Preparation for planting alfalfa in a field starts about 18 months to 2 cropping seasons prior because of herbicide rotation restrictions and need to adequately manage soil pH in some fields. Alfalfa is the 3rd most grown crop in Gage, Jefferson, and Saline counties after corn and soybeans. There was approximately 16,000 acres of alfalfa grown in 2022 in the three counties with around 5,600 acres in Gage, 5,100 acres in Jefferson, and 5,400 acres in Saline based on data from CropScape.
In terms of herbicide rotation restrictions, we need to count back the months from our two primary alfalfa planting windows in southeast Nebraska that are August and April. As of today, there are situations where it wouldn’t be recommended to plant alfalfa until spring of 2025. To learn more about herbicide rotation restrictions, please consult the label on all herbicides used in the prior two crops. For example, Warrant Ultra is labeled for soybeans and can be applied through beginning bloom (R1) stage of soybeans. The Warrant Ultra label states “to avoid crop injury do not plant alfalfa, sunflowers, sugar beets, grain sorghum within 18 months.” If Warrant Ultra was used as a postemergence product in June of 2023, it would be advised to not plant alfalfa until April of 2025. As a reminder, abnormally dry conditions and drought can lead to a slower breakdown of some herbicides. Therefore, start evaluating your intended spring herbicide programs for corn, soybean, and wheat now on potential fields where you would like to rotate to alfalfa in the future.
Managing acidic soil is critical for all crops, but even more so for alfalfa. Learn more about lime use for soil acidity management in our NebGuide G1504 at extensionpubs.unl.edu. Alfalfa is more easily established and more productive during the life of the stand with a soil pH between 6.2 and 7.5 in the top 6 to 8 inches. There is some variation in the target pH (6.3 to 6.9) to reach in acidic soils due to regional differences in subsoil pH and research/recommendations from nearby land-grant universities. It can take 2 to 3 years for Ag lime to reach its full effect on neutralizing soil acidity. Some are thinking why not use pel-lime. Yes, pel-lime is the finer and most reactive part of ag lime, so it reacts quickly in the first 6 months. However, pel-lime rates are often too low to be able to move the current soil pH to the target pH.
The initial soil buffer pH, lime quality, lime rate, tillage/incorporation, and weather are all factors impacting how long prior to planting alfalfa steps on managing soil pH should start. I would suggest the same time frame as we discussed for herbicides, 18 months to 2 cropping seasons. Look at your most recent soil test results from your preferred fields to plant alfalfa in next. The quickest solution to managing soil pH may be in front of you, pick the field that doesn’t have low soil pH! I encourage landowners and renters to reach a reasonable agreement through lime cost sharing, adjusting cash rent, or guaranteed land tenure and reimbursement given the importance of soil pH in the short and long-term.
For inquiries about these and other agronomy-related information from Nebraska Extension, contact me at or 402-821-1722. Know your crop, know your tech, know your bottom line at croptechcafe.org.
