Pasture is the primary source of forage for organic dairies, and organic livestock production regulations require a minimum of 120 grazing days per animal.
In the northern United States, this requirement is typically met by a May to October grazing season. Profitability depends on pastures that provide a season-long supply of high-quality forage.
Here, we’ll share the results from a pasture forage study on Minnesota dairy farms, and species selection guidelines for pasture renovations. By effectively managing pastures and selecting forage species, farms can influence the quality of pasture forage for grazing dairy animals.
Research: Forage quality
Nine Minnesota grazing dairy farms were monitored in a study that measured monthly changes in the forage quality of pastures over a two-year period. Farms covered a wide geographical area across Minnesota, and represented a range of herd sizes, pasture sizes and pasture management strategies.
Results
Results from across the nine farms include:
- Spring pasture dry matter (23.96 percent) was higher than summer (23.52 percent) and fall (19.76 percent) pasture dry matter (Table 1).
- Seasonal average crude protein concentrations were 21.01, 20.11 and 23.93 percent for spring, summer and fall.
- Seasonal NDF concentrations were 46.63, 49.25 and 45.97 percent for spring, summer and fall grazing, respectively.
Table 1: Average pasture forage quality measures
| Time | Dry matter | Crude protein | NDF |
|---|---|---|---|
| Spring | 23.96a% | 21.01b% | 46.63a% |
| Summer | 23.52ab% | 20.11b% | 49.25b% |
| Fall | 19.76b% | 23.93a% | 45.97a% |
Pasture forage quality changes across the grazing season. This is why you should test forage quality throughout the grazing season, to determine if you need to supplement livestock or renovate pastures to improve the forage quality.
Supply livestock with consistent forage quality from the pasture. Knowing the quality of forage in pasture will help you determine the best grazing management strategy.
Selecting species for pasture renovation
Monoculture vs. diversity
Compared to monocultures, diversity:
- Reduces the risks associated with losing any single pasture species.
- Provides for variable resource use within a field.
- Supplies potentially more uniform biomass during the growing season.
- Improves soil health.
How to increase pasture diversity
You can increase pasture diversity by adding grasses and forbs, and increasing numbers of species within grasses and forbs.
An example is to grow nitrogen-fixing legumes with grasses. Although legumes supply nitrogen to grasses and provide a higher-energy feedstuff, legumes are generally less persistent and require higher levels of soil fertility than grasses.
Increase diversity in a farm's forage base by planting mixtures in individual pastures, and by planting separate pastures with different species.
Optimum number of species
There are many disagreements about the ideal number of species to include in pasture mixtures.
Most agronomic guidelines recommend using a small number of species in grazed mixtures. Research in the northeast United States found that six to nine grass species were more productive than a white clover-orchardgrass mixture.
Selecting grass species
When selecting pasture grass species, consider yield potential, palatability and survival of grasses. Select species that:
- Are winter hardy.
- Have good seasonal yield distribution.
- Are rust-resistant.
Quite possibly, variety is as or more important than specie choice.
Pasture systems
At the West Central Research and Outreach Center in Morris, researchers are measuring the performance of dairy cows grazing two unique pasture systems designed to maximize seasonal forage yield and quality, and extend the grazing season:
- System 1 increases within-field species diversity targeting perennial cool season, polyculture pastures to enhance multi-seasonal productivity (spring, summer and fall).
- System 2 will increase across-landscape diversity achieved by adding a combination of perennial polycultures and annual warm-season grasses fertilized with livestock manures.
Regional differences in soil fertility and rainfall may favor different pasture species in other locations.
Mixtures and seeding rates
Our current pasture species mixtures and seeding rates, in pounds per acre, are as follows:
- Perennial ryegrass (4 pounds), white clover (2 pounds), red clover (3 pounds) and chicory (2 pounds).
- Orchardgrass (3 pounds), meadow fescue (6 pounds), chicory (1 pound) and alfalfa (10 pounds).
- Perennial ryegrass (3 pounds), meadow fescue (8 pounds), white clover (4 pounds), red clover (2 pounds) and chicory (1 pounds)
Grazing systems using these different approaches to achieve diversity require biological, environmental and economic analysis.
Reviewed in 2018