Modern disc mowers are good at what they do. They can mow at alarming speeds, bounce over rocks and ruts, and cut close enough to make a field look like a fairway. Yet, how close is too close when it comes to cutting height for most forage crops?

Alfalfa is a good candidate for a low cutting height to maximize yield. The plants always regrow from crown buds, and the old stems don’t offer much benefit to the plant. As long as the crown isn’t damaged, alfalfa can be cut at whatever height meets the farm’s goals for ash content, yield, and digestibility.

The same can be said for most forage legumes (birdsfoot trefoil being an exception). Forage quality will always be reduced with lower cutting, but even the base of the alfalfa stem has some digestible nutrients that are worth feeding to certain animal groups.

Mix that alfalfa with grass, however, and the equation may change. In contrast to alfalfa, most forage grasses benefit from the stubble left behind. A high cutting height of 4 or more inches will favor the grass in the stand, while a low cutting height will favor the alfalfa. Thus, a close cut may be a good way to help manage overly aggressive grasses and could help keep the alfalfa as the dominant species in the field.

Pure grass stands can handle a large variation in cutting height, but most species prefer to be cut at around 4 inches. Some annual grass species, such as sorghum sudangrass, must be cut at 6 or 8 inches in order to facilitate future harvests.

No matter what forage crop you are mowing, cutting height is always a controllable factor that affects yield, quality, and potentially the life of the stand. While some operations may be able to tailor their cutting height to meet the needs of certain forage species, animal groups, or other criteria, the reality is that most farms will use the same mower for everything. At Miner Institute, we have found that leaving 3.5 inches of stubble seems to be a good compromise for the alfalfa/grass mixtures on our farm. Choosing your cutting height wisely is an easy step that could pay you dividends in the long run. Cut it close if you choose, but don’t cut into your bottom line.

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(c) Hoard's Dairyman Intel 2024
June 27, 2024
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