Alfalfa is a high-value forage crop prized for its excellent nutritional profile, particularly its high protein content (15% to over 20% crude protein). This legume is a foundational feed for dairy cattle and other livestock, influencing animal productivity and farm economics. To capture maximum nutritional value, harvesting must be executed with precision. Hay quality is determined by management decisions during cutting, curing, and baling. The goal is to minimize dry matter loss and preserve the nutrient-dense leaves, which hold the majority of the protein.
Determining Optimal Timing
The most influential factor affecting alfalfa quality is the plant’s maturity stage at cutting. As the plant matures, crude protein decreases, and fiber content (NDF and ADF) increases, reducing digestibility. Highest forage quality (measured by RFV) is found in the bud stage, just before flowers open, but this results in lower yield and can reduce stand persistence.
A balance between high quality and sustainable yield is usually achieved by harvesting at the 1/10th bloom stage, where about 10% of the stems have at least one open flower. Waiting until full bloom maximizes the dry matter yield but yields a hay with significantly lower digestibility, which may only be suitable for livestock with lower nutritional demands. Producers can precisely estimate the quality of the standing crop using tools like the Predictive Equations for Alfalfa Quality (PEAQ), which correlates stem height and maturity stage to the estimated RFV.
A practical approach involves examining stem maturity rather than relying on a calendar date, as development varies greatly with weather conditions. The estimated RFV drops by three to five points per day once the ideal maturity window is reached, meaning the decision must be made quickly. The harvest decision must also account for a favorable three- to five-day weather forecast to allow the cut forage to dry properly without rain damage.
The Cutting Process
Cutting is the first step in preserving quality. The appropriate equipment is typically a mower-conditioner, which performs two actions simultaneously: cutting the crop and conditioning the stems. Conditioning crimps or crushes the thick alfalfa stems to break the waxy cuticle layer, allowing stem moisture to evaporate at a similar rate to the leaves. Without conditioning, the quickly drying leaves will shatter and be lost before the stems are dry enough for baling, resulting in significant protein loss.
Setting the correct cutting height is important for immediate crop quality and the long-term health of the alfalfa stand. A height of two to four inches is generally recommended. Cutting too low (below two inches) risks damaging the plant’s crown, which stores energy reserves for regrowth, and increases the risk of soil contamination, raising the ash content. Leaving stubble, around three inches, helps prop up the cut swath, allowing for better airflow and faster drying.
Curing and Conditioning
Curing reduces the moisture content of cut alfalfa from 75–80% down to a safe baling range of 15–20%. After cutting and conditioning, the alfalfa is left in a wide swath, maximizing exposure to sunlight and air for rapid water loss. Rapid drying is important because the plant continues to respire, consuming stored sugars and starches, until moisture drops below 40%.
To ensure uniform drying, the wide swath is often consolidated into a windrow and may require mechanical manipulation (raking or tedding) to turn and fluff the material. Raking is best performed when the hay is still moist, ideally between 35% and 40% moisture content. Handling the forage below 40% moisture dramatically increases the risk of leaf shatter, causing significant loss of quality and nutrient-rich material.
If raking is necessary when the hay is drier, producers often rake in the early morning when the material is slightly damp from dew, making the leaves more pliable and less prone to breaking. Monitoring moisture content is essential, as baling when too dry loses valuable leaves, while baling when too wet risks significant spoilage. Moisture level is the primary control point for preventing mold growth and excessive heating.
Baling and Storage
The final stage is baling, which must be executed when forage moisture is within a narrow, safe range to prevent losses. The optimal moisture target for dry hay is typically between 15% and 20%. For small square bales, the upper limit is around 20%, but for denser large square or round bales, moisture content should be slightly lower (15% to 18%) to mitigate the risk of spontaneous combustion and heat damage during storage.
Baling at too high a moisture content supports microbial activity and respiration, generating heat that can lead to temperatures above 130°F. This results in heat damage that reduces protein digestibility. Conversely, baling below 15% moisture causes excessive leaf shatter due to brittle leaves, significantly lowering the crude protein. Bale density must be sufficient to maintain shape but not so tight that it traps excess moisture, especially relevant for large-format bales.
After baling, proper storage is necessary to preserve the quality achieved. Bales should be stored in a manner that protects them from rain and ground moisture, ideally under a roof in a shed. If outdoor storage is the only option, bales should be stacked on a well-drained surface (gravel or pallets) and covered with a tarp to reduce moisture reabsorption. Adequate ventilation around stacked bales helps dissipate residual heat and moisture, minimizing the continued risk of mold and spoilage.