Therefore, harvest management of perennial legumes such as alfalfa, red clover, and birdsfoot trefoil requires a compromise between quality and persistence. The intensity at which these forage legumes are harvested should depend on the nutrient needs of the livestock that will be consuming the forage (Figure 1), as well as the life expectancy of the stand. Because of sudden changes in weather and year-to-year variation in growing seasons, there is no simple rule to follow when making a decision to cut.
Alfalfa also known as lucerne is a popular forage crop grown around the world. It is highly nutritious and palatable for livestock. However, to maintain an alfalfa plant’s productivity and health, timely pruning is essential. This in-depth guide will provide tips on when and how to trim your alfalfa for optimal growth.
When to Trim Alfalfa
The ideal time for trimming alfalfa is when the plants reach the bud to first flower stage which is usually around 28-35 days after planting or after the previous cut. Trimming earlier will reduce yields as the plant has not reached its maximum growth potential. Leaving the trimming too late can reduce regrowth and stand life.
Here are some signs that your alfalfa is ready for pruning:
- The crowns start developing flower buds.
- The stems feel spongy when pinched.
- The lower leaves start turning yellow and dropping off.
- New shoots start emerging from the crown.
How Often to Trim Alfalfa
On average, alfalfa should be trimmed every 4-6 weeks during the growing season for optimal production. However, the interval can vary depending on factors like:
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Variety – Some varieties are more winter hardy and can tolerate more frequent cutting.
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Climate – Hotter and drier conditions will require less frequent cutting.
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Stand age – Young stands can tolerate more frequent harvests than older stands.
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Intended use – Alfalfa for hay can be cut more frequently than when baling or grazing.
Monitor your plants and use the signs above to determine optimal harvest intervals for your situation.
Pruning Height
It is important not to cut alfalfa too short as it needs leaf area for regrowth. A general rule is to leave at least 2-3 inches of stubble after mowing. The shortest stubble that permits rapid regrowth is ideal.
For sickle bar mowers, a cutting height of 3-4 inches is recommended. For disk-type mowers, aim for 2-3 inches. In very dry conditions, leave taller stubble of 4-6 inches.
How to Trim Alfalfa
Alfalfa can be pruned in several ways depending on your needs:
Mowing
Mowing or swathing with a sickle bar or disk mower is the most common method. It is fast and provides an even cut:
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Mow when foliage is dry to avoid leaf loss.
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Mow in the afternoon when carbohydrates have accumulated in the roots.
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Mow from one side to avoid driving on the cut swath.
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Use a windrow merger to speed drying after mowing.
Grazing
You can prune alfalfa through timed rotational grazing:
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Use sheep, cattle, horses or goats.
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Start grazing when alfalfa reaches late bud stage.
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Rotate livestock between paddocks every 20-25 days.
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Avoid overgrazing – leave at least 2 inches of stubble.
Green Chopping
Harvest alfalfa by chopping the entire plant for green feed:
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Time harvest based on livestock needs.
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Chop when moisture content is 65-75%.
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Chop fine (1⁄2-3⁄4 inch) for proper wilting.
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Quickly harvest swaths to maintain quality.
Hand Pruning
While impractical for large fields, you can hand prune using:
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Garden shears for small homestead plots.
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Sickle for larger patches if wildlife habitat is a concern.
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Only prune up to 1/3 of the plant height by hand.
Special Considerations
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Avoid trimming for 5-7 days after herbicide application.
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Leave taller stubble in fall to accumulate nutrients for winter.
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Trim diseased plants separately to avoid spreading infection.
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Irrigate after pruning to stimulate rapid regrowth.
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Apply fertilizer and pest control products after cutting as needed.
Benefits of Pruning Alfalfa
Regularly pruning alfalfa provides many benefits:
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Maintains alfalfa in a vegetative state for higher feed quality.
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Stimulates stooling and uniform regrowth.
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Removes stem and leaf debris that harbor pests.
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Reduces competition from weeds.
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Allows light penetration for lower leaves.
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Removes flowers that decrease palatability and digestibility.
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Provides flexibility to match harvest schedule with weather.
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Maximizes yield and stand life over many years.
By following proper mowing height, timing, and frequency, you can keep your alfalfa stands thick and productive for hay, grazing, or chopping. Use the guidelines in this in-depth pruning guide to get the most out of your alfalfa. With a well-managed pruning regimen, you can get top yields from this nutritious perennial forage crop.
Indicators on Which to Base Cutting Time
The stage of plant development is generally a reliable predictor of energy reserve status and when the plants should be harvested. However, when the weather is extremely cool and cloudy for an extended period and flowering is delayed, energy reserves continue to increase. Under these conditions, which often occur in May, the development of new shoots from the crown indicates that it is time to cut (Figure 3). A harvesting delay after the new crown shoots begin to grow can delay regrowth and reduce yield of the next harvest. Under normal growing conditions, particularly during summer, the development of new crown shoots may not occur until well after full bloom or even after seed set. Therefore, relying on the appearance of crown shoots to begin harvesting is not always advisable.
Relying on the calendar alone to make a decision to harvest is unwise. Light, temperature, and moisture vary from year-to-year and have a direct effect on maturation. The most consistent method to determine when to harvest is the stage of plant development in conjunction with calendar date, because seasonal weather variations can alter the relationship between stage of development and energy reserve.
Figure 3. An alfalfa crown with new crown shoots.
Seeding and establishment year
During the year of establishment, seedlings need a high level of energy reserves in order to persist through the winter. For spring seedings made without a companion crop, two harvests can generally be made the first year, provided the crop has adequate rainfall and optimum levels of soil nutrients. The first harvest can be made before flowers begin to appear, but waiting for the alfalfa to flower will ensure greater energy reserves in the roots. Alfalfa will generally reach this stage of development between 60 and 70 days after emergence. The second harvest should either be made before September 1, to ensure an adequate buildup of energy reserves for winter, or be delayed until after the first killing frost (24°F) in the fall or after mid-October. Occasionally, when the second harvest is made before September and there are good fall growing conditions, a third harvest may be made after a definite killing frost. When mid-October or later harvests are made, a high stubble (6 inches) should be left for ground cover to protect the crowns and to catch snow for added insulation.
Spring seedings made with a companion crop such as oats are usually harvested for the first time based on the maturity of the companion crop. Alfalfa harvests made after the companion crop has been harvested should follow the same guidelines as for alfalfa seeded without a companion crop.
The spring harvest of a fall-seeded alfalfa crop should be based on plant development and vigor. If the alfalfa plants look vigorous and the roots are well developed, spring cuttings can be made at bud-to-early-bloom stages. If plants are small and poorly developed, it is best to wait until mid-bloom stage before harvesting.
The intensity of cutting management (the number of cuttings made per year) should be based on the desired quality and life expectancy of the crop. If the goal is to have a long-lived stand, then a long cutting interval should be considered. If the crop is being grown under a short rotation (three years or less), then more cuttings may be desirable to maximize forage quality.
The first cutting in the spring can be made when the crop is in the bud-to-early-bloom stage. There is generally limited environmental stress during the spring and the alfalfa crop can normally tolerate early cutting. Harvesting at the bud stage has allowed producers to get more cuttings per year, increase their production, and improve the quality of their forage. However, in order to cut this early, producers should have optimum levels of soil pH, phosphorus, and potassium, and plants should be allowed to reach the first-bloom stage at least once during the year.
Cuttings made during the summer (second, third, and fourth cuttings) should be made when the crop is in the bud- to-early-bloom stage of development. Some producers are attempting to cut when the alfalfa is even less mature than recommended. A cutting interval that is consistently shorter than 30 days can be extremely stressful to the stand because energy reserves cannot be stored in the taproots and crowns. Low energy reserves lead not only to poor regrowth (which results in poor yields), but also to an actual loss of stand–sometimes in one year.
Alfalfa, unlike red clover or birdsfoot trefoil, generally maintains production during short periods of dry weather because of its deep and extensive root system. However, during extended periods of dry weather, alfalfa growth is reduced and flowering may occur on short, stunted plants. Cutting during these stressful periods does not weaken alfalfa plants or cause stand reductions. If feed is badly needed, these stands of drought-stressed alfalfa can be controlled grazed. If adequate late summer or fall growth occur after the alfalfa plants have been drought stressed, an additional harvest can be made in the fall with less risk of stand loss than if the alfalfa was not drought stressed.
During the late summer and early fall, alfalfa plants are preparing for winter by developing cold resistance and storing energy reserves in their roots. Depending on the timing, fall harvest may interfere with this process. Harvesting alfalfa at a time that allows only a few weeks of regrowth before the herbage is killed by frost greatly reduces energy reserves in the roots. Late harvesting also removes stubble which catches snow and insulates plants from extremely cold air temperatures. Both situations increase the risk of alfalfa winter kill.
Winter environmental conditions can aggravate the effects of fall harvesting. Temperatures of 5°F will injure alfalfa crowns and roots. Soil and snow serve as insulation between the alfalfa plant and cold air temperatures. Lack of snow increases the risk of winter kill. Wet soils freeze and thaw more intensively, which increase the amount of frost heaving. Dont fall harvest fields that have a history of frost heaving or of accumulating little snow cover.
Risks to stand persistence can be minimized by:
- Taking at least one harvest during the summer at 1/10 bloom or greater.
- Fall harvesting young stands because young stands are less susceptible than old stands to winter injury.
- Maintaining high soil fertility levels.
- Fall harvesting alfalfa varieties that have good disease resistance and winter hardiness.
Although fall harvesting increases the risk to stand loss (compared with not fall harvesting), the need for forage or the value of the forage may be greater than the risk. Making the decision to cut in the late summer or fall requires weighing the risk of winter injury against the need for the forage. Use the scoring system in Table 3 to assess the risk of late summer or fall harvesting alfalfa.
Table 3. Calculating risk of alfalfa winter injury due to late summer or fall cutting. Enter the score for answers which describe your management. Adapted from: C.C. Sheaffer, University of Minnesota, 1990
Optimum levels of potassium in the soil enhance the storage of energy reserves in alfalfa roots. Maintaining high reserves of energy in the roots as winter begins does improve the ability of alfalfa to overwinter and support good spring growth. It is important that adequate potassium be available during the late summer and early fall because the storage of energy reserves for winter survival occurs during this time. Applying potassium fertilizer after the plants go dormant for the winter does not benefit energy reserve storage.
How to cut alfalfa for faster recovery
FAQ
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