switchgrass selection as a “model” bioenergy crop: a history of the process

b i o m a s s a n d b i o e n e r g y 3 4 ( 2 0 1 0 ) 8 5 1 – 8 6 8

Avai lab le a t www.sc iencedi rec t .com

ht tp : / /www.e lsev i er . com/ loca te /b iombioe

Switchgrass selection as a ‘‘model’’ bioenergy crop: A historyof the process

Lynn Wright*, Anthony Turhollow

Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, Bldg.1062, Oak Ridge, TN 37831, USA

a r t i c l e i n f o

Article history:

Received 9 March 2008

Received in revised form

18 January 2010

Accepted 19 January 2010

Available online 11 February 2010

Keywords:

Herbaceous energy crops

Panicum virgatum

Sorghum bicolor

Crop yields

Environmental issues

Lignocellulosic

Weather

* Corresponding author present affiliation: WE-mail address: [email protected] (L.

0961-9534/$ – see front matter ª 2010 Elsevidoi:10.1016/j.biombioe.2010.01.030

a b s t r a c t

A review of several publications of the Oak Ridge National Laboratory’s Biofuels Feedstock

Development Program and final reports from the herbaceous crop screening trials show

that technology, environmental, and funding issues influenced the decision to focus on

a single herbaceous ‘‘model’’ crop species. Screening trials funded by the U.S. Department

of Energy in the late 1980s to early 1990s assessed thirty-four herbaceous species on a wide

range of soil types at thirty-one different sites spread over seven states in crop producing

regions of the U.S. Several species, including sorghums, reed canarygrass, wheatgrasses,

and other crops, were identified as having merit for further development. Six of the seven

institutions performing the screening included switchgrass among the species recom-

mended for further development in their region and all recommended that perennial

grasses be given high research priority. Reasons for the selection of switchgrass included

demonstration of relatively high, reliable productivity across a wide geographical range,

suitability for marginal quality land, low water and nutrient requirements, and other

positive environmental attributes. Crop screening results, economic and environmental

assessments by the Biofuels Feedstock Development Program staff, and Department of

Energy funding limitations all contributed to the decision to further develop only switch-

grass as a ‘‘model’’ or ‘‘prototype’’ species in 1991. The following ten year focus on

development of switchgrass as a bioenergy crop proved the value of focusing on a single

‘‘model’’ herbaceous crop. The advancements and attention gained were sufficient to give

government leaders, policymakers, farmers, and biofuel industry developers the confi-

dence that lignocellulosic crops could support an economically viable and environmentally

sustainable biofuel industry in the U.S.

ª 2010 Elsevier Ltd. All rights reserved.

1. Introduction only was briefly explained and justified in reports and

Switchgrass was selected as the single ‘‘model’’ herbaceous

crop species deserving of further Department of Energy sup-

ported research in 1991 even though managers of the Herba-

ceous Crops Program (HECP) at ORNL had originally planned

on selecting at least one annual, one perennial, and one

legume for further research [1]. The selection of switchgrass

rightLink Consulting 111 CWright).er Ltd. All rights reserved

proceedings papers prepared by Oak Ridge National Labora-

tory (ORNL) scientists at the time [1–3] and briefly addressed in

a 2005 switchgrass research summary paper [4]. Our paper

examines ORNL publications and reports, as well as subcon-

tractor publications and reports in more detail to explain the

model crop selection process. All ORNL and subcontractor

reports have been made publically available on the Biofuels

ross Winds Cove Rd, Ten Mile, TN 37880, USA. Tel.:þ1 865 376 0037.

.

mailto:[email protected]

http://www.elsevier.com/locate/biombioe


Feedstock Information Network website [5]. A subset of the

data available in those reports is included in this paper to

provide a summary of observed yields reported as bone dry

weights. The concluding summary of lessons learned and

conclusions draws to some extent from publications resulting

from the focused switchgrass crop development efforts and

bioenergy project developments as well as from the initial

multiple species screening trials.

1.1. Biofuels feedstock developmentprogram background

The Department of Energy (DOE) became involved in investi-

gating biomass resources as early as 1977 by co-funding field

research that had been initiated by the U.S Department of Agri-

culture (USDA) on woody crops, sugar cane, and tropical grasses.

DOE quickly established its own energy crop research effort with

the issuance of two Program Research and Development

Announcements on ‘‘Fuels from Woody Biomass’’ and ‘‘Fuels

from Aquatic Species.’’ In 1978 DOE asked ORNL to provide

advice and support in the selection and management of the

woody biomass projects and the Solar Energy Research Institute

(SERI) to support the aquatic research effort. By 1982, DOE had

fully transferred technical and administrative management of

the Short Rotation Woody Crops Program (SRWCP) to ORNL and

funds were provided to ORNL to initiate a program focused on

herbaceous crops research (the HECP) in 1984.

1.2. Goals and requirements of the herbaceous cropsprogram solicitation

The HECP was initiated in 1984 with a request for proposals

(RFP) for herbaceous crop screening focused on the Southeast

(exclusive of subtropical areas) and the Midwest/Lake States

[6]. The RFP was limited to herbaceous lignocellulosic crops

(grasses and legumes), influenced largely by a well-regarded

report issued by the Office of Technology Assessment (OTA)

[7] that had identified these potential biomass resources as

second in size only to wood.

The overall goal of the HECP was ‘‘to develop data and

information that will lead to commercially viable systems for

producingherbaceousbiomass for fuelsandenergy feedstocks.’’

Important was the desire to achieve the goal in ways that would

minimize adverse environmental effects [8]. The direction of the

HECP and some of the important crop selection criteria were

clearly established by the following words in the initial RFP:

‘‘Three major factors influenced the initial focus of research in the

program. First was the desire to increase the production of

biomass for energy without significantly reducing food produc-

tion. This led to the decision to concentrate on species for

marginal croplands and on species that can be grown as winter

crops. Second was the decision to produce fuels or energy feed-

stocks rather than chemicals. This meant the program would

initially include a minimum of research on hydrocarbon crops,

because evaluations of hydrocarbon-producing species that will

grow in the United States have concluded that the hydrocarbon

products will be more valuable as specialty chemicals, primarily

lubricants, than fuels. Third was the desire to have the greatest

possible impact on total biomass energy use. This led to the

decision to emphasize lignocellulosic crops.’’

The RFP requested that different intensities of manage-

ment be part of the initial screening process as well as a range

of site types, including both marginal and good agricultural

land, so that relationships among site quality, management

inputs, and yields could be established. Land was considered

marginal if limited by erosiveness, excessive wetness, soil

chemistry constraints, rooting constraints, or climate issues.

Proposals deemed responsive included a minimum of two

species, one of which had to be a forage crop commonly grown

in the test site region. The other crop(s) could be annual or

perennial but their inclusion had to be explained and justified.

An evaluation of soil loss potential associated with each crop

was also required. Of the thirteen proposals received, five

organizations were selected to participate in the Southeast

and Midwest species screening trials that began in 1985 [9].

Those regions were chosen for study because large areas of

marginal cropland were potentially available and there were

relatively few environmental restrictions on productivity. In

1988, two additional institutions were added to the species

screening effort to achieve a broader coverage of potentially

available site types.

2. Herbaceous crop screening

2.1. Descriptions of the herbaceous screening projects

Four universities [Auburn, Cornell, Purdue, and Virginia

Polytechnic Institute and State (referred to as Virginia Tech)]

and one private company (Geophyta in Ohio) were selected to

perform herbaceous crop screening for bioenergy feedstock

potential beginning in 1985 (Fig. 1). Iowa State University and

North Dakota State were added to the screening program in

1988. A wide variety of warm and cool season grasses, legu-

minous perennials, and several annuals were included in the

screening trials (Table 1). Table 2 associates the Latin names

with the common names of each species tested. Table 3

provides information about each of the test locations.

2.2. Screening trial results and recommendations

Key results of the seven herbaceous crop screening projects

are summarized in the tables and text below and a more

detailed technical manuscript published only online [10]. Crop

yields were quite variable among investigators, sites, and

years with climate (a La Nina/El Nino/La Nina) oscillation

occurring between late 1984 and June 1989 [11] likely playing

a large role. Maps of typical La Nina (cool phase) and El Nino

(warm phase) effects show different effects across the range

of project locations for each season [12], thus is it difficult to

clearly link crop establishment problems and crop yields in

the screening projects to climate oscillation effects. This is

especially the case in 1985, when crops were planted at

different times from early spring, to summer, to fall. Never-

theless, most investigators claimed linkages between estab-

lishment difficulties and reduced growth observations to

Fig. 1 – Location of herbaceous crop field testing sites sponsored by the U.S. Department of Energy’s Biofuels Feedstock

Development Program.

b i o m a s s a n d b i o e n e r g y 3 4 ( 2 0 1 0 ) 8 5 1 – 8 6 8 853

weather conditions, so a brief attempt is made at describing

climate conditions by year.

In 1985 the Corn Belt experienced excessive moisture in the

spring while the Ohio Valley and Mid-Atlantic States and Lower

Coastal Plain experienced rainfall below normal especially in

later summer and fall. In most locations, the small-seeded

perennial crops either totally failed or did not show enough

growth to harvest in 1985. USDA summaries of 1986 growing

conditions indicated that the drought conditions in the

southeast and Mid-Atlantic States were the worst in over 100

years. Even so, most projects experiencing establishment

failure in 1985 had moderate to good success in 1986, though

with a great deal more effort (and a little watering in some

cases). Spring 1987 was warm and dry in most of the eastern US

with the Ohio Valley and Mid-Atlantic States experiencing

some drought. For projects with established crops, the warm

dry spring and summer of the La Nina year of 1988 appeared

linked to reduced growth conditions (especially in Indiana and

Ohio) and the crop establishment efforts in North Dakota

totally failed due to very warm and dry conditions. Yet, the

Iowa project had good success with planting new crops in 1988,

possibly because the drought began ameliorating there sooner.

By 1989 the eastern US was wetter than normal and the

perennial crops in their 4th or 5th years in New York, Indiana,

Ohio, Virginia, and Alabama were established and growing

well; the crops in their 2nd growth year in Iowa were showing

good to excellent growth, and the 1st year crops in North

Dakota were surviving and in some cases showing good growth

even though North Dakota remained dry. Although 1990 was

one of the warmest years on record, timely rains during the

spring and summer resulted in reasonable to good yields in the

continuing North Dakota and Iowa projects. The warm year of

1991 also brought good rains to North Dakota and northern

Iowa, but less rain for the screening site in southern Iowa. The

dry and cool year of 1992 brought less rainfall than normal to

the North Dakota trials but rain at critical times sustained crop

yields in Iowa. Rainfall and temperature likely affected the

Tennessee study of the potential of successional vegetation as

a bioenergy feedstock, but was not a large factor.

2.2.1. Auburn University – AlabamaAuburn University initially established four annual grasses,

four perennial grasses, and one perennial legume and later

added two perennial grasses [13]. Yield results for the original

nine crops in four physiographic provinces of Alabama are

summarized in Table 4. Yields of annual species were more

variable (likely related to rainfall levels) than the yields of the

perennial species. The higher yield variability plus higher

production costs of the annuals lead to the recommendation

to drop annuals and to focus on perennials for future crop

development. Johnsongrass, a warm season perennial

‘‘weed,’’ performed better than other perennials in the first

two seasons but its growth rate decreased in the following

years. All other warm season perennials; switchgrass, ber-

mudagrass, and the legume, sericea lespedeza, established

more slowly but continued to increase yields over the five

years. The success and reliability of the perennials encour-

aged the Auburn University investigators to add evaluation of

subtropical tall grasses in 1986 and a switchgrass variety trial

in 1988. The tall grasses achieved yields of 17–32 Mg ha�1 with

energy cane showing the highest yields. All switchgrass vari-

eties established quickly in the normal rainfall year of 1988

but by 1990 the lowland variety, Alamo, had achieved yields

more than five times that of the original upland test variety,

Table 1 – Species screened by Herbaceous Crops Program 1985–1992.

Species Institutiona and year of project start

Auburn Cornell Geophyta Purdue VA Tech ISU NDSU

1985 1985 1985 1985 1985 1988 1988

Grasses: Annualb

Maize (w) X X X X

Pearl millet (w) X

Foxtail millet (w) X

Rye (c) Xc Xc Xc Xc

Sorghum, forage (w) X X

Sorghum, sweet (w) X X

Sorghum � sudangrass (w) X X X

Sudangrass (w) X

Grasses: Perennial

Bahiagrass (w) X

Bermudagrass (w) X

Big bluestem (w) X X

Crested wheatgrass (c) X

CRP mixture of grasses (c/w) X

Eastern gamagrass (c) X

Energy cane (w) X

Intermediate wheatgrass (c) X

Johnsongrass (w) X

Napiergrass (w)

Redtop (c) X

Reed canarygrass (c) X X Xd X X

Smooth bromegrass (c) X

Switchgrass (w) X X X X X X X

Tall fescue (c) X X Xd X

Timothy (c)/redtop (c)/clover (c) X X

Weeping lovegrass(w) X X

Wheatgrass mixture (c) X

Legumes: Annual

Soybeans X

Legumes: Perennial

Alfalfa Xe X X Xf Xe

Birdsfoot trefoil X X X X

Crownvetch X

Flatpea X X

Serecia lespedeza X X X

Sweet clover X X

Other

Forage brassica X

Kale X

Kochia X

Meadow (mixed grasses & legumes) X

a Institutions are Auburn University, Cornell University, Geophyta, Purdue University, Iowa State University (ISU), North Dakota State

University (NDSU).

b All crops are designated as either cool season (c) or warm season (w) crops. Scientific names are given in Table 2.

c Rye was always interseeded among other species or as the cool season species in a double crop system – most often with sorghums but also

double cropped with corn, Johnsongrass, sericea lespedeza, switchgrass, and bermudagrass at Auburn.

d Reed canary canarygrass should be one word grass and tall fescue were grown alone and interseeded with sorghum.

e Alfalfa was intercropped and grown alone.

f Alfalfa was intercropped with sorghum and sorghum � sudangrass.


Cave-in-Rock (up to 34.6 Mg ha�1 versus 6.7 Mg ha�1) in 1990

[14]. Auburn University recommended that further research

should focus on only a few perennial species such as

switchgrass, sericea lespedeza, and energy cane [13]. The

advantages of switchgrass were described as: (a) established

from seed, (b) harvested and stored as hay, (c) used for both

biomass and forage, (d) relatively low lignin content, and (e)

high genetic variability within the species provides excellent

opportunities for improvement by selection and breeding. The

discovery of the high yield potential of the switchgrass variety

Alamo was a major factor in the acceptance of switchgrass as

a suitable model species.

Table 2 – Scientific names of species screened.

Common name inUnited States

Latin name

Grasses: Annual

Maize (w) Zea mays L.

Pearl millet (w) Pennisetum americanum L. (Leeke)

Foxtail millet (w) Setaria italica (L.) P. Beauv.

Rye (c) Secale cereale L.

Sorghum, forage (w) Sorghum bicolor L. (Moench)

Sorghum, sweet (w) Sorghum bicolor L. (Moench)

Sorghum � sudangrass

(w)

Sorghum bicolor� S. bicolor var sudanense

Sudangrass (w) Sorghum bicolor var sudanense

Grasses: Perennial

Bahiagrass (w) Paspalum notatum (Flugge)

Bermudagrass (w) Cynodon dactylon L. (Pers.)

Big bluestem (w) Andropogon gerardii (Vitman var.

gerardii)

Crested wheatgrass (c) Agropyron desertorum (Fisch. Ex Link)

Schult

CRP mixture of grasses

(c/w)

–

Eastern gamagrass (c) Tripsacum dactyloides L.

Energy cane (w) Saccharum hybrid

Intermediate wheatgrass

(c)

Thinopyrum intermedium (Host) Barkw. &

D.R. Dewey)

Johnsongrass (w) Sorghum halenpense L. (Pers.)

Napiergrass (w) Pennisetum purpureum

Redtop (c) Agrostis gigantean L.,

Reed canarygrass (c) Phalaris arundinacea L.

Smooth bromegrass (c) Bromus inermis Leyss

Switchgrass (w) Panicum virgatum L.

Tall Fescue (c) Festuca arundinacea (Shreb)

Timothy (c)/redtop

(c)/clover(c) mixture

Phleum pratense/Agrostis gigantean L.,/

Trifolium pratense

Weeping lovegrass (w) Eragrostis curvula

Wheatgrass mixture (c) –

Legumes: Annual

Soybeans Glycine max L.

Legumes: Perennial

Alfalfa Medicago sativa L.

Birdsfoot trefoil Lotus corniculatus

Crownvetch Coronilla varia

Flatpea Lathyrus sylvestris

Serecia lespedeza Lespedeza cuneata

Sweet clover Melilotus officinalis (Melilotus alba)

Other

Forage brassica

(mostly Kale)

Brassica oleracea

Kale Brassica oleracea

Kochia (also known as

fireweed and burning

bush)

Kochia scoparia L. (Roth)

Meadow (mixed

grasses & legumes)

–

Note: The grasses are designated as either cool season (c) or warm

season (w) crops, varieties differed between most projects except

switchgrass where ‘Cave-in-Rock’ was used everywhere except

North Dakota where ‘Sunburst’ was used.


2.2.2. Cornell University – New YorkCornell University evaluated a total of six grasses (one annual)

and six legumes plus ‘‘meadow’’ distributed over eight loca-

tions [15,16]. In the first year of the project (1985) several of the

crops did not get planted or their growth was inadequate for

harvesting (Table 5). Some crops replanted in 1986 were not

harvested in that year. Since production results were available

for only 3 or 4 years, comparisons were made based on the 3

best years of growth. By the final year of screening (1989), yields

of surviving species or combinations of species ranged between

4.4 and 12.1 Mg ha�1 (Table 5). Evaluation of the potential for

energy crops in the region was based on modeling studies as

well as on field trials. The investigators concluded that ‘‘careful

management of better-drained’’ soil resources and proper

selection of plant species grown for biomass will provide an

annual yield of dry matter in the Great Lakes Region on the

order of 10–12 Mg ha�1. Recommended species varied for well-

drained versus the poorly drained soils [16]. On moderately to

well-drained soils, the grass-legume mixtures, alfalfa brome-

grass and timothy-redtop-red clover were considered to be the

most promising. Switchgrass showed promise for well-drained

sites, but establishment problems and weed competition

experienced in the trials were a concern. On poorly drained

soils (such as the Madalin and Rhinebeck soils in northeastern,

NY and the Erie soils near Ithaca), reed canarygrass performed

well and was recommended as a high potential species under

a one cut harvest system timed to coincide with drier soil

conditions. Relatively low input ‘‘meadow’’ species also per-

formed well on wet soils where tillage is not possible.

2.2.3. Geophyta – OhioGeophyta evaluated three annual grasses, four perennial

grasses, and two legumes in a wet area of northern Ohio

(Table 6) [17]. The 1985 late summer planting was mostly

unsuccessful. Only rye did not need replanting. Challenging

planting conditions in spring 1986 forced two or three

attempts at replanting small-seeded perennial grasses.

Smooth bromegrass, tall fescue and reed canarygrass could

not be successfully established in one or more sites. Yield

response to fertility was significant at all three sites with

additional nutrients resulting in yield increases for the grasses

(but not legumes). Yields results in Table 6 are averaged over

100 kg N ha�1 and 170 kg N ha�1 fertility levels. Two harvests

per season were tested on sub-plots but rejected as

a management method. The investigator concluded that the

most promising energy crops were forage sorghum, rye double

cropped with sorghum � sudangrass, and reed canarygrass

[17]. However a close look at the reported data [Table 6],

reveals that switchgrass successfully established at all three

test sites but the reed canarygrass did not, and that 4th year

switchgrass yields were only somewhat less than reed can-

arygrass. Both switchgrass and reed canarygrass

demonstrated greater yield reliability across years than the

annual grasses (Table 6). Rye double cropped with

sorghum � sudangrass produced more reliable yields than

forage sorghum alone, which had establishment failures in

1985 and 1986. The investigator noted that the cool season

grasses (including reed canarygrass) always had green leaves

(higher nutrient levels) at fall harvest, while switchgrass and

sorghum had the lowest nutrient concentrations at fall

harvest (suggesting greater potential for sustainable produc-

tion). The Ohio project also had some weed-only plots and one

recommendation was to conduct further study on fertilizing

abandoned fields.

Table 3 – Descriptions of herbaceous crops screening test sites.

Research Institutions/sitelocations

Soil type Slope and class Quality Limitation(s)

Auburn University

(Alabama)

4 Sites represent the physiographic provinces of AL, ‘‘all soils good for crop production if erosion minimized on

slopes’’

Camden, AL; Lower

Coastal Plain 32�000N,

87�190W

Mabis fine

sandy loam

NA NA Fragipan and acidic

subsoil, erosive

Winfield, AL; Upper

Coastal Plain 33�530N,

87�520W

Savannah loam 2–10% slopes NA Fragipan and erosive

Camp Hill, AL, Piedmont

Plateau 32�490N,

85�390W

Cecil sandy loam NA NA Acidic, erosive

Crossville, AL Appalachian

Foothills 34�170N,

85�580W

Hartsells fine

sandy loam

2–5% slopes NA Erosive on slopes

Cornell University (New York) 8 Sites with 6 soil series, each a unique combination of use and production limitations

Geneva, NY 42�520N, 77�000W Honeoye, silt

loam

10% Slope Excellent Erosion

Aurora, NY 42�450N, 76�410W Kendia, silt loam Minimal slope Prime None

Freeville, NY 42�300N, 76�210W Mardin, acid

glacial till

Minimal slope Marginal Strongly acid, low-fertility,

fragipan

Ithaca, NY Halme farm 42�270N,

76�27 W

Erie soil, fine silt Minimal slope Marginal Wetness, acidity, stones,

low-fertility

Ithaca, NY Caldwell farm 42�270N,

76�27 W

Collamar, fine

textured

Less slope Marginal Erodible

Ithaca, NY Caldwell farm 42�270N,

76�27 W

Collamar-e, fine

textured

More slope Marginal Erodible

Northeast, NY Willsboro farm

44�21 N, 73�230W

Rhinebeck, fine

texture clay

Minimal slope Marginal Wetness

Northeast, NY Willsboro farm

44�21 N, 73�230W

Madalin, fine

texture clay

Minimal slope Marginal Wetness

Geophyta (Ohio) 3 Sites in northeast part of state with varying levels of wetness

Site 1 –Ottawa Co. w 41�30 N,

83�030W

Toledo or Lucus

silty clay

0–2% Adequate soil pH and

high fertility

Occasional wetness, tiled

Site 2 – Sandusky Co. w 41�220N,

83�040W

Toledo or Lucus

silty clay

2–6% Adequate soil pH

and fertility

Moderate wetness, no tile

Site 3 – Erie Co. w 41�220N,

82�470W

Toledo or Lucus

silty clay

0–2% Low soil pH and

low available P

Frequent wetness, no tile

Purdue University (Indiana) 5 Sites in 3 regions of state with range of soil qualities and slope effects compared

Purdue Agronomy Farm

40�290N,86�590W

Chalmers silty

clay loam

0–2% slope Good Minimal

Southern Purdue Agricultural

Center 38�210N,86�490W

Zanesville silt

loam

8–12% slope Marginal, previous

crop tall fescue

Fragipan, erosion, droughty

Southeastern Purdue Agricultural

Center 39�010 N,85�320W

Cincinnati silt

loam

8–10% slope Marginal, previous

crop tilled corn

Erosion, fragipan, poor

drainage

Throckmorton Purdue Agricultural

Center 40�170N,86�540W

Slidell silt loam 0–2% slope Excellent, previous

crop tilled corn

Minimal

Throckmorton Purdue Agricultural

Center 40�170N,86�540W

Slidell silt loam 6–8% slope Excellent, previous

crop tilled corn

Erosion

Virginia Tech (Virginia) 12 Site in 3 locations representing 3 soils representative of the piedmont region of the southeastern U.S., (location

values are county centers)

Lunenberg County 3 study

sites w 36�550N, 78�140W

Appling sandy

loam

6 & 7% slopes Poor, coarse textured Strongly acidic highly

erosive low nutrient

Amelia County 3 sites N facing

slopes 3 sites S facing slopes

w37�550N, 77�580W

Cecil 8 & 9% slopes Poor, long-term erosion Acidic highly erosive

Orange County 3 study

sites 38�140N, 77�580W

Davison 9 &10% slopes Not quite as poor Strongly acidic, highly

erosive

Iowa State University (Iowa) 2 Sites in 2 regions of state, with good and marginal soils compared

Ames, IA: Bruner Farm

42�010N, 93�460W

Harps silty clay

loam

0–1% slope Class I

SOM ¼ 7%

Highly productive, corn/soybean/

oat rotation in 1987

pH of 8.0 2 m rooting depth


Chariton, IA: McNay Farm 40�580N,

93�250W

Clarinda fine silty,

Clearfield fine

silty and

Grundy silty clay

loam

2–7% slope Class III

SOM ¼ 4%

Lower productivity soil,

conventional red clover

prior use

Erosive Droughty pH of

6.8 high clay layer in B

horizon

limits roots

North Dakota State Univ (North Dakota) 5 Dryland sites and 1 irrigated site representing 3 major soil areas in North Dakota

Prosper, ND Red River Valley 46�570N,

97�010W

Gardena Silt loam level Productive, Lacustrine sediments Moderate rainfall

Hettinger, ND Missouri Plateau

46�000N, 102�380W

Shambo Silt loam 0–2% Productive, Alluvium Very low rainfall

Glenfield,(a), ND Drift

Prairie 46�270N, 98�330W

Barnes loam to

Siva loam

NA Productive, Glacial till Low rainfall

Leonard, ND Red River Valley 46�390N,

97�140W

Hecla Loamy fine

sand

Nearly level Marginal, CRP land Wind erosion Moderate

rainfall

Glenfield (b), ND Drift Prairie 46�270N,

98�330W

Buse loam Crests of hills Marginal, CRP land, glacial till Low rainfall

Carrington, ND Drift Prairie, irrigated

46�570N, 97�010W

Emrick loam level Productive with irrigation;

glacial till

Requires irrigation


2.2.4. Purdue University – IndianaPurdue University initially planted three annual grasses, three

perennial grasses and two perennial legumes in spring 1985

with additional crops added in 1988 [18]. The sorghums

generally produced higher yields than the perennial grasses

but of the perennial species investigated, switchgrass

obtained the highest biomass observed (up to 17 Mg ha�1) in

a single year (1989) (Table 7). Switchgrass yields in the range of

9–12 Mg ha�1 were more common and consistently greater

than tall fescue and reed canarygrass at equal nitrogen

fertilizer applications (Table 7) [18]. Reported advantages of

switchgrass included minimal fertilizer input requirements,

persistence, and effectiveness in reducing soil erosion.

Establishment problems did occur with switchgrass at the

poorest site.

The sweet sorghum yields reported in Table 7, where the

results are averaged over four different soil types, hides the

large variation among sites experienced by the sorghums.

Table 8 shows results during the drought year of 1988 when all

crop yields were lower than in 1987 (except for alfalfa) but the

sorghum yields at two of the sites (T-Flat and T-Slope) are

particularly low [19]. At those two locations, double cropping

of rye with sorghums resulted in very low yield of the

sorghums because the rye depleted the soil moisture in the

spring and no rainfall occurred till July. Sorghum double

cropped with rye and with high fertilizer levels was often

a very productive management option in other years, though

it required more inputs than switchgrass. Interseeding

sorghum into perennial grasses was not a viable option.

Economic analysis indicated that biomass feedstock produc-

tion could be economically viable on marginal land in the

Midwest and could compete favorably for land with tradi-

tional crops [20]. Sorghum� sudangrass, sweet sorghum, reed

canarygrass, and switchgrass were identified as promising

crops for Midwest production. Based on production costs

alone, the most promising crops appeared to be switchgrass

and sweet sorghum. Simulation studies on switchgrass sug-

gested that the production costs may be competitive with crop

residue costs and that if managed with low fertilizer appli-

cation and harvest of mature forage, economic returns would

be maximized [21].

2.2.5. Virginia Tech – VirginiaVirginia Tech evaluated four grasses and four legumes. This

study provided a particularly good evaluation of both warm

and cool season perennial grasses in comparison with

sorghum � sudangrass on marginal cropland (Table 9).

Planting in 1985 occurred in early or late summer with most of

the cool season species and sericea lespedeza needing

replanting or over seeding; sorghum � sudangrass performed

well and the switchgrass and weeping lovegrass stands were

good to excellent by spring 1986 [22]. Only the latter two

species, (both warm season grasses) were recommended for

further study. Virginia Tech initiated management studies on

switchgrass and weeping lovegrass in 1988 [23]. While both

species continued to show promise as relatively low input

energy crops, yields and stand vigor declined in the weeping

lovegrass trials after 4 years, leaving switchgrass as the most

promising species. The management studies demonstrated

that no-till management could be successfully used to estab-

lish perennial grasses and to reduce soil loss on sloping

marginal land and that the deep rooting depth of switchgrass

was a contributor to its productivity and to soil carbon

enhancement.

2.2.6. Iowa State University – IowaYields of several annual grasses, perennial grasses, and

legumes grown in pure stands and mixtures were compared

on a marginal (Chariton) and a good (Ames) agricultural site

between 1988 and 1992 [24,25]. The perennial crops (reed

canarygrass, big bluestem, switchgrass, and alfalfa) estab-

lished poorly or not at all in 1988 at Chariton, while the annual

crops (sorghum varieties and maize) preformed well (Table 10).

All perennial grasses were successfully re-established at

Chariton in 1989. Sweet sorghum and sorghum � sudangrass

hybrids, in a variety of cropping systems, produced higher

yields than any other annual or perennial species, on both

good and marginal soils under varying climate conditions

(Table 10).However, estimated annual soil loss for sorghum

varieties was 5 and 35 Mg ha�1 at Ames and Chariton,

respectively, whereas for perennial grasses or alfalfa esti-

mated soil loss was less than 2 Mg ha�1 at both sites. Economic

analysis of multiple cropping systems with average Iowa

Table 4 – Biomass yields (dry Mg haL1) of herbaceous crops produced in four physiographic regions in Alabama 1985–1989.a

Location, physiographic region and species 1985 1986 1987 1988 1989

Camden; Lower Coastal Plain

Sweet sorghum ‘Meridian 81’ 21.4 6.8 0.2 3.8 19.5

Pearl milletb 11.8 3.1 NP NP NP

Maize ‘Dekalb 689’ NP NP NP 0.7 13.5

Rye ‘Winter Grazer 70’ LP 7.5 NP 3.6 4.9

Switchgrass ‘Cave-in-Rock’ NH 1.5 2.9 7.0 12.1

Bermudagrass ‘Coastal’ NH 1.0 5.0 6.0 6.6

Sericea lespedeza ‘Serala’ NH 1.3 5.7 7.9 8.3

Winfield; Upper Coastal Plain

Sweet sorghum ‘Meridian 81’ NP 23.6 1.8 14.0 4.8

Pearl millet 13.6 5.2 NP NP NP


Rye ‘Winter Grazer 70’ LP 5.0 NP 3.2 3.1

Johnsongrassb 10.8 11.6 2.9 7.0 4.8

Switchgrass ‘Cave-in-Rock’ 0.4 6.6 4.8 8.4 6.1

Tall Fescue ‘Kentucky 31’ NH 2.6 5.9 3.9 9.0


Sericea lespedeza ‘Serala’ NH 4.7 4.6 8.2 8.0

Camp Hill, Piedmont


Pearl millet 16.4 6.5 NP NP NP


Rye ‘Winter Grazer 70’ LP 7.0 3.8 3.7 5.9




Sericea lespedeza ‘Serala’ 5.6 6.0 5.4 4.5 5.6

Crossville, Appalachian Foothills


Pearl milletb 11.0 3.6 NP NP NP


Rye ‘Winter Grazer 70’ LP 3.3 2.5 1.2 3.6



Bermudagrass ‘Coastal’ 1.9 2.9 7.2 5.9 8.2

Sericea lespedeza ‘Serala’ 4.2 4.6 5.2 6.6 7.7

a The experimental plots (4.5� 6 m) were laid out in randomized complete block designs, with four replicates at each site. Annual grasses were

fertilized with 120 kg N ha�1 and perennial grasses received 100 kg N ha�1. Soil P and K were maintained at moderate levels. Perennials were

harvested two or three times per season, annuals were harvested only once. The Auburn final report [13] provided statistics on yields averaged

over location rather than years. NP ¼ not planted, NH ¼ planted but not harvested, LP ¼ late summer planting, thus not harvested till next year.

b No varietal names were given for pearl millet or Johnsongrass.


equipment utilization assumptions showed breakeven farm-

gate prices (in 1993$ per dry weight crop unit) for single crop

sorghums of $30–$42 Mg�1 and perennials grasses of $39–

$74 Mg�1 [25,26]. Switchgrass was the least costly perennial,

with breakeven prices of $39 and $48 Mg�1 at Chariton and

Ames, respectively, which was lower than any of the inter-

cropped systems. The Iowa State analysis demonstrated that

switchgrass competed well even with the higher-yielding

sorghums and intercropping systems when an environmental

perspective was considered together with the economics.

2.2.7. North Dakota State University – North DakotaThe North Dakota trials between 1988 and 1992, evaluated

numerous perennial and annual crops (Tables 11 and 12) plus

some additional crop combinations not included in the tables

at six sites [27]. Due to establishment year failures, all

perennial crops had to be reseeded in 1989 with watering in

some cases to achieve successful establishment. By

September 1989, reasonable to good stands of grasses had

been obtained but the legumes were not successful. Annuals

successfully established in 1988 but produced low yields and

did not set grain at the driest site. The six sites included one

western irrigated site plus five sites in the eastern half of

North Dakota with two of those in the Red River Valley. Site

had a large effect on establishment success and yields. Overall

perennial crops yields were highest at Leonard, a marginal site

with good soil moisture located along the Red River (Table 11).

Although switchgrass was the highest yielding perennial

grass where it successfully established, it only successfully

established in the two most eastern sites. The most robust

grass performance across all sites was demonstrated by the

three wheatgrasses. As might be expected, highest overall

annual crop yields occurred at the irrigated site (Carrington)

(Table 12). Of the five annual crops tested, forage sorghum and

Table 5 – Biomass yields (dry Mg haL1) of herbaceous crops produced at eight locations in New York, 1985–1989.a

Site, soil type, crop, and best harvest times 1985 1986 1987 1988 1989

Geneva; Honeoye

Alfalfa ‘Oneida’/bromegrass ‘Saratoga’ – mid June, early Sept ND 8.8 10.2 12.6 11.6

Flat pea‘Lathco’ – mid Aug NP 4.5 9.7 5.3 12.1

Sudangrass ‘Piper’ – late Augb NP NP 10.9 3.1 NP

Switchgrass‘Cave-in-Rock’ – mid Aug NP 1.4 7.4 3.3 6.5

Timothy ‘Climax/common redtop/red clover ‘Arlington’ – mid Jul ND 7.1 6.0 4.8 9.5

Aurora; Kendaia

Kale ‘Maris Kestral’ – one cut, date not givenc NP 4.5 6.4 NP NP

Sudangrass ‘Piper’ – late Augb NP 7.4 ND ND ND

Freeville; Mardin

Flat pea‘Lathco’ – mid Aug NH 5.4 8.5 4.3 9.0

Kale ‘Maris Kestral’ – one cut, date not given 7.4 8.7 3.5 NP NP

Switchgrass ‘Cave-in-Rock’ – mid Aug NH 4.2 3.5 3.2 ND


Ithaca (Halme farm); Erie

Eastern gamagrass –early Oct NP NH 7.9 7.0 4.5

Meadow (mixed grasses and legumes)– mid Jul NH 3.6 3.9 3.8 5.4

Reed canarygrass, common – mid Jul NH 4.4 5.8 7.5 4.9

Sudangrass ‘Piper’ – late Augb NP 3.1 NP NP NP


Ithaca (Caldwell farm); Collamar

Alfalfa bromegrass – mid Jun, early Sep NP 2.1 7.4 8.9 9.1

Flat pea ‘Lathco’ – mid Aug NP NH 8.8 9.2 10.0

Switchgrass ‘Cave-in-Rock’ – mid Aug NP 1.1 6.9 7.7 10.0

Timothy ‘Climax/common redtop/red clover ‘Arlington’ – mid Jul NP 2.0 8.5 7.8 9.8

Ithaca (Caldwell farm); Collamar-e

Alfalfa bromegrass – mid Jun, early Sep NP 2.1 10.3 10.2 10.6

Flat pea ‘Lathco’ – mid Aug NP NH 8.4 6.6 11.6

Switchgrass ‘Cave-in-Rock’ – mid Aug NP NH 8.3 6.4 9.6

Timothy ‘Climax/common redtop/red clover ‘Arlington’ – mid Jul NP 3.7 9.8 9.2 12.0

NE New York (Willsboro farm); Rhinebeck

Kale ‘Maris Kestral’ – one cut, date not given 1.4 5.8 NP NP NP

Meadow (mixed grasses and legumes) – mid July NH 4.5 2.3 4.9 7.2

Reed canarygrass, common – mid July LP 3.2 5.4 4.0 5.1

Switchgrass ‘Cave-in-Rock’ – mid Aug LP NH 2.6 3.8 5.5

Timothy ‘Climax/common redtop/red clover ‘Arlington’ – mid Jul LP 6.5 4.7 3.0 5.5

NE New York (Willsboro farm); Madalin

Kale ‘Maris Kestral’ – one cut, date not given 2.2 5.1 NP NP NP

Meadow (mixed grasses and legumes) – mid July NH 4.7 1.1 5.7 6.7

Reed canarygrass, common – mid-Jul LP 3.3 5.9 4.5 7.7

Switchgrass – ‘Cave-in-Rock’ mid Aug LP NH 2.5 3.7 4.6

Timothy ‘Climax/common redtop/red clover ‘Arlington’ – mid Jul LP 4.8 3.9 2.9 7.2

a New York trials of all crops included thee fertilizer levels and two harvest strategies for most crops. Yields reported here are only from the

intermediate fertilizer level (which differed for each crop and location) and from the harvest strategy resulting in higher multiyear yields.

The final report prepared by Cornell University [15] shows yield results under all harvest scenarios and all fertilizer levels. Yields values are the

average of four replicates of each cropping system. ND ¼ no data reported but reasons not explained, NP ¼ crop not planted, NH ¼ crop not

harvested, LP ¼ late summer planting, thus not harvested till next year.

b Sudangrass was double cropped with forage brassica and one or both crops failed at least 1/3 of the time.

c Kale was dropped from the study after 1987 at all sites.


sorghum–sudangrass achieved the highest production in

most years across all sites. An annual weed, kochia, provided

the most surprising results. In annually seeded plots, kochia

had yields nearly as high as the sorghums on the better sites

and it performed better than all perennials species at the

poorest sites [27]. Kochia was not given serious consideration,

however, because of its characteristics as a serious weed in

the region. Economic analysis concluded that if kochia was

excluded, then forage sorghum and sorghum � sudangrass

were the most profitable biomass crops [28]. However,

switchgrass and some of the wheatgrasses were more profit-

able than the common small grains grown in the eastern Red

River Valley area. The report concluded that herbaceous

biomass cropping was economically feasible in the Northern

Great Plains with several species. Since switchgrass had

shown promise, but poor establishment, the final report

Table 6 – Biomass yields (dry Mg haL1) of herbaceous crops with one harvest per season at three locations in Ohio1986–1989.a

Site description and crop 1985b 1986 1987 1988 1989

Site 1 – Occasionally wet

Alfalfa ‘Apollo II’ LP 2.7 4.2 4.2 4.6

Timothy ‘Toro’ LP 3.8 4.7 3.6 4.9

Switchgrass ‘Cave-in-Rock’ LP, F 5.3 4.7 4.6 9.0

Tall Fescue ‘Fawn’ LP, F 5.1 5.1 3.6 5.2

Birdsfoot trefoil ‘Norcen’ LP 3.3 6.7 6.0 4.8

Reed canarygrass ‘Venture’ LP, F 5.1 7.1 6.6 10.3

Forage sorghum ‘Dekalb FS25E’ NP 22.0 17.9 5.1 4.3

Forage sorghum ‘Growmark S214’ NP NP 20.7 5.9 6.3

Rye/Sorghum � sudan ‘Dekalb ST6þ’ LP 23.5 24.3 9.1 14.9

Site 2 – Moderate wetness

Alfalfa ‘Apollo II’ LP 1.7 3.8 3.2 4.2

Timothy ‘Toro’ LP 3.6 3.8 3.1 5.4


Tall Fescue ‘Fawn’ LP, F NP NP NP NP

Birdsfoot trefoil ‘Norcen’ LP, F 2.6 6.7 5.3 4.9

Reed canarygrass ‘Venture’ LP, F 5.1 6.0 5.8 9.0




Site 3 – Frequent wetness

Alfalfa ‘Apollo II’ LP, F 2.0 3.8 3.3 4.3

Timothy ‘Toro’ LP 3.2 3.2 2.5 4.8


Tall Fescue ‘Fawn’ LP, F – 3.6 3.6 5.1

Birdsfoot trefoil ‘Norcen’ LP, F 1.8 5.9 4.2 4.5

Reed canarygrass ‘Venture’ LP, F NP NP NP NP




a Crops were screened using two levels of weed control management, two fertility levels and two cutting strategies at one site in a randomized

complete block design with three replications of each treatment. Yields reported here are from the 1-cut per yr strategy but averaged over

fertility and weed control levels. Switchgrass was only crop with a strong positive response to weed control. Fertility responses were variable

from year to year. Complete details on fertilization rates and responses, and switchgrass response to weed control and many other details are

provided in the Geophyta final report [17]. LP ¼ late summer planting thus not harvested till next year, F ¼ failure, NP ¼ not planted.

b All perennials were planted in fall of 1985, crops noted as ‘‘LP, F’’ survived the heavy rains following by soil crusting then frost upheaval, but

only rye was in good condition the following spring. Thus all perennials were replanted in spring of 1996 along with the planting of sorghum

varieties.


recommended that further research on switchgrass was

needed in the Northern Great Plains.

2.2.8. Oak Ridge National Laboratory – TennesseeAn ‘‘old field’’ successional vegetation study was conducted

at ORNL in 1986 through 1988, providing a comparison with

the species screening results. The study sites were a recently

abandoned soybean field and a long abandoned pasture [29].

Species diversity was high in both areas with the abandoned

pasture having a higher percentage of grasses and sericea

lespedeza than the abandoned cropland. The latter had more

compositae that are typical weeds in cropland. Treatments

included combinations of lime, nitrogen and phosphorus

levels and harvest frequency. Biomass yields on abandoned

pasture ranged from 1.6 to 7.2 Mg ha�1 across treatments

and years while biomass yields on abandoned soybean fields

ranged from 3.2 to 8.7 Mg ha�1. The successional vegetation

was responsive to liming and fertilizers, although to a lesser

extent than crops such as sweet sorghum and switchgrass.

The fertilizer response was not sufficiently strong, however,

to compensate for the added cost of the fertilizer applica-

tions. Harvest frequency had little effect on total yield but

did affect botanical composition. The largest variable was

year, with highest yields of all treatments occurring in 1988.

A preliminary economic assessment suggested the most

cost-effective treatment was no fertilization for an overall

cost of a large round bale at field edge of about $10Mg�1

($1990) [29].

2.2.9. Summary of screening project recommendationsThe crops recommended for further study and/or development

by each crop screening project are summarized in Table 13.

While switchgrass was recommended by six of the seven

projects, and performed reasonably well in the seventh project,

it certainly was not always at the top of the recommendation

list. Several of the projects evaluating sorghums, tended to see

a sorghum variety as being the more likely energy crop choice

of farmers in their region. Cushman et al. [30] reported that the

major observation across all screening projects was the supe-

riority of both the sorghums and switchgrass under drought

Table 7 – Biomass yields (dry Mg haL1) of four grasses showing response to fertilization in Indiana 1985–1989.a

Species and fertilization levels (kg N ha�1) 1985 1986 1987 1988 1989

Sweet Sorghum ‘M81E’ 4 Sitesb 4 Sites 4 Sites 4 Sites

0 18.8 13.8 11.9 7.8 NP

50 20.9 19.4 16.2 9.3 NP

100 23.4 20.5 17.8 9.3 NP

150 25.7 22.4 17.1 9.3 NP

Switchgrass ‘Cave-in-Rock’ 1 Sitec 3 Sites 4 Sites 4 Sites

0 SP, F 8.7 8.6 5.2 8.8

50 SP, F 10.4 11.1 7.4 13.7

100 SP, F 10.8 12.4 9.3 15.8

150 SP, F 12.0 12.2 8.9 16.2

200 SP ,F 12.5 12.9 9.3 17.4

Tall Fescue ‘Forager’ 2 Sites 3 Sites 4 Sites 4 Sites

0 SP, F 2.9 5.5 2.5 4.5

50 SP, F 5.1 7.1 4.1 7.6

100 SP, F 5.9 7.8 5.4 9.2

150 SP, F 7.5 8.9 6.6 10.4

200 SP, F 9.0 9.3 7.1 11.0

Reed Canarygrass ‘Venture’ 1 Sitec 3 Sites 4 Sites 4 Sites

0 SP, F 4.2 5.1 2.6 3.7

50 SP. F 7.3 7.6 3.8 6.1

100 SP, F 6.7 9.2 5.6 8.0

150 SP, F 8.1 10.9 6.8 9.8

200 SP, F 9.6 12.3 7.6 11.4

a Management conditions tested in Indiana, in addition to fertilization, included conventional versus no-till, with and without herbicide for the

sorghums and one cut per year versus two cuts per year. Fertilizer results are reported for only some of the crops screened. These data were

derived from graphed results in the Purdue University final report [18]. Results at the fertilizer level of 100 kg N ha�1 are most suitable for

comparisons with the screening results from other projects reported in this paper. SP ¼ spring plant, F ¼ failure.

b Indicates the numbers of sites contributing to the average yield reported. Each treatment was replicated four times at each site.

c Results from only 1 sites indicates that switchgrass and reed canarygrass were more difficult than other crops to establish and they took

longer at some sites to become well-enough established to harvest.


conditions. From an economic perspective, both sorghums and

switchgrass generally stood out as having higher potential than

other crop choices. It was concluded that sorghum may have

potential for meeting economic requirements in the Midwest,

but not the Southeast [30]. The only other crop that was rec-

ommended for further study by more than one project was

reed canarygrass. Energy cane and other subtropical grasses

Table 8 – Biomass yields (dry Mg haL1) of herbaceous biomass

Crop

T-Flat(excellent cropland) (excell

Alfalfa ‘’Hi-Phy’ 17.36

Birdsfoot trefoil ‘Fergus’ 8.03

Tall fescue ‘Forager’ 6.22

Reed canarygrass ‘Venture 5.99

Switchgrass ‘Cave-in-Rock’ 9.90

Rye, Annual Winter 3.88

Sorghum � sudangrass ‘FFR-201’ 4.86

Sweet sorghum ‘M81-E’ 2.20

a Yields reported in this table are averaged across five fertilizer levels a

microclimate effects within a given year. Yields were not reported for all c

report. This data summary was retrieved from Herbaceous Energy Crop

derived from an unpublished (and no longer available) annual report from

produced some very high yields that suggested further work

might be merited in the subtropical US. The ORNL graphic

(Fig. 2), drawn in 1991, showing both the woody and herbaceous

crops considered to be high potential by both woody and

herbaceous screening projects, included switchgrass, reed

canarygrass, sorghum, and tropical grasses as the herbaceous

crops of choice.

crops during the drought year of 1988.a

Site

T-Slopeent cropland)

SEPAC(marginal cropland)

SIPAC(marginal cropland)

13.28 9.98 1.62

6.31 5.88 5.25

3.52 4.28 6.73

4.10 5.12 6.27

6.49 8.58 7.13

3.29 3.42 2.42

4.26 11.19 12.77

1.70 12.77 21.03

nd across other management alternatives. The focus is on soil and

rops by year and management strategy in the Purdue University final

s Program annual report for 1988 [19] with the data being originally

Purdue University.

Table 9 – Biomass yields (dry Mg haL1) of warm and cool season herbaceous crops with one harvest per year on three soiltypes in the Piedmont of Virginia 1986–1989.a

Soil type and cropb 1985 1986 1987 1988 1989

Appling Soils – SW facing

Sorgum–sudangrass ‘Southern States’ (W) 4.2 4.8 – 6.0 1.1

Weeping lovegrass ‘Commom’(W) 2.8 0.5 9.2 13.7 7.8

Switchgrass ‘Cave-in-Rock’ (W) 1.1 5.2 8.6 8.1 8.0

Sericea lespedeza ‘Common’ (W) F – 4.1 4.8 6.5

Tall Fescue ‘Forager’ (C) LP 1.0 3.3 2.4 2.9

Crownvetch ‘Penngift’(C) LP, F – – – –

Birdsfoot Trefoil ‘Fergus’ (C) LP – 3.7 2.1 2.9

Flatpea (C) LP – – – –

Cecil Soils – SW facing

Sorgum–sudangrass ‘Southern States’ (W) 12.9 11.2 9.0 12.0 6.8



Sericea lespedeza ‘Common’ (W) F 4.7 6.6 9.3 7.0


Crownvetch ‘Penngift’(C) LP, F 1.3 3.6 9.2 9.4

Birdsfoot Trefoil ‘Fergus’ (C) LP 1.7 7.1 7.6 9.7

Flatpea (C) LP 1.7 4.1 5.9 11.5

Cecil Soils – NW facing






Crownvetch ‘Penngift’(C) LP, F – 5.2 8.1 9.0

Birdsfoot Trefoil ‘Fergus’ (C) LP 2.0 8.6 6.7 7.6

Flatpea (C) LP 2.3 3.9 6.2 7.7

Davidson Soils – SW facing





Tall Fescue ‘Forager’ (C) LP, PF 1.4 8.0 5.2 6.9

Crownvetch ‘Penngift’(C) LP, PF 0.4 3.6 7.2 10.6

Birdsfoot Trefoil ‘Fergus’ (C) LP, F 0.7 5.9 7.6 9.1

Flatpea (C) LP – 2.5 2.6 12.9

a The basic screening study by Virginia Tech consisted of small plots (4� 6 m) of all species planted side by side in randomized complete blocks

with four replications at each of 12 sites. Each soil type and orientation scenario was duplicated at three sites within a soil type. Results shown

are the average of the 3 sites. F ¼ failure; PF – partial failure; LP ¼ Late summer planting (normally August) harvested the following year. Failed

and partially failed plantings were re-established in 1986. The Virginia Polytechnic Institute and State University (VPI) final report [22] provides

details of all methods and data on crop composition, soils studies, economic analysis, erosion analysis, no-till establishment procedures, and

physiological studies. VPI included only years 1986–1989 data in their statistical analysis.

b The variety of the crop is specified where information was provided; warm season crops are designated with a (W) and cool season crops with

a (C) after the common name.


3. Discussion of major crop selection factors

The goals and objectives of the HECP as stated in 1987 reflec-

ted sensitivity to environmental concerns and to working with

industry. The 1987 HECP Annual Progress Report [30] stated

that the overall goal of the HECP was to work with industry

and university researchers to provide a technology base that

would allow industry to develop commercially viable systems

for producing herbaceous biomass for fuels and energy feed-

stocks. The specific objectives of the HECP (paraphrased)

included (1) identifying the land resource available, (2) iden-

tifying the productivity potential of appropriate species, (3)

defining cost-effective management techniques, and (4)

establishing the environmental acceptability and economic

feasibility of herbaceous energy crops.

The 1987 HECP Report noted that the best yields for ligno-

cellulosic crops were coming from annual grasses but there

was substantial concern expressed about the amount of

erosion associated with annual crops. Data reported by the

USDA/SCS in the 1982 National Resources Inventory [31],

showed further reason for concern. About 50% of the total

cropland base had a low erodibility factor of <10, meaning

that almost any crop could be planted on this land using

conventional tillage with an expectation that water-caused

erosion would remain less than the 11.2 Mg ha�1 [a level

Table 10 – Biomass yields (dry Mg haL1) of nine of the thirteen crop systems tested on marginal and good cropland sites inIowa 1988–1992.a

Site description and crop system 1988 1989 1990 1991 1992

140 kg N ha�1

Ames (good)

Reed canarygrass (RCG) ‘Venture’ 5.5 7.9 10.3 7.9 6.8

Switchgrass (SWG) ‘Cave-in-Rock’ 8.3 8.3 10.6 10.3 15.3

Big bluestem (BBS) ‘Sunny View’ 6.4 6.4 11.4 7.7 12.4

Sweet sorghum (SS) ‘M-81E’ 17.5 15.3 20.7 16.5 17.4

Sorghum � sudangrass (SSH) ‘FFR201’ 14.6 16.3 15.3 16.7 15.6

SS þ Rye double crop total, Rye ¼ ’Aroostock’ 12.0 19.0 19.6 20.5 NP

SSH þ Rye double crop total, Rye ¼ ’Aroostock’ 14.0 19.1 15.1 14.2 NP

Maize (grain þ stover) ‘Pioneer 3377’ 11.3 17.8 16.6 11.5 11.7

ALF/SS intercrop Alfalfa ¼ ‘Arrow’ NP 15.9 15.5 18.0 11.9

ALF/SSH intercrop Alfalfa ¼ ’Arrow’ NP 16.3 15.4 17.1 10.9

Chariton (marginal)

Reed canarygrass (RCG) ‘Venture’ NH 6.3 11.8 9.9 10.9

Switchgrass (SWG) ‘Cave-in-Rock’ NH 6.5 8.3 10.7 15.8

Big bluestem (BBS) ‘Sunny View’ NH 2.9 9.4 6.4 10.5






ALF/SS intercrop Alfalfa ¼ ‘Arrow’ NP 10.2 13.4 NP NP

ALF/SSH intercrop Alfalfa ¼ ’Arrow’ NP 9.9 15.4 NP NP

70 kg N ha�1

Ames (good)

Reed canarygrass (RCG) ‘Venture’ 5.2 5.8 7.2 6.8 4.5

Switchgrass (SWG) ‘Cave-in-Rock’ 7.7 8.0 11.6 11.2 13.8

Big bluestem (BBS) ‘Sunny View’ 5.7 6.9 10.7 8.3 11.1






ALF/SS intercrop Alfalfa ¼ ‘Arrow’ NP 16.9 14.9 17.4 11.1

ALF/SSH intercrop Alfalfa ¼ ’Arrow’ NP 18.1 13.6 17.1 10.3

Chariton (marginal)

Reed canarygrass (RCG) ‘Venture’ NH NH 11.3 7.9 7.9

Switchgrass (SWG) ‘Cave-in-Rock’ NH NH 6.6 8.9 12.4

Big bluestem (BBS) ‘Sunny View’ NH 3.1 9.7 5.5 9.2






ALF/SS intercrop Alfalfa ¼ ‘Arrow’ NP 9.5 11.7 NP NP

ALF/SSH intercrop Alfalfa ¼ ’Arrow’ NP 10.1 14.1 NP NP

a Thirteen crops systems were evaluated on a good and marginal location in a randomized complete block in a split plot arrangement with four

replicates. The main plots were cropping systems planted in strips 6 m wide by 31 m long with four sub-plots 6 � 7 m. Due to space constraints

the following cropping systems were not included in this table: (1) alfalfa 1 and 2 cut systems, (2) soybeans in three-year rotation with maize and

sweet sorghum, (3) sweet sorghum double cropped with winter rye in 3 year rotation with maize and soybean, and (4) reed canarygrass

intercropped with sweet sorghum � sudangrass. Also up to four fertilizer levels were tested, only two are summarized here. All crops were first

seeded in spring 1988, a drought year. Abbreviations are as follows: NP¼ not planted, NH¼ not harvested. Reseeding of some stands occurred in

spring 1989. Many more details are provided in the Iowa State University final report [24]. A 2001 publication [25] reports partial data.


deemed acceptable by USDA’s Soil Conservation Service

(SCS)]. However, there was still an issue with wind erosion on

much of that land. Of particular concern was the 12% of the

cropland base with an erodibility factor of 50þ which

accounted for over 42% of water-caused erosion on U.S.

cropland. Of that erosion loss, about 70% was associated with

row crops. The 1982 USDA/SCS report [31] stated that annual

row crops had an average annual soil loss rate of 66 Mg ha�1,

while hay crops (perennial and annual) average only

5.5 Mg ha�1.

Table 11 – Biomass yields (dry Mg haL1) of perennial herbaceous crops produced at six sites in North Dakota 1988–1992.a

Site description and crops 1988b 1989 1990 1991 1992

Prosper – Red River Valley – productive

Bromegrass, common 6.6 6.2 5.8 4.8

Intermediate (I) wheatgrass ‘Ohae’ 10.2 7.3 6.7 5.8

Crested wheatgrass ‘Nordan’ 9.1 7.7 7.3 5.5

Reed canarygrass ‘Palaton’ NH NH 5.7 6.3

Brome–alfalfa 6.7 6.3 5.1 5.2

I & western wheatgrass 9.7 7.3 7.1 5.8

CRP mixture 8.7 7.0 6.6 6.1

Switchgrass ‘Sunburst’ NH 7.3 9.3 10

Big Bluestem ‘SD 43’ NH 4.4 5.9 NR

Hettinger – Missouri Plateau – productive

Bromegrass, common NH 2.0 4.0 NR

Intermediate (I) wheatgrass ‘Ohae’ 4.6 3.5 4.9 NR

Crested wheatgrass ‘Nordan’ 4.1 2.7 3.9 NR

Brome–alfalfa NH 2.1 4.1 NR

I & western wheatgrass 3.9 2.7 4.7 NR

CRP mixture 4.8 2.7 5.1 NR

Glenfield Good – Drift Prairie – productive






CRP mixture 2.1 6.9 3.3 4.1

Leonard – Red River Valley – marginal

Bromegrass, common NH 9.6 5.6 5.7



Reed canarygrass ‘Palaton’ NH 6.6 8.5 11.9



CRP mixture 10.5 14.5 6.4 6.1

Switchgrass ‘Sunburst’ NH 12.5 8.6 12.8

Big Bluestem ‘SD 43’ NH NH 5.7 NR

Glenfield Poor – Drift Prairie – marginal




Reed canarygrass ‘Palaton’ NH NH 3.4 NR



CRP mixture 1.1 5.7 2.9 2.7

Switchgrass ‘Sunburst’ NH NH 3.5 NR

Carrington d Drift Prairie – irrigated




Reed canarygrass ‘Palaton’ NH NH 4.9 4.3



CRP mixture 8.8 10.0 6.1 5.9

bAll crops were planted in 1988 but not harvested due to marginal stands.All crops were reseeded in fall 1988 or spring 1989.

a Perennial crops were planted in a randomized complete block in a split plot arrangement evaluating species and nitrogen levels. Reported

yields are averaged across three replicates all nitrogen levels. NH ¼ not harvested, NR ¼ no information reported.


The erosion concerns associated with growing annual

crops on the types of marginal land included in the

herbaceous screening trial studies were verified by several

of the collaborators; with the best erosion potential

summary tables produced by at Virginia Tech [10,22] and

Iowa State University [10,24]. The USDA data, plus the

verification of erosion problems with annual row crops in

the screening trials had a large influence on the selection of

a perennial crop for further development as an energy crop.

A statement quoted from the 1987 HECP progress report

shows the belief that energy crops should be perennial

crops:

Table 12 – Biomass yields (dry Mg haL1) of annual herbaceous crops produced at 50 kg N haL1 on six sites in North Dakota1988–1992.a

Site description and crops 1988 1989 1990 1991 1992

Prosper – Red River Valley – productive (fallow)b

Sorghum � sudan ‘Dekalb ST6E’ 9.4 11.0 18.5 15.7 13.7

Forage sorghum ‘FS25E’ 13.0 13.2 23.3 15.8 15.9

Foxtail millet ‘German’ NP 10.7 16.5 14.3 11.0

Common kochia 14.4 11.3 19.4 NR 15.1

Maize ‘Pioneer 3974’ grain only (recrop in 1988) 2.0 5.9 10.2 7.9 7.4

Hettinger – Missouri Plateau – productive (fallow)b

Sorghum � sudan ‘Dekalb ST6E’ 7.3 6.2 7.2 4.7 NR

Forage sorghum ‘FS25E’ 7.0 5.6 4.7 3.7 NR

Foxtail millet ‘German’ 2.1 6.5 8.8 4.0 NR

Common kochia NP 9.7 14.3 6.6 NR

Maize ‘Pioneer 3974’ grain only NP 4.1 NR NR NR

Glenfield Good – Drift Prairie – productive (recrop)b



Foxtail millet ‘German’ 7.0 11.2 8.9 9.0 9.0

Common kochia, NP 5.8 10.7 9.6 8.7

Maize ‘Pioneer 3974’ grain only NP NR 9.3 4.3 2.8

Leonard – Red River Valley – marginal (fallow)b



12.0Foxtail millet ‘German’ 3.2 7.4 13.3 11.2 8.0

Common kochia 10.3 NR 8.8 NR 6.5

Maize ‘Pioneer 3974’ grain only 3.0 5.1 9.3 4.8 5.1

Glenfield Poor – Drift Prairie – marginal (recrop)b

Sorghum � sudan ‘Dekalb ST6E’ NP 5.0 9.0 17.1 10.4

Forage sorghum ‘FS25E’ NP 4.0 8.7 16.3 9.6

Foxtail millet ‘German’ NP 6.2 NR NR NR

Common kochia NP 7.5 6.3 10.2 NR

Carrington – Drift Prairie – irrigated (recrop)b

Sorghum � sudan ‘Dekalb ST6E’ 18.0 9.5 18.0 17.1 NR

Forage sorghum ‘FS25E’ 19.1 12.1 17.9 18.6 NR

Foxtail millet ‘German’ 10.6 8.3 12.9 14.6 NR

Common kochia 8.6 NR NR NR NR

Maize ‘Pioneer 3974’ 10.2 NR 10.9 9.7 NR

a Annual crops were established at most sites in 1988 in a randomized complete block design with split–split plot arrangements, where crop or

recrop was the mainplot, species the subplot, and nitrogen level the sub-subplot. The nitrogen level � species interation was generally non-

significant so only yields from 50 kg N ha�1 were reported. NP ¼ not planted, NR ¼ no information reported. Full details of methods and

additional results are provided in the North Dakota State University Final report [27].

b Biomass yields were generally 1–1.2 Mg ha�1 higher in comparisons of planting on fallow versus recrop land, but data from fallow land was

not always available for all crops, so the data is from recrop plantings on the sites where indicated.


‘‘Annual crops, especially energy crops that will leave little

residue on the soil, are not appropriate for significant acre-

ages of cropland. Perennial energy crops, especially grasses,

are suitable for almost all cropland and potential cropland.

They provide an opportunity to produce a crop on erosive

land, yet achieve acceptable levels of soil protection.’’

At the conclusion of the herbaceous crop screening studies

between 1990 and 1992, funding limitations imposed by

Congress on DOE and subsequently by DOE on the HECP [10],

meant that DOE and ORNL agreed that it would be prudent to

focus further crop development effort on a single model

energy crop. Thus a combination of technology and environ-

mental issues, together with funding limitations, led to the

selection of switchgrass as the ‘‘model’’ herbaceous crop

species.

4. Lessons learned and conclusions

The screening trials each had both unique and common prob-

lems and enough similarity in results to derive some lessons for

moving forward with the development of energy crops. The ten

years of focus on switchgrass that followed the screening trials

both verified the importance of the lessons learned during the

screening and found solutions to some of the problems.

Lesson 1 As with most agricultural enterprises, climate vari-

ation is an uncontrollable factor that poses risk,

particularly in achieving successful establishment of

crops without irrigation.

Lesson 2 Experience and understanding of best establishment

techniques can result in successful establishment

Table 13 – Species recommended for further developmentor study by the seven herbaceous screening projects.

Institution Recommended crops

Virginia Tech Switchgrass and weeping lovegrass

Auburn University Switchgrass, sericea lespedeza, and

energy cane

Purdue University Sweet sorghum,

sorghum � sudangrass, switchgrass,

and reed canarygrass

Iowa State University Switchgrass and intercropped

sorghums

North Dakota State

University

Forage sorghum,

sorghum � sudangrass, several

wheatgrasses, and switchgrass,

Cornell Alfalfa/bromegrass mixture, and

timothy/redtop/red clover, and

switchgrass, for the well-drained soils;

Reed canarygrass for the poorly

drained soils.

Geophyta Forage sorghum, intercropped

sorghum � sudangrass, and reed

canarygrassa

a Switchgrass was not recommended by Geophyta; probably due

to establishment and weed competition problems. But the reported

data showed that once established, switchgrass yields increased

each year and nearly equaled that of reed canarygrass in the 4th

year. During the same period sorghum yields dropped

dramatically.


even under less than perfect climate conditions.

Investigators at Virginia Tech specifically identified

techniques not known by all investigators during

their initial establishment attempts [23]. For example

Fig. 2 – Woody and herbaceous species considered by DOE’s Bi

potential as energy crop feedstocks in 1991. Herbaceous screen

they proved that no-till plantings can produce very

successful switchgrass stands using commonly

available farm implements. They found that delay-

ing planting until soil is adequately warm is impor-

tant and that insect pests must be controlled if

seedling damage occurs. Virginia Tech investigators

also showed that seed quality (overcoming

dormancy) is an important aspect of establishment.

Seed dormancy can be broken by stratification and/

or after-ripening. After-ripening using elevated

temperatures and controlled seed moisture appears

to have promise as a means for large-scale

commercial dormancy breaking.

Lesson 3 Establishment success is important to the long-term

success of perennial grasses and a critical compo-

nent of this success is good weed control (Parrish et

al, 2005), [32]. Several practical guides to switchgrass

establishment describe both mechanical and chem-

ical methods for controlling weeds.

Lesson 4 Switchgrass (and most perennial grasses) require two

to three years to achieve mature stand yield levels.

Lesson 5 Switchgrass was often not the highest yielding energy

crop candidate, but the combination of relatively reli-

able yields over varying climate conditions and rela-

tively low input requirements reduces risk to the

grower; biological advantages such as deep roots

provide the environmental benefits of carbon

sequestration potential and erosion minimization,

plus other characteristics such as good wildlife habitat

all combine to make switchgrass an economically and

ecologically viable energy crop candidate.

ofuels Feedstock Development Programs having high

ing studies had not been completed in the striped area.


Lesson 6 The yields obtained for most of the perennial grasses

during the screening trials (often less than

10 Mg ha�1) do not represent yield potential. Focused

management studies and breeding of switchgrass as

the model, showed that variety selection, matching

of varieties to sites, and optimized management can

easily result in the doubling or tripling of yields for

a given species [4]. An analysis of factors affecting

yields, based on results of the focused switchgrass

studies, demonstrated that even when all treat-

ments and varieties were grouped together yields

exceeded those found in the early trials, sometimes

by very large amounts [34].

Lesson 7 There are tradeoffs to consider in determining

whether to harvest switchgrass once or twice per

growing season, with the trade-off sometimes being

a larger harvest with two cuts but a lower quality of

the feedstock for bioenergy and higher harvest costs.

Harvest timing and number can also affect the long-

term vitality of the stand but results are often mixed,

possibly due to interactions with nutrient manage-

ment. The recommendation for a one cut approach

combined with relatively low nitrogen applications

appears to be clearer for the lowland varieties than

the upland varieties [23,33,35,36].

Lesson 8 A vastly greater understanding of switchgrass has

been obtained with the focused studies on switch-

grass that has been conducted since 1990 not only in

the US but also in Canada and Europe. Also a number

of new varieties have been developed. Consequently,

a much better basis exists for using switchgrass as

a bioenergy crops species. While other species might

perform as well or better than switchgrass, it will

take a similar or higher level of focused study to

develop any new energy crop species for widespread

commercialization.

Lesson 9 The value of switchgrass as a ‘‘model’’ for perennial

grasses has been demonstrated, leading to its choice

for inclusion as a dedicated crop in some proposals

for commercial demonstration of biofuels produc-

tion. Now it is time to broaden further research to

include other species and types of crops that may be

more economic in some regions of the country or

more suitable for specific conversion technology

requirements.

A few key selection criteria had a large effect on how the

herbaceous species screening process was conducted and on

which specieswere deemed to have high potential.McLaughlin

described the considerations that supported selection of

switchgrass as a ‘‘model’’ energy crop species [3]. One of the

more important criteria was that the land base for switchgrass

was believed to be quite large. McLaughlin noted that the land

most likely to be used for herbaceous crop production was the

approximately 19.4 million hectares of marginal land that had

severe restrictions for conventional crop production. Envi-

ronmentalcriteria were also extremely important. Switchgrass

was believed to be a species that, if used for bioenergy

production on large-scale, could contribute a wide range of

environmental benefits such as improvement of soil carbon by

sequestering carbon belowground, improved erosion control,

reduced fertilizer and pesticide requirements (relative to

conventionally grown annual crops), and a capacity for

providing wildlife cover. Yield potential was important, and

a few early examples of high yield probably resulted in focusing

more attention on switchgrass, but high yield potentials must

be (and were) balanced against the input requirements to

identify potential for positive economic returns to the growers.

Acknowledgements

This research was sponsored by the Department of Energy’s

Biomass Program and performed at Oak Ridge National Labo-

ratory (ORNL). ORNL is managed by UT-Battelle, LLC, for the U.S.

Department of Energy under contract DE-AC05-00OR22725. The

long-term support of the DOE Biomass Program, and especially

John Ferrell of that group, has been greatly appreciated. Much

credit goes to ORNL staff, Janet Cushman, Sandy McLaughlin,

Lynn Kszos, and Bill Johnston for the many reports and papers

on herbaceous crops that they prepared during their tenures as

managers and/or project leaders of herbaceous crops research.

Very importantly, we would like to recognize the researchers

who carried out the herbaceous crops screening trials and

concluded those trials with excellent final reports documenting

the results. We also thank the ORNL reviewers, Erin Wilkerson

and Stan Wullschlager, who greatly improved this document

with their input.

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Acronym definitions

BFDP: Biofuels Feedstock Development ProgramHECP: Herbaceous Energy Crops ProgramRFP: request for proposalsSRWCP: Short Rotation Woody Crops ProgramORNL: Oak Ridge National LaboratoryDOE: Department of EnergyUSDA: United States Department of AgricultureSERI: Solar Energy Research InstituteOTA: Office of Technology Assessment




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