24 May Evaluate Alfalfa Stands with Confidence – Count Stems
It’s that time of year when we’re all itching to get out into the field – whether it’s to do that all-important first cut of alfalfa or determine if an alternative crop should be rotated in. Evaluating alfalfa stands is an important factor in crop rotation or stand take-out decisions. Older stands or a winter-damaged stand may still have enough ‘oomph’ to go for that important first-cutting harvest, especially if you need summer feed. But sparse or aged-out stands may lack the yield potential to deliver adequate yields in later cuttings. This is especially true when considering more productive summer cropping alternatives can be planted, such as forage sorghum, sorghum-sudangrass or millet.
It’s important to remember that the first cutting of alfalfa in spring is the most important cutting of the growing season! The first cutting is the highest yielding cutting for fall dormant alfalfa varieties grown in regions with cold winters. What’s more, forage quality from first cutting alfalfa beats cuttings during summer, when comparing cuttings made at the pre-flowering bud stage. This stage occurs when flower buds begin to form near the top of stems and is normally considered the best growth stage for harvesting solid yields of dairy-quality hay. So, it’s important to evaluate stands with confidence when thinking about yields over the course of the summer.
Perform alfalfa stem counts when alfalfa is actively growing. Stem counts provide a more accurate gauge of yield potential than plant counts. University research results suggest that 55 stems per square foot are needed to achieve full yield potential in established pure alfalfa stands.
Mixed stands with grass may require fewer stems per square foot to achieve full yield potential. There’s a judgment call to make but some research suggests that about 30-35 stems per square foot in established alfalfa-grass mixed stands can be adequate when the grass component is actively growing and contributing its fair share to yield.
What about stem counts in first-year alfalfa stands? Research with elite varieties in first-cutting spring yields of stands established late the previous summer, showed optimum yield was achieved with about 67-70 stems per square foot or greater. Young plants with small crowns typically have fewer crown buds, ‘thinner’ stems and smaller leaves, versus fully established plants which have more robust crowns capable of supporting more stem and leaf growth.
Figure 2 Source: Sheaffer-2page-2018-2.pdf (alfalfa.org)
Let the Competition Begin! Young alfalfa plants begin to develop a taproot soon after seedling emergence. As young plants continue to grow, a crown forms near the top of the taproot and stem buds begin to appear and proliferate as the crown grows. Early stand life is characterized by many plants per square foot with single stems, followed by early crown development with low-multiple stems, leading to full crown development with a greater number of stems per plant.
There can be quite a bit of competition during this progression, and stand thinning occurs. Even if your first cutting of a new alfalfa seeding doesn’t achieve high stem count levels of 70 per square foot or greater, that’s no cause for panic if you have an adequate plant count. That’s because expanding plant crown size can fill in some of the gaps needed to achieve 55 stems per square foot in subsequent cuttings as needed for the full yield potential of more mature stands of alfalfa.
Photo 1. These alfalfa plants are shown after the first spring cutting, following late summer sowing the previous year. This represents the first cutting post-seeding. Alfalfa plant counts following this first spring cutting reveal 33 plants per square foot with 82 stems per square foot. These young plants are averaging 2.5 stems per plant now, but as plants continue to grow and crowns enlarge, competitive thinning will occur.
Photo 2. Two-year-old alfalfa plant following cutting. This plant made up for some of the distance from its nearest neighbor plant six inches away, with more than 20 green stems from recent cutting (dark stems from prior year).
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