Use of disease resistant and winterhardy alfalfa varieties will greatly decrease the risk of winter injury due to fall harvesting. Environmental conditions will moderate or aggravate the effects of fall harvesting. Fortunately, the soil and snow generally insulates the crown and root from dangerously low temperature. Amount of snow cover determines the amount of crown and root protection from cold temperatures. Snow cover greater than 6 inches is usually adequate to insulate the crowns and roots from low air temperatures.
Soil moisture is important because water is a better conductor of heat than is air.
Wet soils cool faster than dry soils which may lead to lower soil temperatures. In addition, wet soils will freeze and thaw more extensively which increases the potential for frost heaving. Summer drought stress of alfalfa will reduce the risk of harvesting during the 4 to 6 week dormancy period. Summary Although fall harvesting increases the risk to long-term stand persistence compared to not fall harvesting, it should be considered a management alternative to allow flexibility in alfalfa harvest scheduling. Fall harvesting of alfalfa that has been drought stressed will cause less stand thinning than fall harvesting alfalfa that has not been drought stressed.