Tag Archives: Great Plains

The Prairie Ecologist Article: Lessons From a Project to Improve Prairie Quality – Part 2: Overseeding and Seedling Plugs

Last week, I posted a summary of some findings from a long project to enhance prairie habitat. I focused that post on the lessons we learned from the fire/grazing management portion of the project, including impacts on regal fritillary butterflies. This week, I’m looking at the other half of that project – overseeding and adding seedling plugs to our degraded prairies in order to increase plant diversity. As with last week, you can find all the gritty details, including graphs, tables, and more, by looking at our full final report.


Maximilian sunflower is one of the species we’ve found easiest to establish in degraded prairies. (These particular sunflowers are for illustration only – not from an overseeded site.)

During the five years of the project, we overseeded approximately 500 acres of prairie – focusing mostly on degraded remnant (unplowed) prairies that were missing many characteristic prairie wildflower species. We harvested our own seed from nearby sites, and broadcast it on degraded prairies right after burning them. The prairies were managed with patch-burn grazing, so cattle grazed those burned areas intensively for the remainder of the first growing season and then focused their grazing elsewhere in subsequent years. To measure success of the seedings, I used replicated plots to count the number of new plants that established from seed. Most of the seedings included multiple seeding rates, so I was able to look at the effect of seeding rate on establishment.

In addition to overseeding, we raised and transplanted more than 800 prairie and wetland seedlings into seven different sites, and added several hundred more seedlings to our nursery beds for seed production. Most transplanting was done in the late spring, and plants were watered on the day of transplanting but afterward. We marked (GPS and flags)and attempted to re-locate seedling plugs to evaluate survival, but that didn’t work out very well, and we didn’t find a lot of the plants we’d plugged in. Some of those plants surely died (which prevented us from finding them), but for others, flags disappeared and GPS points weren’t accurate enough to lead us to the small plants we thought were probably there. We did find some, but our estimates of success are pretty fuzzy.

We learned two major lessons from this portion of the project:

1. Overseeding after a burn in a patch-burn grazed prairie can re-establish at least some missing plant species, but the use of a high seeding rate is important.

2. Overseeding seems to be more cost effective than seedlings, assuming abundant seed can be obtained relatively cheaply.

In tallgrass prairies further to the east of us, people have had pretty good, if inconsistent, luck with overseeding prairies without necessarily having to suppress the vigor of surrounding vegetation. We’ve tried that here, and have seen very low success, maybe because our drier climate (25 inches of precipitation per year) increases competition for moisture? Regardless, our best results have come from seeding after a burn – for good seed/soil contact – followed by grazing of the dominant grasses that appear to be the primary competition for new seedlings. Patch-burn grazing works well, but we’ve also had good luck in the past by just grazing intensively for a month or so after seeding, and then pulling the cattle out.


Trails from our ATV and broadcast seeder in recently burned prairie. Broadcasting after a burn helps get the seed/soil contact we need. Experiments with light harrowing as a way to get even more soil contact haven’t shown any obvious results. Note the absolute straight lines I made as I planted this site…

Seeding rate was very important. We started by seeding at about the same rate as we use when we converting cropland to high-diversity prairie – about 1-2 lbs of bulk forb seed per acre. As the project went on, we went as high as 8 lbs, and continued to see better results. At least in our prairies, seeding smaller areas with more seed seems to be more effective than spreading limited seed over large areas.

Because others have incorporated light tillage or harrowing to suppress competition and increase seed/soil contact, we tried some of that as well, but our results were mixed. Some tilled plots showed very high establishment, but others showed less than non-tilled plots. We did find that when we tilled a few inches deep, we didn’t seem to kill any plant species – remembering that these are degraded sites already. I would definitely not recommend that others try tillage on a large scale, but in small plots within degraded grasslands, it’d probably be worth some more experimenting. We had a beautiful set of replicated tilled plots that I hoped would clarify the situation in 2012, but the severe drought overwhelmed that attempt.

Even at our highest seeding rates of 8 bulk pounds of forb seed per acre, the density of established plants was relatively low (in our best sites, we established around 150 new plants per acre) but hopefully high enough to create self-sustaining populations that will grow over time. The plant species that established most readily included:

Maximilian sunflower (Helianthus maximiliani)
Sawtooth sunflower (Helianthus grosseserratus)
Stiff sunflower (Helianthus pauciflorus)
Illinois bundleflower (Desmanthus illinoensis)
Entire-leaf rosinweed (Silphium integrifolium)
Wild bergamot (Monarda fistulosa)
Black-eyed Susan (Rudbeckia hirta)
Purple & white prairie clover (Dalea purpurea and D. candida)
Canada milkvetch (Astragalus canadensis) – in some sites
Illinois tickclover (Desmodium illinoense) – in some sites
In terms of seedlings, we have found that most prairie plants are easily grown in greenhouse situations (with some exceptions) but that some take more than a year to germinate, and then perhaps a full year or more to grow large enough to transplant. When we planted the seedlings into prairies, we clumped them together in groups of 5-10 plants to help form populations that could cross pollinate, and to make it easier to find at least one of the plants we’d put in.

TNC greenhouse Platte River Prairies.

Compass plant seedlings and others in our greenhouse.

We had success with seeding plugs in some situations – particularly in terms of getting wetland sedge species established in restored wetlands – but transplant survival in degraded mesic prairies was mixed at best. Most of our transplanting was done in the late spring, as we hoped to synchronize our planting with the wettest time of the year, but we may experiment with more fall planting in the future. We felt that many of our seedlings may have died because they weren’t in the appropriate soil conditions, which we had to guess at since there were no existing populations of most of the species we were transplanting. Broadcasting seed is probably a better way to match up appropriate plant species with their specific microhabitat requirements.

In our situation, it appears that overseeding is a cheaper and more efficient way to increase plant diversity in degraded prairies. Of course, one big reason it makes sense for us is that we have existing capacity for large-scale seed harvest. If enhancement of degraded prairies is a high priority for a landowner or land management entity, it might make sense to build their own seed harvest capacity. That doesn’t necessarily mean large investments in equipment or people, though a pull-behind seed stripper or combine can be a nice way to harvest large amounts of seed quickly. Large amounts of wildflower seed can also be harvested by hand (our typical method) if you are efficient and organized.

By Chris Helzer from The Prairie Ecologist Website

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Biofuels from Switchgrass: Greener Energy Pastures

Panicum virgatum 'Heavy Metal' Switch Grass in...

Image via Wikipedia

The grass stretched as far as the eye could see, and hundreds more miles beyond that. An ocean of grass—deep enough to swallow a horse and rider—swaying and singing in the steady wind of the Great Plains. § The American prairie—tens of millions of acres— once looked like this. But that was centuries ago, before the coming of the white man, the railroad, and the steel plow. Today, corn and beans hold sway, and the remnants of America’s tallgrass prairie are confined mostly to parks and preserves. § Now, though, in research plots and laboratories in the Plains states and even in the Deep South the seeds of change are germinating. The tall, native grasses of the prairie, so vital to our land’s ecological past, may prove equally vital to its economic future. Such grasses once fed millions of bison. Soon, grown as energy crops, they may help fuel millions of cars and trucks, spin power turbines, and supply chemicals to American industries.

Test plots of switchgrass at Auburn University have produced up to 15 tons of dry biomass per acre, and five- year yields average 11.5 tons—enough to make 1,150 gallons of ethanol per acre each year.
The U.S. Department of Energy (DOE) believes that biofuels—made from crops of native grasses, such as fast- growing switchgrass—could reduce the nation’s dependence on foreign oil, curb emissions of the “greenhouse gas” carbon dioxide, and strengthen America’s farm economy. The Biofuels Feedstock Development Program (BFDP) at DOE’s Oak Ridge National Laboratory (ORNL), has assembled a team of scientists ranging from economists and energy analysts to plant physiologists and geneticists to lay the groundwork for this new source of renewable energy. Included are researchers at universities, other national laboratories, and agricultural research stations around the nation. Their goal, according to ORNL physiologist Sandy McLaughlin, who leads the switchgrass research effort, is nothing short of building the foundation for a biofuels industry that will make and market ethanol and other biofuels from switchgrass and at prices competitive with fossil fuels such as gasoline and diesel.
Not the grass in your backyard
First, a distinction: switchgrass and your suburban lawn grasses—bluegrass and zoysia grass— are about as similar as a shopping-mall ficus and an old-growth redwood. Switchgrass is big and it’s tough—after a good growing season, it can stand 10 feet high, with stems as thick and strong as hardwood pencils.
But what makes switchgrass bad for barefoot lawns makes it ideal for energy crops: It grows fast, capturing lots of solar energy and turning it into lots of chemical energy— cellulose—that can be liquified, gasified, or burned directly. It also reaches deep into the soil for water, and uses the water it finds very efficiently.
And because it spent millions of years evolving to thrive in climates and growing conditions spanning much of the nation, switchgrass is remarkably adaptable.
Now, to make switchgrass even more promising, researchers across the country are working to boost switchgrass hardiness and yields, adapt varieties to a wide range of growing conditions, and reduce the need for nitrogen and other chemical fertilizers. By “fingerprinting” the DNA and physiological characteristics of numerous varieties, the researchers are steadily identifying and breeding varieties of switchgrass that show great promise for the future.

Switchgrass can be cut and baled with standard farming equipment.
Yield of dreams
In the hard, shallow soil of southern Alabama, Dave Bransby is turning cotton fields into swatches of grassland. Some Alabama farmers joke that there’s no soil in Alabama to farm—two centuries of King Cotton and steady erosion haven’t left much behind. Yet Bransby, a forage scientist at Auburn University, has found a crop that thrives there: Among the 19 research sites in the Eastern and Central United States raising switchgrass for the BFDP studies, Bransby’s site holds the one-year record at 15 tons per acre. Those are dry tons weighed after all the moisture’s been baked out. Convert that into ethanol, an alcohol that can fuel vehicles, and it equals about 1,500 gallons per acre. Bransby’s 6-year average, 11.5 tons a year, translates into about 11,500 gallons of ethanol per acre. An added bonus is the electricity that can be produced from the leftover portions of the crop that won’t convert to ethanol.

Many farmers are already experienced at raising switchgrass for forage or to protect soil from erosion. Besides showing great promise for energy production, switchgrass also restores vital organic nutrients to farmed-out soils.
Many farmers already grow switchgrass, either as forage for livestock or as a ground cover, to control erosion. Cultivating switchgrass as an energy crop instead would require only minor changes in how it’s managed and when it’s harvested. Switchgrass can be cut and baled with conventional mowers and balers. And it’s a hardy, adaptable perennial, so once it’s established in a field, it can be harvested as a cash crop, either annually or semiannually, for 10 years or more before replanting is needed. And because it has multiple uses—as an ethanol feedstock, as forage, as ground cover—a farmer who plants switchgrass can be confident knowing that a switchgrass crop will be put to good use.
Farmers working in production mode might not match Bransby’s carefully tended research plots, but if the future brings rises in oil prices—or if environmental taxes are eventually imposed on fossil fuels—energy from switchgrass could prove economically competitive with petroleum and coal, making biomass crops attractive to American farmers. And with recent advances in the technology of gasification, switchgrass could yield a variety of useful fuels—synthetic gasoline and diesel fuel, methanol, methane gas, even hydrogen—as well as chemical by-products useful for making fertilizers, solvents, and plastics.
Strong environmental roots
Annual cultivation of many agricultural crops depletes the soil’s organic matter, steadily reducing fertility. But switchgrass adds organic matter—the plants extend nearly as far below ground as above. And with its network of stems and roots, switchgrass holds onto soil even in winter to prevent erosion.
Besides helping slow runoff and anchor soil, switchgrass can also filter runoff from fields planted with traditional row crops. Buffer strips of switchgrass, planted along streambanks and around wetlands, could remove soil particles, pesticides, and fertilizer residues from surface water before it reaches groundwater or streams—and could also provide energy.
And because switchgrass removes carbon dioxide (CO2 ) from the air as it grows, it has the potential to slow the buildup of this greenhouse gas in Earth’s atmosphere. Unlike fossil fuels, which simply release more and more of the CO2 that’s been in geologic storage for millions of years, energy crops of switchgrass “recycle” CO2 over and over again, with each year’s cycle of growth and use.
The road ahead
One reason BFDP researchers are confident that switchgrass can become an important feedstock for ethanol production is the groundwork that’s already been laid by corn growers. U.S. ethanol production from corn currently totals nearly 2 billion gallons a year. Some of this ethanol is blended with gasoline to make gasohol; some is further refined to make gasoline octane boosters; and some is burned, either in pure (“neat”) form or mixed with a small percentage of gasoline, in fleets of research and demonstration vehicles.
Looking down the road, McLaughlin believes switchgrass offers important advantages as an energy crop. “Producing ethanol from corn requires almost as much energy to produce as it yields,” he explains, “while ethanol from switchgrass can produce about five times more energy than you put in. When you factor in the energy required to make tractors, transport farm equipment, plant and harvest, and so on, the net energy output of switchgrass is about 20 times better than corn’s.” Switchgrass also does a far better job of protecting soil, virtually eliminating erosion. And it removes considerably more CO2 from the air, packing it away in soils and roots.

Switchgrass offers excellent habitat for a wide variety of birds and small mammals.
Back to the future
At the turn of the last century, America’s transportation system was fueled by biomass: 30 million horses and mules, give or take a few million, pulled buggies, hauled wagons, dragged plows. According to Ken Vogel, a U.S. Department of Agriculture forage geneticist helping develop and test switchgrass for the BFDP, replacing animal power with machine power freed up 80 million acres of U.S. land—land that had been used to grow grass and other feed for these millions of animals. Now, at the dawn of the next century, the wheel could begin to turn full circle. On millions of acres of farm land not needed for food crops, fast-growing energy crops of switchgrass—harvested and converted efficiently to clean-burning, affordable ethanol, methanol, or diesel—could once again supply vast amounts of horsepower.
In short, biomass could bring back a 21st-century version of the prairie. And along with the prairie, it could bring a new crop to America’s farms, a boost to U.S. energy independence, and brighter prospects for a clean, sustainable future. According to BFDP and its research partners across the country, that’s a future worth cultivating.
For more information, contact:
Bioenergy Feedstock Development Program

Oak Ridge National Laboratory
P.O. Box 2008
Oak Ridge, TN 37831-6422
865-576-8143 (fax)     Produced for DOE’s Office of Transportation Technologies and the Office of Power Technologies within the Office of Energy Efficiency and Renewable Energy