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Manage forage cutting timeline by more than the calendar

Posted on
May 19, 2017
by
Devin Sawyer    devin_sawyer@rockriverlab.com

Manage forage cutting timeline by more than the calendar

“First cut alfalfa by a certain day in May or June” or “Cut alfalfa stands 28 to 32 days after the prior cut.” For years, these have been the standard rules of thumb for many farmers aiming to achieve dairy quality forage. Passed down from generation to generation, these rules worked at times, but both environment and plant genetics have changed. Making the decision of when to cut heavily dictates forage digestibility and quality – in addition to location and environment effects – and should be enough to drive us to look outside the primitive calendar for guidance.

While many factors can affect forage quality each year, reaping optimal forage is possible by correctly assessing and adjusting those variables that are in our control – first and foremost being the cut timeline. Each crop through the summer provides a new opportunity to fine-tune forage quality for the best animal performance at feedout, with the help of the right forage assessment tool.

FINE-TUNE YOUR FORAGE QUALITY

Over the last 10 years, two research-backed methods outside of the calendar and day-counting have been developed to accurately monitor forage quality and decide on a harvest timeline. Hand harvesting samples (or scissor clips), which applies to all cuttings and all forage types, was the first method to be consistently used. More recently, the PEAQ (Predictive Equations for Alfalfa Quality) method, which applies to the first cutting of alfalfa only, has also been adopted to assess forage quality. Both approaches offer an RFQ (Relative Feed Quality) value to assess quality, and both methods allow us to determine harvest schedule based on quality preferred for feed out, or quality preferred at the point when forage has been harvested and put in the bag, bin, or silo.

PEAQ FORAGE ASSESSMENT

The PEAQ stick utilizes a yardstick-type tool (PEAQ stick) to generate an estimate of Relative Forage Quality, based on plant maturity and plant height. Originally developed at the University of Wisconsin – Madison, this method has been validated across the country. It’s important to note, however, that the PEAQ method applies to first cut only and if assessing an alfalfa-grass stand, the PEAQ method should be set aside for the better option of scissor clipping.

While the PEAQ assessment can only be applied to the first cut of forage, this is typically the best forage crop. Due to a cooler growing environment and above-average fiber digestibility, relative to the following crops, the first crop is one of the most important to accurately assess and develop a proper cut timeline for optimal animal performance.

DETERMINING CUT TIMELINE

The first alfalfa crop harvest should be at PEAQ stick height of 19” - 25” with vegetative or bud alfalfa (or roughly 185 – 215 RFQ) for quality dairy cattle feed. Cutting at this height will yield between 160 and 200 RFQ in the silo, because roughly 10 to 15 units are lost during harvest and fermentation.

Knowing the goal when assessing the timeline for cutting, it’s important to know that five RFQ points (due to one unit of Neutral Detergent Fiber (NDF) increase) are typically lost each day that alfalfa stands and grows in the field. During warm weather, with adequate sun and moisture, this loss can be greater. During cloudy, cooler days, this loss can be less per day.

SCISSOR CLIPPING FORAGE ASSESSMENT

Hand harvesting field samples (or scissor clips) was the first method to be consistently used for forage assessment, outside of the calendar. Scissor clippings apply to all cuttings and all forage types, including pastures. Both this approach and the previously discussed PEAQ stick forage assessment measure nutritive value and offer an RFQ value to assess quality. With a basic understanding of how crops mature each day, both PEAQ and scissor clip methods allow farmers to schedule cutting and harvest to consistently achieve
desired crop nutritive value, where cutting based on the calendar (e.g. 28 to 30 days) continually fails.

Traditionally speaking, second crop alfalfa and after is lower quality than the first, due to lower fiber digestibility. However, assessing value based on a sample gathered via the scissor clipping method can help improve a precision nutrition program by capturing the optimal feed quality from this crop for the animal groups intended.

Scissor clipping focuses on harvesting subsamples throughout the entire field or pasture in an effort to accurately characterize the field. One sample should be harvested for every 10 acres of field. For example, if checking crop quality within a 50-acre field, five single square-foot subsamples should be harvested and composited. The resulting RFQ value from a scissor clipping and subsequent laboratory report corresponds to fiber content and digestibility for the entire field’s crop.

After learning the fresh scissor clip RFQ value, growers can expect to lose 10-15 units of RFQ due to leaf loss and fermentation through harvest and ensiling, and roughly five units of RFQ each day the forage grows in the field (due to around one unit of NDF increase per day). While roughly five units RFQ are lost each day, temperature and rain can also cause positive and negative fluctuations of about five units per day.

The ideal cut timeline for each crop through the summer can then be determined by working back from the desired RFQ at feedout. For example, if scissor clip analysis reports 225 RFQ and 185 RFQ is desired for high performing dairy cattle, the crop should be harvested in five days: 225 RFQ - 5 RFQ units lost each of 5 days (25 RFQ units) – 15 RFQ units lost during harvest/ensiling = 185 resulting RFQ value at feed out.

Utilizing forage assessment tools, such as the PEAQ stick and scissor clipping, to improve harvest timing and precision, will ultimately allow us to control and optimize forage quality. While the calendar can help guide us in a general sense of when the alfalfa cutting window is approaching, better options for correctly and accurately assessing quality forage exist. Farmers should consider taking the extra steps to properly calculate the timeline that will yield optimal quality for animal performance. Farmers should look to this and other available precision agriculture and nutrition tools to improve forage production management and reap rewards in the barn.

To learn more about PEAQ stick and scissor clipping methods, or to watch how-to video demonstrations of these assessment techniques, visit the Rock River Laboratory YouTube page, RockRiverLab1.

Rock River Laboratory

Founded in 1976, Rock River Laboratory is a family-owned laboratory network that provides production assistance to the agricultural industry through the use of advanced diagnostic systems, progressive techniques, and research-supported analyses.  Employing a team of top specialists in their respective fields, Rock River Laboratory provides accurate, cost-effective, and timely analytical results to customers worldwide, while featuring unsurpassed customer service.

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