Fall and winter grazing of alfalfa is a common practice, but there has been limited research on how it affects the subsequent years of production.
Megan Van Emon, Montana State University Extension beef cattle specialist, who works at Fort Keogh in Miles City, Mont., talked about the impacts of winter grazing on alfalfa production.
Van Emon gave results of a project conducted by the former MSU forage specialist, Emily Meccage, before she moved to Pennsylvania.
“One study provided a supplement while cows were grazing alfalfa, so the impacts of the subsequent years of the alfalfa was minimal,” Van Emon said.
The following year’s alfalfa production was a secondary measure in that study.
In 2007-08, another study looked at grazing cows over the long, bitter winter.
“That was the winter that never seemed to quit, but we did seed positive impacts to alfalfa production (the following spring) from grazing that winter,” she said.
The objectives of the initial study were to evaluate the impacts of winter grazing and feeding on alfalfa production and persistence (alfalfa survival over time). In addition, another objective was to let producers and alfalfa growers in Montana and the surrounding region know about the results of the study at field days.
Since field days are an unknown because of COVID-19, Van Emon spoke about the alfalfa treatments in the study and some of the results.
Fields of alfalfa chosen for the study had to have at least a two-year period of greater than 90 percent alfalfa.
In each alfalfa field in the study, there were four exclosures that were paired with four grazing plots. Exclosures are areas being used for grazing, but are areas that are excluded from unwanted wildlife or other animals by using electric or other fencing.
In April 2019, they used a soil penetrometer for some measurements. The penetrometer is a tool used to test the compaction level and tilth of the soil, measured in pounds per square inch.
They also evaluated plant height, stem and plant density, and root scores.
In June 2019, they collected plant biomass and plant height right before the first harvest.
“This study was conducted in Beaverhead County in southwestern Montana and in Custer County in southeastern Montana,” Van Emon said.
In Beaverhead, 81 head of cattle grazed irrigated alfalfa fields. Those cattle ended up weighing 1,102 pounds grazing from Nov. 17, 2018 to Jan. 3, 2019.
“It was more of a stocker-based operation on that irrigated alfalfa,” she said.
In the Custer County study, where Van Emon is located, 142 head of partially-weaned calves grazed on dryland alfalfa.
They grazed from November 2018 to February 2019, and ended up weighing 593 pounds.
One producer was eliminated from the study because he terminated his alfalfa without alerting the MSU researchers, leaving just one field in Custer County for the study.
Results were run separately though a lab because of the difference from an irrigated and a dryland alfalfa field.
In the dryland field from Custer County, stems, plant and height were evaluated in the grazed and ungrazed areas. The result was a P-value.
Metric measurements were converted into English, so the stems were measured in stems per foot squared; the plants in plants per meter squared; and the height in centimeters.
In Custer County in April for the grazed areas, the stems were 38.7 stems per squared foot compared to 41.6 stems in the ungrazed area, with a P value of .82.
The plants were 2.3 in the grazed areas, compared to 2.4 in the ungrazed area, with a P-value of .86.
The penetrometer reading in the grazed area in April was 15.3 compared to 15 for the ungrazed area, with a P-value of .94.
The root score in April for the grazed area was 1.75 compared to 2 for the ungrazed area, with a P-value of .75.
In Beaverhead County in April for the grazed areas, the stems were 34.7 stems per squared foot compared to 36.4 in the ungrazed area, with a P-value of .75.
The plants in April were 2.3 in the grazed areas, compared to 3.5 in the ungrazed area, with a P-value of .12.
The penetrometer reading in the grazed area in April was 19.5 compared to 16.1 for the ungrazed area, with a P-value of .24.
The root score in April for the grazed area was 1.75 compared to 2 for the ungrazed area, with a P-value of .62.
“There weren’t any significant differences in April based on our winter grazing periods, so that is a very good sign that we aren’t having any negativity from grazing in winter months. Alfalfa can provide extra protein and energy, especially for the weaned calves in those cold, winter months.
In June, they evaluated the height in centimeters (but no height data in Beaverhead) and the productivity.
“It showed a greater tendency for ungrazed plots to grow taller than ungrazed plots by an inch, but that wasn’t showing up as having any significant impact on production,” she said.
In Custer County in June, the height was 10 inches compared to 11.1 inches in the ungrazed areas, with a P-value of .10.
In June, the productivity was 6,549 tons, compared to 4,863 in the ungrazed area, with a P-value of .44.
In June in Beaverhead County, the productivity was 6,253 in the grazed area, compared to 5,893 in the ungrazed area, with a P-value of .39.
In both Custer and Beaverhead Counties, production weight was numerically greater in grazed plots than ungrazed plots (but not significantly greater).
“We didn’t see any negative impacts on alfalfa production in the year after grazing,” Van Emon said. “This can give our producers a little more confidence when they are grazing their alfalfa and allow those animals to graze, rather than pulling them off and feeding unharvested forage in these winter months.”
The final conclusions showed there were no significant differences between April data in either location.
“That was a good thing and showed no impacts with grazing on those alfalfa field production while we are baling, so we’re not going to see those differences in bale weights or in number of bales coming off those fields,” Van Emon said.
That allows those calves to be on a higher-quality diet during those winter months.
“Maybe we’re not feeding so much while grazing alfalfa, so we can save some money there,” she said.
The study will be sent to the ag economics department for their input.
Van Emon is hoping to share data at 2020 field days, but those decisions haven’t been made yet.