Alfalfa can be successfully seeded in the spring or fall depending on field weed populations, moisture conditions and timing. Based on higher snowfall, our 2023 spring may be a very successful time to establish new alfalfa stands.
Although it may be tempting to drill or broadcast more seeds into open spaces in thin alfalfa fields, remember that live alfalfa roots emit an ethylene chemical toxin which impedes new alfalfa growth. This “autotoxicity” weakens or kills any new alfalfa plants and accumulates in soil over time. Therefore, it is better to drill into new fields than seed where previous older alfalfa plants have been grown within the past one to two years.
Once established, alfalfa as a perennial can compete well with weeds. If herbicide-resistant weeds are currently growing on fields, then light tillage may be needed to control weeds while creating a firm drilling seedbed. Also, combination light tillage plus herbicide may provide improved seedling establishment.
Since new alfalfa seedlings are very susceptible to herbicide injury, carefully follow any chemical label restrictions. Usually, new alfalfa plants must reach two to four trifoliated leaf development before herbicides are applied; note that 2,4-D usage is not recommended.
Glyphosate-tolerant or Round-Up Ready varieties provide more flexibility for controlling weeds currently growing in fields. Initial glyphosate application should occur between alfalfa emergence and fourth trifoliate leaf growth stages to remove non-glyphosate tolerant alfalfa seedlings and control weeds that are present.
Target seeding 1/4 to 1/2 inch depth in fine-textured soils and 3/4 inch depth in sandy soils. Seedlings placed too shallow will dry out rapidly and die due to poor roots. While seeds planted more than one inch deep may be unable to emerge after germinating. Further establishment guidelines are outlined in the University of Nebraska-Lincoln “Seeding Alfalfa” NebGuide G2247. — Todd Whitney, Nebraska Extension educator
