ORIGINALLY WRITTEN BRADLEY GOERING
Alfalfa is an important forage crop grown successfully in Kansas. In the last four weeks we have covered most of the acres spraying alfalfa weevils. Quality in any forage crop is a desired characteristic of any hay or haylage crop. Being able to estimate quality in the field can be somewhat tricky.
However, the University of Wisconsin has developed a system used during the past several years to estimate the relative feed value of standing alfalfa. It is referred to as the Predictive Equations for Alfalfa Quality or PEAQ.
This unique system measures the plant height from the tip of the stem down to the soil surface and the maturity stage (vegetative, bud or flower). With these two factors, a number for the RFV or relative feed value is established.
As a guideline in Wisconsin and Illinois, if 150 RFV alfalfa hay is desired, then you should harvest when PEAQ indicates 170 RFV. The RFV has been known to drop several points each day. As expected, weather or other factors may cause delays for the farmer.
To begin the process, a producer should select a representative 2-square-foot area in the field. Determine the most mature stem in the sampling area. Measure the length of the tallest stem in the 2- square-foot area and be sure to straighten the stem for an accurate measure. The tallest stem may not be the most mature-don’t use the tip of the highest leaf blade.
Repeat this process another four times in the field. If the field is larger than thirty acres, repeat more times or sample once for every six acres.
A word of caution. This sampling process obviously works in the upper Midwest. For interested producers, I would encourage trying this method and comparing with some samples that you send to a lab.
Once you become comfortable with the procedure, then it may be possible to do some of your own calculating to have an idea of each cutting and when to cut.
To plug the height and maturity of the alfalfa into the PEAQ calculator, you can go to the following website: http://peaq.outreach.uiuc.edu/. Then click on the “How to Calculate PEAQ” button for instructions or the “Calculate PEAQ” if you already have your information to plug in.
The “How To” button opens to more buttons containing PDF files that have a field log sheet plus other useful documents.
If anyone has trouble send an e-mail, I can return an attachment of the information to you.
Bradley Goering can be reached by e-mail at bgoering@thecsb.com, or by telephone at (620) 327-4941.
