Grasses to grow with alfalfa in mixes
Interest in the potential for perennial forage grasses to complement alfalfa for high-quality forage production continues to grow in the North Central USA. Forage mixtures of alfalfa with perennial cool-season grasses offer whole-system (soil, crop, and livestock) advantages over alfalfa monocultures. Our increased knowledge of NDF digestibility has shown additional benefit to using grasses in ruminant diets. But data on the yield and forage-quality potential of alfalfa/grass mixtures with modern grass varieties and harvest management was lacking.
A team of UMN-Extension personnel have been assessing forage yield, quality, and species compatibility of alfalfa/grass mixtures vs. alfalfa monocultures on Minnesota farms for the past eight years. We were fortunate to receive funding for research to establish stands and conduct harvests, collect yield and composition data, and analyze forage quality for multiple years.
The seeding rates are shown below in Table 1. Note that we only seeded 10 pounds of alfalfa seed in the mixtures. Our intent was to have a 50:50 alfalfa: grass stand and for the most part, this was achieved. Seeding rates reflect seed size and number of seeds per pound. The critical factor of success in establishment is good soil to seed contact.
Table 1. Seeding rates for mixtures
|Alfalfa (Alf) = 10 lbs/acre||+ meadow fescue (MF) = 12 lbs/acre|
|Alf 10 lbs + MF 7 lbs||+ tall fescue (TF) = 10 lbs/acre|
|Alf 10 lbs + MF 7 lbs||+ meadow brome (MB) = 15 lbs/acre|
|Alf 10 lbs + MF 7 lbs||+ smooth brome (SB) = 15 lbs/acre|
|Alf 10 lbs + MF 7 lbs||+ orchard grass (OG) = 4 lbs/acre|
Forage quality of most cool season grasses can complement alfalfa in forage by moderating soluble protein concentration and adding greater amount of digestible NDF. Too much focus is often placed on crude protein content of forage and not its digestibility. Greater digestibility allows for greater intake of forage. At the same stage of maturity, grasses exceed alfalfa in the amount of digestible NDF. Matching stage of maturity with alfalfa, especially in the first cutting, can be a challenge with certain species. It is very important to use improved varieties within species of grasses to attain the higher quality forage. This is particularly true for tall fescue and orchard grass varieties.
For lactating cow forage, the mixture of alfalfa with meadow fescue and tall fescue results in higher yields and higher quality forage compared to alfalfa alone and it appears to tolerate the cutting intensity of a four cut system. Meadow fescue and improved orchard grass varieties also perform well. From our trials, smooth brome grass, meadow brome and timothy can yield well, especially in spring, but may not tolerate a four cut system as well. They are better suited to a two or three cut system and also do well in a managed pasture system. Brome grasses can also be used in dry cow and heifer diets at a more mature stage by utilizing different cutting strategies for some fields and even pastures.
Our observations include a concern that newer and improved grass varieties within species such as tall fescue and orchard grass may not have as much cold tolerance as older varieties. However, each of the species tested had greater survival rates when planted in a three species mixture than as a pure stand. Smooth brome and meadow brome grasses showed the typical slower establishment that we expect in brome grass and are better suited to spring seeding with a cover crop. Meadow brome was particularly slow in establishing. This might have been due to the year of establishment; 2012 being a drought year. It did however become very prevalent in the second year. I do believe that meadow brome in particular, is sensitive to cutting height. I would not expect to harvest much of either brome grasses in the seeding year.
Another critical aspect of managing grasses in alfalfa stands is to watch the cutting height. Grasses need to regrow from the stubble above ground left in the field. Alfalfa regrows from the crown, which is below ground. If a mixed stand of grass and alfalfa is cut at a 2" height, the grasses will not grow back as fast as the alfalfa and will be more prone to not surviving. This is particularly a concern with disc mowers. A disc mower needs to be adjusted to a 3- to 4-inch cutting height. This cutting height will also reduce soil contamination in forage.
In conclusion, from the results of this project, meadow fescue is a cool season grass that offers another forage choice in our growing area. Its yield and forage quality would meet or exceed other comparable grasses and also alfalfa. It is also an additional grass to use in mixtures with alfalfa and other grasses.