Estimating Optimal Time to Cut Alfalfa
Every grower tends to have a different strategy of when to begin cutting alfalfa. Some cut on a certain date in May no matter what and continue the cycle every 28 days. Some growers wait until the alfalfa has reached about 10% bloom, which historically provides a good balance between the highest yield without compromising quality.
To measure quality for an area of the field, you could use the scissors technique. This is a good method, but it takes a couple of days to get results from the lab. During that time, the plant has changed.
Another method used to estimate the optimal first cutting date for alfalfa is Predictive Equations for Alfalfa Quality (PEAQ) method. Developed by the University of Wisconsin, PEAQ uses the alfalfa stand height and maturity stage (vegetative, bud or open flower) to estimate the relative feed value (RFV). In general, it is recommended to harvest alfalfa at about 150 RFV for milking dairy herds and 125 RFV for heifers, stock cattle and lactating beef cattle.
You can order an actual measuring stick or use a tape measure and follow these steps as outlined in the May 2021 issue of “Integrated Crop Management News” by Iowa State University Extension and Outreach:
- Choose a representative two-square-foot area in the field.
- Determine the stage of the most mature stem in the area by using the definitions at the top of Table 1.
- Measure the tallest stem in the area. The tallest stem may not be the most mature stem. Measure the stem from the soil surface to the tip of the stem, not to the tip of the leaf. Straighten the stem for an accurate height measurement. Based on stem maturity and stem height, use Table 1 to estimate the RFV of standing alfalfa crop.
- Repeat steps 1-3 in five representative areas across the field.
- To estimate harvest quality, subtract 15-25 RFV units to account for harvest losses during the haylage or hay harvest process, respectively.
- Determine optimum harvest time using the PEAQ estimate, livestock forage quality needs, considerations of upcoming weather forecasts favorable for harvest and drying, and the general assumption that RFV drops three to five points per day.
Alfalfa value is based on quality. For quick calculation, the old standard of $1/point of RFV. (NOTE: The current market is worth more than $1 per point, but we’re going to stick with this for easy math.) If your RFV is 200, one dry matter ton of this forage is worth $200 / dry matter ton. In the Midwest, four cuttings of alfalfa can yield 5 to 7 tons.
High commodity prices also have us reflecting on ways to extend our alfalfa stand. It’s best to keep your cutting equipment sharp. It’s generally recommended to cut a pure stand of alfalfa at two or 2.5 inches from the ground. If you have a mixed species with grass in the mix, cutting it at 2.5 to 3 inches helps maintain the grass stand life.
Good fertility programs, insect management programs and fungicide treatments also impact the quality of alfalfa and corn silage. We will provide information about these topics as the growing season progresses.
Check out other alfalfa articles on The Field Position.