LOVELOCK - Although the water allotment for most of northern Nevada is not very optimistic, the rain showers received last week should help hay producers achieve more typical first cutting yields.
As most hay and dairy farmers know, timely cutting and harvesting of hay is critical for obtaining high quality forage. Dairy producers understand the importance of forage quality to profitability. Poor quality forages increase feed costs and limit milk production in high producing cows.
Unfortunately, harvest and storage management decisions are often made without knowledge of the alfalfa's nutrient value. Knowing the nutrient value of alfalfa in the field would help producers to harvest, store, and inventory the feed resource based on its potential value in dairy rations.
However, the use of conventional laboratory analyses to obtain forage quality status of individual fields for making harvesting decisions is impractical because of the time, labor, and expense required.
Instead, producers often rely on calendar date or maturity to make the best guess of when to harvest high quality alfalfa. But these indicators are not always reliable.
So when is the optimal time to harvest alfalfa? For those who are serious about obtaining high quality alfalfa, there is a method to quickly and easily estimate the forage quality of alfalfa in your fields, and you can do so with reasonable accuracy.
This method, developed at the University of Wisconsin under the direction of Dr. Ken Albrecht, is called PEAQ for "Predictive Equations for Alfalfa Quality." The PEAQ method predicts NDF (neutral detergent fiber) and RVF (relative feed value) by measuring the height of the tallest stem, and determining the maturity stage of the most advanced plant. The equations have been validated not only in Wisconsin but also in numerous other environments from California to New York.
Because these equations are difficult and somewhat time consuming to deal with in a production field situation, tables have been developed using computer spreadsheet programs that help make for rapid in field estimates of NDF or relative feed value (RFV). In alfalfa hay production the RFV is directly related to the NDF level.
Follow these steps to determine your forage quality:
Step 1: Walk through the field and choose a representative 2‑square‑foot area.
Step 2: Determine the most mature stem in the 2‑square‑foot sampling area. (Maturity stages - Late Vegetative, Bud Stage, Flower Stage.)
Step 3: Measure the length of the longest 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 longest stem, use the chart (Stages of Most Mature Stem) to determine the estimated NDF of the standing alfalfa forage.
Step 5: Repeat steps 1 to 4 in four or five representative areas across the field. More samples may be required for fields larger than 30 acres. It should be noted that, "PEAQ Sticks" have been developed that can easily be used to determine plant height and forage quality without referring to the chart.
Producers interested in purchasing a PEAQ stick can do so by visiting Midwest Forage Association's webpage at http://www.midwestforage.org/PEAQ.php, downloading an order form, and mailing it along with a check to MFA.
This procedure estimates alfalfa NDF and RFV content of the standing crop. It does not account for changes in quality due to wilting, harvesting, and storage. These factors may further lower RFV content by 15 to 25 units, assuming good wilting and harvesting conditions. This procedure is most accurate for good stands of pure alfalfa with healthy growth.
How accurate is this method? Across 545 samples in six states, the estimated NDF (using PEAQ) was within three units of the actual wet chemistry NDF in 77 percent of the samples we collected.
The PEAQ method performed consistently across a wide range of environments. An important feature of PEAQ is that it can be used during the entire growing season, not just on the first crop.
The PEAQ method can be used to monitor the NDF/RFV content as the alfalfa crop develops. If your goal is to produce hay at an estimated 40 NDF (dairy quality feed), then cutting must begin before the standing crop reaches 40 NDF, because of the effect of harvest and storage losses.
One must also adjust for the time it takes to cover all harvestable acres. During the spring, NDF increases about 5 units each week.
Last Wednesday, May 8, I estimated NDF at numerous locations around Lovelock. The fields that had enough vegetative growth too measure ranged from 27 to 29 NDF and 175 to 167 RFV. Hopefully, in a few more weeks, it will be ready to cut for dairy quality hay.
If grass is present in the alfalfa stand, begin harvesting earlier. How much earlier will have to be your judgment, based on the grass maturity and amount present.
There are currently no methods for estimating NDF concentration of grasses or grass‑legume stands. But as a reference point, pure grass stands should be cut in late vegetative to very early boot stage for dairy quality feed, and by early heading for other classes of livestock.
The PEAQ procedure is NOT intended to replace laboratory analyses once the forage is stored. It should only be used to give a rapid first estimate of quality of the standing alfalfa forage for purposes of making informed harvest management decisions. But this method is more reliable than timing harvests by calendar date, age or by maturity stage alone.
Source: "Update on Predicting Harvest Time for Alfalfa," R. Mark Sulc, Department of Horticulture and Crop Science, The Ohio State University, Kenneth A. Albrecht, Department of Agronomy, University of Wisconsin-Madison, Vance N. Owens, Department of Plant Sciences, South Dakota State University.
Jerome H. Cherney, Department of Soil, Crop & Atmospheric Sciences, Cornell University.
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