Walk It Out

Farm Journal, May 16, 2008 by Jeanne Bernick

It's late spring and you're anxious to schedule your first alfalfa cutting. Use that extra energy to walk your fields, suggests Dan Wiersma, a Pioneer Hi-Bred International Inc. forage agronomist.

"This is the time of year I tell growers to get out and give their alfalfa a close look," Wiersma says. "Plant height and maturity provide a good sense of forage quality, which helps when setting harvest dates."

He suggests using the Predictive Equation for Alfalfa Quality (PEAQ) method when walking fields. The PEAQ program, developed by the University of Wisconsin-Madison, guides producers in measuring plant height and maturity, which in turn provides a close estimate of Relative Feed Value (RFV) in the field.

By gauging RFV of standing alfalfa, you can determine when to schedule harvest for the first crop and capture the highest forage quality, says David Fischer, University of Illinois Extension dairy specialist and PEAQ coordinator for Illinois.

"As feed costs go up, it is critical to harvest alfalfa at the optimum stage of forage quality," Fischer says. "The PEAQ method is a simple tool to help determine harvest dates."

Proven system. Interest in the PEAQ method to measure alfalfa quality has increased in recent years, Fischer says. On-farm studies conducted by the University of Illinois compared PEAQ calculated values with other alfalfa quality protocols, like the scissor clip method, and concluded PEAQ is a viable option for producers.

This is the 10th year the University of Illinois will use the PEAQ system to monitor alfalfa quality in the state.

"The time has come for forage producers to embrace PEAQ and use it as a management tool to help predict first-cut alfalfa quality," says Mike Rankin, a University of Wisconsin crops and soils specialist. "The system for using PEAQ has now been field-tested over several years and refined for ease of making estimates in the field."

How to PEAQ. The following are PEAQ protocol steps to estimate preharvest alfalfa quality with a simple yardstick or a forage quality stick.

Step 1: Select a representative 2 sq. ft. area in the field.

Step 2: Measure the length of the tallest stem located between the soil surface (next to the plant crown) and the tip of the stem; do not measure to the tip of the highest leaf blade. Straighten the stem for an accurate measure of its length, Rankin suggests.

Step 3: Determine the stage of maturity of the tallest stem. The PEAQ program uses a "3 maturity stage" system to determine maturity: late vegetative (stem less than 12" with no buds), bud stage (stem with one or more nodes with visible buds but no flowers) and flower stage (stem with one or more nodes with open flowers).

Step 4: Repeat this measuring protocol in four or five representative areas of the field. Take additional samples in fields larger than 30 acres.

Step 5: Match the alfalfa height and maturity level data to RFV data using a PEAQ chart.

From this match-up you can determine when to schedule your first cutting, Fischer explains. He recommends cutting when standing alfalfa reaches 170 RFV.

Most crop consultants and Extension offices can supply you with a PEAQ chart. You also can download one from the University of Wisconsin's Web site by visiting www.uwex.edu/ ces/crops/ PEAQTabl.pdf. Another option is to input alfalfa height and maturity data into an online PEAQ calculator. The University of Illinois offers an online calculator at http:// peaq.traill.uiuc.edu.

Pros and cons. The simplicity is what Fischer likes most about the PEAQ quality measurement program. "It's fast and inexpensive, and the only tool you really need is a yardstick," he says.

The program also works across a wide range of environments. When walking through fields to measure alfalfa height, growers are able to take a closer look at their stand and detect any insect, weed or disease problems, Fischer says.

It is important to note, however, that PEAQ results are highly dependent on good sampling technique, Fischer adds. Growers should not use the PEAQ system in fields that are under stress, (from poor growth, for example) waterlogged or weed infested.

"The height and maturity of those alfalfa stands are not going to be representative of a typical alfalfa field in the area," Fischer says.

Hot Tip

To determine alfalfa quality prior to harvest, measure plant height with a traditional yardstick or a PEAQ stick, which can be purchased from the Midwest Forage Association. Go to www.midwest forage.org, and click on "PEAQ Sticks" in the left column. You can e-mail Jeanne Bernick at jbernick@farmjournal.com.