over. This ensures the bottom layer, which is closer to the ground, is exposed to the air. Once the hay is adequately dried, but before the leaves become so brittle that they shatter, a rake is used to gather the material into long, continuous rows called windrows. Raking must be timed carefully; for delicate legume crops like alfalfa, raking when the hay is slightly higher in moisture, around 30 percent, helps prevent the loss of nutrient-rich leaves.
Determining the exact time to bale requires frequent monitoring of the moisture content, as baling too early can lead to spoilage and fire risk. An electronic hay probe is the most common tool used to check this, providing a reading of the electrical resistance within the hay mass, which correlates directly to its water content. For small square bales, a moisture content of up to 20 percent may be acceptable, but denser large round or large square bales require a lower threshold, often 14 to 18 percent, to minimize the risk of aerobic microbial growth and heating in the core.
Operating the Baler
The baler is towed over the windrows, where a pickup mechanism lifts the dried forage from the ground and feeds it into the machine’s compression chamber. Maintaining a straight line and a consistent, moderate speed is important to ensure the bales are formed with uniform density and shape. If the baler moves too quickly, it can leave behind hay or create unevenly formed bales that are prone to slumping.
In a square baler, the hay is pushed into a rectangular chamber where a heavy plunger repeatedly compresses the material, forming a dense flake. When the bale reaches a preset length, a knotting mechanism automatically ties the bale with twine, or sometimes wire, before the finished package is ejected. Round balers operate differently, using belts or chains to roll the hay into a cylindrical chamber, gradually building the bale from the inside out until it reaches a specific size and density.
Once the round bale is fully formed, the operator stops the forward motion, and the machine wraps the cylinder with either twine or a net wrap before ejecting it onto the field. The final density is controlled by tension settings on the machine, which must be calibrated to the moisture content and type of hay being processed. Denser bales, especially the large square variety, offer better storage efficiency but require the driest hay to prevent internal heating.
Post-Baling Handling and Storage
After the bales are ejected onto the field, they should be removed and stored quickly to maintain quality and prevent potential hazards. The initial few weeks are when the hay is most susceptible to internal heating due to residual microbial activity. Bales put up with a moisture content above 22 percent are at a significantly higher risk of spontaneous combustion, which occurs when the heat generated by microbes exceeds the rate of dissipation.
To reduce spoilage, the bales should be stored in a location that protects them from rain and ground moisture. Storing hay inside a barn or shed is the best method for preserving its nutritional value and color. If the hay must be stored outside, it should be covered with a tarp and elevated off the ground using pallets or tires to prevent moisture wicking from the soil. Stacking bales should also allow for some airflow around the sides, particularly for large, dense bales, to help dissipate any residual internal heat and minimize the risk of fire.