Alfalfa always seems to look best this time of year. It helps that we are past the evils of the alfalfa weevil, potato leafhopper and hopefully fall armyworm. Alfalfa looks so good in fact that it is tempting to take one last cutting in this season. Yet we know it is good management to give alfalfa a fall rest before winter to allow root carbohydrate reserves to replenish. So how do you decide if it is okay to make a late summer harvest of alfalfa? First, alfalfa really does need a rest period during the fall to recharge root reserves and survive the winter. The last harvest should come four to six weeks before the date of the first killing frost for your area. For most of Kentucky this will mean taking that harvest before September 15 to October 1. Alfalfa then has the next four to six weeks to regrow enough to replenish the root carbohydrates. After the first hard freeze (24o F or lower), or November 1, a final harvest can be made.
Cutting alfalfa stands during this critical fall rest period will affect the plant response the following year. It can reduce the speed of regrowth in the spring and may reduce the yield of the first cutting. In the worst case, stands may be thinned. The decision to cut or not is not simple. Here are some situations where cutting alfalfa late in the year may be justified.
1) If you need the feed. If you don’t have enough forage for the winter, then taking a late cut is a risk worth taking.
2) Alfalfa well rested and mature. Winter injury from a fall harvest is less if the stand is in bloom at the time of the fall cut, or it has been at least 45 days since the last harvest.
3) The variety has a good disease resistance to the major pathogens of alfalfa like root rot, and wilt.
4) The field has been well managed during the year. Good management would include harvest intervals of 30 days or longer, good weed and insect control, and good soil fertility.
5) To get a companion grass established. Companion grasses such as orchardgrass are often added to alfalfa in the fall. When alfalfa top growth is excessive, the new seedlings cannot compete and establishment is likely unsuccessful. Making a fall cut may be needed to allow for successful grass interseeding.
6) The stands are established but young. Stands that are 18 to 36 months old can withstand fall cutting better because their crowns have less damage due to traffic and root disease.
Deciding whether to cut an alfalfa field in late September or early to mid-October is an individual judgment that should be based on the benefits of the extra yield and quality outweighing the risks of yield and stand loss the following year. Keep in mind that you will never hurt the stand by not cutting during the traditional fall rest period. Happy foraging. ~ Jimmy Henning, for Farmers Pride.