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Evaluating Alfalfa Stands Part II – Renovation Options

Renovation Options and Considerations

Thin stands that need renovated have a few options to consider. Typically, alfalfa’s autotoxicity makes planting into established stands impossible. However, in new stands that are less than 12 months old, there is a chance that reseeding alfalfa in areas that are extremely thin or void of alfalfa may see success. The risk of new seedlings not establishing is still present, but these conditions present the best chance at success, when planting alfalfa into existing alfalfa. It is important to note that dry conditions will hinder the ability of the newly seeded alfalfa to germinate.

High quality grasses like orchardgrass, meadow brome, or tall fescue can be utilized to fill out stands that are thin. For best establishment, use a no-till drill and seed following a late summer or early fall cutting. Depending on the density of the alfalfa stand, drill 4-8 lbs. of orchardgrass, 10-20 lbs. of meadow brome, or 5-10 lbs. of an endophyte free tall fescue. Fall establishment of these species needs to occur soon to ensure germination and growth are enough to keep seedlings alive through the winter. Many require at least six weeks of growth from the time of germination before a hard frost to have good winter survival. Done correctly though, these new plants can begin growth right away in the spring and boost yield while preserving hay quality.

A final option is to seed another legume. Red clover and birdsfoot trefoil in particular are both winter hardy species that can be used to fill out thin stands. While maintaining quality, these legume options are shorter term solutions and may not provide as much yield as grasses. 6-8 lbs. of birdsfoot trefoil or 6-10 lbs. of red clover will adequately fill in a thinning stand. One drawback to these alternative legumes is that hay produced in heavy trefoil and clover stands may require a longer drying period than straight alfalfa. However, both species offer higher quality over an extended maturation time frame, which can extend the cutting window of alfalfa.

In the above renovation recommendations conventional or RoundUp® Ready alfalfa have similar renovation plans, but in stands were RoundUp® Ready alfalfa is planted the addition of another forage species limits the utility of the genetics. The additional herbicide flexibility is gone and renovating stands of RoundUp® Ready alfalfa becomes comparable to conventional stands in terms of management difficulty. The choice between keeping the stand and introducing a new forage species may be more a decision on the longevity of the stand as well as flexibility for in season weed control. If you have stems under the recommended quantity (Evaluating Alfalfa Stands Part 1) and heavy weed pressure, adding an additional species may be a good option. Despite no longer having glyphosate options, renovated RoundUp® Ready alfalfa can still utilize several herbicide options for traditional alfalfa when it goes dormant and early in spring (Weed Control in Alfalfa Post Green Up).

To understand the impact of interseeding on alfalfa stands, we first need to have a solid understanding of what to expect from a pure stand of alfalfa. The quality of alfalfa is superior to most other forages due to high levels of energy and crude protein (CP). Optimizing harvest for an operation’s quality goals will result in more profitable operations and addresses the compromises of yield, quality, and stand longevity (Table 1). Following the same maturity stage, digestibility steadily decreases from 75% to below 60% when going from the bud stage to the full bloom stage, respectively.

Alfalfa Stage Crude Protein (CP) Relative Yield
Bud 22-26% Lowest Potential
Early Bloom 18-22%
Mid-Bloom 14-18%
Full Bloom 9-13% Highest Potential

For pure alfalfa stands, stand density does not affect CP, acid detergent fiber (ADF), or lignin content. Hay quality is affected, however, if the thinness of the stand allows for weed pressure. Undesirable grasses will decrease CP, digestibility, increase neutral detergent fiber (NDF), lower intake and reduce NDF digestibility. Therefore, renovation does not mean a loss in quality, so how does interseeding really affect quality and quantity? In general, perennial grasses offer more quantity compared to quality. On the flip side, the legumes will bring more quality and less quantity. This is another important consideration when it comes to weed control as well; typically legumes will not be as competitive as grasses.

Addition of Perennial Grasses

A study conducted by the University of Wisconsin showed that interseeding a perennial such as orchardgrass increased CP to 20.8% while having 32.9% ADF, 45.5% NDF, and a relative feed value (RFV) of 129. Alfalfa alone in the same study only had 19.5% CP and an RFV of 119. The same study showed yield from the alfalfa/orchardgrass plot produced almost 0.5 ton/ace more than alfalfa alone. While a quality perennial grass will impact hay quality on its own, it can also be beneficial to quality in thin stands by competing with weed species that could degrade the final product. Therefore, the addition of perennial grasses can maintain quality and quantity.

Addition of Legumes

The addition of legumes into an existing alfalfa stand can improve quality and maintain quality as it matures into bloom. However compared to the addition of grasses, the quantity will most likely be lower. It is also important to remember that birdsfoot trefoil and red clover are not nutritionally the same as alfalfa. For example, birdsfoot trefoil, has a higher TDN (Total Digestible Nutrients) from bud to 50% bloom compared to alfalfa. Red clover has higher digestibility compared to alfalfa and previous research suggests that it may be a more nutrient dense forage compared to alfalfa. These are both great additions when renovating an alfalfa stand, quality can be maintained and high quality cutting windows can be extended. The tradeoff is quantity.

References:

Gildersleeve, R., Undersander, D., and Wood, T., “Seeding into an existing alfalfa stand”, University of Wisconsin, Focus on Forage, 5:9

Undersander, D., et. al., “Birdsfoot trefoil for grazing and harvested forage”, North Central Regional Extension Publication 474

Anderson, B., “Adding grass to thinning alfalfa offers a win-win”, University of Nebraska-Lincoln, CropWatch article March, 15, 2018

Source: University of Nebraska CropWatch

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