Switchgrass, Big Bluestem, and Indiangrass

DigitalCommons@University of Nebraska - Lincoln

DigitalCommons@University of Nebraska - Lincoln

Publications from USDA-ARS / UNL Faculty

U.S. Department of Agriculture: Agricultural

_{Research Service, Lincoln, Nebraska}

1995

Switchgrass, Big Bluestem, and Indiangrass

Switchgrass, Big Bluestem, and Indiangrass

Lowell E. Moser

University of Nebraska-Lincoln, lmoser1@unl.edu

Kenneth P. Vogel

University of Nebraska-Lincoln, kvogel1@unl.edu

Follow this and additional works at:

https://digitalcommons.unl.edu/usdaarsfacpub

Moser, Lowell E. and Vogel, Kenneth P., "Switchgrass, Big Bluestem, and Indiangrass" (1995). Publications

from USDA-ARS / UNL Faculty. 2098.

https://digitalcommons.unl.edu/usdaarsfacpub/2098

This Article is brought to you for free and open access by the U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Publications from USDA-ARS / UNL Faculty by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.

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Fig.

32.2.

Seasonal

yield

distribution

of

switchgrass,

big

bluestem, and indiangtass

compared with that of the cool-season gr.asses,

smooth bromegrass, and

tall

fescue. (Modifred

from Waller et al. 1986-)

switchgrasses

from

the

Dakotas

(northern

ecotypes)

flower and mature early and

are

short

in

stature,

while

those

from

Texas and Oklahoma (southern ecotypes)

flower late

and

are

tall

(Cornelius and Johnston 1941;

McMil-lian

1959).

Moving northern

ecot)?es

south

gives

them a

shoder than

normal

photoperi-od, and

they flower

early. The opposite occurs

when southern ecotypes are moved

north,

and

as a result they stay

vegetative

longer

and

produce

more

forage

than

northern

strains

moved south

(Newell

1968).

Flowering

of

the

tall

bluestems,

big

and

sand bluestem

(4. gerardii

var. paucipilus

[Nash]

Fern.), syn. (A.

_hallii

_{Hack.), and}

indi-angrass responds

to

photoperiod

in

a

similar

manner. The

response

to

photoperiod

can be

modifred

by growing

degree days

to

some

ex-tent

since

the flowering

date of

cultivars

will

vary from

year to year.

The

photoperiod

response

also

appears to be associated

with winter

survival. Southern

types

moved

too

far

north

will

not

survive

winters

because

they

continue

growth

too

late

in

the

fall

and do

not

winter

harden

properly. As a general

rule,

these grasses should not be

moved more

than

500

km

north

of

their

area

of origin

because

of the possibility of

stand

Iosses due to

winter

injury.

In

addition

to

pho-toperiod,

the

other factor

that

determines specihc

adaptation

is

response

to

precipita-tion

and the

associated

humidity.

Cultivars

that

are

naturally

adapted

to the

more arid

Great

Plains

states may develop

foliar

disease

problems

when grown

in

the

more

humid

eastern states.

Cultivars

based

on

naturally

adapted eastern germplasm may not be as

tol-erant

to

drought

stress as

cultivars

based on

western germplasm.

Since

these

grasses

are native

to

most

of

North America

(Fig. 32.1), ecotypes or

strains

evolved

that

were

adapted

to

specific

geo-graphic regions, and

the total

range of

each

species is represented by a combination range

of

adapted,

native

ecotypes.

Breeding

pro-grams

of the

USDA

and

some

state

experi-ment

stations have resulted

in

the

develop-ment

and release of

cultivars that

are

adapt-ed

to

specifrc regions of

the

central

and

east-ern US. Cultivar

development programs

for

these

grasses

have

received increased

em-phases

in

recent years.

The two

primary

factors determining

area

of

adaptation

of

specific

cultivars

are

re-sponse

to

photoperiod and

precipitation

and

the associated

humidity, both

of

which

are

in-dicated by the

origin

of the germplasm used to develop speciflc

cultivars. Although

much

of

the

prairie

and grasslands

that

were once oc-cupied

by

these gTasses has been plowed and

converted

into

cropland, remanent prairie

sites

still

exist

in

most

areas

and are

an

in-valuable germplasm resource. Some extensive

native tall-grass prairies are, most

notably,

the

flint hills in

Kansas,

the

Osage

prairie in

Oklahoma, and

the sandhills

of Nebraska.

PLANT

DESCRIPTION

Switchgrass. Switchgrass

is

an

erect warm-season

(Cr)

perennial

grass.

It

grows from 0.5 to 2.0 m

tall,

and most

tillers

produce

a

seedhead

when moisture

is

adequate.

A1-though the plant

resembles

a

loose bunch-grass,

it

has

short

rhizomes, and a stand has

the potential

to thicken

and

form

a

sod. The

depth of switchgrass roots

can be

up to 3

m

(Weaver 1968).

The

inflorescence

is

a

diffuse

panicle,

15-55

cm long,

with

spikelets

at

the

end of long branches.

Spikelets

are

two

flow-ered,

with the

second

floret

being

fertile

and

the

first

one

sterile

or

staminate.

The

seed

unit is

a

fertile floret.

It

is

smooth

and slick

with

an indurate

lemma and palea

that

ad-here

tightly

to the caryopsis. The seed

thresh-es clean and

is

easy

to

process and

plant.

On

average,

there

are

860,000

seeds

kg1, but

large seed

weight

differences exist among

cul-tivars.

Johnson

and Boe

(1982)

found

100

seed weights

from

103 to 201 mg. Switchgrass

is

a cross-pollinated

plant that

is largely

self-incompatible (Talbert

et al.

1983).

Switch-grass has

a

basic

chromosome

number of

nine, and

several

levels

of

ploidy

exist

(Nielsen

1944).

Most

switchgrass cultivars

are either

tetraploids

or hexaploids (Riley and Vogel 1982).

Switchgrasses

have

been

divided

into

low-Iand and upland types. Lowland types

are

taller,

more

coarse,

and generally more

rust

(Puccinia

_{graminis') resistant, they have}

_a

more

bunch-type

growth, and they may

be

more

rapid growing than upland

types. As

in-dicated by the

type

description,

lowland

types are found on

floodplains

and

other

similar

ar-eas

while upland

types are found

in

upland

areas

that

are

r--grass can tolera:.

tions.

It

gro\l's

:

Switchgrass

tc-=

ranging from

-1.!l

Big

Bluestem.

3

nant

species

of::

up

as much as

!

-sites (Weaver

1!:

remanent

prair-:

old cemeteries

::'

occurrence.

In

:,'

eastern Great

P-.

abundant

and

L:

in

good

to

erct,

bluestem

is

an

e:

to sandy soiis su:l The Old

World-:-which were

in::-(Schizachrium

; -.

native, were

i:::

pogoz

spp.

and

,

There are 15 orF-.

in

North

Amenc:.

the

most

comrl:-member.

Big

bluestem

--tall.

Plants ofte:

most plants

ha',-:

dieck

et al.

199-sive

rhizomes.

B:

basal

leaves. ar-i

canopy seldom

a:

root

system

is

r'::

deep as 2.0-2.5

t

of

soil

ranges ::

1968).

In

old

pia:-dense

and toug:

stand

diflicult.

The

inflorescer:

icle

with

general-, though

it

may

va:

A

common nam=

/oof

since

the

.

turkey's foot.

S;

and paired;

the

se,

under most

condt:

staminate. Fenrl:

found on

some

r-;

seed

unit

is the

.:

that

includes

a r.

that

supported

::r

seed

has varying

has

a

twisted

:,;

make

unprocessej

cult

to handle

mec

al

seeding equiprn,

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year. Indiangrass

initiates spring

growth

about

the

same

time

as

big

bluestem

and switchgrass

but

does not develop as quickly.

It

normally may flower

about 4-6

wk later

than

switchgrass

collected

in

the

same

area

(Mc-Kendrick et

al.

1975).

Although

indiangrass

has

a

later

heading date than these

other

warm-season grasses,

shoot

apices

begin

to

elongate

earlier

than

those

of big

bluestem

(Gerrish

_{et al.}

_{1987), and}

_plants

_{can become}

rather

stemmy.

As the

genus name Sorghastrum implies,

indiangrass

appears

to

be

closely

related

to

the

sorghums

(Sorghum

spp.).

Indiangrass

is

the

only

forage grass outside of

the

sorghum

genus

_that

is

known

to

contain

cyanogenic glucosides.

Indiangrasses occurring

in

North

America and improved

cultivars all

have 2n =

40 chromosomes

(Riley

and Vogel 1982).

Indi-angrass

is

cross-pollinated,

but

some

plants

will

produce seed

if

selfed. Rooting can occur down to

about

1.6

m,

and

it

will

grow on soils

with

a

pH

range

from

5.6

to

7.1

(Duke

1928).

IMPORTANCE

AND

USE

In

the past,

these grasses have

contributed

immensely to

the native

ranges of

the central

Great Plains. They have additional

impor-tance as

pasture and

reseeded range grasses

because

of

government

agricultural

pro-grams. Beginning

in

the

1930s,

they

have

been used

to

reseed

former

cropland

during

programs such as

the

Soil

Bank

and

the

Con-servation

Reserve

Program.

In

these

pro-grams,

several

million

hectares

of

land

were seeded

to

either

monocultures

or

mixtures

containing

these grasses.

Improved cultivars

and

improved

seeding and management

prac-tices have

increased

their

use

as

pasture grasses

independent

of farm

programs.

The

reason

for

their

increased use is

that

they

are

the

best-adapted

warm-season grasses

that

can be

used

north of the

areas

where

bermudagrass

(Cyruodon

dactylon

_[L.]

Pers.)

and

other subtropical

grasses are adapted.

In

integrated

grazing systems, based

on

cool-season grasses and legumes,

they

fill

a

need-ed niche

for productive

summer pastures.

In

addition

to

being valuable

as

forage

crops, these grasses also are used

for

conser-vation

purposes

including

roadside

plantings,

waterways,

railroad

and other right-of-ways,

and

wildlife

cover.

Since

switchgrass

is

a

high-yielding perennial

crop,

today there

is

interest

in

using

switchgrass

for

a

biomass crop

for

conversion

into

alcohol

fuels (Parrish

et al.

1990).

Yields

up to

16-17

mt

ha-l

have

been reported (Cherney et

al.

1990;

Parrish

et

al.

1990).

Assuming

a 757o extraction

effrcien-cy (Dobbins

et al.

1990),

ethanol

yield

would

be 330

L

of

ethanol per

mt

of biomass,

which

suggests

ethanol yields

up

to

5300-5600

L

ha

1 _{could be produced}

_from

_switchgrass.

CULTIVARS

Breeding

work

first

began on these grasses

in the

Great Plains states

during the

1930s.

Initially,

numerous

accessions (ecotypes or

strains) were

collected

and

evaluated

(Vogel

and Gabrielsen 1986). One or more of the

bet-ter

accessions were selected and increased

for

evaluation

in

additional

environments,

often

with the

assistance

of

the

Soil

Conservation Service. Based on these

tests,

the

accessions

often were released

directly

as

cultivars

with-out any

additional

breeding

work.

The switch-grass

cultivars

'Blackwell' and 'Nebraska

28'

were

released based

on

this

ecotype

evalua-tion

procedure.

This

same

system

continues

to

be used

to

develop

the

initial

cultivars of

these species

for

geographic

or climatic

areas

where adapted

cultivars

are

not

available. More recently, other

cultivars

have been

de-veloped

using

more-sophisticated

breeding procedures.

Currently,

grass

breeders

work-ing

on these species are

using population

im-provement breeding procedures

including

re-stricted recurrent

phenotypic

selection

(RRPS)

_and

_{modifrcations}

_of

_between

_and

within family

selection

(Vogel

and

Pedersen

1993).

The

switchgrass

cultivar'Tlailblazer'

was developed using RRPS. Breeding

work

on

these grasses

is

currently

being conducted

at

several

state and USDA

research

stations. The breeding

work

emphasizes

improving

es-tablishment,

forage

yield

and

quality,

and

dis-ease resistance. Genetic studies

in

each

ofthe

species

indicates

that

there

is

genetic

varia-tion for

all

the

traits

studied

to date and

that

it

should be possible

to

develop

improved

cul-tivars

of

these

grasses

(Vogel

_and

Moore

1993).

The

principal cultivars

that

are

available

for

use as forage grasses

are

listed

in

Tabte

32.1. Since

latitude oforigin

and photoperiod

response

are

the

primary

determinates

of

area

of

adaption

with

growing

degrees days

having modifying

effects,

the adaptation

zone

for cultivars

can be based on

the

USDA

plant

hardiness zone map

(Fig.

32.3). Released

cul-tivars

of these grasses

are best

adapted and

most productive

in

areas

where

annual

pre-cipitation

exceeds 450 mm.

CULTURE

AND MANAGEMENT

f

i

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(

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22222222r2-TABLE

32.1.

Principal cultivars of switchgrass, big bluestem, and indiangrass and their area or areas of adaptation

Cultivar Origin ofcollection T}pe Adaptation zones"

Switchgrass Dacotah Forestburg Sunburst Nebraska 28 Summer Pathfinder T!ailblazer Blackwell Cave-in-Rock Kanlow Alamo Tall bluestems Bison Bonilla Niagara Champ Pawnee Roundtree Kaw Goldstrike Garden Indiangrass Tomahawk Holt Nebraska 54 Oto Rumsey Osage Lometa Llano North Dakota South Dakota South Dakota Nebraska Nebraska Nebraska, Kansas Nebraska, Kansas Oklahoma Southern Illinois Oklahoma Texas North Dakota South Dakota New York Nebraska, Iowa Nebraska Iowa Kansas Nebraska Nebraska

North and South Dakota Nebraska Nebraska Nebraska, Kansas Illinois Kansas, Oklahoma Texas New Mexico upland upland upland upland upland upland upland upland upland/lowland Iowland Iowland big bluestem big biuestem big bluestem intermediate big bluestem big bluestem big bluestem sand bluestem sand bluestem 2,3, tpper 4 3,4 3,4

3,4

3,4,5

4,5

4,5

Iower 5, 6, 7

5,6,7

6,7

7,8,9

2,3 3, upper 4 3, 4, upper 5 4 lower 4, 5 4, 5, upper 6 lower 5, 6, 7 4,5 4,5 3, upper 4 4 lower 4, 5 5, upper 6 5,6 6,7 lower 6, 7, 8 7.8

'Zones are indicated in Figure 32.3.

prairie

grasses may be

difficult

to establish

if

recommended

establishment

practices are ig-nored.

The problem

in

obtaining satisfactory

stands may be due to competition

with

weeds,

planting

too deep, problems

in

metering

seed,

and

problems

with

low-quality

or

dormant

seed. Seed

of

both big

bluestem and

indian-grass are considered to be "chaffy" because

of

pubescence, awns, and other appendages

that

remain

with

the seed (Chap. 31). Seed, as

har-vested, may

contain

a considerable

amount of

stem pieces

and other

inert

matter,

so

clean-ing the

seed

to

a

high

level

of

purity

may

be

impossible.

Special

grassland

drills

with

ag-gTessive seed-feeding mechanisms

and

agita-tors are

needed

to

handle

this

chaffy

seed.

The seed can be aggressively processed

to

re-move

the

hair

and

awns

(Brown et

al.

1983),

which makes

it

possible

to plant this

chaffy

gTass seed

with

conventional

seeding

equip-ment. Switchgrass seed is

slick

and dense and can be cleaned

to

a

very high

purity,

so

seed-ing

with

many

types of seeders is possible.

These grasses

can

be

seeded

as

monocul-tures

or

as

mixtures.

Switchgrass

is

best

managed as a monoculture since

it

tends to be

earlier than

other

warm-season grasses and

is very competitive.

If

switchgrass is used

in

a

mixture,

not more than20Vo of the

mixture

by

seed eount

should

be

switchgrass. Growth

of

big

bluestem and indiangrass

is

quite

com-patible,

and a

mixture

of these two diversifres

the

pasture

species base. Seed

lots

of

these grasses,

particularly

if

they have not

been

processed, can have

low

purity,

and

germina-tion

may be low due to

dormant

seed. As a

re-sult,

seed

should

be

priced

and

seeded

on

a

pure live

seed (PLS) basis.

Pure

live

seed

is

calculated by

multiplying

the purity (the ratio of actual

seed

to total

weight) by the

germination.

For

example,

if

the

seed

tag

indicated

85Vo

purity

and

90%

germination,

PLS

₌

0.85

tpurityt x

0.90

tgerminationt

₌

0.765,

or

77Vo

PLS.

This

means

that

1 kg of bulk

seed

would contain

0.77

kg

of

PLS.

If

the

de-sired

seeding

rate

for

a

grass,

like

big

bluestem,

is

7

kg ha-l, then

7

kg

har

+ 0.77 = 9.1 kg ha-l

bulk

seed is required. About 9 kg of

bulk

seed

from

that particular

seed

lot

would

need

to

be planted per

hectare.

The

actual

amount of

bulk

s

ommended amol

seed

lot

quality.

I

of these grasses

400

PLS

m-2, rn'l

ha-1

for

switchgr

big bluestem, an

diangrass

if

an 860,000, 350,00(

switchgrass,

big

respectively

(An

tion in

average :

per kilograrn),

a

seed

units

and

Parrish

(19921 :

unit

of

bulk

seec

be of more use t,: Seed dormanc'

tain cultivars

ar Seeding

failures

seed dormanc]- .

tion. Although

e

germinate

und€ Simple dormanc'

aged long enougt

norrnal

germinat

to Association

cf

dures

(Justice

1!

stratifrcation

ri-l:

water

and

then

:

fore

the

germr:

higher

tempera:-.

tion

percentage :

mant

seed

and

i

amount

of seed

:

4

wk

upon

plan:,

ally

seeded

in

ia:

ducers should

r-:

chilling

if

thei'

rvant to see hor'. :

1y

germinate r','i:

dormancy

can':

€

]-ear-old seed *--Seed

should

h,,'

and shouid

nc:

i

can have

good

may have poor >:

ditions. These

grasse.

,

atures

than

c',- .

germination

:e:

big bluestem.

:.:.

and

10.3'C.

re=;,

Optimum

ger:

switchgrass

r-a.;

seedling devei-:

1984).

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wann, which

is

the

same

time

that

annual

weeds develop.

Most dicot

(broadleaf) weeds

can be controlled

with

2,4-D

(2,4-dichloro-phenoxyacetie

acid). Generally, 2,4-D

should

be applied

after the

seedlings have

five

leaves

and

there

is a

canopy

of

weeds above the

seedlings so

most of

the

spray lands on

the weed canopy.

Switchgrass and

big

and

sand

bluestem have seedling atrazine

(6-chloro-N-ethyl-N'-[methylethyl]-

1, 3,

5-triaz

ine-2,4-diamine) tolerance

(Martin et al.

1982), and atrazine has been

previously

approved for use

as a preemergence herbicide on these grasses.

These

grasses

have seedling

and

mature

plant

tolerance to other herbicides (R. A.

Mas-ters and

K.

P. Vogel, personal

communica-tion),

but

at

present,

they

are

not

labeled

for

use on these grasses except

for

special condi-tions. Herbicide labels change annually, and a

herbicide may

not

be

approved

for

use

on

a

specifrc grass even

though

the

grass

is

toler-ant

of

the herbicide.

Producers need

to

check

labels and local sources of herbicide

informa-tion

for

recommendations.

In

many

cases the only way weed

competition

may be reduced is

by infrequent

clipping or

grazing

for a

short

period

with

a high

stocking

rate

(mob-graz-ing).

A

seeding of these grasses

generally

will

not be ready

to

graze

the establishment

year,

but

vegetation may be removed as hay

during

the

establishment year.

Fertilization. These warm-season prairie

grasses require adequate soil

fertility

levels to

maintain

optimum

sustained

yields although

they

can

tolerate

low-fertility

conditions

bet-ter than

most cool-season grasses. On an acid,

low-P soil, unfertilized

switchgrass

and

big

bluestem were found to

yield

50Vo as much as

cool-season grasses

that

received

high

levels

of

lime

and

fertilizer

(Jung

_{et al.}

1988).

An-other study

shows switchgrass

yields

were 12Vo less

on

soils

with

5

mg

kg-1

P

as

com-pared

with

soils

with

35 mg

kg1

P

while

cool-season grass

yields

were 357o

smaller

on the

low-P soils

(Panciera

_and

_Jung

1984).

On acidic,

low water-holding

capacity soils,

first-cut

switchgrass yields were found to be two to

three times greater

than

those

of

tall

fescue

(Festuca

arundinacea

Schreb.)

yields

on sites

with N

and

four times greater

on sites

with-out N, which

shows

that

N

use efficiency was

greater

for

switchgrass

than for

tall

fescue

(Staley et

al.

1991).

These warm-season

prairie

grasses

usually

are

effective users

of

organic

N

in

the

soil

since

their

greatest

N

demand

comes when

the soil is warm and mineralization

is

pro-ceeding rapidly. The

timing

of

N

application

is

critical

in

the

maintenance

of

warm-season

grass stands. Nitrogen

fertilizer

should

be

added

in late

spring, when

the

war:m-season

grass has

started

active

growth

and

invading

cool-season

plants have

completed

most

of

their

spring

grorth

(Rehm et

al.

1976).

IfN

is

applied too

early

in

the

spring

or

in

the

previ-ous

autumn,

cool-season

plants

will

utilize

it

since the warm-season gtasses are

not

active.

The stimulated

cool-season

invaders

will

in-crease

rapidly

and

utilize

the

soil

moisture

in

spring. Later, during the

period of

warm-sea-son grass

growth,

soil

moisture

will

be

deplet-ed and the warm-season

plants

will

decline

in

stand and productivity. Eventually,

the

re-duced

vigor allows them

to

be

replaced by

cool-season

plants. Nitrogen

fertilizer

should

be

applied

in

amounts

that

will

be

fully

uti-lized by the

warm-season g"asses

during

the

growing

season,

with

no

carryover N

to

stim-ulate

cool-season

growth

in

the autumn.

On

most

soils,

N

and P are the only fertilizers

that

are

required

on a

routine

basis.

Nitrogen

fertilization

rates

can be

estimated

based on

annual precipitation.

In

areas

that

receive

450

mm

of

precipitation,

50

kg

har

of

N

are

often

adequate

while

areas

that

receive over

750

mm

may often

require

over 100 kg

ha

1

_of

N to optimize

forage yields.

Grazing

and

Harvest

Management.

These

grasses

will

be ready

to

graze

in late

spring,

about

the time the

cool-season grasses have completed

their

spring growth.

Since switch-grass

is the

earliest

of these grasses,

a

com-mon mistake

is

to begin grazing

switchgrass

too late.

If

switchgrass

availability

exceeds

the

livestock

needs,

the plants

will

mature,

producing stemmy reproductive

tillers.

For-age

quality

and

utilization

will

be

very

poor,

and

animal

performance

will

be

unsatisfacto-ry.

Big

bluestem

is

later

in

maturity than

switchgrass, and

forage

quality

does

not

de-crease

as

rapidly

with maturity

as

it

does

with

switchgrass.

Indiangrass

is

generally-less

mature

at

any given calendar

date

than

switchgrass

or big

bluestem.

Grazing

of

indi-angrass

pastures should

not

be

delayed,

be-cause once

indiangrass

reaches

the

heading

stage,

it

becomes

rather

stemmy and does

not

retain its quality

very

well.

Grazing of switchgrass should begin

when

it

is about 30 cm

tall.

Cattle

will

graze

switch-grass

rather

uniformly,

taking

it

layer

by

lay-er if

stocked so consumption

nearly

equals

growth rate.

With an

appropriate

stocking

rate,

switchgrass can be

continuously

stocked

until

the

forage

is

gone.

Stocking

rate

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