Alfalfa Herbicide Rotation Restrictions

Scott Newell – Alfalfa Outreach Specialist, Dr. Mark Renz – Associate Professor, Perennial Crops Extension Weed Specialist

Planting is expensive. Checking the label isn’t. Avoid costly mistakes when seeding alfalfa and check rotational restrictions now!

As we move into alfalfa season in Wisconsin, it is important to double-check herbicide records for the field you will be planting into. Many common herbicides used for commercial crop production contain restrictions on the label when rotating to alfalfa. A rotation restriction is the interval between herbicide application and when alfalfa planting can occur with no injury under normal conditions. Planting alfalfa before the recommended rotation interval stated on the label may lead to injury of the stand or even establishment failure.

Fighting the advent of more herbicide-resistant weeds in commercial agriculture, we are seeing more mixtures of active ingredients (AI) and more use of soil-incorporated pre-emergent herbicides to control them. By their nature, these AI have residual efficacy to control weeds through the season and require a combination of warm temperatures and adequate moisture to break down. Many of these can have adverse effects on alfalfa establishment if residual levels are high enough, so the registering companies have studied the time from application at which there is little risk of alfalfa injury.