By Lynnae Ylioja, MSs, AAg, Range Management Extension Specialist, Outlook
February 2025
The decline of legumes over time in a perennial pasture stand is a common challenge in the Prairies. Incorporation of a legume in a hay or pasture stand results in higher quality feed compared to a grass mix, while helping to meet fertility requirements through nitrogen fixation. While the longevity of legumes varies by species, management practices play a much larger role in how long those plants persist in a stand. Good grazing and haying practices and proper fertility are essential for maintaining those legumes.
When a producer is considering reintroducing a legume into a pasture where the legume component has declined, they may want to consider the following:
- It is generally not economical to add a legume back into a stand that still has over 50 per cent legume component.
- Autotoxicity can be problematic for reintroducing alfalfa into an old alfalfa stand if there is more than one plant per 12-18 inches². Autotoxicity is a process where old alfalfa plants release a chemical into the soil to reduce the establishment of new alfalfa seedlings.
- If alfalfa autotoxicity or disease is an issue in your stand, consider rotating to a different legume like sainfoin, red clover or Cicer milkvetch. Sainfoin and Cicer milkvetches are both non-bloat legumes with yields only slightly lower than alfalfa.
- Reintroducing a legume into a stand may not always be the best method of rejuvenation for a pasture. Visit the Beef Cattle Research Council’s page on Rejuvenating Tame Pastures for more information on deciding which rejuvenation method will work best for your operation.
There are three factors that can increase the chance of establishment success when reintroducing a legume into an existing stand:
- Suppress the competition from the existing stand. This gives the established legume the chance to compete for light, water and nutrients. Suppressing the competition from the existing stand is often done with a heavy grazing event or a light herbicide application. It is important that heavy grazing is used in appropriate conditions and is not done while the soil is wet because this can lead to soil compaction.
- Maximize the seed to soil contact. Drilling in seed when possible is generally the most recommended method of seeding because it helps ensure the seed has good contact with the soil. Good seed-to-soil contact ensures that young seedlings are protected from the sun and temperature fluctuations while also having access to soil moisture, needed for germination. Other methods to improve seed-to-soil contact include using harrows after broadcasting or trampling the stand with livestock.
- Moisture is essential. Forages can be difficult to establish at the best of times, but without moisture, there is a low chance of success. Seeding forages late in the fall (frost or dormant seeding) or early spring is usually the best for taking advantage of existing moisture. Alternately, timing seeding with upcoming rain is an option. These factors vary greatly depending on the year and location. Note that when forages are seeded late in the spring or into the summer, there is often not enough moisture available to establish roots down far enough to reach the stable soil moisture supply, which is essential for seedlings to survive heat of the summer months. In these cases, the forages might germinate and die.
There is no prescriptive “one size fits all” recipe when it comes to reintroduction of legumes into an existing forage stand and producers may need to be creative to determine what works best within the context of their operation. The best method to ensure success will vary depending on the soil type, topography, pasture access and the level of moisture in any given year for that field. If you aren’t sure where to start, asking neighbours about their experiences will help you understand what works and what doesn’t in your area.
Regardless of location, focusing on suppressing competition, seed-to-soil contact and timing seeding with moisture availability will increase the chance of success.
For more information on rejuvenating old hay stands or pastures with legumes, please contact your local range management extension specialist or the Agriculture Knowledge Centre at 1-866-457-2377.