Assessing alfalfa stands and predicting quality: Tools you can use this season

By Katelyn Goldsmith, Vita Plus dairy specialist

As we move through spring, we’re gearing up for first-crop alfalfa.  Three simple tools and practices can be used to assess your alfalfa stands, predict quality, and estimate harvest timing.

Alfalfa ring and stem counts
If you question whether a mature or thin alfalfa stand is good enough for another growing season, using an alfalfa ring and stem counts can estimate yield potential of the field.  You can purchase an alfalfa ring or make one by simply welding a cable into a ring that is 19 inches in diameter.

University of Wisconsin-Madison Extension experts suggest the following process when using an alfalfa ring:  In the field, place the ring in three to four sections that are representative of the overall field and count the number of stems within the ring.  Only count stems tall enough to be harvested by the mower.  Divide your count by two to determine stems per square foot.

A stand with 55 stems or more is not likely to be yield-limiting.  Remember, this is an estimation of potential yield.  Actual yield will probably be less than this estimate depending on management and environmental conditions.  This method is best for predicting current yield potential of the field. It’s suggested to also assess root and crown health in the fall to determine future yield potential of the stand.

Predictive equations for alfalfa quality measuring
Using a measuring stick alongside predictive equations for alfalfa quality (PEAQ) is a helpful tool to predict pre-harvest first-cut alfalfa quality.  Developed by agronomists at the University of Wisconsin-Madison, this method can be done using either a normal measuring stick and a PEAQ chart or with a special PEAQ measuring stick.

To use the PEAQ method, begin by choosing a 2-foot square area representative of the field.  Determine and record the stage of the most mature stem in the area.  Then measure the height of the tallest stem in the area.  Measure from the soil surface to the top tip of the stem (not the tip of the leaf).  If using a special PEAQ stick, read the corresponding relative feed value (RFV) printed on the stick where the top tip of the stem reaches.  If using a normal measuring stick, record the height of the stem and use a PEAQ chart to estimate the RFV.  Repeat this procedure in five to 10 areas of the field to obtain a whole-field RFV average.

The PEAQ method should only be used for estimating first-crop quality and is most accurate for good stands of pure alfalfa with healthy growth.   This procedure estimates the forage quality of the standing crop.  It does not account for quality differences that can occur during wilting, harvesting and storage.  For later cuttings or assessing an alfalfa-grass stand, scissor clippings are a better tool to estimate quality.

Scissors clippings
The scissors clippings method provides valuable information to estimate current pre-harvest quality.  This information can be used to schedule cutting and harvest to achieve desired harvest and nutritive value goals for the crop.

To collect scissors clippings, chose a 1-square-foot section representative of the field, avoiding headlands.  Within that section, use a scissors to cut the plants to the same height that they will be cut when harvested.  In a bucket, cut these plants into smaller, one-inch sections.  Repeat this process for every 10 to 15 acres of the field.  For example, in a 40-acre field, collect three to four samples.

Once the samples are collected in the bucket, thoroughly mix the contents to create a representative sample of the field to send to a laboratory.

Alfalfa will lose four to five relative forage quality (RFQ) units each day.  When you receive your results from the laboratory, look at the reported RFQ value and then subtract four to five units for each day that has passed since the date of the laboratory analysis.  This gives your estimate of the current RFQ.  To determine the best day to harvest, factor in harvest losses.  An estimated 10% to 15% of forage quality will be lost during harvest under the best conditions.  Remember to consider the field conditions, soil types, age of stand and alfalfa purity when determining harvest timing.

Using these simple tools can help ensure a viable alfalfa stand and predict quality for first-cutting.  For more information or help in accessing tools such as an alfalfa ring, PEAQ stick, PEAQ charts, or scissor clippings, contact a member of the Vita Plus team.