Overcoming acid soil sensitivity in alfalfa

Authors: Samac, Deborah; MISSAOUI, ALI - University Of Georgia

Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: 3/10/2026
Publication Date: 4/15/2026
Citation: Samac, D.A., Missaoui, A. 2026. Overcoming acid soil sensitivity in alfalfa. Forage Focus. March 2026:16-17.

Interpretive Summary:

Technical Abstract: A key factor in successful alfalfa establishment is to test soil pH and make timely adjustments. Alfalfa grows poorly in acidic soil below pH 6.7 and there are currently no commercially available alfalfa cultivars with tolerance to low pH. In acid soils with a high mineral content, the primary factor limiting plant growth is toxicity from aluminum and manganese, which become soluble at low pH, and are taken up by plant roots resulting in root stunting and cracking. Acid soil should be treated with lime at least 12 months prior to seeding of an alfalfa stand, preferably with the rotation crop, to allow for reaction with the soil and remixing with tillage. However, liming is not practical in some locations and can be uneconomical for large areas, or where transportation costs are prohibitive. The most effective strategy to improve alfalfa production in low-pH soil is the development of cultivars with improved tolerance to low soil pH and aluminum. Several methods for screening plant materials with acid soil and aluminum tolerance have been devised. For alfalfa, experimental populations developed from selection done in greenhouse conditions and in cell culture were never commercialized due to poor forage production in field conditions. More recently, scientists at the University of Georgia have identified low pH tolerant germplasm starting with field performance and yield in low pH soils, then used the germplasm for pre-breeding and to understand the mechanism of tolerance. A collection of 1,200 alfalfa accessions from areas around the world with low soil pH were screened for 4 years in low pH soil pH a high aluminum concentration. The top 200 accessions were advanced for testing in additional locations. With funding from USDA-NIFA-Alfalfa Seed and Alfalfa Forage Program, plots will be established in Spring 2026 in four states (Georgia, South Carolina, Alabama, and Minnesota) in locations with low soil pH. Each line will be evaluated for biomass yield, plant architecture, winter hardiness, and fall dormancy over two production years. Root system architecture will be evaluated at the end of the experiment. The lines at each location with greatest yields and other positive traits will be used to create new experimental populations and to identify DNA markers associated with low pH tolerance. These experiments will identify alfalfa genotypes with acceptable yield under low pH conditions and characterize the inheritance of yield and stand persistence in low pH soils. Additionally, resources will be developed to allow alfalfa breeders to incorporate low pH and Al tolerance in adapted cultivars that will benefit growers.