No. 7 Article 6/May 8, 2009

Time for Alfalfa Watch

Alfalfa producers, consultants, and dealers across Illinois can benefit now from the Alfalfa Watch project, which helps predict optimum date for the first cutting by monitoring plant development and quality. Alfalfa plant growth and nutrient quality indicators are reported twice weekly at

Alfalfa Watch estimates preharvest quality in the field using the Predictive Equations for Alfalfa Quality (PEAQ) technique, which predicts fiber and relative feed value (RFV) based on the height of the tallest stem and stage of plant maturity in a sampling area. The method, developed at the University of Wisconsin, has been used in Illinois for many years and is a reliable guide for determining the optimum harvest date for first cutting.

At the PEAQ website, you can calculate PEAQ, enter and track your own PEAQ values, and view PEAQ values by county and region in Illinois.

Because approximately 15 to 20 RFV units are lost during harvest and storage, alfalfa needs to be cut at 165 to 170 RFV using PEAQ to have 150 RFV of harvested forage. Some fields in the southern third of Illinois are at this point or rapidly approaching it.

A change in RFV of 3 to 5 points per day in the standing forage has been noted, so adjustments need to be made for total harvesting time. This adjustment means that alfalfa may have to be harvested prior to 165 to 170 RFV as indicated by PEAQ.

PEAQ is not designed to balance rations, and it does not account for quality changes due to wilting, harvesting, and storage. The procedure is most accurate for good, healthy stands of pure alfalfa.

Many alfalfa seed companies have PEAQ measuring sticks that indicate the RFV of standing alfalfa based on height and stage of maturity. A PEAQ stick is also available through the Illinois Forage and Grassland Council for $10 by writing IFGC, P.O. Box 233, Greenville, IL 62246 or e-mailing Matt Bunger (

Lastly, producers need to balance the PEAQ technique with short-term weather forecasts.--Jim Morrison

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