WATERTOWN Wis. — Alfalfa can be a high quality source of protein for dairy cow rations.
“Perhaps it makes more sense to grow alfalfa this year than buy soybean meal,” said John Goeser, animal nutrition director at Rock River Lab and adjunct professor in the animal and dairy science department at the University of Wisconsin.
Alfalfa presents great potential rewards for dairymen, said Goeser during an Alfalfa Livestream presentation.
“It is a perennial crop, it can bring quite a bit of protein and it has very digestible fiber and sugar,” he said.
However, Goeser said, growing alfalfa also has some risks.
“Historically we’ve been managing three- to five-year stands, but more recently we’ve had winterkill, so our stand life has been down to three years,” he said.
Goeser identified aspects of alfalfa that can bring value to dairy operations in 2022.
“Inflation is running rampant and the dollar is not working as hard for us, so investments we make in a perennial crop may look better in years to come,” he said. “Feed costs are at the higher end of long-term trends with soybean meal around $400 per ton.”
All dairymen should know what it costs to grow a ton of alfalfa on their farm.
“It costs from $550 to $680 per year for an acre of alfalfa that produces 5 to 8 tons of dry matter over a three- to five-year life stand at 90% dry matter basis,” Goeser said. “That estimates about $95 per ton for alfalfa.”
“The first cutting is the most important cutting from a profitability and animal nutrition standpoint,” said Glenn Shewmaker, University of Idaho Extension emeritus forage specialist.
During the Livestream event, Shewmaker discussed a study that was completed in three locations — south-central Idaho, south-central Wisconsin and central Pennsylvania.
The researchers evaluated three varieties over several cuttings and started cutting the alfalfa at the vegetative stage and harvested every five days for that cutting.
“In Idaho, the yield will increase during the first cutting at 120 pounds of dry matter per acre per day and during the summer cuttings the rate of yield increase is much higher,” Shewmaker said.
“For forage quality, the rate of decline was minus 0.3% of NDF digestibility per day,” he said. “That is very important because it is related to the amount of intake an animal can sustain and therefore the amount of protein and energy they get from that forage product. The rate of decline is much higher in harvest two and three.”
In Wisconsin, Shewmaker said, the yield increased 130 pounds per acre per day and the NDF digestibility rate of decline is a little higher at minus 0.4%.
“You need to use local information and your historical records,” he said.
Earl Creech, professor and extension agronomist at Utah State University, has done a lot of research on alfalfa weed management.
“All herbicides labeled for alfalfa cause injury to alfalfa,” he said. “Even with Roundup Ready alfalfa, we see injury if we apply when the temperatures are really cold.”
When alfalfa is established, it is a resilient plant because it has a deep tap root.
“Time heals all wounds when it comes to alfalfa herbicides,” Creech said.
“However, there’s an exception. When alfalfa is a young, establishing seedling, it’s a real weakling,” he said. “It’s a small-seeded plant, so any stress or unfavorable condition it experiences during establishment will cause it to die.”
All herbicide labels have instructions regarding restrictions and potential herbicide impact on subsequent crop growth.
“Alfalfa planting intervals vary widely across herbicides from four to 34 months, so follow whatever the label says,” Creech said. “It is important to plan, read labels and know which herbicide to use.”
External factors can influence the length of persistence of herbicides.
“One of the major ones is soil texture,” Creech said. “All soils have a magnetism that interacts with the magnetic charge on herbicide molecules, which influences how much herbicide moves in the soil.”
Sandy soils have less charge per unit area, Creech said.
“That means we can see more herbicide movement,” he said. “Clay soils have more charge per unit, so there is less herbicide movement.”
If herbicide is applied on a sandy soil followed by an alfalfa planting, the herbicide will dilute quicker and the plants can grow without impacting the alfalfa stand establishment.
“On heavier soils the herbicide may still be concentrated in the top inch of soil and then we’ve got a problem when we plant alfalfa one-quarter to one-half of an inch deep,” Creech said.
Herbicide breakdown happens differently based on the soil temperature.
“For the two to three months during the winter when the soil is frozen, there is no microbial activity,” Creech said. “The herbicide going into that cold period and the herbicide in the soil coming out of the cold period are identical because nothing has happened, but in the warmer months the soils are active and the herbicide breaks down more readily.”
Tillage can help reduce herbicide residual by mixing the soil.
“In less tillage situations, we can have a concentration of the herbicide at the top of the soil surface,” Creech said. “Headlands and overlap areas are places we’ll have a higher concentration of previous crop herbicide and where it will be likely to see herbicide injury on an alfalfa stand.”
Alfalfa producers can use a field bioassay to evaluate the field they plan to seed to alfalfa. For the test, alfalfa seed is planted in a bucket of dirt taken from the field and also in a bucket of dirt taken from an adjacent field that is safe for herbicide residual.
“Watch the alfalfa growth for the next three to four weeks to compare the field in question versus the safe field,” Creech said. “Watch for the color, stunting or anything that suggests there’s something in the soil that’s unfavorable for alfalfa growth.”
If the alfalfa growing in both buckets looks identical, Creech said, then the field is safe for alfalfa planting.
“This is a good way to help avoid a bad situation by planting into contaminated soil,” he said.