Eight Great Reasons to Seed Grass with Your Alfalfa Hay

March 23, 2023 / Alfalfa, Forages, Newsletter

Margaret A Smith, PhD, Forage Agronomist

Photo: Alfalfa with 30% grass mix, courtesy of Jerry Cherney, Forage Extension Specialist and Professor of Agriculture at Cornell University

Most of the hay stands in the upper Midwest are seeded with only alfalfa. If you’re growing alfalfa hay, you may want to consider adding grass to your hay mix for greater diversity in plant species, insect communities, soil microbiological communities, and response to environmental conditions. There at least eight great reasons to consider diversifying and seeding grass with your alfalfa hay:

Grass in the hay mix can improve the nutritional profile of the hay. Grass fiber in the vegetative stages is more highly digestible than that from alfalfa at comparable stages of growth.
Grass improves drying speed in the windrow (this tendency varies among grass species).
Grass as a percentage of the hay stand can improve hay yields.
Grass-alfalfa mixtures yield and survive better on soils with sub-optimal drainage. In fields with variable soil conditions, hay yields with grass in the stand can also be more consistent throughout the year.
Grass helps maintain hay yields and quality as alfalfa plant populations decline with time.
Grass extends the life of the hay stand.
Mixed alfalfa and grass stands have lower populations of potato leafhoppers and alfalfa weevils compared to pure alfalfa stands.
Grass roots interspersed with alfalfa roots improve erosion control in sloping hayfields, particularly as stands age.

Best Grasses for Hay Mixes

The best grasses for alfalfa hay companions are meadow fescue, tall fescue (soft-leaved and endophyte-free), and orchardgrass. For milking herds, meadow fescue, with the highest quality of these (in northern climates), is a great choice. For more diversity and higher grass yields in this mix, include some tall fescue or orchardgrass. For growing beef in the feedlot or dry cows, tall fescue and orchardgrass are excellent choices. Meadow bromegrass can be a good addition to a diverse hay mix, particularly in hotter and drier areas; Alaska bromegrass can also add diversity and is extremely winter hardy.

Festulolium, perennial and Italian ryegrasses can also contribute high quality forage to a diverse hay mix but are less winterhardy, will not provide long term persistence, and are slower to dry than other species. They’re better suited for haylage or grazing systems.

Smooth bromegrass and timothy are not as productive as these other grass species. They contribute nicely to a first hay cutting but produce less than other grasses during the warmer, later summer months. In addition, they don’t survive well in more intensive three- or four-cut hay systems.

Ratios of Grass to Alfalfa

Hay from a stand with a ratio of 30-40% grass has the potential to match or surpass alfalfa yields from pure stands and to have higher feeding quality. We suggest seeding a 25:75 or 30:70 grass-alfalfa ratio, as the grass percent will increase with the age of the stand. Percent grass in the stand is also influenced by weather conditions at the time of seeding. Ample moisture following seeding will favor grass establishment, while dry conditions will favor the alfalfa.

Grass-alfalfa ratios can even change within a growing season. Research from Cornell University demonstrated that because cool-season grass growth peaks in the spring, the grass percentage in a mixed hay stand also changed within a growing season (with the percent grass highest at first cutting and less in subsequent cuttings).

This response to weather at seeding, the change in hay stand composition over time, and the differences in grass productivity within a growing season may well result in different grass to alfalfa ratios than planned for. This may seem frustrating but can contribute to overall resiliency of the forage supply on the farm.

Managing grasses in the hay stand

The composition of mixed grass-alfalfa hay stands will be more variable than straight alfalfa. Be prepared to evaluate the stand and adjust cutting schedules based on grass growth, especially for the first cutting, to avoid grass heading out before harvest. Base subsequent harvests on alfalfa growth stage. For best coordination of grass heading and alfalfa flowering times in the spring, select grass varieties that are late maturing within their species.

Grass comprising 40% or less of a mix with alfalfa will get the nitrogen needed for growth from the companion alfalfa plants. When grass percentages climb above 40%, supplemental N may be needed to optimize yields.

For best regrowth and extended productivity, cut hay stands containing cool-season grasses at a 3.5” to 4” height, rather than the to 2” to 3” height recommended for pure alfalfa stands.

Feeding Mixed Alfalfa-Grass Hay

With the diversity and variability in mixed hay stands, it’s especially important to test each hay cutting for quality before including that hay in your livestock rations. Feed testing takes the guesswork out of ration formulation!

Don’t compare Relative Feed Value (RFV) of grass-hay mixes with straight alfalfa hay. RFV was developed for comparisons of pure alfalfa and isn’t a good measure of mixed hay’s feed value. Relative Forage Quality (RFQ) gives a more accurate estimate of a grass’s fiber digestibility and potential impact in the diet.

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Digging Deeper: Eight Great Reasons to Add Grass

Here’s a more in-depth look at the eight reasons listed above.

1. Grass in the hay mix can improve the nutritional profile of the hay. Grass fiber in the vegetative stages is more highly digestible than that from alfalfa at comparable stages of growth.

Grasses contain 20-30 percentage points higher digestible fiber (NDFD48) than legumes do at comparable growth stages (grass leaves are more digestible than alfalfa stems). A 25:75 ratio of grass to alfalfa in a hay mix will raise the average NDFD48 of the hay approximately five percentage points compared to a pure alfalfa stand cut at the same maturity. [b,g]

In addition, grasses have lower non-fibrous carbohydrates (readily fermentable carbohydrate) than both alfalfa and corn silage. This may seem like a negative factor, but too much readily fermentable carbohydrates in high corn silage or grain rations can lead to rumen acidosis, reduced feed intake, and lameness (founder) in milking cows and feedlot beef finishers. More grass fiber slows the overall rate of carbohydrate digestion in mixed rations. [d,m]

2. Grass improves drying speed in the windrow (this tendency varies among grass species).

This is true for stands of 30% or more grass—particularly in the first cutting when developing, immature grass stems are part of the forage mix—which help add loft to the windrow, increasing air flow. Later cuttings will contain only grass leaves. In addition, most grasses contain less water than alfalfa does. Some grasses, though, dry more slowly than others: perennial and Italian ryegrasses contain more water (therefore, lower dry matter percentage at harvest than other grasses) so are slower to dry. [n]

3. Grass as a percentage of the hay stand can improve hay yields.

University of Minnesota researchers compared alfalfa hay stands with mixed stands, which included nine cool-season grass species, each seeded by itself with the alfalfa (2-species hay mixes, only). Yields were measured each year through the third production year at Underwood (west central MN), Hutchinson (west of Minneapolis), and Avon (northwest of Minneapolis). The alfalfa and grass content of the hay stands varied widely across the three sites. Success of grass in the mixed seedings was more successful at Underwood than Hutchinson. Certain alfalfa grass mixtures consistently had greater yields than alfalfa alone. Tall fescue was the most consistent grass contributing to higher yields, with orchardgrass second. Of the nine species evaluated, orchardgrass had the highest percent of grass in the mixes. (This corroborates farmers’ observations that “orchardgrass can take over a hay stand.”) Mixtures with tall fescue and orchardgrass also produced the most digestible fiber and the most potential milk production per acre. [n,o]

4. Grass-alfalfa mixtures yield and survive better on soils with sub-optimal drainage. In fields with variable soil conditions, hay yields with grass in the stand can also be more consistent through the year.

In the Northeastern U.S., on soils with more variable drainage and lower overall productivity potential than many soils in the upper Midwest, alfalfa-grass mixes out yielded pure alfalfa stands. Dry matter yield was 0.1 to 0.4 T/a higher for every 10% unit increase in grass percentage. [a]

5. Grass helps maintain hay yields and quality as alfalfa plant populations decline with time.

The best grasses as alfalfa hay companions—meadow fescue, tall fescue and orchardgrass—are more winter hardy, have few disease problems, typically live longer than alfalfa, and persist as alfalfa populations decline. In addition, grasses provide competition and slow weed infestations in hay stands. [d]

6. Grass extends the life of the hay stand.

Grass crowns (or sod) stand up better to traffic than alfalfa crowns do. Fall grass growth catches more snow than alfalfa stubble alone, which helps insulate the alfalfa crowns making them better able to withstand large temperature swings and avoid freezing damage in the winter.

Extending the life of a hay spreads fixed costs over more years and hay harvests. [n]

7. Mixed alfalfa and grass stands have lower populations of potato leafhoppers and alfalfa weevils compared to pure alfalfa stands.

Iowa State University entomologists compared insect population in pure alfalfa stands, alfalfa-orchardgrass mixes and alfalfa-smooth bromegrass mixes. They found that alfalfa-forage grass intercrops reduce potato leafhopper and alfalfa weevil pest populations compared with the alfalfa monocultures. [h]

8. Grass roots interspersed with alfalfa roots improve erosion control in sloping hayfields, particularly as stands age sloping hayfields.

Wisconsin researchers evaluated erosion in no-till alfalfa and an alfalfa-bromegrass mix when terminating stands in the fall. Erosion occurred in the early spring before no-till corn planting. Fall-killed alfalfa did not provide enough ground cover (less than 30 percent). But fall-killed stands that contained 40% grass, provided 30-40% ground cover in the spring, bringing erosion to within the allowable limit without affecting corn yields. [k]

In addition, the longer the life of a hay stand is extended through improved management—including having a grass component in the stand—the more soil erosion can be reduced by not having to rotate out of hay as frequently.