Cutting management of alfalfa is important to optimize yield, quality and persistence. Harvest schedules are dependent on the type of livestock being fed and the appropriate forage quality goals. Some dairy farmers place more emphasis on high-quality, frequently cut, good yielding stands that last for 3 years and are less concerned about alfalfa persistence. Others farmers will delay harvesting with the goal of higher yields and greater plant persistence, but lower feed quality.
Forage crops decline in feeding value as they mature. In a pure alfalfa stand, once alfalfa buds appear, feeding value will decline about 0.2% per day in crude protein and about 0.4% per day in digestibility. Short delays in cutting result in significantly lower forage quality.
Of course, finding a window of dry weather can complicate things even further. With a large acreage of forage, it is advisable to start cutting earlier to ensure the later cut material will still have adequate quality.
Forage Quality Goals
For a high-producing dairy herd, forage must be high in digestible energy and protein. The benchmark analysis for alfalfa for high-producing dairy cows is considered to be 20% crude protein (CP), 30% acid detergent fibre (ADF), and 40% neutral detergent fibre (NDF). This high quality requires an aggressive, early starting 3-cut system. Beef feedlots should also strive for earlier cut, higher quality alfalfa forage.
For beef cows, the most appropriate hay is higher in grass content, more mature and higher yielding, and is therefore lower in protein and digestibility. Many recreational horse owners prefer hay that is more mature and contains more grass. Because it is very important that horse hay not be "rained on" and be entirely free of mould, waiting for the right weather is the priority.
First-Cut Sets the Pace
The first-cut harvest date will dictate the total season harvest schedule. In Ontario, an early first cut is necessary for a 3-cut harvest schedule before the end of August.
As a general rule of thumb, for high quality, first-cut forage should be cut at mid-bud to late-bud stage. Refer to Table 1 Developmental Stages Of Legumes. Cutting at the pre-bud (vegetative) or early-bud stage will result in reduced yields and may weaken the stand. Extremely low fibre levels may result in nutritional problems. Delay cutting fields that have been weakened by winter stress to allow plants to recover.
The Predictive Equations for Alfalfa Quality (PEAQ) method uses both stage of maturity (vegetative, bud, flower) and stem height to estimate the NDF of the alfalfa in a standing crop. A PEAQ stick has been developed, that incorporates the NDF estimates onto an easy-to-read measuring stick, which can be used in the field.
For beef cow hay, where yield and persistence are greater priorities than quality, cutting after one-tenth bloom (flower) is more appropriate.
Table 1 Developmental Stages Of Legumes
Stage Of Maturity Definition
Late vegetative No visible buds. Stem at least 12" tall.
Early bud Visible flower buds on at least 1 stem.
Mid bud 50% of stems have at least 1 bud.
Late bud 75% of stems have at least 1 bud.
No visible flowers.
First bloom Flowers on at least 1 stem.
1/10 bloom 10% of stems have at least 1 flower.
Mid bloom 50% of stems have at least 1 flower.
Full bloom 75% of stems have at least 1 flower.
With alfalfa-grass mixtures, grasses have the overall effect of increasing fiber levels and lowering protein. Grasses lose quality when heading occurs, so mature grasses can significantly lower quality. A compromise between yield and quality with grasses occurs at "early head emergence from the boot". Timothy and smooth bromegrass will mature much later than orchardgrass and reed canarygrass, but are less tolerant to frequent cutting schedules.
Second & Third-Cuts
Subsequent second and third cuttings of alfalfa may be in intervals of approximately 30 days (mid-bud) to 40 days (early flower) or more, depending on whether the goal is high quality or maximum persistence and yield.
Frequent harvests with short cutting intervals of less than 35 days puts stress on alfalfa that can reduce winter survival and first-cut yield the following year. Conversely, a long interval between cuttings will rebuild plant reserves and enhance winter survival.
Critical Fall Harvest Period
Harvesting before the "Critical Fall Harvest Period " allows the plants to regrow and build sufficient root energy reserves for winter survival and persistence, as well as vigorous spring growth and good first cut yields. The Critical Fall Harvest Period is approximately 6 weeks long and varies with location. Refer to Figure 5-4 of Publication 811 "Agronomy Guide" for a map detailing the Critical Fall Harvest Period in your area.
The risk of alfalfa winterkill increases by harvesting during the Critical Fall Harvest Period, and should be weighed against the immediate need for forage. Yield sacrificed by not harvesting during this period is usually easily regained in first cut yield the following year. Cutting before this period can also enhance dandelion control since the alfalfa has time to canopy before dandelions make their autumn comeback.
Late Autumn Cutting
After a hard fall frost, alfalfa can be harvested without lowering root reserves, but there are risks. Leaving at least 6 inches of fall growth will aid in catching snow, which insulates the soil from cold temperatures. The stubble also helps alfalfa plants survive ice sheeting by protruding through the ice, allowing the movement of air for respiration. Unlike grasses, fall regrowth of alfalfa does not cause "smothering," but ice sheeting does.
For more information, refer to "Alfalfa Winter Kill Risk Factors" and "Predicting Alfalfa Quality Using PEAQ" on the OMAF Forage Website at www.gov.on.ca/OMAFRA/ english/crops/field/forages.html, or from the Agricultural Information Contact Centre at 1-877-424-1300.