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for up-to-the-minute statewide PEAQ and Scissors Cut Results
For more information, click on the topics below:
PEAQ Chart PEAQ Sampling Procedure PEAQ Stick Use Examples
Scissors Cut Sampling Procedure Scheduling Alfalfa Harvest Using PEAQ and Scissors Cut
The Minnesota Forage and Grassland Council and the Minnesota Extension Service are
co-sponsoring a state-wide Scissors Cut Program again this year. The Scissors Cut Program was implemented several years ago to monitor first cutting alfalfa quality across the state. This program has proven to be very beneficial for alfalfa producers in timing the first crop harvest. Researchers have recently developed another tool to be used in the prediction of alfalfa harvest timing. Predictive Equations for Alfalfa Quality, or better known as PEAQ, is a method to predict forage quality by plant maturity and plant height. The PEAQ stick provides producers the opportunity to sample fields as often as they wish. Relative Feed Value (RFV) data from both the Scissors Cut forage tests and PEAQ estimates will be posted below as soon as data is available.
PEAQ Sticks are available from MFGC for $10.00 each, plus $3.00 shipping. A discount is available for large orders. Order your PEAQ Stick today:
- by mail - send request with payment to: MFGC, 411 Borlaug Hall, 1991 Buford Circle, St. Paul, MN 55108.
- with credit card - phone, fax, or email your request: phone: (651) 436-3930; fax: (651) 436-7210; or email: mfgc@umn.edu.
| Estimating Alfalfa RFV in the Field Using PEAQ | ||||
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Step 1: Choose a representative 2-square-foot area in the field. Step 2: Determine the most mature stem in the 2-square foot sampling area using the criteria shown in the table at the right. Step 3: Measure the length of the tallest stem in the 2-square-foot area. Measure it from the soil surface (next to plant crown) to the tip of the stem (NOT to the tip of the highest leaf blade). Straighten the stem for an accurate measure of its length. The tallest stem may not be the most mature stem. Step 4: Based on the most mature stem and length of the tallest stem, use the chart at the right to determine estimated RFV content of the standing alfalfa forage. Step 5: Repeat steps 1 to 4 in four or five representative areas across the field. Sample more times for fields larger than 30 acres. NOTE: This procedure estimates alfalfa RFV of the standing crop. It does not account for changes in quality due to wilting, harvesting, and storage. These factors may further lower RFV by 15 to 25 points, assuming good wilting and harvesting conditions. This procedure is most accurate for good stands of pure alfalfa with healthy growth. |
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Procedures to be followed when taking PEAQ or Scissors Cut samplings. If you have additional
questions please contact Paul Peterson at peter072@tc.umn.edu.
PEAQ Sampling Procedure
1. Choose a representative 2 ft2 area to sample.2. Determine the growth stage (vegetative, bud, or bloom) of the most mature stem in that 2 ft2
area. This may not be the tallest stem.3. Measure the length of the tallest stem in the 2 ft2 area. Straighten the stem and measure it from
the soil surface to the stem tip (not the leaf, bud, or bloom tip).4. Based on the most mature stem and the length of the tallest stem, use the correct side of the
PEAQ stick and read the scale to predict RFV. Alternatively, height of the tallest stem can be
measured with a yardstick and the RFV determined from the PEAQ table.5. Repeat steps 1 to 4 in at least 5 representative areas of the field and average the RFV values.
Sample more times for fields larger than 30 acres.
The PEAQ procedure is accurate for pure stands of alfalfa between 16 and 40” tall. It works for
all cuttings except fall cuttings.It does not account for changes in quality due to wilting, harvesting, and storage. These factors
may further lower RFV by 15 to 25 points, assuming good wilting and harvesting conditions.
We suggest doing PEAQ sampling on Mondays and Thursdays beginning when alfalfa is 16” tall
(in contrast to 12” tall for scissors cut samples).Please post your PEAQ results as soon as possible after you’ve obtained them on the Alfalfa
Harvest Alert web site. Additional data that can be posted is average PEAQ maturity stage and
average PEAQ tallest stem height. Calculate average PEAQ maturity stage by averaging numeric
values of the most mature stem determination at each sampling location in the field. Calculate the
average to the nearest 0.1 using the following scale: vegetative=1, bud=2, and bloom=3.
Scissors Cut Sampling Procedure
Begin collecting samples when spring growth of alfalfa is about 12 inches tall, generally the
second or third week of May.Take samples on Monday and Thursday mornings before 9 AM so results can be available by
Tuesday and Friday. Continue sampling until the field is harvested or when forage quality drops
below desired harvest quality. Consistent early morning sampling is important to reduce day to
day variability due to differential accumulation of nonstructural carbohydrates in alfalfa herbage
on sunny versus cloudy days.At each sampling date, sample 5 to 8 representative locations within the field and combine into
one sample weighing 0.5 to 1 lb. Scissors cutting height should be determined by the anticipated
cutting height at harvest (generally 2 to 4 inches).The Scissors Cut NIR equations were developed with samples of spring growth from pure
alfalfa stands. Thus, any dead material, grass, and/or weeds must be removed from the sample
for accurate results. If the field has a significant amount of any of these, a properly procured
scissors cut sample will likely indicate higher forage quality than is actually in the field.
Place the sample in a paper bag clearly marked with identifying information. Send/take samples
to a National Forage Testing Association certified laboratory and indicate that the samples are
fresh (scissors cut).As soon as possible after sample results are available, ensure that they are posted on the Alfalfa
Harvest Alert web site.
Considerations for using Scissors Cut and PEAQ results to schedule alfalfa harvest:
1. Set RFV goal for harvested feed. Match forage quality to animal needs:
Lactating Dairy Cows 150 RFV
Heifers, Stockers, and Lactating Beef 125 RFV
2. Make adjustments for field losses. Even under the best conditions, an average of 15% of the dry
matter and 20 RFV points are lost during harvesting. Thus, cutting when the standing alfalfa is
170 RFV will compensate for that loss if you have a goal of 150 RFV in the feed.
3. Make adjustments for total harvesting time. Standing alfalfa typically losses 3-5 RFV points per
day as it matures. Thus, if you estimate that it takes you two weeks to harvest first cutting, and if
an average of 150 RFV is your target for the feed, you must begin harvesting one week before
RFV of the standing alfalfa is 170. Seven days with RFV dropping an average of 4 units per day
equals a drop of 28 RFV points per week. Thus, for this example, harvest should begin when
the scissors cut and/or PEAQ estimate indicates standing forage quality of 198 RFV.
4. Make adjustments for local field conditions. The scissors cut and PEAQ procedures are for pure
alfalfa stands. Alfalfa-grass mixtures will reach the target forage quality earlier. Stands on sandier
soils will begin growing earlier and thus mature earlier and drop in quality earlier, unless
conditions become dry (mild drought delays maturation and thus slows forage quality decline).
South-facing slopes mature earlier than north-facing slopes.
If the most mature stem in the 2-square foot sampling area is in the vegetative stage, use the green ("vegetative") side of the PEAQ stick to estimate RFV of the tallest stem in the sampling area.
If the most mature stem in the 2-square foot sampling area is in the bud stage, use the blue ("bud") side of the PEAQ stick to estimate RFV using the tallest stem in the sampling area (which may not be in bud stage).
If the most mature stem in the 2-square foot sampling area is in the bloom stage, use the pink/magenta ("bloom") side of the PEAQ stick to estimate RFV using the tallest stem in the sampling area (which may not be in the bloom stage).
Estimated RFV = 233. Note that most mature stem in sampling area is vegetative, so green side of PEAQ stick is used to estimate RFV.
Estimated RFV = 226. Note that in this case the tallest stem was also the most mature stem; thus, the bud (blue) side of the PEAQ stick was used to estimate RFV.
Estimated RFV = 205. Note that even though this tallest stem was vegetative, the pink/magenta (bloom) side of the PEAQ stick was used to estimate RFV because the most mature stem in the sampling area was in bloom stage.
Estimated RFV = 170. Note that most mature stem in sampling area is in bloom stage, so pink/magenta (bloom) side of PEAQ stick is used to estimate RFV.
INCORRECT Procedure. Note the bloom in the foreground; the bloom (pink/magenta) side of the PEAQ stick should have been used to estimate RFV as 210, even though the tallest stem is only in the bud stage (blue RFV 225).
