PEAQ: Predicting When To Harvest Alfalfa

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It’s not new, but the PEAQ (predictive equations for alfalfa quality) technique is reliable, says Jim Morrison, Extension educator, crop systems, Rockford Extension Center, University of Illinois. PEAQ predicts optimum dates for first cuttings by monitoring plant development and quality.

The method estimates fiber and relative feed value (RFV) based on the height of the tallest stem and the stage of plant maturity in a sampling area. The Illini PEAQ Web site gives an overview of the technique and helps calculate and track PEAQ values. PEAQ measuring sticks are available from alfalfa companies and through membership in the Illinois Forage and Grassland Council.

“Since approximately 15-20 RFV units are lost during harvest and storage, alfalfa needs to be cut at 165-170 RFV – calculated using PEAQ – to have 150 RFV of harvested (high-quality) forage alfalfa,” Morrison says. RFV of 172 in the field equates to alfalfa 26” tall and in the bud stage.

RFV can change three to five points per day in standing forage, so cutting may have to begin before alfalfa reaches a 165-170 PEAQ value, he adds.

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.

Below A short Growmark FS video, called Using The PEAQ Stick, shows how simple the method is.

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