How Late Is Too Late To Harvest Alfalfa In The Fall?

By Jessica A. Williamson

Extension Forage Specialist

With the dry summer that was bestowed upon most of Pennsylvania these past few months, many farmers are finding themselves short on necessary feed to get through the winter and may be pushing the limits to get one last cutting in. When it comes to harvesting alfalfa for the final cutting, how late is too late?

Most of Pennsylvania experienced a very dry summer, possibly inhibiting the “normal” yields that would be expected from forage crops, causing a shortage in feed to get through the winter. With more and more farmers planting emergency forages this fall to fill the void, the thought of taking a later cutting of alfalfa also lingers.

Historically, it is recommended that the final cutting of alfalfa be removed no later than 4-6 weeks before the first killing frost – and this advice is still viable today! This will help ensure plants have adequate time to regrow and store the necessary nutrients to over-winter and begin growth in the spring. Before deciding whether or not to make a final harvest later than the traditional, “safe” harvest window of 4-6 weeks before a killing frost, several aspects should be assessed.

With more winter-hardy varieties of alfalfa available, tradition is beginning to be tested with producers taking their final cutting later into the fall. If winter-hardiness is part of the improved genetics utilized on your operation, the improved winter-hardiness could possibly allow the alfalfa to withstand a slightly later cutting.

Stand age is also indicative of whether or not a later cutting should be removed. 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. If the alfalfa stand has not been allowed to flower at least once during the growing season, no matter the variety, it is at a much higher risk for winter kill and therefore should not be harvested after the 4-6 week period before a killing frost.

If there is proper soil pH and fertility, 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.

Source:psu.edu