Alfalfa Fall/Winter Management

• Select alfalfa varieties that have good winter hardiness ratings and that are resistant to crown and root diseases. Dryland or creeping-rooted varieties generally have a better winter survival rate. Plants that have larger and deeper-set crowns are protected from physical damage and tend to have a lower incidence of winter injury.

• Alfalfa grows best in a soil pH greater than 6.5. If the pH is less than 6.0, there is a greater risk of winter injury.

• Good snow cover prevents winter injury. Leave enough crop residue as a snow catch and insulation, even without snow catch this layer of stubble/trash helps. Leave at least six inches of stubble (15 cm) or uncut strips to act as a snow catch.

• Winter injury also results from a lack of carbohydrates, or energy reserves, being stored in the roots and crowns before the first killing frost. Alfalfa will experience a killing frost when the temperature goes below -5 degrees C.

• The more times you cut alfalfa, the higher the potential for winter injury. If the interval from the last cut is less than 40 days, avoid harvesting during the fall critical period. The fall critical period is 4 to 6 weeks before the first killing frost.

• If cutting during the critical period, weigh the risk of winter injury and the need for cattle feed. Do not cut alfalfa during the fall critical period two years in a row.

• Under poor drainage conditions, there is a higher incidence of winter injury. High fall soil moisture retards plant dormancy and may lead to winter injury. Dormancy refers to a number of developmental and physiological changes that occur in response to decreasing day length, reduced air temperatures and drier soils. Drier soils are also better insulated that wet soils.

• Balanced fertility produces healthy plants and offers protection. Potassium is vital for developing plants, disease resistance and good winter survival. Low soil potassium hinders the root storage of carbohydrates and reduces the plant’s ability to get ready for winter. Phosphorous also aids in good root development and promotes vigourous spring growth.

• Young alfalfa stands are more resistant to winter injury. The roots and crowns are healthier with less traffic damage and fewer diseases.