When is the best time to harvest alfalfa?

Making the decision on when to cut alfalfa is a difficult one. For feed quality, it is pre–bud, but from a plant health standpoint it is when the alfalfa plant is one – tenth bloom or full bloom. At one – tenth bloom, root reserves are at the highest before the plant thinks to reproduce. Could there be a compromise?

This is where walking the field becomes important around pre–bud. The crown will begin to sprout new shoots. This is the sign that the previous generation is nearing completion. This is also still a point where the forage quality will be high. While out checking stage of maturity, it is also a good time to evaluate for abnormalities, leaf size, shape, and color. All of these can tell you a lot about plant health.

When out checking your fields, do the following:

1. Look at stems for discoloration and evidence of disease or insects
2. Have a sweep net with you to check for insect presence (no net? Your hat will work).
3. Sweep 10 times and take a look. Note: some caution here: when replacing your hat to it’s holder, keep in mind that you may have captured some stinging or biting insects, as well.
4. The new growth on the crown signals crop vigor and time to bring in the mower.

Be aware of cut height and be careful not to shatter the new growth or damage the crowns. Tracking yields and quality along with knowledge of nutrient applications will assist in making future nutrient supplementation following harvest. Look back to those observations while evaluating stands and formulating a feed plan.

For every ton of dry matter (DM), the removal of nutrients is 60 pounds of Nitrogen, 12 pounds of Phosphorus, 60 pounds of Potassium, 5 pounds of Magnesium, 28 pounds of Calcium, and 5 pounds of Sulfur. Alfalfa will also respond favorably to Boron – a micronutrient that is limited in the soil and is highly leachable.

Applications following harvest of Potassium, Magnesium, Sulfur, and Boron will help maintain yields and plant health. Although alfalfa is a Nitrogen fixer, most varieties are only 65 – 80% efficient in gathering enough Nitrogen to support rapid regrowth, so do not forget to add the Nitrogen. Adding Nitrogen with top dress can be beneficial.

Just remember that when evaluating the proper time to cut, you may also want to take the opportunities to check for and address abnormalities, insects, or disease pressures. Taking care of alfalfa will help future forage quality and soil health.

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