2005 Year in Review

From the Fields – Alfalfa Watch

When should the first cutting of high quality alfalfa be made? Traditionally, alfalfa has been harvested at a certain stage of maturity or by a calendar date. Variations in weather and growth patterns from year to year make these unreliable.

The major factor affecting alfalfa quality is maturity. So the best guide is to harvest forage as indicated by quality.

To help alfalfa producers monitor quality and plant growth and decide the date of first cutting, University of Illinois Extension is again conducting an Alfalfa Watch project across the state. From now until early June, progress reports on alfalfa plant development and nutrient quality indicators will be reported twice weekly and made available at local Extension offices, posted on the Web at Illini PEAQ and available through various media.

What is the Alfalfa Watch project? The project consists of using a method of estimating preharvest quality in the field called PEAQ (Predictive Equations of Alfalfa Quality). PEAQ consists of predicting fiber and relative feed value (RFV) based on the height of the tallest stem and stage of plant maturity within a sampling area. This method, developed by the University of Wisconsin-Madison, has been used in Illinois for many years and found to be a reliable guide to help producers in determining the optimum harvest date for the first cutting.

Since about 15 percent of the dry matter is lost during harvesting, if the goal is to have harvested forage of 150 RFV then it should be cut at 165 to 170 RFV based on the in-field PEAQ estimate.

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 the 165 to 170 RFV mentioned above.

PEAQ is not designed to balance rations. It does not account for quality changes due to wilting, harvesting, and storage. The procedure is most accurate for good stands of pure alfalfa in healthy condition. Subsequent cuttings for high quality can be made by either stage of maturity or harvest interval.

At the PEAQ Web site, one can learn how to calculate PEAQ, enter and track your own PEAQ values view PEAQ values for Illinois by region and by county, and more. For instance, as of May 2 the average PEAQ RFV value for the southern region was 172, while for the northern region it was 242.

Many alfalfa seed companies have a PEAQ measuring stick that will indicate the RFV of standing alfalfa based on the height and stage of maturity. Finally, producers need to balance the PEAQ technique with short-time weather forecasts.

by  Editor, theCity1.com
May 16, 2005