Every fall, there is interest in cutting alfalfa for the second time. The concern that always exists is that the cutting of alfalfa the second time in a season will affect the winter-hardiness of the crop and reduced yields will result the following spring. For some fields, this is a major concern. For other fields, this concern is something that is not a major issue. This article will deal with the issues that are related to cutting alfalfa stands in the fall.
A rule of thumb for fall cutting alfalfa is that there should be no regrowth of the alfalfa or six inches of regrowth. No regrowth will result when the alfalfa is cut and the ground is cold. This is when the alfalfa is cut later in the fall. Six inches of regrowth will result when we have 4 to 6 weeks of warm weather with warm soil temperatures. No regrowth means that the root reserves have not been depleted and the plant will go into the winter strong. If there is below six inches of regrowth on the alfalfa plant, this means that there will be some depletion of the root reserves and the plant is more susceptible to winter injury.
Newer fields are less susceptible to winter injury. Young, healthy plants will be less likely to suffer from winter injury. With older alfalfa plants, there is generally some crown injury that has occurred over the years. This crown injury makes the plants less tolerant to cold soils and therefore the likelihood of injury increases. With the older fields, the likelihood of winter injury is higher and poor timing of cutting of the alfalfa will increase the likelihood of injury.
Wet soils are less likely to have winter injury with alfalfa plants. Wet soils have less dramatic temperature swings through the winter months. Quick temperature swings in the soil can do damage to alfalfa stands. It takes time for alfalfa plants to harden off in the fall. If a dramatic temperature swing occurs in late October or early November with no snow cover, the risk of crown injury goes up. This is less likely to happen in a wet soil.
Leaving strips of uncut alfalfa in a field that is cut in the fall will help reduce winter injury potential. These strips have the potential to catch snow cover and provide a thicker insulating blanket of snow for the alfalfa through the winter. This means that the likelihood of seeing an extremely low temperature is less.
Cutting alfalfa for a second time in a year can be a profitable venture with healthy fields. Proper fertility is essential to have success with taking a second cut. Timing related to fall frost is important. Older stands will be more likely have issues than younger stands. Stands that have adequate soil moisture are less likely to have a problem than dry fields. Consider these facts when looking at whether to cut your alfalfa filed for a second time this year.
By Dave Cubbon, P Ag