Forage deficits cost money. Sometimes they even cost opportunity, forcing cattle sales when the market is not at its optimum, and hot, dry conditions have limited carrying capacity.
A renewable way to bridge the forage gap cool-season grasses can leave is through the establishment of native warm-season grass (NWSG) pastures for both grazing and haying. It's a trend Gary Bates says he's seeing across Mid-South cattle operations.
"We are primarily a cool-season grass state, about 90% of our pastures are tall fescue," says Bates, University of Tennessee (UT) forage specialist at Knoxville. "We have good production in the spring and in the fall, but we are limited during the summer. Warm-season grasses would get us more production during the June, July and August time periods."
In the Mid-South, NWSG generally means one of five species: big bluestem, little bluestem, eastern gamagrass, indiangrass and switchgrass. All are tall, deep-rooted perennials, drought tolerant and high yielding. They generally begin rapid growth in April, going semidormant in late August. All can produce excellent quality hay, often with higher yields than cool-season grasses.
WARM-SEASON GRASSES TAKE TIME
So what's the downside? Bates says the biggest challenge these grasses present is that they take about three years for full establishment. That means those areas planted to a NWSG won't provide any forage the first year, and only 50 to 75% of the eventual yield the second year.
"It's not till the third year that you see the full yield. Sometimes, it's a real challenge for a producer to take that land out of their normal rotation," Bates says.
But for those producers who make the commitment, the payout can be pretty good. Bates says studies of UT grazing steers on NWSG show weight gains at 2 pounds a day. And maintaining body condition on cows with these forages is not an issue. In addition, unlike some fescues, there are no issues with toxicity.
In the Mid-South, variety trials at the University of Kentucky have shown a wide range of annual yield potential for NWSG. Average tons-per-acre yields were as follows: big bluestem, 3.9; eastern gamagrass, 4.9; indiangrass, 4.6; and switchgrass, 5.3. For comparison, Kentucky 31 fescue averaged 3.1 tons per acre in the trial.
Bates says from a management standpoint, bluestems and indiangrass (alone or in blends) are the easiest to manage and provide the best gains for cattle. They are also the easiest to establish. Next on the "easy" list is eastern gamagrass. Switchgrass, he says, is the most challenging to establish. In addition, Bates warns in some cases this forage can be toxic to horses. (See table for comparisons of NWSG types.)
EVALUATE YOUR OPTIONS
While NWSG can be planted almost anywhere, Bates says the better the ground, the better the yield. Areas with little weed pressure, low pH and moderate to low fertility are good candidates for planting. Land recently cleared of timber often makes a good site. Crop ground is another good option, especially if it has been planted previously to cotton, soybeans, small grains or corn.
Planting NWSG on hay and pasture ground, normally carrying cool-season forages, presents more of a challenge. When old sod is removed, Bates says weed pressure can be high. Bermudagrass fields are probably the poorest candidates for NWSG, he adds. The bermuda is hard to control without killing the NWSG. In this case, one or two summers of glyphosate use, or an imazapyr-based herbicide, will be needed to create a foundation for the new grasses.
Before fertilizing, Bates says it's important to soil-test. NWSG is adapted to low-nutrient environments. If the pH is below 5, add lime, as recommended. For hay, nitrogen (up to 120 pounds per acre) can provide some increased production, but it can also increase weed competition. Don't fertilize until stands are at least a foot tall. Prescribed burns once every two or three years are also useful with NWSG during the dormant season. Be sure to take all precautions and apply for all necessary permits.
A SOUND PROCESS
NWSG is planted using no-till or conventional mechanical methods. Bates adds no-till is the preferred planting method in most cases. He recommends first treating emerged weeds at 10 to 14 days prior to planting. Seed is drilled, with the drill calibrated for the seed selected. Planting too deep is a common reason for failed NWSG plantings. Eastern gamagrass, given its larger seed size, is often seeded using a corn planter (traditional or vacuum).
Planting rates will vary with blends. When looking at a pure stand and drilling it, here is what Bates recommends: Seed big bluestem at a rate of 9 pure live seed (PLS) pounds per acre; little bluestem at 7; eastern gamagrass at 12; indiangrass at 7; and switchgrass at 6.
If planting in a conventional seedbed, be sure the soil is not too loose (meaning your shoe sinks in more than a quarter-inch when walking the field). If it is loose, cultipack the bed or wait for a rain to firm it. Seed can be broadcast, but this calls for a higher seeding rate. Bates says sowing Eastern gamagrass is not recommended. After sowing, properly cover the seed with a cultipacker or a drag.
Because NWSG seed can have more chaff than some grasses and even be high in dormancy, a calculation exists to help the buyer know how much "live seed" he is getting. This PLS number is a measure of the proportion of a seed lot that is able to germinate. To figure PLS, germination percentage is multiplied by purity percentage. These figures are on the seed or shipping tag.
Bates says PLS rates for most switchgrass will be in the 80 to 90% range; for bluestems and indiangrass, the rates are in the 40s to the 80s.
A sample calculation from UT shows seed with a germination of 54%; firm/dormant at 12%; inert matter at 3.10%; and weed seed at 1.40%. Total germination will be 66% (54% plus 12%). Purity will be 95.50% (100 minus 3.10 minus 1.40). Then, expressed as decimals, multiply germination times purity (0.6600 x 0.9550), which results in a 63.03% PLS. To plant 1 acre at a PLS rate of 6 pounds to the acre (6 pounds/0.6303), it will take 9.5 bulk pounds of seed.
GRAZING AND HAYING
In the Mid-South, NWSG is generally at optimal hay-production quality in June. These grasses need to be harvested late-boot to early seed-head emergence. Any later and they can become stemmy. Eastern gamagrass tends to mature before the other four species discussed. It will be followed by switchgrass, the bluestems and indiangrass.
Six to eight weeks after the first cutting, NWSG will generally be ready for a second, depending on weather. Bates stresses the importance of leaving 8 inches of stubble. A shorter height will result in poor stands and reduced yield as weed pressure increases.
Cattle can graze these grasses, but Bates says it's important not to let them get below the 8-inch mark and to allow about four weeks between grazing for adequate regrowth.
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