Fall is an important time to ensure that hay fields are properly managed, and attention is paid to details that will help to ensure their survival through the winter. Fall harvest management can be the greatest determining factor of forage stand longevity.
Regardless of whether the hay field is grass or legumes, residual height should be a primary concern for the last cutting of forage. Ensuring proper residual height will allow the forages adequate leaf material to photosynthesize and regrow top growth, as well as store carbohydrates at the base of the plant to overwinter. Grasses should not be cut lower than 4 inches in the fall, but a residual height of 5 inches or greater would be preferred.
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.
Alfalfa stand age is also indicative of whether 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 no less than a 4-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.
In both grass and legume hay fields, the fall is an ideal time to apply lime if the soil pH is not ideal for the desired crop. The weather patterns throughout the winter allow the lime to neutralize the soil during the non-growing season, in turn resulting in a less acidic pH in the spring during the growing season. A current soil test is the best way to determine if and how much lime is recommended for a hay field.