Fall options for thin alalfa stands | TSLN.com

Fall options for thin alalfa stands

Forage producers usually want alfalfa fields to produce for at least 4- or 5-years after seeding before being converted to another crop. So, what should producers do when their alfalfa stands fall below 10 plants per square foot; or a heavy weed populations emerge; or the annual forage yields drop off below half?

For thin alfalfa stands, the temptation may be to drill or broadcast more alfalfa seeds to fill open spaces between plants. However, this practice is NOT recommended; since live alfalfa roots emit an ethylene chemical toxin into soil impeding growth of new alfalfa. This allelopathy effect also called ‘autotoxicity’ weakens or kills any new emerging alfalfa. Autotoxicity also accumulates more in soil over time; meaning older alfalfa stands have increased toxin levels compared to newer stands. Therefore, it would be better to find a new replacement alfalfa field than seed into an existing thin stand.

The next decision for thin fields might be to delay mowing of the alfalfa to increase harvest tonnage. Once it has been decided to convert a thin alfalfa field to another crop, potential winter injury on plants lacking 6 or 8 inches of recommended regrowth is no longer a concern.

For retained thin stands, an updated weed control plan may be needed following herbicide label carryover rotation restrictions. Finally, consider interseeding with perennial grasses such as brome, fescue, orchard grass or native grasses to increase forage production for the next growing season.

The bottom line is wait 4 weeks to over a year after established plants have been killed before drilling new alfalfa seed into previous alfalfa field. Further, when converting a thin alfalfa field into an alternative ‘cash crop’ like corn or grain sorghum, opportunity arises for fall or winter alfalfa graze-out of thin alfalfa fields.

–UNL Extension

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