PEAQ Alfalfa Monitoring - U of I Extension

News Release

PEAQ Alfalfa Monitoring

This article was originally published on May 15, 2008 and expired on July 15, 2008. It is provided here for archival purposes and may contain dated information.

Alfalfa producers, consultants, and dealers in Illinois can benefit now from the Alfalfa Watch project. It monitors plant development and quality and helps time the first cutting. Alfalfa plant growth and nutrient quality indicators are reported twice weekly at this website

Alfalfa Watch estimates the pre-harvest quality in the field using the Predictive Equations of Alfalfa Quality (PEAQ) technique. PEAQ consists of predicting fiber and relative feed value (RFV) based upon the height of the tallest stem and stage of plant maturity within a sampling area. The method, developed at the University of Wisconsin, has been used in Illinois for twelve consecutive years and it is a reliable guide to determine the optimum harvest date for first cutting.

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

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

A change of 3 to 5 points of RFV 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 the height and stage of maturity. Producers need to balance the PEAQ technique with short-term weather forecasts.

Since maturity is the main factor affecting forage quality, timely harvest of alfalfa is the best strategy for obtaining high quality forage. For local PEAQ numbers in Ogle County you may call U of I Extension at (815) 732-2191 or go to and follow the ag and natural resources links to the web site above.

Source: Jim Morrison, Extension Educator, Crop Systems,

Pull date: July 15, 2008