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 US. Forage mixtures of alfalfa with perennial cool-season grasses offer whole-system (soil, crop, and livestock) advantages over alfalfa monocultures. Our increased knowledge of neutral detergent fiber (NDF) digestibility has shown additional benefit to feeding of grasses in ruminant diets. But data on the yield and forage quality potential of alfalfa/grass mixtures with modern grass varieties and harvest management has been lacking.
Yield and forage quality research
A team of UMN-Extension personnel has 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 forage mixtures used in study.
|Seeding rate for mixtures|
|Third grass in mix|
|Mix||Alfalfa||Meadow fescue (MF)||Specie||Rate|
|pounds per acre||lb/A|
|2||10||7||Tall fescue (TF)||10|
|3||10||7||Meadow brome (MB)||15|
|4||10||7||Smooth brome (SB)||15|
Cool-season grasses enhance forage quality
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 put on crude protein content of forage and not the digestibility.
Greater digestibility allows for greater intake of forage. 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 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 orchardgrass varieties.
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 and it appeared to tolerate the cutting intensity of a four-cut system. Meadow fescue and improved orchard grass varieties also performed well. From our trials, smooth bromegrass, 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. Bromegrasses 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 different species had greater survival rates when part of a three species mixture compared to when in a pure stand. Smooth brome and meadow bromegrasses showed the typical slower establishment that we expect in bromegrass 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, as 2012 was 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 bromegrasses in the seeding year.
Manage cutting height
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 adjusted to a 3-4" cutting height. This cutting height will also help to reduce soil contamination in forage as well.
In conclusion, from the results of this project, meadow fescue is a cool season grass that offers another forage choice in our growing areas. Its yields and forage quality would meet or exceed other comparable grasses and also compare with alfalfa. It also offers an additional grass to use in mixtures with alfalfa and other grasses.