BEST PRACTICE GUIDELINESFor Applicants to DEFRA’S Energy Crops Scheme

GROWINGSHORT ROTATION

COPPICE

GROWINGSHORT ROTATION

COPPICE

Contents

INTRODUCTION 3

WHY GROW ENERGY CROPS? 4

WHAT IS SRC? 5

WHERE TO GROW SRC? 6

Site selection 6

Plantation design 7

LAND PREPARATION 8

PLANTING MATERIAL 9

ESTABLISHMENT 11

Planting 11

Establishment year management 14

Cutback 14

CALENDAR OF ACTIVITY 16

GENERAL MANAGEMENT 18

Headlands and rides 18

Fertilisation 18

Nitrate Vulnerable Zones 19

Pests and diseases 19

HARVESTING 22

Rod harvesting 22

Direct-chip harvesting 22

Billet harvesting 23

YIELD 24

BIODIVERSITY 25

REMOVAL OF SRC 26

POPLAR SRC 27

Site 27

Planting material 27

Planting 27

Management 27

Yields 28

Harvesting 28

Removal 28

REFERENCES 29

CONTACTS 30

3

Introduction

This booklet has been produced by the Department ofEnvironment, Food and Rural Affairs (DEFRA) to introducefarmers to a new crop. It provides guidance on the choice ofsite, planting techniques, crop management and harvestingmethods required when growing short rotation willow orpoplar coppice as an energy crop. The booklet summarisescurrent agronomic techniques and, therefore, may need to bemodified as further experience is gained. Please check thatyou have the latest copy of the booklet with the DEFRAoffice at Crewe.

This booklet should be read in association with the EnergyCrops Scheme booklet, “Establishment grants for shortrotation coppice and miscanthus” which outlines therequirements for claiming grant to establish the crop.

There is further information on short rotation coppice in theForestry Commission Information Note “The establishmentand management of short rotation coppice - a practitioner’sguide” (Tubby and Armstrong, 2002).

Energy crops are used as fuel in powerstations and heating systems. Insubstitution for fossil fuels, they have thepotential to reduce emissions of thegreenhouse gas carbon dioxide. Energycrops will need to contribute if the UK isto meet its:

• obligation under the Kyoto Protocol toreduce greenhouse gas emissions by 12.5per cent below 1990 levels by 2012;

• domestic goal to generate 10% of thenation’s electricity from renewable sourcesby 2010.

This provides a significant opportunity forthe energy crop industry.

Currently the major energy crop grown inthe UK is short rotation coppice (SRC),primarily willow, although poplar has beenused occasionally and may be planted morecommonly in the future following the

production of varieties more suited tocoppicing. This booklet concentrates onwillow SRC, although a section relatingspecifically to poplar has been 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 “Grants forestablishing 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

4

Woodchip boiler for heat ARBRE power station fuelled by woodchip

Why grow energy crops?

5

SRC (short rotation coppice) consists ofdensely planted, high-yielding varieties ofeither willow or poplar, harvested on a 2 –5 year cycle, although commonly every 3years. The osier, a shrub willow, is parentalstock to the majority of willow varietiesplanted for use as an energy crop. SRC is awoody, perennial crop, the rootstock orstools remaining in the ground afterharvest with new shoots emerging thefollowing spring. A plantation could beviable for up to 30 years before re-plantingbecomes necessary, although this dependson the productivity 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 up to4m in height. During the winter afterplanting the stems are cut back to groundlevel to encourage the growth of multiplestems i.e. coppiced. Generally three yearsafter cutback and again during the winter,the crop is harvested. The equipment usedfor harvesting will have been specificallydeveloped for the purpose and depends onthe fuel specification of the customer/end-user. Most operations other than plantingor harvesting can be completed usingconventional 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 per year(odt/ha/yr) depending on site and efficiencyof establishment.

Willow SRC 3 months after planting

Mature willow SRC

What is 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 but notpermanent waterlogging. Where land isprone to flooding most years, the willowwill survive but consideration must begiven to operational requirements,particularly the need to harvest in winter.Annual rainfall of 600-1000mm is ideal.

SRC can be established on a wide range ofsoil types from heavy clay to sand includingland reclaimed from gravel extraction andcolliery spoil. Clay or sandy loams thatretain moisture but are well aerated areideal soils. Establishment may be slow onheavy clays as they tend to be cold in springalthough, once established, SRC grown onthese soils can be highly productive. Wherecompaction may prove to be a problem,sub-soiling to a depth of 40cm will be necessaryto ensure maximum root development. SoilpH should 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 in theground for up to 30 years and can reach 7-8 metres in height prior to harvest. Itsimpact on the local landscape, ecology,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 significant adverseimpact on the environment. Thisconsultation takes up a significant part of the3-month application process time. To speedthe process potential growers may wish tocontact organisations that may be affectedby the planting of the crop in advance, e.g.local councils for bylaws relating to publicrights of way or the county archaeologist tocheck the records for any importantarchaeological remains. Where a proposedsite is adjacent to a river or on a floodplain,the Environment Agency should beconsulted.

Another factor to consider is soil erosion.Compared to many crops, SRC has largeareas of open ground within the crop duringestablishment. On light, sandy soils this canlead to wind erosion of the soils and alsosome damage to the newly emerged shootsdue to abrasion. On sloping sites, soils canbe eroded following heavy rain.

6

Where to grow SRC?

SRC in the landscape

7

Willow roots, which are fibrous in nature,will penetrate down to field drains and it isrecommended that SRC is planted at least30 metres from any drains that areconsidered important. When choosing asite consider the life of the drainage systemin relation to the expected life of the SRCplantation.

To be eligible for grant the proposed sitemust be at least 3ha in total, although thiscan be made up of smaller plots. However,to ensure economies of scale for all fieldoperations larger plantations are better.The most appropriate field shapes arethose that minimise the need for short rowlengths or require no changes in directionduring field operations. Choosing fieldsthat can be harvested economically is ofcritical importance. For ease of operationsthe ideal site would be flat or with a slopeof no more than 7%. It is stronglyrecommended that the slope of the fieldshould not exceed 15%.

Appropriate access must be available for allmachinery involved in establishing andharvesting the crop. Gate widths should beat least 4.5m but it is recommended that ifnew gates have to be installed they shouldbe up to 7.2m in width. Bridge height orweight restrictions should also beconsidered where necessary. Ideally areasfor transferring and storing the harvestedcrop should be adjacent to the coppice.

Plantation design

The plantation design should fit in with thesurrounding landscape and advice relatingto this can be obtained from ForestryCommission Guideline Note 2 (Bell &McIntosh, 2001). Operationalrequirements must also be taken intoaccount. Headlands of at least 8 metres inwidth are necessary at both ends of therows to allow for vehicle turning. Whereonly one trailer will be available at harvestor the harvester has an integral trailer, rowlengths should be restricted to a maximumof 200 metres to avoid the need to reversealong the rows to off-load. Where two ormore trailers will be available, row lengthscan be longer. However, if liquid sludge isto be applied using an umbilical system, themaximum row length should be 400metres. Rides of 4 metres should be leftalong the edges of the crop to allowmachinery access for willow beetle controlif required. A maximum of 20% openground is allowed within a SRC plantationunder the ECS.

Edge of SRC plantation

The importance of efficient landpreparation for SRC cannot be stressedtoo highly. As SRC is a long-term, perennialcrop, ensuring ideal conditions atestablishment will reap benefits at first andall subsequent harvests.

Weed control is a critical part of coppiceestablishment. Complete eradication of allinvasive perennial weeds is essential priorto planting. One or two applications of aglyphosate-based herbicide, applied at theappropriate rate, should be carried out inthe summer/autumn prior to springplanting. 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. Itshould then be ploughed to a depth of atleast 25cm and left to over-winter. On

lighter land it may be more appropriate tospring plough. Power harrowing of the siteshould be carried out immediately beforeplanting.

Sludge cake, well-rotted farmyard manureor other bulky organic manure with a lowavailable nitrogen content can beincorporated into the soils prior toploughing. This is particularly beneficial onlight soils where it will increase moistureretention and help to condition the soil.The DEFRA Code of Good AgriculturalPractice for the Protection of Water (1998)must be adhered to when applying organicmanures.

Rabbits, if present, must be kept out of thecrop at least during the first two years andideally up to first harvest, to allow the cropto mature beyond its vulnerable stage.Rabbit fencing should be erected to BritishStandard, buried and turned out. DEFRAand the Department of Trade and Industry(DTI) have produced a leaflet on rabbitmanagement techniques for SRC (McKillop& Dendy, 2000).

8

Land preparation

9

Access to the ECS is not restricted tospecified varieties of willow. However,several willow varieties, bred specifically foruse as SRC energy crops, are listed in theForestry Commission Information Note“Poplar and willow varieties for shortrotation coppice” (Tabbush, Parfitt andTubby 2002). The recommended varietieshave been through trials to ensure highyields, erect growth habit and resistance to,or tolerance of, disease. The list is updatedas information on new varieties becomesavailable and provides a useful source ofinformation when selecting plantingmaterial.

Melampsora rust is the most common

fungal disease of willows. Ideally, a mix ofwillow varieties with diverse rust tolerancecharacteristics, referred to as “mix types”,should be used. Details of these varietalcharacteristics are available in the ForestryCommission Information Note referred toabove or from material providers. Recentresearch has also shown that mixedplanting can lead to reduction in damagecaused by willow beetles, the main pestspecies of willows.

European Plant Breeders’ Rights protectthe majority of varieties and cropharvested on the farm cannot be used asplanting material. Further information canbe obtained from the holders of Rights.

Willows are planted either as cuttings orrods. Only licensed producers shouldconduct willow propagation. Rods orcuttings are taken from one-year-oldmaterial that is harvested betweenDecember and March when the plants aredormant. They must be either plantedimmediately or stored at -2 to -4˚C, wherecuttings will remain viable for severalweeks and rods up to 3 months. Theyshould only be taken from cold store and

Planting material

Planting material

Planting Cut and trimmed willow rods stems, generally 1.5 –

3m long

Cuttings Cut fresh from rods andbetween 18 – 20cm in length

Planting rods

10

delivered to the planting site on themorning of planting. If rods/cuttings are leftin temperatures above 0˚C a break in theirdormancy will occur, adventitious roots will

develop and the buds may burst. This willlead to a reduction in water and nutrientcontent and consequently reduced viability.

Willow cuttings colour-coded by variety

Planting material

11

Establishment

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’. Willow rodsof 1.5-2.5 metres length are fed into theplanter by two or more operativesdepending on the number of rows beingplanted. The machine cuts the rods into18-20cm cuttings, inserts the cuttingsvertically into the soil and firms the soilaround each cutting. 15,000 cuttings perhectare is the current standard commercial

planting density using this method. Lowerdensity planting may lead to thicker stemsand consequently larger chip size.Therefore, planting densities down to12,000 cuttings/ha may be appropriatewhere quality of chip is of moreimportance than 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 developed whichlays whole rods horizontally into furrowsopened by discs at 2-8cm depth. The rodsare laid end to end with a slight overlap, thesoil covers them and is consolidated tominimise moisture loss. Distance between

A ‘step planter’

Establishment

12

rows can be controlled but as the shootstend to grow randomly along the length ofthe rods there is no way to accuratelycontrol density.

Planting should ideally take place after thelast frosts but as early as February if soilconditions allow. Planting can be successfulas late as June but late planting is bestavoided as the longer the first growingseason the better in order to take theplants successfully into winter and cutback.Another factor is that late planting has torely on planting material from cold store,i.e. harvested earlier in the year. This willrestrict the material available, especially ascuttings start to lose viability after a fewweeks in storage.

Willows should be planted in twin rows0.75 metres apart and with 1.5 metres

between each set of twin rows. This spacingallows standard agricultural machinery fittedwith wide tyres to work across the crop. Aspacing of 0.59 metres along the rows whenplanting cuttings will give a planting densityof 15,000/ha, the commercial standard (seediagram opposite).

The site should be rolled immediately afterplanting to consolidate the soil for effectiveherbicide application. Pre-emergenceresidual herbicide should be applied within3-5 days of planting.

If the site was previously grassland or long-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 before rootor shoot development.

A ‘lay-flat planter’

1313

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, dependingon soil conditions. In the case of rods,shoots develop randomly along the lengthof the rod but the stem heights will besimilar to those from cuttings.

No fertiliser should be applied during theestablishment year.

The coppice should be monitored carefullyfor pests, weed growth and general healthduring the establishment year. If remedialweed control proves necessary, a hoodedband sprayer, specifically designed for useon SRC, should be used.

Cutback

During the winter following planting thewillow is usually cut back to within 10cm ofground level to encourage the developmentof the multi-stemmed coppice. The work

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

Growth shortly after planting

should be carried out as late as possible inthe winter but before bud-break, generallylate February. The most effective machinesare modified mowers/reapers as these givea clean cut to the stems.

A contact herbicide should be applied aftercutback to control those weeds that havegrown during the establishment year. It isimportant that the herbicide is appliedbefore coppice bud-break otherwise the

crop will be damaged. Generally the use ofsystemic/translocated contact herbicidesshould be avoided due to the risk of cropdamage although some, e.g. amitrole, havebeen shown to be safe when applied beforebud-break.

Another option is to use a mix of amitroleand pendimethalin (residual herbicide)after cutback. The addition of the residualherbicide helps maintain weed-free

14

Establishment

Plantation prior to cutback

15

conditions until canopy closure. Again, ifused, this mix must be applied before bud-break.

5 – 20 shoots will emerge from eachcutback stool depending on the variety.

Within 3 months of cutback, canopyclosure will have occurred providingnatural weed control due to reduced lightat ground level.

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Headlands and rides

Headlands and rides should be grassed andcut 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 can beapplied to SRC as a fertiliser if it isconsidered feasible by the local WaterCompany under UK sludge regulations andtheir own guidelines. Accurate nutrientrequirements of the crop are still under

research but where treated sewage sludgehas been applied the subjective view ofgrowers is that it is beneficial. Under theCode of Good Agricultural Practice for theProtection of Water (COGAP 1998), nomore than 250kg organic nitrogen/ha/yearcan be applied to agricultural land. WillowSRC has a low demand for nitrogen (N)and the current UK recommendations forapplication are 40, 60 and 100kg N/ha/yrfor the 1st (i.e. after cutback), 2nd and 3rdyears of the harvest cycle respectively(Johnson P. 1999). Where the soil has highresidual N levels from previous cropping ora high soil organic matter level, these ratesshould be reduced.

No fertiliser should be applied during theestablishment year, i.e. from planting untilafter the post-cutback herbicideapplication has had time to be effective.

Unfortunately, due to the growth form ofSRC and the equipment currently available,fertiliser application can be difficult in year2 of the harvest cycle and impossible inyear 3. Opportunities to work over thecrop usually have to be taken in year 1 aftercutback and, where possible, in year 2.However, treated sewage sludge in liquidform can be applied using a dribble bar fedby an umbilical system. This allows thesludge to be applied directly to the groundsurface through a series of pipes fed fromthe dribble bar with no contamination tothe crop and it can be used on coppice upto 2.5 metres in height. Application shouldbe at the rates given above.

18

General management

Liquid sludge application using dribble bar

The use of composted sewage sludgeapplied using standard agriculturalspreaders is being investigated to assessthe benefits of applying up to 3 times theannual limit of total N, i.e. 700-750kg N/ha,in 1 application. Currently sludge cake orcomposted organic wastes, which containvery little plant available N, may be appliedat rates of 500kg N/ha in 1 applicationevery 2 years, in areas not sensitive tonitrate leaching (COGAP 1998). Thepotential of composted sludge is that itcould be applied after cutback and againafter harvest when there are few practicaldifficulties with working over the crop,although the height of the stems must beless 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 for eachyear of the 3-year harvest cycle. Theremaining nitrogen is held within theorganic component of the compost and isnot leached out. DEFRA will issue moreguidance on this as results from theinvestigations become available.

Nitrate Vulnerable Zones

A mature SRC plantation, i.e. afterestablishment, will have a dense,widespread root system and this, combinedwith a long growing season, enables thecrop to efficiently utilise nutrients.Research, in the UK and areas ofScandinavia with similar growing

conditions, has shown that the uptake ofavailable nitrogen by SRC is very effectiveand, consequently, nitrate leaching is muchlower than that from fertilised grassland orarable land. Also with SRC there is no soildisturbance to 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 fertiliser isapplied during the establishment year, i.e.after planting and before cutback. The rootsystem will not have fully developed andwould not be able to utilise the additionalnutrients.

Although from research to date SRC willprove to be a beneficial crop for plantingwithin Nitrate Vulnerable Zones, it isessential that all DEFRA regulationsrelating to these zones are complied with.

Pests and diseases

Rust is the most important disease of SRC,caused by a number of fungi calledMelampsora. Rusts can infect both theleaves and stems of willow and, as they canadapt rapidly to changing circumstances,can successfully infect a whole crop ifappropriate measures are not taken.

19

Monocultures of willow, i.e. block plantingof single varieties, are highly susceptible torust damage. The UK and European PlantBreeding Programmes, one of whose aimsis to identify varieties that are resistant torust, recommend that at least 5 differentvarieties be planted in a random mix ateach site. The Forestry CommissionInformation Note by Tabbush, Parfitt andTubby (2002) gives details of appropriatemixes. The use of fungicides is notrecommended for economic, practical andenvironmental reasons.

Chrysomelids (willow beetles) are themost important insect pest of willow SRC.

Their numbers can build up rapidly inspring and, as both adults and larvae feedon the leaves, they can cause considerabledamage to the crop. For example, removalof 90% of the leaves in summer can reducethe yield by as much as 40%. Adult willowbeetles over-winter in rotting wood, underthe bark of trees and in similar habitatsshort distances from the coppice. Astemperatures start to rise in the spring, theadults move into the edge of the coppice,start feeding, mate and then graduallymove further into the crop.

If beetle numbers reach 100 adults ormore shaken from the canopy per square

20

General management

Melampsora rust on willow leaves

metre of ground surface, then either a localapplication of an appropriate insecticidedirected specifically to where the beetlesare congregating or a spray applied fromthe edges of the coppice if the beetles aremore dispersed, will save the crop fromfurther damage. Overspraying a matureplantation would prove costly, not onlyfinancially but also ecologically as theinsecticides used are not specific to theirtargets and would therefore damage manynon-target and beneficial insects. Beetlepopulations do tend to fluctuate betweenyears so a large infestation one year doesnot necessarily mean that it will occuragain. Planting a mix of willow varieties canhave a beneficial effect as the beetles tendto feed preferentially on some varietiesbefore moving onto others and this slowstheir spread through the coppice.

Browsing animals such as rabbits and deercan also cause damage to SRC but mainlyduring establishment.

The Game Conservancy Trust hasproduced a booklet describing integratedpest management techniques for SRC(Tucker & Sage, 1999) which includessections on willow beetles and rust.

21

Willow beetle larvae

Adult willow beetles

Harvesting generally takes place on a 3-year cycle, the first harvest being 3 yearsafter cutback. The work is carried outduring the winter, after leaf fall and beforebud-break, usually mid-October to earlyMarch. SRC can be harvested as rods, chipsand billets (see table below).

End-users will generally require the fuel inthe form of wood chip, to a maximum size.They may also need the wood chip dried toa particular moisture content (MC). Forexample, willow is generally in the range45-60% MC at harvest but end-users maywant a MC below 30%.

The type of harvesting machinery used willdepend on the end-user’s requirements.Details of the latest machinery available tobuy or hire can be obtained from BritishBioGen’s Energy Crops Network (see‘Contacts’ section).

Rod harvesting

A number of machines are available for rodharvesting most of them producing looserods which need to be off-loaded intoheaps on the headlands or on farm. Thereis some wastage with this method as rodsare left in the field and after collection from

headlands. However, loose rods do dry bynatural convection and do not deterioratewith time. ‘Bundler’ harvesters cut wholestems, bind them and then cut them intobundles 2.5 metres long. The bundles canbe stacked on headlands or on farm andcan dry down to approximately 30% MC in3-4 months.

Chipping of dried whole rods or bundlestends to result in shattering of the materialrather than chipping; therefore, where chipsize and quality are important, chippingfresh material is recommended.

Direct-chip harvesting

Specifically designed SRC headers fordirect chipping of the crop have been fittedto forage harvesters: the stems are 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 of thefuel, is lost. Also the fungal and bacterial

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Harvesting

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

spores produced during decompositionconstitute a health hazard.

As the fuel will be needed all year, storage,drying and prevention of decompositionmust be considered. The use of graindriers, ventilated-floor-driers and low-rateaeration using ducts are all beinginvestigated, although it is currentlyconsidered uneconomic to dry wood chipby any method other than natural air-drying. It is important to ensure that theenergy used in producing wood chip forfuel is kept to a minimum.

Billet harvesting

Intermediate between rod and direct chipharvesting is billet harvesting. The stemsare cut whole, cut further into billets andblown into an accompanying trailer. Due tothe spaces between the billets, naturalventilation occurs within storage pilespreventing the difficulties associated withchip storage. However, depending on thefuel specification of the end-user, the billetsmay need to be chipped prior to use.

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Direct-chip harvesting

24

Yield

SRC yields will vary according to thelocation of the site. Soil type, wateravailability, general husbandry, and pest andweed control will also affect yield. Yieldfollowing the first harvest of a number ofcommercial sites was in the range 5-9odt/ha/yr. However, planting densities atmany of these sites were 12,000cuttings/ha rather than the current

standard of 15,000 cuttings/ha. Yieldsshould also increase at second and thirdharvests. Average yields from experimentalplots growing new varieties, some of whichare now commercially available, havereached more than 18 odt/ha/yr. Breedingprogrammes continue to produce varietiesthat out-perform older varieties.

Harvested woodchip

25

Biodiversity

Headland flora

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 presence ofinvertebrates, 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 the 3-year harvest cycle. For example, skylark,lapwing, yellow wagtail and snipe are oftenfound in newly planted, cutback andharvested SRC. Species of highconservation value such as bullfinch, reed

bunting and song thrush have been notedto regularly hold territories in SRC duringthe breeding season.

Headlands and rides provide furtherhabitat opportunities for a wide range ofplants and animals, for example, 14 speciesof butterfly have been recorded on SRCheadlands.

Many of the species that use the habitatsassociated with SRC will predate pestspecies. For example, two of the birdscommonly associated with SRC, the gardenand willow warblers, are two of the mostimportant consumers of defoliatinginvertebrates. Therefore, any managementpractice that enhances the conservationpotential of the crop is likely to provevaluable for pest management.

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-sprayed witha glyphosate-based contact herbicide to killthe willow. Running either a sub-soiler ora large diameter disc along the rows closeto the stools will sever the main structuralroots, which run horizontally from thestools. When the shoots have died back,the stools themselves can be mulched byuse of a bush-hogger (heavy-duty grass-topper or pulveriser) into the top 5-10cmof soil. 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/early autumnand the stools again allowed to shoot.When the shoots are 15cm or more inheight, the herbicide should be applied, thestructural roots cut and, following death ofthe shoots, the stools mulched. Dependingon soil type, the stools can be ploughed inprior to winter. This will allow an early re-seeding the following spring.

26

Removal of SRC

Poplar has been used as a short rotationcoppice crop on a small scale to date, oftenplanted adjacent to willow SRC to providevisual diversity.

Site

Poplar grows best in deep fertile soils,although it will grow in most conditions. Themain exceptions are shallow soils and sitesthat remain waterlogged. Soil pH shouldideally fall in the range 5.5 - 7.5, althoughresearch suggests that there are varietiestolerant to soil pH outside this range.

Preparation of the site should be the sameas that for willow SRC, taking care toensure eradication of all weeds. The soilshould be well cultivated to a depth of atleast 25cm. Where compaction is present,sub-soiling should be carried out to a depthof 40cm.

Planting material

Most new poplar varieties have been bredfor high yield but as a single stem crop.Also a number of varieties planted in themid-1990’s succumbed to rust as theirresistance broke down. However, currentbreeding programmes aim to produce highyielding varieties that will coppice morereadily and have long term resistance torust. The current recommended andapproved poplar varieties for SRC arelisted in the Forestry CommissionInformation Note, “Poplar and willowvarieties for short rotation coppice”(Tabbush, Parfitt and Tubby 2002).

Poplar varieties are controlled under theForest Reproductive Material Regulations,which are in place to improve the quality ofpoplar varieties, increase production andensure that the most suitable varieties areused. These Regulations also control themarketing of poplar varieties so thatreproductive material is only available fromregistered sources.

Planting

Planting should take place as early aspossible in the spring but avoiding frost. Thedensity of planting has generally been lowerthan that for willow at 10-12,000cuttings/ha. The cuttings are 20-25cm longand must have an apical bud within 1cm ofthe top of the cutting. This means that

27

Poplar SRC

Poplar SRC

poplar cannot be planted using ‘stepplanters’, as the cuttings have to be manuallyprocessed to ensure the presence of theapical bud. Consequently, modified cabbageplanters have to be used but due to theridged nature of poplar stems, the cuttingsoccasionally block the planter mechanisms.The ‘lay-flat planter’ is currently being testedfor planting poplar rods.

Management

Weed control is very important in theestablishment year, so after planting androlling a residual herbicide should be appliedwithin 3-5 days. Cutback takes place late inthe winter following planting. Due to itsapical dominance, poplar will generallyproduce only 1-3 shoots after cutback.

Melampsora rust is also the most commondisease of poplar, although different speciesof rust affect poplar and willow. Differentpoplar varieties have differentsusceptibilities to rust so it is important toread the latest version of the ForestryCommission’s ‘varieties’ Information Notereferred to above. As with willow, it isrecommended that a mix of varieties beplanted.

Willow beetles are also an important pestof poplars and should be treated either byspraying localised colonies or, if thepopulation reaches 100 or more adultbeetles per square metre of canopy, edge

spraying the coppice in early spring.Overspraying the entire plantation wouldbe ecologically and financially inadvisable.

Yields

Research has shown that poplar can oftenoutperform willow in terms of yield butthis appears to be site specific andhighlights the fact that choosing theappropriate varieties for a site is essential.Unlike willow, poplar tends to producebetter yields when allowed to grow forfour years or more from cutback.

Harvesting

As poplar produces fewer, heavier stems,careful consideration must be given to theharvesting machinery used; it must becapable of dealing efficiently with largediameter, rigid stems. Details of the latestmachinery available to buy or hire can beobtained from British Biogen’s EnergyCrops 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) willgenerally require a large excavator.

28

Poplar SRC

Bell S, McIntosh E 2001. Short RotationCoppice in the Landscape. ForestryCommission Guideline Note 2. ForestryCommission, Edinburgh

DEFRA 1998. Code of Good AgriculturalPractice for the Protection of Water. DEFRAPublications, London

DEFRA 2000. Establishment grants for shortrotation coppice and miscanthus. DEFRAPublications, London

DEFRA 2000. Grants for establishingproducer groups. DEFRA Publications,London

Forest Reproductive Material Regulations1977. HMSO

Forest Reproductive Material (Amendment)Regulations 1992. HMSO

Johnson P 1999. Fertiliser requirements forshort rotation coppice. ETSU reportB/W2/00579/REP/1

McKillop I G, Dendy J A 2000. Advice onrabbit management for growers of shortrotation willow coppice. DTI/DEFRA, CentralScience Laboratory,York

Sage R, Tucker K 1998. Integrated cropmanagement of SRC plantations to maximisecrop value, wildlife benefits and other addedvalue opportunities. ETSU B/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. Poplarand willow varieties for short rotation coppice.Forestry Commission Information Note.Forestry Commission, Edinburgh

Tubby I, Armstrong A 2002. Theestablishment and management of shortrotation coppice - a practitioner’s guide.Forestry Commission Practice Note.Forestry Commission, Edinburgh

Tucker K, Sage R 1999. Integrated pestmanagement in short rotation coppice - agrower’s guide. Game Conservancy Limited,Fordingbridge, Hampshire

29

References

Energy Crops SchemeRural Development ServiceDEFRAElectra WayCreweCW1 6GLTel: 01270 754000Fax: 01270 754280struct-fund@crewe.defra.gsi.gov.ukwww.defra.gov.uk/erdp/erdphome.htm

Energy Crops NetworkBritish BioGen7th Floor63-66 Hatton GardenLondonEC1N 8LETel: 020 7831 7222Fax: 020 7831 7223info@britishbiogen.co.ukwww.britishbiogen.co.uk

Forestry Commission231 Corstorphine RoadEdinburghEH12 7ATTel: 0845 367 3787Fax: 0131 334 3047enquiries@forestry.gsi.gov.ukwww.forestry.gov.uk

Pesticide Safety DirectorateMallard HouseKings PoolYorkYO1 7PXTel: 01904 455775Fax: 01904 455733information@psd.defra.gsi.gov.ukwww.pesticides.gov.uk

30

Contacts

Text prepared by Barbara Hilton of ADAS Consulting Ltd.

Booklet design by Folio Creative Communication Ltd.

31

Notes

Contacting DEFRAIf you have a query and are unsure about who to talk to inDEFRA, you can call the DEFRA Helpline who will be pleasedto help you to find the right person.

DEFRA Helpline: 0845933 55 77 (local call rate)

DEFRA PublicationsAdmail 6000, London SW1A 2XXTel: 08459 556000

June 2002

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www.defra.gov.uk

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