Dairy quality alfalfa ready to harvest in Northern Lower Michigan

According to GDD, alfalfa in Northern Lower Michigan will be ready to harvest for dairy quality hay June 7-9, 2013.

According to growing degree days (GDD, base 41 degrees F) at the McBain, Mich. weather station, alfalfa in northern Lower Michigan will be ready to harvest for dairy quality hay around June 7-9, 2013. PEAQ (Predictive Equations for Alfalfa Quality) stick measurements taken in area 11 fields Monday, June 3 predicted 36-40 percent NDF. With rain in the forecast Sunday and Monday June 8-9, it will be important to harvest hay quickly when the sun is shining. Harvest mixed alfalfa-grass fields first, because grass matures quicker than alfalfa.

Tracking GDD or taking measurements using a PEAQ stick will result in better quality feed than by going from previous calendar dates of when alfalfa is typically ready for harvest. GDD provides a measure of heat unit accumulation. Because early season growth of alfalfa is related to the sum of heat units, monitoring GDD is an easy and effective way to determine when to harvest to optimize forage quality of first cutting alfalfa.

For alfalfa, GDD is based on the minimum and maximum daily temperatures beginning March 1, using a base of 41 F. The daily calculation is [(maximum temp + minimum temp)/2] - 41. The GDD accumulation is the sum of the daily GDD values across days beginning March 1.

The measure of fiber most commonly used to balance diets of lactating dairy cows is neutral detergent fiber (NDF). The optimum concentration of NDF for alfalfa fed to lactating dairy cows is 40 percent. Michigan State University Extension recommends that dairy hay should be harvested at 40 percent NDF, which normally is at the mid-bud stage of growth, to maximize the yield and quality of feed to lactating dairy cows. Alfalfa containing 40 percent NDF allows reasonable grain concentrations in the diet while maintaining adequate NDF concentrations. Research at Michigan State University demonstrated that both GDD (base 41 F) and PEAQ provide good estimates of NDF for first cutting alfalfa in normal years.

Recommendations are to begin cutting alfalfa at 750 GDD for upright silos and 680 GDD for horizontal silos. According to data collected in the upper Midwest over several years, alfalfa typically averages 38 percent NDF at 680 GDD and 40 percent NDF at 750 GDD. Filling horizontal silos with layers of alfalfa of increasing maturity will allow harvest to begin a little earlier because the layers of alfalfa are blended as the alfalfa is removed from the silo.

Growing Degree Days will reach 680 around McBain, Mich. on Friday, June 7 and 750 on Sunday, June 9. To find the GDD at your closest weather station, go to www.enviroweather.msu.edu, click the link on the top for “Field Crops”, then “Alfalfa Cutting Model” on the left side of the page. You can then select the closest station and track the GDD.

Fields should be scouted for alfalfa weevil damage. Fields with 40 percent damage and have larvae present should be cut as soon as possible for control. Timely cutting kills most larvae, pupae, and some adults. Spraying an insecticide should be considered in fields above threshold that will not be cut in 7 days. Always read and follow insecticide label recommendations. Insecticides listed for control of alfalfa weevil are highly toxic to honeybees. Scout fields daily as harvest approaches and cutting early may be necessary if damage is extensive. For more information on how to identify insect damage, go to: Proper IPM for alfalfa weevils provides a basis for treatment.

If you need help in deciding when to harvest first cutting alfalfa, contact a Michigan State University Extension Educator such as Kathy Lee, .(JavaScript must be enabled to view this email address), Phil Durst, .(JavaScript must be enabled to view this email address), Stan Moore, .(JavaScript must be enabled to view this email address) or me at .(JavaScript must be enabled to view this email address).

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