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Use tools to correctly time first cutting

Chris Torres alfalfa field
TIME TO CUT?: It’s easy to depend on the calendar or your gut instinct to decide when to do first cutting. But there are a lot of tools that you can use to make a more precise cutting and get the best quality feed for your animals.
Ask the Experts: Ron Hoover, Mark Sulc and Phil Kaatz discuss when to properly time first-cut alfalfa and the various tools that can help.

Editor’s note: This is the first in what will be a new Ask the Expert column from American Agriculturist, Ohio Farmer and Michigan Farmer. If you have any questions that you’d like to pose to an expert, email Chris Torres at [email protected] or Jennifer Kiel at [email protected], and we’ll try our best to get you an answer. This week, we’re thinking of first cutting, and factors and tools you should consider.

First cutting of alfalfa and grass will be here sooner than you think. The nice spring weather, except for last Thursday’s chill, has allowed alfalfa and grasses to emerge with some vigor the past couple of weeks.

But how do you know when the ideal time is to do first cutting? Beyond just the time of year or your gut instinct or experience, it depends on a lot of factors: forage yield and quality, and the longevity of the field, among others.

I posed this question of ideal timing for first cutting to Ron Hoover, coordinator of Penn State’s on-farm research program; Mark Sulc, Extension forage specialist with Ohio State University; and Phil Kaatz, Extension educator of forages and field crops with Michigan State University Extension.

They provided some good insights and tools to help guide you to a solid first and subsequent cutting this spring and summer:

When is the ideal time to make the first cutting of alfalfa? 

Ron Hoover: Before addressing first cutting, let’s review some general alfalfa cutting management principles. 

Repeated frequent harvests of alfalfa in the early bud stage will result in lighter preharvest dry matter yields, but the forage will be very high in quality. Annual forage yields might benefit from an extra harvest each year due to frequent cutting intervals. 

The greatest negative that can result from repeated short harvest intervals is the inability of alfalfa to replenish those important crown and root energy reserves needed for regrowth and for winter survival. The depletion of reserve energy can be lessened if one or two cuttings are allowed to regrow longer, perhaps waiting until some shoots have open flower buds. 

Yes, forage quality of flowering alfalfa will be lower, but regrowth vigor and ability to overwinter will be greatly enhanced, and therein lies the dilemma: Do we manage for high quality or higher yields and greater stand longevity?

Penn State recommendations are based on producer goals. If high-quality forage is paramount or the stand is several years old and it will be rotated out of alfalfa within a year, send the mower to the field when some of the first flower buds are observed.

If the field is relatively new or the previous winter was stressful, or several more years of alfalfa production are desired, harvest should be delayed slightly. As noted earlier, early cutting-induced stress on reserve energy can be reduced by allowing subsequent harvests to reach full bud or early bloom at least once during the year. 

Many alfalfa varieties marketed now have been selected to tolerate earlier or more frequent cuttings than older varieties.

Recent research from some other universities have sought to fine-tune cutting management recommendations. University of Wisconsin forage agronomists have developed the PEAQ technique of estimating forage relative feed value based on alfalfa height and maturity. The focus is determining when to harvest when alfalfa forage of a certain quality is the goal.

Extension articles from the University of Minnesota and Michigan State University similarly suggest using a growing degree day calculation to determine when to make first cutting of forage that meets specific forage quality goals.

Cutting recommendations can change greatly for mixtures of alfalfa and cool-season grass. Because many cool-season grasses mature earlier than alfalfa, we recommend cutting based on the maturity of the grass. This practice can be challenging for the longevity of the alfalfa, as noted earlier. Waiting to cut mixtures based on the maturity of the alfalfa can result in the cool-season grasses having matured to the fully headed or early anthesis stages, resulting in low-quality grass forage.

However, if the percentage of grass in the mix is much less than that of alfalfa, the higher-quality alfalfa can blend up the overall forage quality enough that the quality of the mixture can still be acceptable.

When it comes to alfalfa, at what height should you aim to cut that first cutting?

Mark Sulc: It totally depends on your forage quality goals, which should be based on the livestock to be fed.

The height of the alfalfa drives the fiber content, measured as neutral detergent fiber, or NDF, and NDF concentration should be the basis of when you harvest the alfalfa because it affects animal intake.

Here are some alfalfa forage NDF concentrations for different livestock groups:

  • Average-producing dairy cows: 42% to 46% NDF, longest stems are 29 to 30 inches.
  • High-producing dairy cows in early lactation: 35% to 40% NDF, longest stems are 20 to 21 inches.
  • Lactating beef cows: 45% NDF, longest stems are 31 to 32 inches.
  • Dry (gestating) beef cows: 50% NDF, longest stems are 37 to 38 inches.
  • Horses: 42 to 46% NDF, longest stems are 29 to 30 inches.

One can estimate when alfalfa is near these targets in the field by measuring the height and knowing the growth stage of alfalfa. For details on this, see the Ohio State forages page for fact sheets and a video on how to estimate alfalfa growth.

It’s important to note that in order to hit the desired target, you will have to start a little earlier than indicated above because the curing process raises the NDF due to loss of leaves, loss of sugars during curing and other factors. So, shoot to harvest alfalfa when it is at least 3 units lower in NDF than the above targets.

Phil Kaatz: Depending on the type of livestock that the alfalfa will be used for, my answer will vary.

If you are cutting for high-quality dairy forage, I would start cutting first cutting at 28 inches in height. This will provide a good compromise between yield and quality. If you are cutting for beef quality, then I would cut according to maturity level starting at one-tenth bloom.

Height is not the only criteria that you can use for alfalfa cutting, especially if there are extenuating circumstances, like a frost or extended cool, wet weather that can change the way alfalfa reacts.

How about if you’ve just established the alfalfa or grass?  

Sulc: For spring seedings, we recommend giving alfalfa 60 days of growth after emergence. Then you can harvest it.

After that, follow the procedure above, but always end the last harvest by the first week of September to give it a fall rest to store energy reserves for winter and for the following spring regrowth.

Kaatz: A new seeding that has just been planted this spring should have a 60-day waiting period prior to cutting. It’s always best to remember this is a perennial crop, and establishment is critical for the entire life of the stand.

Likewise for a grass-legume mix, it’s important to allow adequate time for the plants to be established.

Should you consider cutting when it’s cooler, to achieve higher quality, even if the height of the forage is shorter?

Sulc: If you cut when it is very short — shorter than the ranges indicated above — then the quality will be too high in most cases, even for high-producing dairy cows.

Some hay markets give a premium for super high-quality alfalfa, so in those instances go right ahead, especially if the premium makes up for the lower yield. But keep in mind, though, that the super high-quality alfalfa usually won’t help the animal produce more or do better.

In fact, if the fiber is too low, other sources of fiber will have to be added to make up for the alfalfa not having enough fiber for good digestive health.

Alfalfa rarely is too short in the cool, early spring, unless it’s a weakened stand or has been damaged. In those cases, it needs more time to replenish energy reserves and recover.

The primary time alfalfa will be very short and ready to harvest is under dry or hot conditions. The crop may flower when it’s really short. Generally, if you are at 30 days of regrowth it is safe to cut, and if it’s flowering quite a bit, it won’t put on much more yield after that, so you might as well cut it so it can start a new regrowth cycle.

Kaatz: There is always a trade-off between yield and quality, especially for first cutting. Alfalfa will normally mature according to accumulated heat units most years. So if it’s been cooler, the alfalfa will usually not be as tall and have higher quality and reduced yield.

I recommend having a goal for forage quality based on the animals being fed. Alfalfa plant height and quality are highly correlated. This has been confirmed and the use of the PEAQ (predictive equations for alfalfa quality) stick was developed based on this research. I know of dairy producers that want very high quality and will sacrifice yield for the quality.

One other factor is that the alfalfa stand life will also be compromised with a shorter time if a producer chooses to harvest early for high quality.  

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