How to Approach Failed Alfalfa Stands: The How’s? Why’s? And what to do next to prevent more failed stands in the future. Spring flooding has resulted in farmers dealing with – among other things – failed alfalfa stands. Widespread winterkill mean that some farmers had to write off as much as 80 percent of their stands. Portions of surviving stands also were lost.
To soften the blow, additional alfalfa stand were seeded and then, to add insult to injury, those stands were lost as well. So was reseeding alfalfa back into the fields a good decision? Maybe. Maybe not.
Once a stand of alfalfa is killed – regardless of how – the autotoxic compounds are released into the soil. How long they remain and what affect they have on a new alfalfa seeding depends on several factors, including:
Time Between Seedings
On sandy soils, toxins are more available and more easily taken up so the autotoxic effects are more severe. However, they also don’t stick around as long because the toxin is believed to leach faster through the root zone. Heavier textured soils like clay mean the toxins are better adsorbed in the soil particles. The results are less distinct but last longer.
Autotoxic compounds are microbially degraded over time, so warm, moist soils reduce the persistence of the toxins. Tillage also affects the level of toxins in soil. More aggressive tillage will better mix and dilute the toxins.
The age of the existing alfalfa stand also has an impact on autotoxicity with younger plants containing fewer toxins than older ones. The time between eliminating an old stand and planting a new one greatly impacts the effects of autotoxicity, as well. The impact of autoxicity is lessened the longer you wait to seed a new stand. Studies show that the density of an alfalfa stand doesn’t make much of a difference on autotoxicity.
Farmers who lost an entire established alfalfa stand to winterkill that was seeded before last year, should wait to reseed that field until next year. Most experts agree that it’s best to have one year between the termination of an existing stand and the seeding of a new one.
Lost alfalfa stands seeded last spring or fall, can be reseeded with alfalfa without worrying too much about autotoxicity. The same goes for new seedings from this spring. In those cases, you might want to reseed during late summer. Another option is to interseed into the thin or dead areas.
If there are large dead patches in otherwise productive stands, experts suggest filling those patches with something other than alfalfa. Perennial cool-season grass, red clover or ryegrass are good choices for long-term production. Small grains work only for one-cut options.
When alfalfa stands become thin, you may be tempted to no-till alfalfa into the existing stand. This is not a good ideas since plant competition and autotoxicity work against the development of seedlings. If you are interested only in thickening the stand, use a species besides alfalfa. Seeding orchard grass into thinning alfalfa stands may allow you to get a few more years of production.