Alfalfa is a perennial legume valued as a forage crop due to its high protein content and digestibility. The most important decision impacting the feed quality and long-term health of an alfalfa stand is the timing of the cut. This timing affects the immediate nutritional value of the harvested hay or haylage, the plant’s ability to survive winter, and subsequent yields. Managing an alfalfa stand requires balancing the immediate need for quality forage with the long-term goal of stand persistence.
Balancing Quality and Yield
The decision of when to cut alfalfa is fundamentally a trade-off between maximizing forage quality and total biomass yield. This relationship is inverse: as the plant matures, the total tonnage of dry matter increases, but the nutritional value decreases significantly.
The decline in quality is driven by the increasing accumulation of lignin, a rigid compound that provides structural support to the plant stem. Lignin increases the fiber content (Neutral Detergent Fiber and Acid Detergent Fiber), which lowers the overall digestibility of the forage for livestock.
Harvesting alfalfa early captures the highest protein and digestibility but sacrifices tonnage and can deplete the plant’s root energy reserves. Conversely, delaying the cut until full bloom maximizes the dry matter yield, but the resulting forage has a much lower feed value, suitable only for animals with lower nutritional needs.
Using Growth Stages to Determine Harvest
The method for determining the optimal harvest time involves monitoring the plant’s physical growth stages. The plant’s maturity is a reliable indicator of its nutritional profile, as quality declines predictably with age. Observing the buds and flowers provides a visual guide for hitting a target quality level.
The vegetative stage, characterized by stem growth without visible buds, offers the highest forage quality, but cutting at this point is too aggressive for stand health and results in low yield.
For producers aiming for high-quality feed, such as for high-producing dairy cows, the bud stage is often the target. This occurs when one or more nodes on the stem show small, tight buds, maximizing quality while providing an acceptable yield.
The standard compromise is the early bloom stage, or approximately one-tenth bloom, when flowers are visible on about 10% of the stems. This stage is recommended because it provides a good balance between high yield and acceptable quality, while allowing the plant time to replenish root reserves. The Predictive Equation for Alfalfa Quality (PEAQ) uses the stage of maturity and the height of the tallest stem to estimate the Neutral Detergent Fiber (NDF) content in the standing crop.
Modifying Harvest Based on Weather and Season
Weather and the time of year often force adjustments to the ideal growth stage timing. The first cut of the season is typically the heaviest in yield, but it is often delayed due to cool spring temperatures or the need to manage high weed pressure. Forage quality declines most rapidly in the spring and early summer due to the rapid accumulation of fiber, making the timing of this first cut important.
Moisture conditions also influence the decision to cut, as a sudden rain event can cause nutrient loss through leaching and increase the risk of mold. Since alfalfa hay requires several days of dry weather for proper curing, producers may be forced to cut slightly earlier or later than the ideal growth stage to ensure a dry window for harvesting. Making haylage or baleage, which requires less dry-down time, can mitigate this weather risk.
Fall management requires adherence to a critical fall harvest period, typically about six weeks before the first killing frost. This is when the plant actively translocates energy from its leaves to its roots in preparation for winter dormancy.
Harvesting during this time severely depletes the root reserves needed for winter survival, increasing the risk of winterkill and reducing the yield of the first cut the following spring. It is safest to either cut well before this period to allow for full regrowth, or to delay the final “salvage cut” until after a killing frost has stopped the plant’s growth.
Managing Alfalfa for Long-Term Stand Health
Proper cutting timing is rooted in the plant’s physiological need to manage its root carbohydrate reserves. Alfalfa uses the energy stored in its taproot to fuel the initial burst of regrowth after each cut and to survive the winter. Following harvest, the plant draws down these reserves until the new growth is tall enough (approximately 6 to 8 inches) to produce more energy through photosynthesis than it consumes.
It typically takes about 35 to 42 days between cuts for the plant to fully replenish its root energy stores and initiate the next cycle of growth. Aggressive cutting schedules, which involve shorter intervals, do not allow sufficient time for this replenishment, leading to lower vigor, reduced yields, and a shorter stand life. Conversely, allowing longer intervals between cuts improves the long-term persistence of the stand.
The height at which the plant is cut also influences stand health and regrowth. Leaving adequate stubble, generally 3 to 4 inches, protects the crown buds from damage and allows for more rapid regrowth. Taller stubble height in the late fall is also beneficial for trapping snow, which acts as an insulating layer to protect the alfalfa crowns from extreme cold.