Harvest schedule for first cutting alfalfa

Growing degree day differences abound across Michigan in 2015 from north to south.

An example of a PEAQ stick measurement.

An example of a PEAQ stick measurement.

Alfalfa producers wanting to harvest alfalfa according to forage quality will want to keep a close eye on the growing degree days (GDD) in the next 10-15 days. Using the calendar as the standard for harvesting alfalfa can lead to forages harvested at neutral detergent fiber (NDF) levels unsatisfactory for production goals. The importance of harvesting a hay crop on time can make a big difference in the fiber and energy levels for alfalfa. There is a usually a short window of opportunity to harvest alfalfa at a particular goal since NDF levels can change rapidly with increasing temperatures. Many dairy producers have a goal of 40 percent NDF. Data collected over a period of years suggests that an growers using an upright silo should begin harvesting at 750 GDD for alfalfa with 40 percent NDF + 3 percent most years. The current recommendation for producers using bunk silos is to begin cutting at 680 GDD corresponding to value of about 38 percent NDF. Using GDD is an important tool that should only be used for first cutting.

Alfalfa GDD is calculated by averaging the daily high and low temperatures for a 24-hour day, dividing by 2 and then subtracting the base of 41 degrees Fahrenheit. The season total is the sum of daily growing degrees beginning March 1 through today. Anything less than 41 F gets zero GDD for the day. Example: the daily high and low for today was 60 F and 40 F. The average is 50 F, minus 41 F (base) equaling 9 GDD. Current information is available at weather stations placed throughout Michigan. To get information for a weather station near you, go to Michigan State University Enviro-weather.

2015 Growing degree days base 41 F (average method) beginning March 1 from MSU Enviro-weather.

Location (number of reporting stations)

Current GDD base 41 F

Predictions GDD base 41 F

 

Date

May 18

May 24

Southwest (15)

 

 

Ave.

609

716*

High

667

765*

Low

494

611

South Central (10)

 

 

Ave.

590

707*

High

667

786*

Low

529

645

Southeast (4)

 

 

Ave.

562

684*

High

595

729*

Low

519

636

West Central (12)

 

 

Ave.

511

614

High

598

716*

Low

443

515

East Central (16)

 

 

Ave.

485

587

High

582

697*

Low

407

495

North Central (4)

 

 

Ave.

371

431

High

395

457

Low

342

397

Northeast (1)

Ave.

330

403

Northwest (9)

 

 

Ave.

373

441

High

432

495

Low

310

375

Upper Peninsula (3)

 

 

Ave.

279

328

High

328

396

Low

231

276

* Represents target number above 680 GDD for bunk silo harvest starting point. Target number is 750 GDD for upright silo starting point.

Growers with alfalfa and grass mixed stands should not use the GDD method to establish your cutting schedule. Consider harvesting these fields before harvesting the pure alfalfa stands. Grasses have higher NDF content than alfalfa cut at the same age. Spring harvest of alfalfa-grass mixtures is based on alfalfa maximum height and the proportion of grass in the stand. Michigan State University Extension suggests that producers consider harvesting fields that have the most grass first so purer alfalfa stands can be harvested at the appropriate NDF levels. If wet weather delays harvest, you may want to harvest the purest alfalfa stands first since fields with grass will likely be past the optimum NDF levels and may be better used for dairy rations requiring higher fiber, or for dry cows and heifers.

Another method for evaluating the current stage of maturity for alfalfa is the PEAQ (Predictive Equations for Alfalfa Quality) stick method. This method takes more time because you need to walk your alfalfa fields and select several spots in the field to get an accurate reading. The PEAQ stick uses both alfalfa stem height and maturity to predict forage quality. One must be able to know the different stages of growth of alfalfa (early bud, mid bud, late bud, early bloom and full bloom). A study conducted in six states across a wide range of environments estimated NDF within three units of actual wet chemistry in 77 percent of samples collected. PEAQ sticks should only be used for first and second cuttings of pure alfalfa fields that receive adequate moisture and growing conditions.

For more information, contact Phil Kaatz at .(JavaScript must be enabled to view this email address) or 810-667-0341.

 

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