Dairymen often demand the very highest quality hay for their cows. As a result, alfalfa producers are encouraged to cut their hay earlier and earlier. How do these shorter cutting intervals affect the productivity of the alfalfa?
When alfalfa is cut, the plant uses energy stored in the roots to regrow. The alfalfa plant continues to draw on the roots until the top growth is about 8 to 12 inches tall. Then the plant has enough leaf area to provide not only for continued growth, but to put some energy back into the roots for storage. The longer the alfalfa is allowed to grow, the more energy can be stored in the roots.
A continual short cutting schedule, such as continually harvesting in the bud stage or earlier, will not allow the alfalfa to sufficiently replenish root reserves before being cut again. The result is a plant that is continually getting weaker and will not be vigorous, compete well with weeds or withstand disease. For this reason, many stands in this area quickly become weedy and need to be taken out after only a very few seasons.
Dairy quality hay is cut in the bud stage. At this stage, the crown bud regrowth is less than 1/2 inch on 10 to 50% of the crown. The 1/10 bloom stage is when 50 to 75% of the crown have regrowth from 1/2 to 3/4 inches tall. Cutting in the bud stage throughout the season compared with cutting at 1/10 bloom will reduce yield by 15%, increase weediness by 200% and increase harvest costs by 1/3 (more cuttings per season).
In a 2 year, 2 location study, cutting sooner than 30 days in the spring and fall gave only a little higher TDN (52.2 @ 30 days vs. 52.7 @ 22 days in May; TDN same @ both days in September) but up to 1/2 ton more yield. In the summer, cutting at 22 or 26 days gave the highest TDN but yields were much lower. Because alfalfa does not mature at the same rate throughout the season to optimize yield and quality it is not possible to cut on a fixed schedule, even though this is certainly most convenient. Cutting at longer intervals (30 days) in the spring and fall then switching to shorter intervals (22 to 26 days) during June and July gave the best tonnage while sacrificing very little quality.
An alternative is to make no attempt to make milking quality hay during the summer, but instead to cut at longer intervals and use the hay for dry stock or horses. The added tonnage partially offsets the lower price, and the long-term life and productivity of the stand is greatly benefited.
November 5, 1999