Extension > Agriculture > Dairy Extension > Forages > Seeding grasses with alfalfa: This old idea makes cents today
Seeding grasses with alfalfa: This old idea makes cents today
Including grasses in some of your new alfalfa seedings is worth considering. Years ago, mixing grasses with alfalfa was standard practice, whether seeding an oat companion crop and/or including timothy or smooth bromegrass with the under-sown alfalfa. The increased availability of grass herbicides and the evolution of how we estimate forage quality contributed to the movement away from grasses towards alfalfa monocultures. However, recent developments in forage testing have helped restore the respect that grasses somewhat unfairly lost.
Reasons to seed grass with alfalfa:
- Yield. Harvested yield is the single largest driver of profitability when producing stored forage, and alfalfa-grass mixtures often yield more than alfalfa alone. The fixed costs of forage harvesting are large so every cutting needs to produce a bountiful harvest. A small grain or Italian/annual ryegrass companion crop with a spring seeding provides greater seeding-year yield than direct-seeded alfalfa. Sod-forming grasses like reed canarygrass or smooth bromegrass enable traffic on the field when more soil moisture is present and will accelerate drying rate, reducing the potential for weather-related losses. Orchardgrass and tall fescue have good fall growth that enables a productive fall harvest/grazing while providing more residue than just alfalfa stubble to catch snow and insulate alfalfa crowns.
- Drying rate. Grasses with stems present accelerate swath drying rate. Grasses that produce stems with every growth cycle such as reed canarygrass, smooth bromegrass, and timothy create more fluffy swaths that dry faster. Note though that some leafy grasses with shiny surfaces such as tall fescue and the ryegrasses will not speed drying rate.
- Persistence. Fall growth/residue of grasses provides better snow catch and insulation than alfalfa stubble alone, so alfalfa crowns are better protected from winter injury. Also, if winter hardy grasses are used, they provide insurance if the alfalfa does winter kill.
- Feeding value. At similar stages of maturity, grasses have higher NDF than legumes, but considerably higher NDF digestibility. The relative feed value (RFV) index is a good index for alfalfa quality, but it tends to undervalue the feeding value of grasses. The new relative forage quality (RFQ) index provides a better reflection of grass's higher fiber digestibility and the impact of that on energy and intake potential. Many dairymen feed straw to add fiber to their rations; forage grasses provide that fiber in a more digestible form.
- Natural weed suppression. Weeds are opportunists that encroach in perennial forage stands when too much bare soil is exposed for too long. Some grasses improve the speed with which full soil cover is achieved during the seeding year. Many grasses also provide more long-term cover, particularly if broadcast seeded or if they are sod-formers. This reduces opportunities for weeds to establish.
- Erosion control. This is a major advantage of a small grain companion crop.
- Bloat. While not an issue with haylage or hay, grass-alfalfa mixtures have less bloat potential than pure alfalfa when grazed.
- It's natural. Prairies are diverse mixtures of grasses and legumes, not legume monocultures. While our forage production methods are certainly more intensive than the native prairie-bison system that used to dominate much of western and southern Minnesota, surely there is some sound ecological basis to the complex design of natural forage stands.
Some management considerations with alfalfa-grass mixtures:
- Short rotations. To maximize yield potential and capitalize on alfalfa's fixed nitrogen in crop rotations, on many dairy farms, it is most profitable to plan to keep alfalfa stands only three to four years. Grasses with less dependable long-term persistence but high production and quality such as tall fescue, festulolium, and perennial ryegrass may have potential in these shorter rotations.
- Seeding rates. The trick is to seed enough grass to make a legitimate contribution, but not seed competitive grasses too heavily. Frequency and height of cutting can influence alfalfa:grass ratios. For examples, closer and/or less frequent cutting reduces orchardgrass percentage.
- Seeding methods. Broadcast seeding is probably the best method for seeding alfalfa-grass mixtures, especially when using bunch grasses, to provide more even cover. An obvious exception is a small grain or Italian/annual ryegrass companion crop, which can be drilled, and the perennial forages broadcast. Avoid seeding alfalfa in the same row with competitive grasses.
- Seeding timing. Since there are few herbicide options for alfalfa-grass mixtures, August may be the best time to seed them if soil moisture is adequate, since weed competition is less then compared to spring.
- Swath management. Wide swaths speed drying rate and reduce potential for weather-related losses. This is especially important if leafy grasses are used.
- Fertility. Adequate levels of potassium are important to maintain legumes with competitive grasses because grasses extract soil potassium more efficiently than legumes. Manure is a great fertility source prior to seeding or immediately after cutting.
Table 1. Some grass options for seeding with alfalfa in Minnesota.
| Grass Species | Rate (lb/ac) | Alfalfa (lb/ac) | PROS | CONS |
| Small Grain harvested at boot stage | 1 - 1.5 bu/ac | 12 - 15 | High seeding-year yield Good erosion/weed control due to rapid emergence/cover |
Moderate quality Too competitive if seeded too heavily or harvested after boot stage |
| Italian (annual) Ryegrass |
2 - 5 | 12 - 15 | High seeding-year yield High quality, leafy Good snow catch/insulation |
Difficult to wilt to hay moisture Too competitive if seeded too heavily or in same row with alfalfa |
| Annual Ryegrass | 2 - 5 | 12 - 15 | High seeding-year yield Good quality |
Difficult to wilt to hay moisture Produces seedhead during every growth cycle Too competitive if seeded too heavily or in same row with alfalfa |
| Reed Canarygrass | 5 - 7 | 7 - 10 | Very winter hardy Sod former High yield once established Yield distribution matches alfalfa Not too competitive in short rotation Speeds drying rate |
Coarse/unpalatable if too mature Sometimes slow to establish Can dominate in older stands |
| Smooth Bromegrass | 6 - 10 | 7 - 10 | Very winter hardy High spring yield Sod former Not competitive Speeds drying rate |
Limited presence in summer/fall harvests First cutting during stem elongation reduces persistence |
| Timothy | 2 - 5 | 7 - 10 | Very winter hardy High spring yield Not competitive Speeds drying rate |
Limited presence in summer/fall cuts |
| Orchardgrass | 2 - 5 | 7 - 10 | High yield Yield distribution matches alfalfa Good fall yield Leafy regrowth |
Too competitive if seeded too heavily Susceptible to winter injury |
| Tall Fescue | 4 - 8 | 7 - 10 | High yield Yield distribution matches alfalfa Good fall yield Leafy regrowth |
Difficult to wilt to hay moisture Susceptible to winter injury Too competitive if seeded too heavily or in same row with alfalfa |
| Festulolium | 4 - 8 | 7 - 10 | High short-term yield Good quality |
Difficult to wilt to hay moisture Susceptible to winter injury |
| Perennial Ryegrass | 4 - 8 | 7 - 10 | High quality | Difficult to wilt to hay moisture Susceptible to winter injury |
