ST. PAUL, Minn. (5/3/2010) --For high-quality forage, prepare to take first harvest earlier than normal this year. The early warm weather this spring has perennial forage stands off to the races.
Forage stands that shouldn't be harvested early include those for animals with low to medium nutritional needs, and stands that suffered some winter injury and thus need more time to build more below-ground energy reserves to power second-crop growth. Also, if you need more "effective fiber" in your ration, allowing more maturation before first harvest may make sense.
As pure alfalfa stands develop in spring, their relative feed value (RFV) generally declines 3-4 units per day, while relative forage quality (RFQ) declines 4-5 units per day. These changes correspond with neutral detergent fiber (NDF) concentration increasing 0.5 percent units per day, and NDF digestibility decreasing 0.5 percent units per day. NDF values reflect the amount of forage an animal can consume. As NDF percentages increase, dry matter intake generally decreases.
To assist growers with first-harvest scheduling, University of Minnesota Extension coordinates a 'scissors-cut harvest-alert' program in central Minnesota, led by Extension crops educator Dan Martens. Beginning the first week of May, several alfalfa fields around central Minnesota will be sampled for standing-crop quality every Monday and Thursday, in collaboration with farmers and commercial forage testing labs.
Results will be shared online at www.extension.umn.edu/forages, via radio at KASM (Albany and Princeton area) and KLTF (Little Falls), and via phone at 1-800-964-4929, ext. 5081. These results help with planning, although alfalfa development can vary greatly with location, soil type, stand health, etc. Monitor your own stands closely.
A useful tool to estimate quality of standing forage is a Predictive Equations of Alfalfa Quality (PEAQ) stick or yard stick. PEAQ sticks use maturity and height to estimate RFV/RFQ of pure alfalfa stands, and can be purchased from the Midwest Forage Association (www.midwestforage.org). The currently available RFQ-PEAQ sticks provide good estimates of RFV, but recent Wisconsin and Minnesota data have shown that stick readings should be adjusted to provide a better estimate of RFQ.
Based on northeastern U.S. data, Cornell University has developed guidelines to estimate standing-crop quality of alfalfa/grass mixtures based on alfalfa height and an estimate of grass percentage. The assumption is that the target standing-crop NDF for 'dairy-quality' forage ranges from 38 percent for pure alfalfa to 50 percent for pure grass. Based on their data, a 70:30 alfalfa:grass mixture is ready to harvest when the alfalfa is 29 inches tall; a 50:50 mixture is ready when alfalfa is 24 inches tall, and a 30:70 mixture when alfalfa is 19 inches tall. More information on harvest scheduling is available on the Extension forages website at www.extension.umn.edu/forages.
Any use of this article must include the byline or following credit line:
Paul Peterson is a forage agronomist with University of Minnesota Extension.
Media Contact: Catherine Dehdashti, U of M Extension, (612) 625-0237, firstname.lastname@example.org