rehabilitation of open cut coal mines using native grasses
TRANSCRIPT
Rehabilitation of open cut coal mines using native grasses: Management guidelines
Prepared by Charles Huxtable
D e p a r t m e n t o f S u s t a i n a b l e N a t u r a l R e s o u r c e s
Cover illustrations, from left to right: • The spikelet of the native pasture grass,
Austrodanthania setacea. • A good stand of Taranna wallaby grass
(Austrodanthonia richardsonii) at Ravensworth mine, 1 year after sowing.
• A brush harvester for native grass seed built for the rehabilitation trials, and designed by J. Ryan of Cooma.
Acknowledgments Funded by the Australian Coal Association Research Program
(ACARP). Initiated by the Hunter Coal Environment Group. Thanks to Chris Nadolny and Ian Cole for reviewing the contents. Thanks to Evelyn Roberts for editing.
Published by: Centre for Natural Resources
Department of Sustainable Natural Resources
Parramatta
April 2003
© NSW Government ISBN 0 7347 5291 1 CNR2002.021
Contents
Page
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Why use native grasses? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Options for vegetation including native grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Where to use native grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Choosing suitable native grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Selecting and sowing seed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Controlling weeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Managing native grasses on rehabilitation sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Further reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table
Table 1. Recommended species for rehabilitation of coal mine spoil in the Hunter Valley . . . . . . 8
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Rehabilitation of open cut coal mines using native grasses: Management guidelines
INTRODUCTION
These guidelines provide a brief summary of the species of Australian native grasses and their management that are recommended for rehabilitation of open cut coal mines in the Hunter Valley. The information is based on the results of 5 years of research carried out on mine sites during 1994–1999.
WHY USE NATIVE GRASSES?
Native grasses are a diverse group of plants with a range of attributes which make them important components of vegetation in the landscape. Because of their diversity, native grasses play an important role in mine rehabilitation as components of reconstructed vegetation communities and for a range of post-mining landuses. Native grasses are environmentally friendly, contribute to overall biodiversity and can be grown in association with native trees, shrubs and forbs (small broad-leaved plants) on minesites.
Some native grasses have a high forage value for livestock and can tolerate low soil fertility and drought. These attributes make them a desirable choice where land is intended for grazing after mining.
Introduced pasture species have been used for mine rehabilitation in the past, but compared to native grasses they have the following disadvantages:
• They can be costly to maintain. • They tend to need more fertile soil and to be less drought tolerant. • A pasture containing only Rhodes grass tends to develop when introduced pastures (which
usually include Rhodes grass) are not managed properly.
A trial of mixed species at Howick mine, 2 years after sowing. After 1 year, 17 native grasses and 7 native forbs were established at this site.
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Rehabilitation of open cut coal mines using native grasses: Management guidelines
OPTIONS FOR VEGETATION INCLUDING NATIVE GRASSES
To rehabilitate land, native grasses can be grown alone or with trees and/or shrubs. Native forbs can also be included in pastures containing native grasses.
WHERE TO USE NATIVE GRASSES
• On topsoil that has been taken from pre-strip areas dominated by native grasses. • On areas with raw spoil, where topsoil is not available. • On areas of low fertility topsoil that contains few seeds from introduced plants.
These situations give native grasses a competitive advantage because the soil has one or more of the following features:
• few seeds of introduced plants • many seeds of native plants • low fertility.
Where there is a risk of soil erosion, other soil conservation measures may be necessary.
Although it was not sown, the native species blown grass (Lachnagrostis filiformis), was growing on a trial site at Ravensworth mine, in the spring of 1998. Native grasses can establish from reserves of seed in topsoil used for a rehabilitation site.
CHOOSING SUITABLE NATIVE GRASSES
Native grasses should be selected mainly for their ability to survive the local soil and climatic conditions on the mine sites. Species that originally grew locally are desirable, but are not essential.
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Rehabilitation of open cut coal mines using native grasses: Management guidelines
Recommended species
Table 1 lists recommended species, their seasonal growth patterns, recommended sowing times and special attributes.
As many suitable species as possible should be sown, with a minimum of three warm season perennial (WSP) species and two year-long green perennial (YGP) species. Cool season perennial (CSP) and cool season annual (CSA) species can be added if they are available.
For raw spoil, the best YGP species are wallaby grasses and plains grass. The best WSP species is windmill grass. (Table 1 lists the scientific names.)
For saline, alkaline dispersible topsoil, the best YGP variety is Taranna wallaby grass; the best WSP species are Queensland bluegrass, native millet, windmill grass and couch.
For better quality topsoil (loam to loamy clays with slightly acid to neutral pH and low salinity), the best YGP species are wallaby grasses and plains grass. The best WSP species are Queensland bluegrass, pitted bluegrass, native millet, windmill grass, blown grass, umbrella grass and early spring grass. For highly acidic, sodic loamy sand, the best WSP species are wiregrass, pitted bluegrass, couch, slender rat’s tail and tall windmill grass.
Yanganbil grass (Austrostipa bigeniculata), a native, growing on raw spoil at Howick mine, 2 years after sowing.
Windmill grass (Chloris truncata) growing at Ravensworth mine, showing the level of groundcover 4½ years after sowing.
SELECTING AND SOWING SEED
When selecting and sowing native grass seed, consider:
• dormancy • viability • form of seed sown (degree of cleaning) • sowing depth • soil moisture • temperature.
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Rehabilitation of open cut coal mines using native grasses: Management guidelines
Taranna wallaby grass growing on good topsoil at Preparation of a rehabilitation site at Howick Ravensworth mine. Mine, October 1997.
Pitted bluegrass (Bothriochloa decipiens) seed in it’s uncleaned form, as harvested by a brush harvester.
Diamond harrows were used to rake in wallaby grass seed after sowing at Howick mine.
To maximise establishment, consider:
• seed source and quality • sowing rate • sowing technique • multi-phase sowings and species diversity • fertiliser application at the time of sowing.
CONTROLLING WEEDS
Weed control is absolutely essential during the first year, and probably later also.
A herbicide with the active ingredients picloram and triclopyr (for example Grazon®*) can be used to control galenia, because that type of herbicide has little adverse effect on native grasses. Competition from Rhodes grass and couch is a major threat to establishment of sown native grasses. These plants can be spot sprayed with a post-emergent herbicide containing the active ingredients glyphosate, diuron or atrazine (for example Roundup®) or another post-emergent herbicide.
* Other suitable herbicides include 4Farmers Tri-Pick®, Generex Trichloram®, Picker® and Grass-Up®. Mention of the product names given in this brochure is not intended to imply endorsement of one product over another equivalent product. Herbicides should be used only as instructed by the directions on the container label.
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Tabl
e 1.
Rec
omm
ende
d sp
ecie
s for
reh
abili
tatio
n of
coa
l min
e sp
oil i
n th
e H
unte
r Va
lley
Com
mon
nam
e Sc
ient
ific
nam
e#
Gro
wth
Sp
ecia
l fea
ture
s pa
ttern
Bun
derr
a w
alla
by g
rass
* Au
stro
dant
honi
a
YG
P G
ood
colo
nise
r, to
lera
tes
raw
spo
il, g
ood
fora
ge v
alue
, pre
fers
hea
vier
soils
, tol
erat
es g
razi
ng.
ringe
d w
alla
by g
rass
* A.
cae
spito
sa
YG
P G
ood
colo
nise
r, to
lera
tes
raw
spo
il, g
ood
fora
ge v
alue
, tol
erat
es g
razi
ng.
Hum
e w
alla
by g
rass
* A.
ric
hard
soni
i cv.
Hum
e Y
GP
Goo
d co
loni
ser,
tole
rate
s ra
w s
poil,
goo
d fo
rage
val
ue, t
oler
ates
gra
zing
. Ta
rann
a w
alla
by g
rass
* A.
ric
hard
soni
i cv.
Tar
anna
Y
GP
Goo
d co
loni
ser,
wid
e so
il to
lera
nce,
tole
rate
s ra
w s
poil,
goo
d fo
rage
valu
e, to
lera
tes
graz
ing.
smal
lflow
er w
alla
by g
rass
* A.
set
acea
Y
GP
Goo
d co
loni
ser,
tole
rate
s ra
w s
poil,
goo
d fo
rage
val
ue, t
oler
ates
gra
zing
. pl
ains
gra
ss*
Aust
rost
ipa
aris
tiglu
mis
or
YG
P G
ood
colo
nise
r, to
lera
tes
alka
linity
and
raw
spo
il, m
oder
ate
fora
ge v
alue
,A.
big
enic
ulat
a to
lera
tes
graz
ing.
spea
rgra
ss
A. s
cabr
a Y
GP
Goo
d fo
rage
val
ue w
hen
in g
reen
leaf
, dro
ught
tole
rant
, tol
erat
es g
razi
ng.
slen
der b
ambo
o gr
ass
A. v
ertic
illat
a Y
GP
Goo
d fo
rage
val
ue w
hen
in g
reen
leaf
, dro
ught
tole
rant
, tol
erat
es g
razi
ng.
shor
thai
r plu
meg
rass
D
iche
lach
ne m
icra
ntha
C
SP
Goo
d fo
rage
val
ue, g
erm
inat
es fr
om to
psoi
l see
d ba
nk.
com
mon
whe
atgr
ass
Elym
us sc
aber
C
SP
Very
hig
h fo
rage
val
ue, g
erm
inat
es fr
om to
psoi
l see
d ba
nk.
blow
n gr
ass
Lach
nagr
ostis
filif
orm
is
CSA
G
ood
colo
nise
r, go
od fo
rage
val
ue, g
erm
inat
es fr
om to
psoi
l see
d ba
nk.
wire
gras
s*
Aris
tida
ram
osa
WSP
Pr
efer
s lo
w fe
rtilit
y so
ils, p
oor f
orag
e va
lue,
dro
ught
tole
rant
, goo
dco
loni
ser.
re
dgra
ss/p
itted
blu
egra
ss*
Both
rioc
hloa
W
SP
Goo
d co
loni
ser,
smal
l pla
nt b
asal
are
a bu
t sur
vive
s dr
ough
t wel
l.
mac
ra/d
ecip
iens
win
dmill
gra
ss*
Chl
oris
trun
cata
W
SP
Goo
d co
loni
ser,
low
fora
ge v
alue
, dro
ught
tole
rant
, tol
eran
t of v
ery
poor
tops
oil a
nd ra
w s
poil,
sho
rt-liv
ed p
eren
nial
.ta
ll w
indm
ill g
rass
* C
hlor
is v
entr
icos
a W
SP
Goo
d co
loni
ser,
low
fora
ge v
alue
, dro
ught
tole
rant
, tol
eran
t of v
ery
poor
tops
oil a
nd ra
w s
poil,
long
-live
d pe
renn
ial.
barb
ed w
ire g
rass
C
ymbo
pogo
n re
frac
tus
WSP
Pr
efer
s po
or s
oils
, low
fora
ge v
alue
, sen
sitiv
e to
gra
zing
, ver
y dr
ough
tto
lera
nt.
Rehabilitation of open cut coal mines using native grasses: Management guidelines
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Rehabilitation of open cut coal mines using native grasses: Management guidelines
Que
ensl
and
blue
gras
s*
Dic
hant
hium
seri
ceum
W
SP
Req
uire
s be
tter q
ualit
y to
psoi
l, pr
efer
s he
avie
r bla
ck s
oils
, mod
erat
efo
rage
val
ue, d
roug
ht to
lera
nt.
cotto
n pa
nic
gras
s D
igita
ria
brow
nii
WSP
G
ood
fora
ge v
alue
, pre
fers
bet
ter s
oils
, ger
min
ates
from
tops
oil s
eed
bank
. um
brel
la g
rass
D
igita
ria
diva
rica
tissi
ma
WSP
M
oder
ate
fora
ge v
alue
, pre
fers
bet
ter s
oils
, ger
min
ates
from
tops
oil s
eed
bank
. ea
rly s
prin
g gr
ass
Erio
chlo
a ps
eudo
acro
tric
ha
WSP
N
atur
ally
col
onis
es to
psoi
l and
raw
spo
il fr
om s
eedb
ank
or s
urro
unds
.M
ay b
e sa
lt-to
lera
nt. C
an fo
rm e
xten
sive
sta
nds
with
goo
d gr
ound
cove
ran
d go
od fo
rage
val
ue.
nativ
e m
illet
Pa
nicu
m d
ecom
posi
tum
W
SP
Mod
erat
e fo
rage
val
ue, p
refe
rs h
eavi
er s
oils
, may
be
salt
tole
rant
.ha
iry p
anic
Pa
nicu
m e
ffusu
m
WSP
G
ood
fora
ge v
alue
, ger
min
ates
from
tops
oil s
eed
bank
.
# Sc
ient
ific
plan
t nam
es a
ccor
ding
to W
heel
er, J
acob
s an
d W
halle
y 20
02.
CSP
=
cool
sea
son
pere
nnia
l. M
ost g
row
th a
nd s
eedi
ng o
ccur
s du
ring
cool
mon
ths.
The
plan
t liv
es fo
r mor
e th
an 1
yea
r.Y
GP
= ye
ar-lo
ng g
reen
per
enni
al. M
ost g
row
th a
nd s
eedi
ng o
ccur
s in
the
cool
er m
onth
s, bu
t the
pla
nt g
row
s th
roug
hout
the
year
, in
resp
onse
to ra
in. T
he p
lant
live
s fo
r m
ore
than
1 y
ear.
CSA
=
cool
sea
son
annu
al. T
he p
lant
ger
min
ates
, gro
ws,
seed
s an
d di
es d
urin
g th
e co
oler
mon
ths.
It liv
es fo
r onl
y 1
year
.W
SP
= w
arm
sea
son
pere
nnia
l. M
ost g
row
th a
nd s
eedi
ng o
ccur
s du
ring
war
m m
onth
s. Th
e pl
ant l
ives
for m
ore
than
1 y
ear.
An
aste
risk
(*) i
ndic
ates
spe
cies
whi
ch w
ere
sow
n du
ring
thes
e pr
ojec
ts.
Coo
l sea
son
pere
nnia
ls, y
ear-l
ong
gree
n pe
renn
ials
and
coo
l sea
son
annu
als
shou
ld b
e so
wn
in e
arly
to m
id-a
utum
n (M
arch
to A
pril)
.W
arm
sea
son
pere
nnia
ls s
houl
d be
sow
n in
ear
ly to
mid
-aut
umn
(Mar
ch to
Apr
il) o
r ear
ly s
prin
g (S
epte
mbe
r).
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Cereal rye
Rehabilitation of open cut coal mines using native grasses: Management guidelines
MANAGING NATIVE GRASSES ON REHABILITATION SITES
Different species of native grasses respond differently to a variety of management techniques. Grazing, slashing burning and fertiliser application can be used to maintain the desired pasture composition and diversity, and minimise invasion by weeds and exotic grasses.
Grazing favours some species such as redgrass, Queensland bluegrass and wallaby grasses. However, grazing is harmful to other grasses such as barbed wire grass, kangaroo grass and native sorghum. High intensity grazing for short periods (such as in time-control cell grazing) provides the most uniform defoliation, forcing animals to eat both palatable and unpalatable species.
Slashing has similar effects, but lacks the selectivity of low intensity grazing. Compared to grazing, slashing also lacks the effects of addition of urine and manure, and soil disturbance by hoofs.
BBuunnddeerrrraa
Cereal rye
Bunderra wallaby grass 6 months after it was sown with a cover crop of cereal rye at Rix’s Creek mine.
GGaalleenniiaa SSaallssoollaa
A severe infestation of the weeds galenia (Galenia pubescens) and soft roly poly (Salsola tragus) at a rehabilitation trial site.
Burning was one of the methods used to control Rhodes grass (Chloris gayana) before native grasses were sown in a rehabilitation trial at Warkworth mine in October 1998.
Some native grasses are able to compete with vigorous introduced grasses such as this self-sown slender bamboo grass (Austrostipa verticillata) growing amongst phalaris and Rhodes grass sown at Howick mine 5 years earlier.
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Rehabilitation of open cut coal mines using native grasses: Management guidelines
Low intensity burning benefits kangaroo grass by reducing the amount of dead material and stimulating new leaf growth and seed germination.
FURTHER READING
Huxtable, C. H. A. 1999, Rehabilitation of open-cut coal mines using native grasses: Management guidelines, final report to the Australian Coal Association Research Project (ACARP), ACARP Report No. C6004. AMIRA. Melbourne.
Huxtable, C. H. A., Sawicki, A. J. and Streat, J. 1997, Rehabilitation of open-cut coal mines using native grasses, final report to the Australian Coal Association Research Project (ACARP), ACARP Report No. C3054. AMIRA. Melbourne.
Waters, C., Whalley, W. and Huxtable, C. 2000, Grassed-up: Guidelines for revegetating with Australian native grasses, NSW Agriculture.
Wheeler, D. J. B., Jacobs, S. W. L. and Whalley, R. D. B. 2002, Grasses of New South Wales, 3rd edn, Botany, School of Environmental Sciences and Natural Resource Management, University of New England, Armidale NSW, 2351.
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