County Ag News
Alfalfa fields will continue to produce for a number of years. However, after three or four years the stand declines to a point where the amount of alfalfa is minimal resulting in very low yields of hay or forage. At this point producers wonder what their options are to either seed additional alfalfa or to interseed with other plants such as clover or grasses.
Attempts to thicken an existing stand of alfalfa by interseeding more alfalfa will not be successful due to autotoxicity. Autotoxicity in alfalfa is described as a process in which established alfalfa plants produce a chemical or chemicals that escape into the soil and reduce establishment and growth of new alfalfa if seeded too soon following the old stand.
Studies have shown that a field should be planted to an alternative crop for two years before seeding it back into alfalfa. Research suggests that the benefits of overseeding on yield are not seen unless the alfalfa stand is less than 5 plants/ft2 or 40 stems/ft2. Older alfalfa stands that carry a heavy weed load of species such as dandelion or quackgrass may be better candidates for rotation to another crop rather than for overseeding to extend the stand life.