Can Managing Calcium Improve Alfalfa Yield and Quality?

Dan Davidson, Agronomist PhD, CPAg, CCA

Managing calcium improved alfalfa yield based on a pilot study conducted on our farm in Northeast Nebraska.

While alfalfa provides its own nitrogen, good producers know that to harvest high yields, they must apply phosphate, potassium and sulfur annually. But what about calcium? We know that all plants need calcium since it is classified as a secondary macronutrient along with magnesium and sulfur. Despite its importance, this macronutrient is undervalued by high-yield growers and should be more central when looking to maximize this legume’s production.

Calcium plays a role in cell division and elongation, cell wall development and expansion, flower bud and fruit survival, nitrate uptake and metabolism, enzyme activity and sugar transport and starch metabolism. The image shows a calcium-deficient leaflet on the left.

When growing alfalfa, calcium deficiency not only affects the leaves but also the animals that eat alfalfa as forage. The extractable calcium soil test and base saturation levels often appear sufficient enough. However, if you are looking for high digestible quality alfalfa, you also have to assure enough calcium is available in the alfalfa cuttings.

Broadleaf crops like cotton, peanuts and soybeans will benefit from managing calcium in the plant. Modulating calcium and enabling it to be more mobile in plants is a key benefit of Fortalis®. Calcium, while sufficient by tissue tests, isn’t always available to meet demand at sites of growth such as leaf axils, flower buds, or fruiting bodies. Since calcium is considered immobile, alfalfa plants don’t naturally recycle it to support new growth.

Croda/Plant Impact, the makers of Fortalis, asked me to run a pilot study on alfalfa on my farm in Northeast Nebraska. Producing high-yield alfalfa is one of my passions and I am on the hunt for a 10-ton (per year) yield in my rainfed area. Each additional bale I can harvest per acre takes me closer to that goal, and while this is challenging, I am crafting the right program to achieve these higher yields, knowing it will take a lot of time, and trial and error.

This year, I took off four cuttings of alfalfa a season on a 27- to 30-day cycle, starting with the third week of May, with the last ending during the same period in September. I applied Fortalis on my alfalfa along with a recommend rate of Priaxor fungicide in half of the 50-acre field, following the second and third cutting when there was 4 inches of regrowth. The other half of the 50-acre field received Priaxor alone. Both sides also received a foliar feed during both applications with a total application volume of 15 gallons per acre. Alfalfa was harvested with a John Deere 568 baler at a diameter of 68.5” inches and calculates the number of bales per acre. At this size the alfalfa bales weigh about 1600 pounds each.

In summary, the Fortalis (+) treatment produced 8 and 4 total additional bales for the third and fourth cuttings, respectively, compared to the untreated check. However, the fourth cutting was down by about 10 bales compared to the long-term average for that cutting. I attributed the poor fourth cutting regrowth to the wet and cool summer that unexpectedly extended harvest cycles till the crop ran out of time, heat and sunlight to produce a good cutting.

Third Cutting – total of 87 bales

+ Fortalis, 25 acres, 47.5 bales =
– Fortalis, 25 acres, 39.5 bales

Fourth Cutting – total of 52 bales

  • + Fortalis 26 bales, 22 acres = 1.18 bales/A
  • – Fortalis 26 bales, 25 acres = 1.04 bales/A

There were an additional 0.32 bales/A x 25 acres = 8 bales or 6.4 tons (8 bales x 1600 lbs./A ÷ 2000 lbs./ton = 6.4 tons)

There were an additional 0.18 bale/A x 22 acres = 4 bales or 3.2 tons (4 bales x 1600 lbs./A ÷ 2000 lbs./ton = 3.2 tons)

I admit that this wasn’t a robust experiment with exact measures and weights and replications. It should be considered more of a pilot study and Plant Impact intends to evaluate this response more closely in a replicated trial. However, based on my intuition, the results are meaningful enough for me to consider this as a standard practice in 2019.

Additionally, I question the benefit of treating the fourth cutting due to the lack of time to build yield. I also question whether fungicide was of any value and whether I should have used an insecticide. Generally, we don’t have any disease issues warranting a fungicide since alfalfa is cut every month. However, there is a myriad of insects in any alfalfa that could be controlled.

In retrospect I should have pulled core samples from bales harvested from the treated and untreated portions of the field, a practice which I could easily implement next year. It would be interesting to see how Fortalis may have improved forage quality. I will probably repeat the project on a new field of alfalfa and run forage analysis at the same time.

Dan Davidson is a PhD agronomist, part-time farmer and soybean expert from Nebraska who consults with soybean checkoff and industry on crop production, marketing, and product development projects.

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