Since harvesting during the hardening period disrupts carbohydrate accumulation in the roots there is increased risk of stand loss associated with fall harvesting. This leads to the traditional recommendation not to harvest alfalfa 4 to 6 weeks before the first killing frost. However, advances in alfalfa breeding and overall alfalfa management allow greater flexibility in fall harvest management than traditionally recommended. The real question is a economic gamble. Alfalfa that has been drought stressed this summer has had extended periods between harvests and has had an opportunity to build up root carbohydrate reserves over a year with normal rainfall.
Young stands are less susceptible to winter injury due to fall harvesting than older stands.
Length of harvest interval during the growing season is more important than date of fall harvest in determining alfalfa stand survival. Maintaining soil fertility levels is extremely important in reducing risks associated with fall harvesting. 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.