Mark Renz, Associate Professor and Extension Specialist, University of Wisconsin
This summer is shaping up to be a great year for volunteer wheat in our late summer seeded alfalfa stands. This “weed” often raises questions about whether it should be managed or not in alfalfa stands. It can provide valuable forage the following spring (1-2 tons DM/A) but its forage quality is less than alfalfa and dense infestations reduce alfalfa survival. To better understand these issues and what the impacts of successful control would be we established experiments at three locations throughout Wisconsin. Results are summarized in this factsheet. Key points are below. Based on results we recommend maintaining volunteer wheat biomass so that it is < 35% of the total forage the following spring. This will minimize the impact to alfalfa stand density while providing high yields the following spring. To attain this level of control we recommend applying an herbicide that will provide at least 70% control of volunteer wheat in the fall.
- Glyphosate and sethoxydim applied when volunteer wheat is 4-6 inches tall provided high levels of control that persisted through spring resulting in near pure stands of alfalfa.
- Controlling volunteer wheat protected alfalfa stem density, with applications to 4-6” tall wheat providing 22% higher stem density than later timings (6-12” tall).
- Yield the following spring was highest in treatments with low volunteer wheat control but wheat was between 47 and 85% of the forage biomass.
- Forage quality was reduced in treatments that had substantial amounts of wheat in the forage (> 35%) resulting in approximately a 5% reduction in Milk/ton of forage.