By Justin Brackenrich and Jessics A. Williamson
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, root mass, as well as store carbohydrates at the base of the plant to overwinter.
Cutting grasses too late and too low during the later parts of the year, will result in the removal of the carbohydrates the forage stored all summer long. This loss of carbohydrates will reduce bud formation and crown tissue, and inevitability lead to a lower yield in the spring of the subsequent year. Information provided by Michigan State University says that removing 50% of less of leaf mass will result in little to no damage to root structure. After a 50% removal, the damage is great. This is very important when considering winter cutting management and how the plant can bounce back from this harvest and its winter survivability.
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 and restore roots to over-winter and begin growth in the spring. Before deciding whether 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. With that said, it is always important to understand your variety and know that improved winter heartiness does not mean push the envelope as far as possible.
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, especially potassium, 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 it is worth it for your operation, the benefits need to be weighed with the risks. Often in fall cuttings the yields are low, but the machinery costs are the same as any other cutting. This makes the price per ton very different. Make sure to factor this into your decisions when thinking about cutting or not.Source : psu.edu