by Tamara Scully
Native warm season grasses are playing a growing role in pasture management. These multi-use grasses are a primary way of establishing and maintaining wildlife habitat, are used for biofuel, and are being promoted for use under drought conditions. Recent research at the University of Tennessee’s Center for Grasslands Management has demonstrated that native warm season grasses are a viable and profitable alternative for grazing and forage systems in the Northeastern United States.
According to Patrick Keyser, Ph.D, Director of the Center, a three-year research project quantifying the use of these native grasses in cattle grazing programs has shown that these plants are very valuable as a forage crop.
One reason why these native warm season grasses are being studied as an alternative forage is the “tremendous root systems that these native grasses develop,” Keyser said. They have been observed at up to nine feet in heavy soils. This root system makes them invaluable during drought or overly dry growing seasons. Their use can also decrease fescue toxicosis and they can be harvested both for biomass and forage in the same season.
Gains on forage
Research pastures were seeded to one of three types of native grasses. A switchgrass, a big blue stem and Indian grass mix, and an eastern gamagrass were tested. In all plots, beef cattle were grazed after adequate plant establishment, which occurred during the second growing season. Some plots did have to be seeded more than once to become established. The native warm season grasses are perennials, with the potential to live for decades once established, and with proper management.
The pastures were maintained by grazing the number of cattle needed and “trying to capture the growth that was there,” Keyser said. The average daily gains (ADG) on the grasses, as well as the Animal Unit Days per acre were calculated, and then combined for overall beef production per acre figures.
All three native warm season grasses offered ADG at 1.98 or above, all three years, with 2.79 being the maximum seen. The Indian grass and big blue stem mix offered the most ADG through the season. For all of the grasses studied, the gains on an early season only, 30-day graze, where the grasses were then harvested as a biofuel crop, exceeded the ADG seen in the full season graze. Beef production per acre figures were “disproportionately produced early in the year,” Keyser said, but over the entire season, “the gains we are seeing are really high for grass.”
Difference between years were primarily due to management issues. The stocking density was too low the first year to keep up with the flush of spring growth. They over-adjusted the second year and the grass suffered by being over-grazed, Keyser said.
The gains were calculated on a 600-pound steer basis. This was replicated with dairy heifers. Heifers, as expected, didn’t have as much of an ADG as the steers. But they showed higher ADG on native warm season grasses than typical on cool season pastures, and had “good, hearty gains during the summer months.”
Tall fescue had previously been studied on the same pastures, and the big blue stem/Indian grass mix provided virtually the same gain per acre as the tall fescue. The big blue stem mix provided gain in the summer, when “tall fescue is giving us virtually nothing.”
Economic calculations concluded that the cost of native warm season grass forage is less than other typical grasses. They require very low inputs, and provide high gains. Calculations show roughly a 30 percent increase in profit grazing beef cattle on the native forages, with $184/head being saved on a per head basis, when compared to the usual forage mixes.
The native warm season grasses work well in a rotational grazing system. The key is to graze at the proper heights, and to provide enough rest. The best advice is to “maintain a vigorous canopy,” Keyser said. “‘It takes grass to grow grass’ is very true with natives.”
One challenge is to keep their rapid spring growth in check. The stocking density can be high until early June, about 2,000 pounds/acre. When growth slows in late summer, a stocking density of 1,500 pounds/acre should be adapted. Native grasses should be grazed at 28 inches, and grazed down only to 15 inches. This grazed canopy height is key to allowing photosynthesis to continue, and allowing the pasture to rejuvenate. The lower part of the native grasses is not as palatable as the upper portions. Cattle will eat the leaves, but not the stem, which becomes coarse at low heights. Below eight to 12 inches, there is no leaf surface anyway, so there is no point trying to graze lower, Keyser said.
Taller grasses provide wildlife nesting and brooding habitat, as well as better palatability and better use of the forage. The taller height also excludes weed establishment, and increases stand vigor.
In a rotational system, the native warm season grasses can be grazed continually, providing good forage without stressing the grass, as long as the pasture has had adequate rest and regrowth. “They are still getting enough rest to allow you to get the utilization out of them that you want,” Keyser said, allowing grazing into fall .
The native grasses are not all as equally palatable to the animals, with big bluestem and Indian grass mixes being preferred over the eastern gamagrass or switchgrass. No eye issues or hoof issues were seen grazing the native grasses.
While the protein content of the native warm season grass hay is about 10 percent, it is a “perfectly adequate number,” and reflects the “bypass protein” effect. Animal performance exceeds what would be expected with the measured protein levels, Keyser said.
Harvesting early in the season makes a higher quality hay. A high cutting, leaving a minimum of eight inches, is needed to maintain the “photosynthetic potential to recover after total defoliation,” Keyser said. “Hay harvest is a lot harder on a plant than grazing.”
The early hay cutting can be done without concern about adding nitrogen. Trials with added nitrogen applied at different rates following an early cutting showed little difference in plant performance. If a second cutting is planned, it should be done by late summer, and it is best not to do so on an annual basis, in order to maintain pasture vigor, Keyser said.
Mixing native warm season grasses with crimson clover or hairy vetch can be detrimental. The early season growth of these cool season legumes can suppress the native warm season grasses, and have a negative impact on the grass stand. If they are mixed, managing the early flush of growth of the legumes is crucial.
Mixing cereal rye, an winter annual, with the native warm season grasses can extend the grazing season. The native warm season grasses go dormant in the winter, offering no winter forage. While this combination is promising, “be very meticulous getting that cool season annual off,” Keyser said.
Native season warm grasses offer producers a flexible crop, with good animal performance and gains, as well as economic benefits and conservation gains. “Until you get into corn silage, you don’t do any better than that number,” Keyser said, referring to the average daily gains seen on native warm season grasses. “We really can be very effective using natives.”
A video presentation, “Using Native Grasses for Livestock in the Eastern U.S.,” can be viewed on the USDA NRCS youtube channel www.youtube.com/user/usdanrcsentsc/videos