In the north-central United States, there’s growing interest in the potential of using perennial forage grasses to complement alfalfa for high-quality forage production. Forage mixtures of alfalfa with perennial cool-season grasses offer whole-system (i.e., soil, crop and livestock) advantages over alfalfa monocultures.
Research about neutral detergent fiber (NDF) digestibility shows many benefits to feeding ruminants grasses. However, there’s a lack of data on the yield and forage quality potential of alfalfa-grass mixtures with modern grass varieties and harvest management.
Research: Yield and forage quality
To better understand alfalfa-grass mixtures, researchers assessed forage yield, quality and species compatibility of alfalfa-grass mixtures vs. alfalfa monocultures on Minnesota farms. For more than eight years, researchers established stands and conducted harvests and collected and analyzed data.
Table 1 shows the seeding rates. Researchers only seeded 10 pounds of alfalfa seed in the mixtures with the intent to have a 50:50 alfalfa-grass stand. For the most part, this was achieved.
Seeding rates reflect seed size and the number of seeds per pound. Good soil-to-seed contact is the critical factor for successful establishment.
Table 1: Seeding rates for the study’s forage mixtures
|Mix||Alfalfa||Meadow fescue (MF)||Third grass in mix: Specie||Third grass in mix: Rate|
|1||10 pounds per acre||12 pounds per acre||--||--|
|2||10 pounds per acre||7 pounds per acre||Tall fescue (TF)||10 pounds per acre|
|3||10 pounds per acre||7 pounds per acre||Meadow brome (MB)||15 pounds per acre|
|4||10 pounds per acre||7 pounds per acre||Smooth brome (SB)||15 pounds per acre|
|5||10 pounds per acre||7 pounds per acre||Orchardgrass (OG)||4 pounds per acre|
Forage quality of most cool-season grasses can complement alfalfa by moderating soluble protein concentration and adding greater amounts of digestible NDF. Too much focus is often put on a forage’s crude protein content and not its digestibility.
Greater digestibility allows for greater forage intake. At the same stage of maturity, grasses exceeded alfalfa in the amount of digestible NDF.
Matching stage of maturity with alfalfa, especially in the first cutting, can be challenging with certain species. It’s very important to use improved varieties within species of grasses to attain the higher-quality forage. This is particularly true for tall fescue and orchardgrass varieties.
Meadow fescue and orchardgrass
Meadow fescue’s yields and forage quality meet or exceed other cool-season grasses and make it comparable to alfalfa. This cool-season grass is a viable forage choice for alfalfa-grass mixtures.
For lactating cow forage, the mixture of alfalfa with meadow fescue and tall fescue resulted in higher yields and higher-quality forage compared to alfalfa alone. In addition, it appeared to tolerate the cutting intensity of a four-cut system.
Meadow fescue and improved orchardgrass varieties also performed well.
The trial showed smooth bromegrass, meadow brome and timothy can yield well, especially in spring, but may not tolerate a four-cut system as well. They’re better suited to a two- or three-cut system and also do well in a managed pasture system.
Bromegrasses can also be used in dry cow and heifer diets at a more mature stage by using different cutting strategies for some fields and even pastures.
One of the concerns from the observations is that newer and improved grass varieties within species such as tall fescue and orchardgrass may not have as much cold tolerance as older varieties.
However, each species had greater survival rates when part of a three-species mixture compared to a pure stand.
Smooth brome and meadow bromegrasses showed the typical slower establishment expected in bromegrass. They’re better-suited to spring seeding with a cover crop.
Meadow brome was particularly slow to establish. This might have been due to the seeding year, as 2012 was a drought year. However, it did become very prevalent in the second year.
Meadow brome is particularly sensitive to cutting height, and you shouldn’t expect to harvest much of either bromegrasses in the seeding year.
Another critical aspect of managing grasses in alfalfa stands is to watch the cutting height. Grasses need to regrow from aboveground stubble left in the field. Alfalfa regrows from the crown, which is belowground.
If a mixed stand of grass and alfalfa is cut at a 2-inch height, grasses won’t grow back as quickly as the alfalfa and will be more prone to die-back.
This is a particular concern with disc mowers, which need to be adjusted to a 3- to 4-inch cutting height. This cutting height will also help to reduce soil contamination in forage as well.
Reviewed in 2018