It is recommended to allow a minimum of 30 days between the last harvest and the first killing frost in the fall to allow alfalfa plants time for sufficient carbohydrate accumulation. It is important to know the average date of the first killing frost in your area when determining the last harvest date. Frost-freeze dates for Chouteau County are estimated with 90% accuracy. Big Sandy is September 21, Fort Benton and Geraldine are September 24, Loma is September 22, and Iliad is September 18. It is equally important that a stand is healthy, with adequate soil nutrient reserves, entering winter. The healthier the stand, the lower the chance of winter injury and/or winterkill occurring.
Stand age, productivity, and health also have implications on the likelihood of winter injury occurring. After harvesting is usually a good time to evaluate stand health. Once the plants have reached approximately two to three inches in height, it is practical to do a stem count. In order to do this, you can use a PVC or metal square that measures approximately 1 foot x 1 foot. Throw the square randomly throughout your field in 20-30 spots and count the number of stems within each square.
A healthy, productive stand will have at least 55 stems per square foot. A “marginal” stand will have somewhere between 40 and 55 stems per square foot, and an unhealthy stand will have less than 40 stems per square foot. Plant counts are also helpful, although a little more difficult to quantify. In a healthy stand, the goal is to have at least three plants per square foot. Sometimes it can be hard to tell whether a given plant is coming from one crown or two, as plants can become intertwined, making them indistinguishable from one another.
The complete article titled Fall Considerations of Alfalfa was written by Emily Glunk, former Montana State University Extension Forage Specialist, and is located at The Montana State University Extension Forage Website located at http://msuextension.org/magazine/articles/1344.
Montana State University U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action provider of educational outreach.
