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Best Practice GuidelinesFor Applicants to Defra’s Energy Crops Scheme
Growing Short Rotation Coppice
Introduction 4
Why grow energy crops? 5
What is SRC? 6
Where to grow SRC 7Site selection 7Plantation design 8
Land preparation 9
Planting material 10
Establishment 12Planting 12Establishment year management 13Cutback 14
Calendar of activity 16
General management 18Headlands and rides 18Fertilisation 18Nitrate Vulnerable Zones 19Pests and diseases 19
Harvesting 22Rod harvesting 22Direct-chip harvesting 22Billet harvesting 23
Yield 24
Biodiversity 25
Removal of SRC 26
Poplar SRC 27Site 27Planting material 27Planting 27Management 28Yields 28Harvesting 28Removal 28
References 29
Contacts 30
Contents
3
This booklet has been produced by the Department of Environment, Foodand Rural Affairs (Defra) to introduce farmers to a new crop. It providesguidance on the choice of site, planting techniques, crop managementand harvesting methods required when growing short rotation willow orpoplar coppice as an energy crop. The booklet summarises current agronomic techniques and, therefore, may need to be modified as furtherexperience is gained. Please check that you have the latest copy of thebooklet with the Defra office at Crewe.
This booklet should be read in association with the Energy CropsScheme booklet, “Establishment grants for short rotation coppice andmiscanthus” which outlines the requirements for claiming grant toestablish the crop.
There is further information on short rotation coppice in the ForestryCommission Information Note “The establishment and management ofshort rotation coppice – a practitioner’s guide” (Tubby and Armstrong, 2002).
4
Introduction
Energy crops are used as fuel in powerstations and heating systems. In substi-tution for fossil fuels, they have thepotential to reduce emissions of thegreenhouse gas carbon dioxide. Energycrops will need to contribute if the UKis to meet its:
• obligation under the Kyoto Protocolto reduce greenhouse gas emissionsby 12.5 per cent below 1990 levelsby 2012;
• domestic goal to generate 10% of thenation’s electricity from renewablesources by 2010.
This provides a significant opportunity forthe energy crop industry.
Currently the major energy crop grownin the UK is short rotation coppice (SRC), primarily willow, although poplar hasbeen used occasionally and may be
planted more commonly in the future following the production of varietiesmore suited to coppicing. This bookletconcentrates on willow SRC, although asection relating specifically to poplar hasbeen included.
Defra provides grants to assist with theestablishment of SRC under the EnergyCrops Scheme (ECS), part of the EnglandRural Development Programme (ERDP).Grants are also available for setting up SRCproducer groups to facilitate harvestingand supply to the energy market. Fulldetails can be found in the ECS booklets“Establishment grants for short rotationcoppice and miscanthus” and “Grantsfor establishing producer groups”.
For details of support available for energycrops, contact the Defra office at Creweor visit the ERDP website:www.defra.gov.uk/erdp/erdphome.htm
Why grow energy crops?
5Woodchip boiler for heat ARBRE power station fuelled by woodchip
6
SRC (short rotation coppice) consists ofdensely planted, high-yielding varieties ofeither willow or poplar, harvested on a 2– 5 year cycle, although commonly every3 years. The osier, a shrub willow, isparental stock to the majority of willowvarieties planted for use as an energycrop. SRC is a woody, perennial crop, therootstock or stools remaining in theground after harvest with new shootsemerging the following spring. A plantation could be viable for up to 30years before re-planting becomes necessary, although this depends on theproductivity of the stools.
Willow SRC is planted in the spring usingplanting material produced by specialistbreeders and equipment specificallydesigned for the purpose. The willow will
grow rapidly in the first year reaching upto 4m in height. During the winter afterplanting the stems are cut back toground level to encourage the growth ofmultiple stems i.e. coppiced. Generallythree years after cutback and again during the winter, the crop is harvested.The equipment used for harvesting willhave been specifically developed for thepurpose and depends on the fuel specification of the customer/end-user.Most operations other than planting orharvesting can be completed using conventional farm machinery.
In the UK, yields from willow SRC at firstharvest are expected to be in the range 7– 12 oven dry tonnes per hectare peryear (odt/ha/yr) depending on site andefficiency of establishment.
What is SRC?
Willow SRC 3 months after planting Mature willow SRC
The key determinants of SRC yield arewater availability, weed control, light andtemperature.
Willow SRC will produce good growthwhere there is sufficient soil moistureavailable within 1 metre of the soil surface.It can withstand seasonal flooding butnot permanent waterlogging. Whereland is prone to flooding most years, thewillow will survive but consideration mustbe given to operational requirements,particularly the need to harvest in winter.Annual rainfall of 600-1000mm is ideal.
SRC can be established on a wide rangeof soil types from heavy clay to sandincluding land reclaimed from gravelextraction and colliery spoil. Clay or sandyloams that retain moisture but are wellaerated are ideal soils. Establishment maybe slow on heavy clays as they tend to becold in spring although, once established,SRC grown on these soils can be highlyproductive. Where compaction may proveto be a problem, sub-soiling to a depthof 40cm will be necessary to ensure maximum root development. Soil pHshould be in the range 5.5 – 7.
Site selection
A site must meet the requirements of theECS, these can be found in theEstablishment Grants booklet.
As a perennial crop, SRC is likely to be inthe ground for up to 30 years and canreach 7-8 metres in height prior to harvest.Its impact on the local landscape, ecolo-gy, archaeology and public access musttherefore be considered alongside theoperational parameters.
Under the ECS, a proposed SRC site isassessed and consultation takes place toensure there will be no significantadverse impact on the environment. Thisconsultation takes up a significant part ofthe 3-month application process time. Tospeed the process potential growers maywish to contact organisations that maybe affected by the planting of the crop inadvance, e.g. local councils for bylawsrelating to public rights of way or thecounty archaeologist to check the recordsfor any important archaeological remains.Where a proposed site is adjacent to ariver or on a floodplain, the EnvironmentAgency should be consulted.
Another factor to consider is soil erosion.Compared to many crops, SRC has largeareas of open ground within the cropduring establishment. On light, sandysoils this can lead to wind erosion of thesoils and also some damage to the newlyemerged shoots due to abrasion. Onsloping sites, soils can be eroded followingheavy rain.
Willow roots, which are fibrous in nature,will penetrate down to field drains and itis recommended that SRC is planted at
Where to grow SRC
7
SRC in the landscape
least 30 metres from any drains that areconsidered important. When choosing asite consider the life of the drainage system in relation to the expected life ofthe SRC plantation.
To be eligible for grant the proposed sitemust be at least 3ha in total, althoughthis can be made up of smaller plots.However, to ensure economies of scalefor all field operations larger plantationsare better. The most appropriate fieldshapes are those that minimise the needfor short row lengths or require nochanges in direction during field operations. Choosing fields that can beharvested economically is of criticalimportance. For ease of operations theideal site would be flat or with a slopeof no more than 7%. It is strongly recommended that the slope of the fieldshould not exceed 15%.
Appropriate access must be available forall machinery involved in establishing andharvesting the crop. Gate widths shouldbe at least 4.5m but it is recommendedthat if new gates have to be installedthey should be up to 7.2m in width.Bridge height or weight restrictionsshould also be considered where necessary. Ideally areas for transferringand storing the harvested crop should beadjacent to the coppice.
Plantation design
The plantation design should fit in withthe surrounding landscape and advicerelating to this can be obtained fromForestry Commission Guideline Note 2(Bell & McIntosh, 2001). Operationalrequirements must also be taken into
account. Headlands of at least 8 metresin width are necessary at both ends ofthe rows to allow for vehicle turning.Where only one trailer will be available atharvest or the harvester has an integraltrailer, row lengths should be restrictedto a maximum of 200 metres to avoidthe need to reverse along the rows to off-load. Where two or more trailers will be available, row lengths can be longer.However, if liquid sludge is to be appliedusing an umbilical system, the maximumrow length should be 400 metres. Ridesof 4 metres should be left along theedges of the crop to allow machineryaccess for willow beetle control ifrequired. A maximum of 20% openground is allowed within a SRC plantationunder the ECS.
Where to grow SRC
Edge of SRC plantation8
The importance of efficient landpreparation for SRC cannot be stressedtoo highly. As SRC is a long-term,perennial crop, ensuring ideal conditionsat establishment will reap benefits at firstand all subsequent harvests.
Weed control is a critical part of coppiceestablishment. Complete eradication ofall invasive perennial weeds is essentialprior to planting. One or two applicationsof a glyphosate-based herbicide, appliedat the appropriate rate, should be carriedout in the summer/autumn prior tospring planting. Ideally the first herbicideapplication should take place in mid-summer with a follow-up application inautumn to control any further flush ofweeds. An additional application justbefore planting in spring may be necessaryon some sites. Spring spraying alone isunlikely to be effective.
If required the site should be sub-soiled toa depth of 40cm to remove compaction.It should then be ploughed to a depth ofat least 25cm and left to over-winter. Onlighter land it may be more appropriateto spring plough. Power harrowing ofthe site should be carried out immediatelybefore planting.
Sludge cake, well-rotted farmyardmanure or other bulky organic manurewith a low available nitrogen content canbe incorporated into the soils prior toploughing.This is particularly beneficialon light soils where it will increase moisture retention and help to conditionthe soil. The Defra Code of GoodAgricultural Practice for the Protection ofWater (1998) must be adhered to whenapplying organic manures.
Rabbits, if present, must be kept out ofthe crop at least during the first twoyears and ideally up to first harvest, toallow the crop to mature beyond its vul-nerable stage. Rabbit fencing should beerected to British Standard, buried andturned out. Defra and the Department ofTrade and Industry (DTI) have produced aleaflet on rabbit management techniquesfor SRC (McKillop & Dendy, 2000).
Land preparation
9
Defra and the British Horse Industry Confederation
Joint Research on the Horse Industry in Great Britain
10
Planting material
Access to the ECS is not restricted tospecified varieties of willow. However,several willow varieties, bred specificallyfor use as SRC energy crops, are listedin the Forestry Commission InformationNote “Poplar and willow varieties forshort rotation coppice” (Tabbush, Parfittand Tubby 2002). The recommendedvarieties have been through trials toensure high yields, erect growth habitand resistance to, or tolerance of, disease.The list is updated as information onnew varieties becomes available andprovides a useful source of informationwhen selecting planting material.
Melampsora rust is the most commonfungal disease of willows. Ideally, a mix ofwillow varieties with diverse rust tolerance characteristics, referred to as“mix types”, should be used. Details ofthese varietal characteristics are availablein the Forestry Commission InformationNote referred to above or from materialproviders. Recent research has also shownthat mixed planting can lead to reductionin damage caused by willow beetles, themain pest species of willows.
European Plant Breeders’ Rights protectthe majority of varieties and crop harvested on the farm cannot be used asplanting material. Further information canbe obtained from the holders of Rights.
Planting material
Planting Cut and trimmed willow rods stems, generally 1.5 – 3m long
Cuttings Cut fresh from rods and between 18 – 20cm in length
Planting rods
11
Willows are planted either as cuttingsor rods. Only licensed producers shouldconduct willow propagation. Rods orcuttings are taken from one-year-oldmaterial that is harvested betweenDecember and March when the plantsare dormant. They must be either plantedimmediately or stored at -2 to -4˚C,where cuttings will remain viable forseveral weeks and rods up to 3 months.They should only be taken from coldstore and delivered to the planting site onthe morning of planting. If rods/cuttingsare left in temperatures above 0˚C a
break in their dormancy will occur,adventitious roots will develop and thebuds may burst. This will lead to areduction in water and nutrient contentand consequently reduced viability.
Willow cuttings colour-coded by variety
Planting
Willows are planted either as cuttings orrods, depending on the type of plantingmachinery used. Details of the latestmachinery available to buy or hire can beobtained from British BioGen’s EnergyCrops Network (see ‘Contacts’ section).
At present, the most commonly usedmachines are ‘step planters’. Willowrods of 1.5-2.5 metres length are fedinto the planter by two or more opera-tives depending on the number of rowsbeing planted. The machine cuts therods into 18-20cm cuttings, inserts thecuttings vertically into the soil and firmsthe soil around each cutting. 15,000cuttings per hectare is the current standard commercial planting densityusing this method. Lower density planting may lead to thicker stems andconsequently larger chip size. Therefore,planting densities down to 12,000 cuttings/ha may be appropriate wherequality of chip is of more importancethan yield.
For small areas of planting, modifiedcabbage planters can be used for plantingcuttings directly. These machines are noteconomic for planting large areas however.
A ‘lay-flat planter’ is being developedwhich lays whole rods horizontally intofurrows opened by discs at 2-8cm depth.The rods are laid end to end with a slightoverlap, the soil covers them and is con-solidated to minimise moisture loss.Distance between rows can be controlledbut as the shoots tend to grow randomlyalong the length of the rods there is noway to accurately control density.
Planting should ideally take place afterthe last frosts but as early as February ifsoil conditions allow. Planting can be successful as late as June but late plantingis best avoided as the longer the firstgrowing season the better in order totake the plants successfully into winterand cutback. Another factor is that lateplanting has to rely on planting materialfrom cold store, i.e. harvested earlier inthe year. This will restrict the materialavailable, especially as cuttings start tolose viability after a few weeks in storage.
Willows should be planted in twin rows0.75 metres apart and with 1.5 metresbetween each set of twin rows. Thisspacing allows standard agriculturalmachinery fitted with wide tyres to workacross the crop. A spacing of 0.59 metresalong the rows when planting cuttingswill give a planting density of 15,000/ha,the commercial standard (see diagramopposite).
The site should be rolled immediatelyafter planting to consolidate the soil
Establishment
12
A ‘step planter’
Defra and the British Horse Industry Confederation
Joint Research on the Horse Industry in Great Britain
13
for effective herbicide application. Pre-emergence residual herbicide shouldbe applied within 3-5 days of planting.
If the site was previously grassland orlong-term set-aside, leatherjacket controlshould be applied. For commercial reasonsit is better to apply the insecticide at thesame time as the pre-emergence residualherbicide but ensure that it is beforeroot or shoot development.
Establishment year management
From each cutting 1 – 3 shoots will ariseand reach up to 4 metres in height by theend of the first growing season, depend-ing on soil conditions. In the case of rods,shoots develop randomly along thelength of the rod but the stem heightswill be similar to those from cuttings.
No fertiliser should be applied during theestablishment year.
A ‘lay-flat planter’
Growth shortly after planting
The coppice should be monitored care-fully for pests, weed growth and generalhealth during the establishment year. Ifremedial weed control proves necessary,a hooded band sprayer, specificallydesigned for use on SRC, should be used.
Cutback
During the winter following planting thewillow is usually cut back to within10cm of ground level to encourage thedevelopment of the multi-stemmed coppice. The work should be carried outas late as possible in the winter butbefore bud-break, generally late February.The most effective machines are modifiedmowers/reapers as these give a clean cutto the stems.
A contact herbicide should be appliedafter cutback to control those weeds thathave grown during the establishmentyear. It is important that the herbicide isapplied before coppice bud-break
Establishment
14
Recommended planting design
1.5m 0.75m
0.59m
0.75m
0.59m
0.59m0.59m
0.59m0.59m
1.5m1.5m 0.75m0.75m
Plantation prior to cutback
otherwise the crop will be damaged.Generally the use of systemic/translocat-ed contact herbicides should be avoideddue to the risk of crop damage althoughsome, e.g. amitrole, have been shown tobe safe when applied before bud-break.
Another option is to use a mix of amitrole and pendimethalin (residualherbicide) after cutback. The addition ofthe residual herbicide helps maintainweed-free conditions until canopy closure. Again, if used, this mix must beapplied before bud-break.
5 – 20 shoots will emerge from each cutback stool depending on the variety.Within 3 months of cutback, canopyclosure will have occurred providing natural weed control due to reducedlight at ground level.
15SRC stool
Cal
end
ar o
f ac
tivi
ty
The
follo
win
g t
able
pro
vid
es a
n i
nd
icat
ion
of
the
tim
ing
of
maj
or
acti
viti
es d
uri
ng
th
e fi
rst
two
har
vest
cyc
les
of
a w
illo
w S
RC
pla
nta
tio
n u
nd
er a
3-y
ear
rota
tio
n.
Year
Pe
rio
d
Act
ivit
y-1
Ja
n -
Ju
n•
Con
side
r si
te s
elec
tion
and
liais
e w
ith n
eigh
bour
s, lo
cal a
utho
ritie
s, a
rcha
eolo
gist
s, e
tc.
•Pr
epar
e ev
iden
ce o
f m
arke
t fo
r SR
C
•Pr
epar
e an
d su
bmit
Def
ra E
stab
lishm
ent
Gra
nt a
pplic
atio
n
Jun
- S
ep•
1st
appl
icat
ion
of g
lyph
osat
e-ba
sed
herb
icid
e
Oct
- D
ec•
1st
or 2
nd a
pplic
atio
n of
gly
phos
ate-
base
d he
rbic
ide
•In
corp
orat
e sl
udge
cak
e if
requ
ired
•Su
b-so
iling
•Pl
ough
ing
•O
rder
ing
cutt
ings
1Ja
n -
Mar
•Er
ect
rabb
it fe
ncin
g w
here
nec
essa
ry
Mar
- M
ay•
2nd
or 3
rd a
pplic
atio
n of
a g
lyph
osat
e-ba
sed
herb
icid
e
•Po
wer
har
row
ing
and
pla
nti
ng
•R
olli
ng
an
d a
pp
licat
ion
of
pre
-em
erg
ence
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idu
al h
erb
icid
e (t
og
eth
er w
ith
leat
her
jack
co
ntr
ol
if n
eces
sary
)
•M
onito
r fo
r pe
sts
and
chec
k ra
bbit
fenc
ing
Jun
- D
ec•
Mon
itor
for
pest
s, m
aint
ain
rabb
it fe
ncin
g an
d ch
eck
over
all c
rop
heal
th
•Re
med
ial w
eed
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rol i
f re
quire
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2Ja
nFe
bC
utb
ack
and
gap
upas
nece
ssar
y
Pre-planting Establishment
Rem
eda
wee
d co
ntro
f r
equ
red
2Ja
n -
Feb
•C
utb
ack
and
gap
up a
s ne
cess
ary
Feb
- M
ar•
App
licat
ion
of c
onta
ct h
erbi
cide
Ap
r -
Jun
•A
pply
liqu
id s
ludg
e/fe
rtili
ser
as r
equi
red
•M
onito
r fo
r pe
sts
and
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k ra
bbit
fenc
ing
Jun
- D
ec•
Mon
itor
for
pest
s an
d di
seas
es a
nd m
aint
ain
rabb
it fe
ncin
g
3M
ar -
Au
g•
App
ly li
quid
slu
dge/
fert
ilise
r if
requ
ired
and
prac
ticab
le
•M
onito
r fo
r pe
sts,
par
ticul
arly
will
ow b
eetle
4M
ar -
Au
g•
App
ly li
quid
slu
dge/
fert
ilise
r if
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ired
and
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le
•M
onito
r fo
r pe
sts
and
dise
ases
, tr
eat
as n
eces
sary
Oct
- D
ec•
Agr
ee h
arve
stin
g da
tes
and
deliv
ery
sche
dule
with
end
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•H
arve
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gan
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end
use
r as
fre
sh m
ater
ial
•H
arve
stin
g, s
tora
ge a
nd d
ryin
g
5Ja
n -
Feb
•H
arve
stin
g, s
tora
ge a
nd d
ryin
g
Feb
- M
ar•
App
ly c
onta
ct h
erbi
cide
if n
eces
sary
•A
pply
liqu
id s
ludg
e/fe
rtili
ser
as r
equi
red
•St
orag
e an
d dr
ying
of
harv
este
d m
ater
ial
•D
eliv
ery
of c
hip
to e
nd u
ser
Mar
- A
ug
•M
onito
r fo
r pe
sts,
par
ticul
arly
will
ow b
eetle
and
spr
ay a
s ne
cess
ary
•St
orag
e an
d dr
ying
of
harv
este
d m
ater
ial
•D
eliv
ery
of c
hip
to e
nd u
ser
6M
ar -
Au
g•
App
ly li
quid
slu
dge/
fert
ilise
r if
requ
ired
and
prac
ticab
le
•M
onito
r fo
r pe
sts
and
dise
ases
, tr
eat
as n
eces
sary
7M
ar -
Au
g•
App
ly li
quid
slu
dge/
fert
ilise
r if
requ
ired
and
prac
ticab
le
•M
onito
r fo
r pe
sts
and
dise
ases
, tr
eat
as n
eces
sary
Oct
- D
ec•
Har
vest
ing
t
Headlands and rides
Headlands and rides should be grassedand cut twice a year. This regime providessome support for vehicle movements atharvest whilst also encouraging theestablishment of beneficial flora.
Fertilisation
Digested, i.e. treated, sewage sludge canbe applied to SRC as a fertiliser if it isconsidered feasible by the local WaterCompany under UK sludge regulationsand their own guidelines. Accurate nutrient requirements of the crop are stillunder research but where treatedsewage sludge has been applied the subjective view of growers is that it isbeneficial. Under the Code of GoodAgricultural Practice for the Protection ofWater (COGAP 1998), no more than250kg organic nitrogen/ha/year can beapplied to agricultural land. Willow SRChas a low demand for nitrogen (N) andthe current UK recommendations forapplication are 40, 60 and 100kg N/ha/yrfor the 1st (i.e. after cutback), 2nd and3rd years of the harvest cycle respectively(Johnson P. 1999). Where the soil hashigh residual N levels from previouscropping or a high soil organic matterlevel, these rates should be reduced.
No fertiliser should be applied during theestablishment year, i.e. from plantinguntil after the post-cutback herbicideapplication has had time to be effective.
Unfortunately, due to the growth formof SRC and the equipment currentlyavailable, fertiliser application can bedifficult in year 2 of the harvest cycle
and impossible in year 3. Opportunitiesto work over the crop usually have to betaken in year 1 after cutback and, wherepossible, in year 2. However, treatedsewage sludge in liquid form can beapplied using a dribble bar fed by anumbilical system. This allows the sludge tobe applied directly to the ground surfacethrough a series of pipes fed from thedribble bar with no contamination to thecrop and it can be used on coppice up to2.5 metres in height. Application shouldbe at the rates given above.
General management
18Liquid sludge application using dribble bar
The use of composted sewage sludgeapplied using standard agriculturalspreaders is being investigated toassess the benefits of applying up to 3times the annual limit of total N, i.e.700-750kg N/ha, in 1 application.Currently sludge cake or compostedorganic wastes, which contain very littleplant available N, may be applied at ratesof 500kg N/ha in 1 application every 2years, in areas not sensitive to nitrateleaching (COGAP 1998). The potential ofcomposted sludge is that it could beapplied after cutback and again afterharvest when there are few practicaldifficulties with working over the crop,although the height of the stems mustbe less than 50cm. Only 5-10% of thenitrogen would be released per year,i.e. during the growing season whentemperatures rise the composted sludgewould provide up to 70kg N/ha/yr foreach year of the 3-year harvest cycle.The remaining nitrogen is held within theorganic component of the compost andis not leached out. Defra will issue moreguidance on this as results from theinvestigations become available.
Nitrate Vulnerable Zones
A mature SRC plantation, i.e. after estab-lishment, will have a dense, widespreadroot system and this, combined with along growing season, enables the cropto efficiently utilise nutrients. Research, inthe UK and areas of Scandinavia withsimilar growing conditions, has shownthat the uptake of available nitrogen bySRC is very effective and, consequently,nitrate leaching is much lower than thatfrom fertilised grassland or arable land.
Also with SRC there is no soil disturbanceto promote mineralisation.
Nitrate leaching has been recorded in thefollowing situations:
• after green cover removal in the landpreparation phase,
• during the establishment year wherenitrogen has been applied as fertiliser,and
• after final removal of the crop.
It is therefore important that no fertiliseris applied during the establishment year,i.e. after planting and before cutback.The root system will not have fullydeveloped and would not be able toutilise the additional nutrients.
Although from research to date SRC willprove to be a beneficial crop for plantingwithin Nitrate Vulnerable Zones, it isessential that all Defra regulations relating to these zones are complied with.
Pests and diseases
Rust is the most important disease ofSRC, caused by a number of fungicalled Melampsora. Rusts can infectboth the leaves and stems of willowand, as they can adapt rapidly to changing circumstances, can successfullyinfect a whole crop if appropriate measures are not taken.
Monocultures of willow, i.e. block plantingof single varieties, are highly susceptible torust damage. The UK and European PlantBreeding Programmes, one of whoseaims is to identify varieties that areresistant to rust, recommend that at least5 different varieties be planted in a ran-dom mix at each site. The Forestry
19
Commission Information Note byTabbush, Parfitt and Tubby (2002) givesdetails of appropriate mixes. The use offungicides is not recommended for economic, practical and environmentalreasons.
Chrysomelids (willow beetles) are themost important insect pest of willowSRC. Their numbers can build up rapidlyin spring and, as both adults and larvaefeed on the leaves, they can cause considerable damage to the crop. Forexample, removal of 90% of the leavesin summer can reduce the yield by asmuch as 40%. Adult willow beetles over-winter in rotting wood, under the barkof trees and in similar habitats short
distances from the coppice. As tempera-tures start to rise in the spring, the adultsmove into the edge of the coppice, startfeeding, mate and then gradually movefurther into the crop.
If beetle numbers reach 100 adults ormore shaken from the canopy per squaremetre of ground surface, then either alocal application of an appropriateinsecticide directed specifically to wherethe beetles are congregating or a sprayapplied from the edges of the coppice ifthe beetles are more dispersed, will savethe crop from further damage.Overspraying a mature plantation wouldprove costly, not only financially but alsoecologically as the insecticides used are
General management
20
Melampsora rust on willow leaves
not specific to their targets and wouldtherefore damage many non-target andbeneficial insects. Beetle populations dotend to fluctuate between years so alarge infestation one year does not necessarily mean that it will occur again.Planting a mix of willow varieties can havea beneficial effect as the beetles tend tofeed preferentially on some varietiesbefore moving onto others and this slowstheir spread through the coppice.
Browsing animals such as rabbits anddeer can also cause damage to SRC butmainly during establishment.
The Game Conservancy Trust has pro-duced a booklet describing integratedpest management techniques for SRC(Tucker & Sage, 1999) which includessections on willow beetles and rust.
21Willow beetle larvae
Adult willow beetles
Harvesting generally takes place on a 3-year cycle, the first harvest being 3years after cutback. The work is carriedout during the winter, after leaf fall andbefore bud-break, usually mid-October toearly March. SRC can be harvested asrods, chips and billets (see table below).
End-users will generally require the fuelin the form of wood chip, to a maximumsize. They may also need the wood chipdried to a particular moisture content(MC). For example, willow is generally inthe range 45-60% MC at harvest butend-users may want a MC below 30%.
The type of harvesting machinery usedwill depend on the end-user’s require-ments. Details of the latest machineryavailable to buy or hire can be obtainedfrom British BioGen’s Energy CropsNetwork (see ‘Contacts’ section).
Rod harvesting
A number of machines are available forrod harvesting most of them producingloose rods which need to be off-loadedinto heaps on the headlands or on farm.There is some wastage with this methodas rods are left in the field and after collection from headlands. However,loose rods do dry by natural convectionand do not deteriorate with time.‘Bundler’ harvesters cut whole stems,
bind them and then cut them into bundles2.5 metres long. The bundles can bestacked on headlands or on farm andcan dry down to approximately 30% MCin 3-4 months.
Chipping of dried whole rods or bundlestends to result in shattering of thematerial rather than chipping; therefore,where chip size and quality are important,chipping fresh material is recommended
Direct-chip harvesting
Specifically designed SRC headers fordirect chipping of the crop have beenfitted to forage harvesters: the stemsare cut, chipped and then blown into anaccompanying trailer. Although direct-chipharvesting is currently more efficient thanrod harvesting, storage and drying of thefresh wood chip does cause problems.Stored, fresh wood chip can heat up to60˚C within 24 hours and start todecompose. During decompositioncalorific value, i.e. the energy value ofthe fuel, is lost. Also the fungal and bacterial spores produced during decom-position constitute a health hazard.
As the fuel will be needed all year, storage, drying and prevention ofdecomposition must be considered. Theuse of grain driers, ventilated-floor-driersand low-rate aeration using ducts are all
Harvesting
22
Harvested material
Rods Harvested stems up to 8m in length
Billets Cut material, 5 – 15cm long
Chips Cut material, up to 5 x 5 x 5 cm in size
being investigated, although it is currentlyconsidered uneconomic to dry woodchip by any method other than naturalair-drying. It is important to ensure thatthe energy used in producing wood chipfor fuel is kept to a minimum.
Billet harvesting
Intermediate between rod and directchip harvesting is billet harvesting. Thestems are cut whole, cut further intobillets and blown into an accompanyingtrailer. Due to the spaces between the
billets, natural ventilation occurs withinstorage piles preventing the difficultiesassociated with chip storage. However,depending on the fuel specification ofthe end-user, the billets may need to bechipped prior to use.
23Direct-chip harvesting
SRC yields will vary according to thelocation of the site. Soil type, wateravailability, general husbandry, and pestand weed control will also affect yield.Yield following the first harvest of anumber of commercial sites was in therange 5-9 odt/ha/yr. However, plantingdensities at many of these sites were12,000 cuttings/ha rather than the currentstandard of 15,000 cuttings/ha. Yieldsshould also increase at second and thirdharvests. Average yields from experimental
plots growing new varieties, some ofwhich are now commercially available,have reached more than 18 odt/ha/yr.Breeding programmes continue to produce varieties that out-performolder varieties.
Yield
24
Harvested woodchip
Despite the fact that it is essential toeradicate weeds during the establishmentof SRC, once the crop is mature thegrowth of a ground flora is beneficial.Ground cover encourages the presenceof invertebrates, which in turn leads to anincrease in the number of small mammalsand birds found. At least three times thenumber of plant-eating species spend partof their life cycle in the canopy of willowSRC compared to conventionally grownbarley and wheat (Sage & Tucker, 1998).
High numbers of bird species are alsofound throughout the year and over the3-year harvest cycle. For example, skylark,lapwing, yellow wagtail and snipe areoften found in newly planted, cutbackand harvested SRC. Species of highconservation value such as bullfinch,
reed bunting and song thrush have beennoted to regularly hold territories in SRCduring the breeding season.
Headlands and rides provide furtherhabitat opportunities for a wide rangeof plants and animals, for example, 14species of butterfly have been recordedon SRC headlands.
Many of the species that use the habitatsassociated with SRC will predate pestspecies. For example, two of the birdscommonly associated with SRC, thegarden and willow warblers, are two ofthe most important consumers of defoliating invertebrates. Therefore, anymanagement practice that enhances theconservation potential of the crop is likelyto prove valuable for pest management.
Biodiversity
25
Headland flora
After the final winter harvest, the stoolsshould be left and allowed to shoot thefollowing spring. When shoots of morethan 15cm in height have developed, theentire coppice should be over-sprayedwith a glyphosate-based contact herbicideto kill the willow. Running either a sub-soiler or a large diameter disc alongthe rows close to the stools will severthe main structural roots, which runhorizontally from the stools. When theshoots have died back, the stools themselves can be mulched by use of abush-hogger (heavy-duty grass-topperor pulveriser) into the top 5-10cm ofsoil. The field can then be grassed forthe first year following removal and (if
appropriate) used for standard arablecropping the following year. Using thismethod, final harvest to re-seeding, willtake 18-24 months.
To shorten the process, the final harvestcan be taken in late summer/earlyautumn and the stools again allowed toshoot. When the shoots are 15cm ormore in height, the herbicide should beapplied, the structural roots cut and, following death of the shoots, the stoolsmulched. Depending on soil type, thestools can be ploughed in prior to winter.This will allow an early re-seeding the following spring.
Removal of SRC
26
Poplar has been used as a short rotationcoppice crop on a small scale to date,often planted adjacent to willow SRC toprovide visual diversity.
Site
Poplar grows best in deep fertile soils,although it will grow in most conditions.The main exceptions are shallow soilsand sites that remain waterlogged. SoilpH should ideally fall in the range 5.5 -7.5, although research suggests thatthere are varieties tolerant to soil pHoutside this range.
Preparation of the site should be thesame as that for willow SRC, taking careto ensure eradication of all weeds. Thesoil should be well cultivated to a depthof at least 25cm. Where compaction ispresent, sub-soiling should be carried outto a depth of 40cm.
Planting material
Most new poplar varieties have beenbred for high yield but as a single stemcrop. Also a number of varieties plantedin the mid-1990’s succumbed to rust astheir resistance broke down. However,current breeding programmes aim toproduce high yielding varieties that willcoppice more readily and have longterm resistance to rust. The current recommended and approved poplarvarieties for SRC are listed in theForestry Commission Information Note,“Poplar and willow varieties for shortrotation coppice” (Tabbush, Parfitt andTubby 2002).
Poplar varieties are controlled under theForest Reproductive Material Regulations,
which are in place to improve the qualityof poplar varieties, increase productionand ensure that the most suitable varietiesare used. These Regulations also controlthe marketing of poplar varieties so thatreproductive material is only availablefrom registered sources.
Planting
Planting should take place as early aspossible in the spring but avoiding frost.The density of planting has generallybeen lower than that for willow at 10-12,000 cuttings/ha. The cuttings are20-25cm long and must have an apicalbud within 1cm of the top of the cutting.This means that poplar cannot be planted
Poplar SRC
27
Poplar SRC
using ‘step planters’, as the cuttings haveto be manually processed to ensure thepresence of the apical bud. Consequently,modified cabbage planters have to beused but due to the ridged nature ofpoplar stems, the cuttings occasionallyblock the planter mechanisms. The ‘lay-flatplanter’ is currently being tested forplanting poplar rods.
Management
Weed control is very important in theestablishment year, so after planting androlling a residual herbicide should beapplied within 3-5 days. Cutback takesplace late in the winter following planting.Due to its apical dominance, poplar willgenerally produce only 1-3 shoots aftercutback.
Melampsora rust is also the most common disease of poplar, althoughdifferent species of rust affect poplarand willow. Different poplar varietieshave different susceptibilities to rust so itis important to read the latest version ofthe Forestry Commission’s ‘varieties’Information Note referred to above. Aswith willow, it is recommended that amix of varieties be planted.
Willow beetles are also an importantpest of poplars and should be treatedeither by spraying localised colonies or,if the population reaches 100 or moreadult beetles per square metre ofcanopy, edge spraying the coppice inearly spring. Overspraying the entireplantation would be ecologically andfinancially inadvisable.
Yields
Research has shown that poplar canoften outperform willow in terms ofyield but this appears to be site specificand highlights the fact that choosingthe appropriate varieties for a site isessential. Unlike willow, poplar tends toproduce better yields when allowed togrow for four years or more from cutback.
Harvesting
As poplar produces fewer, heavierstems, careful consideration must begiven to the harvesting machinery used;it must be capable of dealing efficientlywith large diameter, rigid stems. Detailsof the latest machinery available to buyor hire can be obtained from BritishBiogen’s Energy Crops Network (see‘Contacts’ section).
Removal
The removal of poplar SRC at the end ofits life is more problematic than willow.The rooting system of poplar includes alarge taproot that grows down into thesoil. Removal of the stools (following finalharvest and spraying off of the shoots)will generally require a large excavator.
Poplar SRC
28
Bell S, McIntosh E 2001. Short Rotation Coppice in the Landscape. ForestryCommission Guideline Note 2. Forestry Commission, Edinburgh
Defra 1998. Code of Good Agricultural Practice for the Protection of Water. Defra Publications, London
Defra 2000. Establishment grants for short rotation coppice and miscanthus. Defra Publications, London
Defra 2000. Grants for establishing producer groups. Defra Publications, London
Forest Reproductive Material Regulations 1977. HMSO
Forest Reproductive Material (Amendment) Regulations 1992. HMSO
Johnson P 1999. Fertiliser requirements for short rotation coppice. ETSU reportB/W2/00579/REP/1
McKillop I G, Dendy J A 2000. Advice on rabbit management for growers of shortrotation willow coppice. DTI/Defra, Central Science Laboratory, York
Sage R, Tucker K 1998. Integrated crop management of SRC plantations to maximisecrop value, wildlife benefits and other added value opportunities. ETSUB/W2/00400/REP
Sludge (Use in Agriculture) Regulations 1989. HMSO
Sludge (Use in Agriculture) (Amendment) Regulations 1990. HMSO
Tabbush P, Parfitt R, Tubby I 2002. Poplar and willow varieties for short rotation coppice. Forestry Commission Information Note. Forestry Commission, Edinburgh
Tubby I, Armstrong A 2002. The establishment and management of short rotationcoppice – a practitioner’s guide. Forestry Commission Practice Note. ForestryCommission, Edinburgh
Tucker K, Sage R 1999. Integrated pest management in short rotation coppice – agrower’s guide. Game Conservancy Limited, Fordingbridge, Hampshire
References
29
Defra and the British Horse Industry Confederation
Joint Research on the Horse Industry in Great Britain
30
Energy Crops SchemeOrganic and Energy Crops NationalImplementation TeamRural Development ServiceDefraElectra WayCrewe CW1 6GJ
Tel: 01270 754 000Fax: 01270 754 088
www.defra.gov.uk/erdp/erdphome.htm
Energy Crops NetworkBritish BioGen16 Belgrave SquareLondon SW1X 8PQ
Tel: 020 7235 8474
www.britishbiogen.co.uk
Forestry CommissionGreat Eastern HouseTenison RoadCambridge CB1 2DU
Tel: 0845 367 3787Fax: 0122 346 0699
www.forestry.gov.uk
Pesticide Safety DirectorateMallard HouseKings Pool3 Peasholme GreenYork YO1 7PX
Tel: 01904 455 775Fax: 01904 455 733
www.pesticides.gov.uk
Contacts
PB 7135 (reprint)© Crown copyright August 2004Printed on material containing 80% post-consumer wasteand 20% Elemental Chlorine Free pulp.
Contacting DefraIf you have a query and are unsure about who to talk to in Defra, you can call the Defra Helplinewho will be pleased to help you to find the right person.
Defra Helpline: 0845933 55 77 (local call rate)
www.defra.gov.uk
Defra PublicationsAdmail 6000, London SW1A 2XXTel: 08459 556000
