Alfalfa Harvest - U of I Extension

News Release

Alfalfa Harvest

This article was originally published on May 6, 2010 and expired on July 6, 2010. It is provided here for archival purposes and may contain dated information.

With the early spring warm-up alfalfa growth is ahead of normal. Time to plan for the first harvest of alfalfa is fast approaching. Alfalfa producers, consultants, and dealers are encouraged to follow the Predictive Equations for Alfalfa Quality (PEAQ) technique, which predicts optimum date for the first cutting by monitoring plant development and quality.

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 by University of Wisconsin, has been used in Illinois for many years and is a reliable guide to predict the optimum date for first harvest.

The Illini PEAQ web site, , provides an overview of the technique, and helps you calculate and track your own PEAQ values. As alfalfa approaches 14 to 16 inches tall, measurements should be taken twice a week to determine the quality standing in the field.

Beginning this year, University of Illinois Extension educators will no longer be formally conducting the Illini PEAQ on-farm measuring and recording of alfalfa growth in the various regions of the state as they have done for the past 13 years. PEAQ is very accurate if producers measure their own individual fields rather than making harvest

decisions based on regional PEAQ values.

The PEAQ procedure is simple - measure the plant height in inches from the soil to the growing tip and determine if the plant is in the vegetative, bud, or flower stage. These measurements predict RFV. Since approximately 15 to 20 RFV units are lost during harvest and storage, alfalfa needs to be cut at 165 to 170 RFV calculated using PEAQ to have 150 RFV of harvested forage. This is recognized as high quality alfalfa. RFV of 172 infield equates to alfalfa 26 inches tall and in the bud stage.

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. Producers need to balance the PEAQ technique with short-term weather forecasts and field conditions.

PEAQ predictions are most accurate for good, healthy stands of pure alfalfa. The method is not designed to balance rations and does not account for quality changes due to wilting, harvesting, and storage. Nutrient analysis will be needed to properly balance rations.

Many alfalfa seed companies have PEAQ measuring sticks that indicate the RFV of standing alfalfa based on the height and stage of maturity. A PEAQ stick is also available through membership in the Illinois Forage and Grassland Council (P.O. Box 233, Greenville, IL 62246; phone 618-664-3590, ext. 3; ).

Since maturity is the main factor affecting forage quality, timely harvest is the best strategy to have high quality alfalfa.

Source: Jim Morrison, Extension Educator, Crop Systems,

Pull date: July 6, 2010