High alfalfa seeding rates result in more seedlings, a canopy that’s more competitive with weeds and a higher first-year forage yield. A longer-lasting stand may be another benefit, say agronomists at Penn State University and the University of Missouri.

In four trials, they spring-seeded three varieties at rates ranging from 3 to 22 lbs/acre. First-year yields were similar at all seeding rates above 3 lbs/acre. The number of plants per square foot decreased fast during the first two years, then the reduction slowed. But higher seeding rates maintained more plants per acre than lower ones.

After five or six years, high-seeding-rate stands were still thicker. But yields were similar for seeding rates of 6 lbs/acre or more because plants in low-seeding-rate plots produced more shoots per plant.

The researchers point out that shoots develop in response to light at the crown level and must compete with weeds to exploit openings left by the death of adjacent plants. They conclude that high seeding rates may contribute to both longer-term weed control and stand longevity.