June 4, 2001

Dairy Specialist Offers Instructions for Making Hay at PEAQ Quality

Dairy producers who raise alfalfa need to set priorities and assess their hay crop carefully if they expect to make the top quality hay needed by the dairy market, according to a North Dakota State University dairy specialist.

Alfalfa should be cut in its early bud stage when it’s relative feed value (RFV) is at 170 to 190 points, says J.W. Schroeder, of the NDSU Extension Service. RFV is a measure of the fiber fractions in forage that dictate digestibility and feed intake potential. By the time alfalfa is chopped or baled, its RFV could have dropped to 150 to 160.

"Forage quality declines 3 to 7 RFV points per day, depending on the weather conditions," Schroeder says. "So prioritize tasks so you can take that first cutting when it’s time. Alfalfa drops about 80 cents per ton in value for every RFV point lost. If the crop loses three points a day, that’s $2.40 per ton lost in quality. With a yield of 2 1/2 tons per acre, you’d lose about $6 per day in forage quality."

Wisconsin agronomists have charted a way to sneak a peek at forage quality before it’s cut. A yardstick is the only equipment needed. Called the PEAQ (Predictive Equations for Alfalfa Quality) scale, it is a method for estimating when to harvest alfalfa in the spring. The idea is to measure the plant’s height, do a stage of maturity analysis, and estimate the field’s forage quality.

It’s simpler than the scissors clip method because producers can do the measuring themselves. That’s not to say PEAQ will replace scissors cut projects. "Scissors clip is an actual measure of quality averaged for a region. Some fields are ahead or behind that average, depending on things like slope, soil, and variety. A person can adapt the PEAQ scale to their own field."

Using the PEAQ chart, there are five steps for predicting first-cut quality at home.

Step 1 -- Choose a representative two-foot-square area in the field.

Step 2 -- Determine the stage of the most mature stem in the area using the following criteria:

• Late vegetative: Stem over 12 inches tall with no visible buds or flowers.
• Early bud: One to two nodes with visible buds; no flowers or seed pods.
• Late bud: More than two nodes with visible buds; no flowers.
• Early flower: One node with at least one open flower; no seed pods.
• Late flower: Two or more nodes with an open flower; no seed pods.

Step 3 -- Measure the height of the tallest stem in the two-square-foot area from the soil surface (crown base) to the top tip of the stem (not the tip of the leaf).

Step 4 -- Based on the most mature and tallest stem, use the chart to estimate relative feed value.

Step 5 -- Repeat the above procedures in five to 10 different areas of the field to obtain a whole field RFV average.

Schroeder notes that this procedure estimates the forage quality of the standing crop and does not account for changes in quality due to wilting, harvesting, and storage. These factors may further lower RFV 20 to 30 points.

As an example of how to use the scale, if the most mature stem in a two-square-foot area has three nodes with visible buds, but no open flowers (late bud) and the tallest stem measures 31 inches from the soil surface, estimated RFV is 153. The feed values bracketed in the chart are harvesting targets. Keep in mind that if you want to blow 150 RFV alfalfa into the silo, you should start cutting at 170 RFV to compensate for harvesting losses.

Another important reminder is that first cutting alfalfa doesn’t often flower normally. It may not flower until late June when quality is low. The rest of the cuttings will flower normally. So flowering is not a good method for determining when to harvest the first cutting.

The purpose of the PEAQ scale is to take the first cutting based on quality, Schroeder notes. Subsequent cuttings can be taken by two choices: day interval or flower stage. In fact, agronomists have shifted their recommendation for cutting alfalfa. They now recommend that most of the Midwest take a three cut system: first cutting by quality and the next two cuts at first flower. Those recommendations still result in dairy-quality hay.

Alfalfa quality production sticks are also now available. The information on the stick is based on a forage quality prediction method developed in Wisconsin. The prediction stick isn’t intended to replace standard lab analysis, so the results shouldn’t be used to formulate rations or as a basis for marketing decisions, cautions the Schroeder.

The prediction stick estimates the forage quality of a healthy standing crop prior to harvest. It can’t account for quality losses that may occur while the crop is curing or during harvest and storage. Prediction sticks are available from various sources. They are available from the Wisconsin Forage Council for $10 each by calling (608) 846-1825.

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Source: J.W. Schroeder, (701) 231-7663, jschroed@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu

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