Ames, Iowa, USA
May 25, 2011
by Brian Lang, ISU Extension field agronomist
With the next dry weather window we will see a lot of first crop forage harvested. Predictive Equations of Alfalfa Quality (PEAQ) monitoring shows alfalfa growth and development running about one week behind normal. Those that usually consider first crop harvest on May 25 need not be too concerned with not harvesting yet. Most of the alfalfa is barely into bud stage at this time.
PEAQ provides an estimate of the quality, measured as Relative Feed Value (RFV), of a crop of first cutting alfalfa standing in the field. Typically, the RFV of first crop alfalfa will decline 3 – 5 points per day as the crop matures. Under the best conditions, 10 to 20 percent of the forage dry matter will be lost at harvest. This amounts to approximately 15 RFV points for haylage and 25 RFV points for hay. Therefore, to end up with 150 RFV alfalfa, which is the minimum quality recommended for high producing lactating dairy cows, you should harvest the crop when PEAQ measurements predict a RFV of 165 to 175 for the standing forage. PEAQ reporting (click on “All Above Counties” on the lower right) shows less than half of the fields being monitored are ready for harvest (176 RFV or less) and the others running 196 RFV or more are still one week or more away from harvest.
Farmers are welcome to follow the progress of these reports, but they are encouraged to use PEAQ in their own fields to best determine first crop harvest of alfalfa. Refer to the PEAQ fact sheet for guidelines on estimating the RFV of your alfalfa fields.
Brian Lang is an Iowa State University Extension field agronomist serving northeastern Iowa. He can be reached at 563-382-2949 or bjlang@iastate.edu.
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