As we move into alfalfa planting 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. 

How to use the alfalfa rotation restriction tables

The documents presented below compile rotation intervals, notes, and pertinent footnotes relating to alfalfa for common herbicides used in Wisconsin corn, soybean, and wheat production. Only herbicides with restrictions ≥8 months for corn and soy and ≥4 months for wheat are presented. For a more complete list of rotation restrictions, including other forage and cover crops, please reference Extension’s Herbicide Rotational Restrictions for Cover and Forage Cropping Systems publication. To view current labels online, visit the WI DATCP website.

The information presented here is compiled for convenience and reference only. Always read, follow, and understand the herbicide label. The label is the law. Always refer to the original label on the product when making final management decisions. 

Special thanks to Colin Van de Loo for help in compiling these data.