By Scout Nelson
Cold nighttime temperatures during late spring are raising concerns among forage producers about possible frost injury in alfalfa fields. Although alfalfa is known for good cold tolerance, freezing temperatures can still damage leaves, buds, and stems when cold conditions last for several hours.
Sara Bauder, SDSU Extension Forage Field Specialist, explained that minor frost damage may occur when temperatures remain slightly below freezing for several hours. More serious injury may develop when temperatures fall below 25°F for four hours or longer. Newly seeded alfalfa often handles cold conditions better than older stands, but seedlings become more vulnerable after reaching the second trifoliate leaf stage.
Alfalfa planted with a nurse crop may survive freezing conditions better than stands seeded alone. Older plants may also lose winter hardiness over time, increasing the risk of injury during late spring freezes. If temperatures remain in the upper 20s, damage may only affect exposed leaves near the top of the canopy and may not greatly reduce yield.
Several conditions influence frost damage, including soil temperature, soil moisture, field location, crop age, and surface residue. Specialists recommend waiting two to four days after a frost event before evaluating fields for injury. Wilted leaves, blackened leaf edges, and brown stems may signal varying levels of frost damage.
When only leaves are affected and buds remain healthy, yield loss is usually limited, and harvest can continue as planned. More severe injury occurs when entire stems wilt and turn brown, which may indicate damage to the growing point. However, new shoots can still develop from crown buds and leaf joints, helping plants recover over time.
If frozen stems reach 20 inches or taller, harvesting may still provide quality forage. Nitrate levels may increase after frost conditions, but dangerous toxin levels are generally not expected in alfalfa top growth.
Maintaining soil fertility and allowing plants to flower before the second cutting may improve stand recovery. While some fields may experience seasonal yield losses, many areas are not expected to face major damage unless freezing temperatures remain for extended periods.
Photo Credit: gettyimages-gabrielabertolini
Categories: South Dakota, Crops, Alfalfa, Sustainable Agriculture