https://www.agweb.com/farmjournal/article/when-to-cut-alfalfa/

When to Make First Spring Cut of Alfalfa and Mixed Alfalfa/Grass

Producers must answer a couple of basic questions when deciding the time of the first spring cutting of alfalfa and mixed alfalfa and grass fields. What’s your hay harvesting schedule? What are your objectives for the harvested hay crop or forage stand?  Harvest schedule decisions tend to be guided by what’s most important. Producer objectives may include harvested yield, nutritive quality of the forage, or vigor and persistence of the perennial stand.

Reaching a high level of all three objectives is unlikely with a single chosen harvest schedule. Producers can generally meet two of the three with a chosen harvest schedule, but not all three. So, there are usually some compromises when harvesting.

In general, more frequent harvests produce forage of higher nutritive quality at an acceptable yield level, but at a sacrifice in stand vigor or longevity. Conversely, the less frequent harvest will produce acceptable yields and a greater degree of stand persistence and plant vigor, but forage of a lower nutritive value.

The maximum dry-matter yield of alfalfa and most forages is often obtained by harvesting the first cutting of the season at nearly full bloom and harvesting subsequent cuttings at 40 to 45-day intervals until late August or early September, referred to as a “3 summer-cut system.” This system produces forage relatively lower in nutritive quality.

Such forage is suitable for livestock on maintenance rations, or slower weight gain livestock enterprises and can be used in low-performance feeding programs. To add additional harvested yield, growers who use a 3 summer-cut system will often harvest the fourth cutting in mid to late October.

For higher value forage

In contrast, high-performance livestock feeding programs require higher nutritive value forage. The optimal compromise for higher forage quality and dry matter yield of alfalfa is to harvest the first cutting at the late-bud to the first-flower stage and to make subsequent cuttings at 32-to-35 day intervals until late August or early-September, often referred to as a “4 summer-cut system.”

For more information: https://crops.extension.iastate.edu/cropnews/2010/05/when-make-first-spring-cut-alfalfa-and-mixed-alfalfagrass