USDA ARS - Breeding Warm-Season Grasses for Biofuel Production

University of Nebraska-Lincoln Author

08/13/2020 Added

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[00:00:00.100](cheerful guitar music)
[00:00:07.650]Good morning, my name is Rob Mitchell.
[00:00:08.960]I'm a research agronomist and research leader
[00:00:10.790]with the USDA Agricultural Research Service
[00:00:12.960]in Lincoln, Nebraska.
[00:00:14.720]I'm here today talking to you a little bit
[00:00:16.540]about perennial grasses for bioenergy
[00:00:18.390]and some of our breeding work we've done historically here,
[00:00:20.610]and it's important for you to understand maybe a little bit
[00:00:23.250]of the history of USDA Ag Research Service.
[00:00:26.030]We started breeding perennial grasses here in 1935,
[00:00:29.181]and so we've got a long history
[00:00:31.320]of breeding perennial grasses.
[00:00:32.550]At that point, most of the breeding was for conservation
[00:00:35.340]and for forage purposes, and primarily in 1935,
[00:00:38.590]Dr. Lawrence Newell started doing his work
[00:00:40.420]to revegetate lands here in Nebraska and the Central US
[00:00:44.250]for areas that had been degraded by the Dust Bowl,
[00:00:47.820]and since that time,
[00:00:49.110]we've moved through about 80, 85 years of research,
[00:00:53.490]and it's really evolved pretty significantly.
[00:00:56.160]So we have gone from working on primarily switchgrass,
[00:00:59.390]big bluestem, and Indian grass,
[00:01:00.850]and now a number of other species.
[00:01:02.750]But as we look at this,
[00:01:04.090]I'm standing in a field of switchgrass,
[00:01:05.347]and this happens to be Liberty switchgrass.
[00:01:07.440]This is the first switchgrass that was released
[00:01:10.360]for bioenergy purposes here,
[00:01:11.610]specifically for this region of the US.
[00:01:15.080]Switchgrass is highly productive.
[00:01:17.020]It's pretty user friendly agronomically.
[00:01:19.500]You can't really tell yet, because it's just kind
[00:01:21.250]of coming out of the boot stage,
[00:01:23.040]but it's got really a nice, smooth seed,
[00:01:25.440]and it flows pretty easy in a drill.
[00:01:27.550]It ends up being very well adapted to this region,
[00:01:30.499]and again, it's quite productive.
[00:01:32.920]And as we look at things from a biomass energy perspective,
[00:01:35.800]and we really have a focused
[00:01:37.740]a lot of our energy on switchgrass,
[00:01:39.590]primarily because of those two things I mentioned,
[00:01:42.430]it's very nice, broadly adapted,
[00:01:44.530]and again, does a really nice job
[00:01:46.320]of producing biomass in an agronomically friendly manner.
[00:01:50.660]Our research unit is embedded within
[00:01:52.830]the University of Nebraska at Lincoln,
[00:01:54.440]and so we work collaboratively with UNL very significantly.
[00:01:58.530]Our history here is as long as I've already mentioned,
[00:02:00.932]but again, we do everything from biomass energy research
[00:02:04.450]to grazing research, to conservation research as well.
[00:02:08.020]So a couple things I'd like to tell you,
[00:02:09.950]maybe just as a little background information
[00:02:11.920]for these perennial grasses is, as their name implies,
[00:02:15.160]they are perennial.
[00:02:15.993]So we plant them once, and we can manage them in perpetuity
[00:02:18.920]if we do a good job taking care of them.
[00:02:21.690]We have switchgrass research sites here
[00:02:23.860]on the Eastern Nebraska Research and Extension Center
[00:02:26.250]that were planted in 1998, so we have well over 20 years
[00:02:29.524]of continuous harvesting on that plant material,
[00:02:32.475]and they're doing very well,
[00:02:34.130]and continuing to be very productive.
[00:02:36.100]It's a little bit muddy,
[00:02:36.933]so we won't be able to get to those sites today,
[00:02:38.910]but one of the neat things about switchgrass
[00:02:42.240]and other perennial grasses
[00:02:43.220]from a biomass energy perspective,
[00:02:44.780]and from an environmental perspective,
[00:02:46.238]is that they do a great job of storing soil carbon.
[00:02:49.525]And so one of the things we've seen in that longterm study,
[00:02:51.960]as I mentioned, started in 1998,
[00:02:54.020]is that we've seen the switchgrass store about a ton
[00:02:57.300]of carbon per acre per year below ground.
[00:03:00.380]So again, it's very effective at mitigating carbon,
[00:03:03.240]and again, really a nice side benefit, if you will,
[00:03:07.380]to the biomass production side of switchgrass.
[00:03:10.730]To turn kind of a little bit to Liberty specifically,
[00:03:13.210]this is Liberty switchgrass, as I've mentioned.
[00:03:15.930]Liberty is really an interesting switchgrass
[00:03:17.640]in that it started out as a cross between Summer and Kanlow,
[00:03:25.770]and you might ask, well, why Summer and Kanlow?
[00:03:28.810]Well, primarily because they're of the same ploidy level
[00:03:32.070]and capable of interbreeding.
[00:03:34.220]The difference is that Summer is an upland type,
[00:03:37.610]and Liberty or Kanlow is a lowland type.
[00:03:41.200]So it's important to understand
[00:03:42.980]that there are two equal types of switchgrass.
[00:03:45.152]Liberty functions as a lowland ecotype,
[00:03:47.730]and most of our lowland ecotypes are more Southern origin,
[00:03:52.000]so they're basically south of Nebraska.
[00:03:55.300]The southern border of Nebraska is
[00:03:56.770]at 40 degrees north latitude,
[00:03:58.640]and most of the lowland ecotypes
[00:03:59.692]of switchgrass develop further south than that.
[00:04:03.480]The upland ecotypes,
[00:04:05.120]which have historically been shorter in stature,
[00:04:07.070]finer leaves, more of a grazing type, if you will,
[00:04:10.155]are more adapted to the Northern climates.
[00:04:12.920]One of the real benefits of incorporating that upland
[00:04:16.840]and lowland plant material together is
[00:04:19.740]that it significantly improves the winter hardiness
[00:04:21.879]of the lowland ecotype.
[00:04:24.310]Kanlow just doesn't reliably overwinter in this area.
[00:04:28.320]While it's alive, it really is very productive,
[00:04:30.190]but we do have winter survival issues with Kanlow.
[00:04:33.610]So what Ken Vogel did was he hybridized Summer and Kanlow
[00:04:38.750]to develop a true F1 hybrid of those two,
[00:04:41.125]and then took that through several cycles of selection
[00:04:44.260]to stabilize the population,
[00:04:45.900]which resulted in the release of Liberty.
[00:04:48.050]So Liberty is a lowland functioning ecotype,
[00:04:51.350]and again, as you can tell, it's got very nice broad leaves.
[00:04:55.130]If you were to compare that to an upland ecotype,
[00:04:58.160]the leaf blade would be about half that width.
[00:05:00.790]The stems are, again, very large and robust,
[00:05:03.500]which allows it to be able to hold itself up
[00:05:06.830]as it's producing a lot of biomass,
[00:05:08.620]so we don't have those lodging issues associated
[00:05:10.468]with these lowland ecotypes.
[00:05:14.470]Liberty, at the field scale, just behind me a little bit,
[00:05:17.670]we've got a long-term field scale production study
[00:05:20.860]of Liberty switchgrass,
[00:05:21.980]compared to mixtures of big bluestem,
[00:05:25.560]Indian grass, and sideoats grama,
[00:05:26.910]and then some of our better material
[00:05:28.890]from a big bluestem perspective growing up the field scale.
[00:05:31.580]Those were planted in 2012.
[00:05:34.600]Liberty, at that field scale site,
[00:05:36.930]is growing and averaging just a little over five tons
[00:05:39.530]of biomass per acre, managed as a field-scale crop,
[00:05:42.950]so managed basically just like a hay crop,
[00:05:46.240]swaffing, baling, hauling the bales off,
[00:05:48.790]its longterm average is just a little
[00:05:50.360]over five tons per acre.
[00:05:52.050]So it has a pretty high production potential,
[00:05:54.520]and at the field scale,
[00:05:56.660]interestingly in the small plot scale,
[00:05:58.990]it's been significantly more productive than that,
[00:06:01.030]so we've got some work to do to try to maintain its ability
[00:06:04.300]to be productive, but also to be able to capture that all
[00:06:07.820]with our currently available harvesting material,
[00:06:11.000]and so at the plot scale, basically,
[00:06:13.790]we've been able to really reliably produce about eight tons
[00:06:17.240]of dry matter per acre with Liberty,
[00:06:20.290]but again, we haven't been able
[00:06:21.123]to recreate that in the field scale.
[00:06:22.920]Six or seven tons is about as high as we've been able
[00:06:25.020]to get at the field scale, but again, longterm reliably,
[00:06:28.550]a reliable yield of over five tons per acre.
[00:06:31.660]So again, just from a recap perspective,
[00:06:35.040]Liberty fits very well from here to the Eastern seaboard.
[00:06:38.242]We have grown it in well over 50 sites in the Central
[00:06:41.232]and Eastern US, and again,
[00:06:43.570]it just fits very well from a production standpoint,
[00:06:47.190]and as the bio economy continues to emerge,
[00:06:50.860]there's no doubt in my mind that Liberty will be
[00:06:52.550]a key player in that emerging bio economy.
[00:06:56.512]Okay, we've now moved over into some big bluestem,
[00:07:00.110]and big bluestem, again,
[00:07:01.520]is a native perennial warm-season grass like switchgrass.
[00:07:04.320]They're both very well adapted to this region.
[00:07:07.320]John Weaver, in some of his early ecological work,
[00:07:09.610]referred to big bluestem
[00:07:10.890]as the king of the tall grass prairie,
[00:07:13.500]and as you look at, historically,
[00:07:15.540]big bluestem in the prairie, it was the dominant.
[00:07:17.960]Anywhere from 50 to 75% of the total biomass
[00:07:20.940]in the native prairies would come from big bluestem.
[00:07:24.660]One of the ways big bluestem differs from switchgrass,
[00:07:27.410]that we were just in, is that big bluestem tends
[00:07:29.900]to be more strongly rhizomatous, so if given its freedom,
[00:07:33.730]it will produce more of a sod,
[00:07:37.360]where this is in a managed field
[00:07:40.550]where we're actually tilling the rows,
[00:07:42.020]we're standing in a tilled row here,
[00:07:44.320]so it's kind of restricting the plant's ability
[00:07:46.130]to develop rhizomes,
[00:07:47.720]but that's one of the real key characteristics
[00:07:50.410]of big bluestem is it produces really a pretty nice sod,
[00:07:53.510]and it really does a nice job of producing biomass.
[00:07:57.800]And as you can see here,
[00:07:58.965]we're just in the stages of development
[00:08:02.020]where switchgrass is just beginning to exert,
[00:08:04.480]still in the boot stage,
[00:08:06.570]moving into that reproductive cycle.
[00:08:08.370]So many of the plants around us are still vegetative
[00:08:11.490]and are just beginning to elongate,
[00:08:13.070]really, from a plant growth and development perspective,
[00:08:15.736]but one of the interesting things about big bluestem is
[00:08:19.150]that it does a very nice job of producing biomass as well,
[00:08:23.010]and you can tell here that much
[00:08:24.850]of the leaf material is carried a little higher
[00:08:26.900]in the canopy in these bioenergy type big bluestems
[00:08:30.390]than would be in some of the grazing types.
[00:08:32.450]The grazing types would tend
[00:08:33.660]to be a little more lower canopy,
[00:08:36.070]whereas the bioenergy types tend
[00:08:37.860]to have a little elevated canopy and leaf growth,
[00:08:40.360]which really does a nice job of spreading out its ability
[00:08:43.430]to produce biomass.
[00:08:44.810]The other thing, as I was pointing out, the big stems,
[00:08:47.260]we kind of jokingly refer to this as our bamboo big bluestem
[00:08:51.150]because of the size of the stems that this will get.
[00:08:53.440]It will get some very large stems,
[00:08:55.380]even as large as the pinky on my finger,
[00:08:57.770]and those are just really large for a perennial grass plant.
[00:09:02.650]When you compare these two from a production perspective,
[00:09:05.452]they're pretty similar.
[00:09:07.240]However, as I mentioned earlier,
[00:09:09.220]switchgrass is agronomically very friendly.
[00:09:12.067]Big bluestem is not quite so friendly.
[00:09:14.350]One of the reasons that big bluestem is not
[00:09:16.530]so agronomically friendly is that it is
[00:09:19.216]in the tribe Andropogoneae,
[00:09:21.140]which basically means bearded man,
[00:09:23.270]and so when you look at their seeds,
[00:09:25.200]their seeds have all of these fine hairs on them
[00:09:27.315]that really make it more difficult for them
[00:09:29.160]to move through a drill.
[00:09:30.500]Now, those can be pretty easily addressed
[00:09:31.742]from a seed conditioning perspective
[00:09:34.410]where we can process the seed,
[00:09:36.140]make it more easy to flow through a drill, but again,
[00:09:38.720]it does create one additional step
[00:09:41.040]that we don't see with things like switchgrass,
[00:09:45.050]but from a plant growth perspective,
[00:09:47.560]boy, big bluestem has a lot of potential.
[00:09:50.070]If we were to compare the two from a grazing perspective,
[00:09:52.360]kind of stepping away from bioenergy for a minute,
[00:09:54.980]if you compare switchgrass to big bluestem
[00:09:56.940]from a grazing perspective, because of all the way
[00:09:59.950]that a big bluestem manages its canopy,
[00:10:02.531]it really maintains a good forage base for us,
[00:10:07.240]so typically if we're comparing big bluestem
[00:10:09.397]and Indian grass in a grazing trial,
[00:10:11.610]big bluestem will far exceed
[00:10:13.100]the average daily gain potential and pounds
[00:10:14.920]of beef production per acre potential
[00:10:17.610]compared to switchgrass.
[00:10:18.670]So again, a lot of things that are really kind
[00:10:21.740]of positive from a grazing perspective about big bluestem,
[00:10:24.530]also tends to be more palatable.
[00:10:26.830]The other thing that's really kind of unique
[00:10:28.500]about big bluestem, compared to switchgrass,
[00:10:31.420]is that very few, comparatively anyway,
[00:10:33.970]very few of the tillers will transition
[00:10:36.290]into that reproductive stage,
[00:10:38.030]whereas most of the tillers
[00:10:38.899]in a switchgrass population will go
[00:10:41.220]into that reproductive stage.
[00:10:42.780]Really only a smaller percentage of those in big bluestem
[00:10:44.910]will transition into the reproductive stage,
[00:10:46.640]so it's a great thing from a grazing, or bioenergy,
[00:10:49.470]perspective, maybe not such a great thing
[00:10:51.470]from a seed production perspective.
[00:10:54.050]So as we look at some of these seed production potentials
[00:10:56.870]in our big bluestems, Indian grasses and switchgrass,
[00:10:59.570]that's a key thing for us to be looking at as we continue
[00:11:03.560]to breed those for any purpose, really,
[00:11:05.700]because we do need to be able to propagate them
[00:11:08.380]from seed and produce an adequate seed deal.
[00:11:10.917](cheerful guitar music)

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USDA ARS - Breeding Warm-Season Grasses for Biofuel Production

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