By JEFF BURBRINK
Extension Educator, Purdue Extension Elkhart County
GOSHEN — I have had several people ask about when the final cutting of alfalfa should be taken. It is a very good question, because if the timing is off, the plants can be weakened and damaged over the winter.
It is recommended that the final cutting of alfalfa be removed no later than 4-6 weeks before the first killing frost. Our average first 32 degree killing frost for Elkhart County falls between Oct. 11-20th. Using that as our target, the last cutting of alfalfa should occur no later than Sept. 1-10th, approximately.
Why? By cutting no later than Sept. 10, we are allowing the alfalfa time to regrow and store the necessary nutrients, particularly carbohydrates, to help the plants over-winter and begin growth in the spring.
Before deciding whether or not to make a final cutting later than the traditional, “safe” harvest window of 4-6 weeks before a killing frost, there are some other considerations. Some of the new varieties of alfalfa are said to be more winter-hardy. The improved winter-hardiness could possibly allow the alfalfa to withstand a slightly later cutting.
The age of the stand can be a factor too. Typically, older stands of alfalfa are more prone to winter kill and should not be mowed past the recommended 4-6 week “critical period” before a killing frost.
In fields where the soil pH is above 6.5 and soil fertility has been maintained well, as well as being well-drained, a later cutting is a possibility. Fall cuttings of alfalfa should have a 6 inch stubble height to ensure enough plant material is present to photosynthesize and rebuild carbohydrate stores necessary to over-winter.
It is important to remember that taking a later cutting (after the critical period before a killing frost), spring yields may suffer, especially with the first cutting. So when deciding whether or not it is worth it for your operation, the benefits need to be weighed with the risks.