•/./• '

Agronomyan dcro pphysiolog yo f fibrehemp .A literatur erevie w

H.M.G.va nde rWer f

CABORepor t14 2 March199 1

Centerfo rAgrobiologica lResearc h (CABO-DLO) P.O.Bo x 14,670 0A AWageningen ,Th eNetherland s AGRONOMYan dCRO PPHYSIOLOG Yo fFIBR EHEMP ,A LITERATUR EREVIE W

H.M.G.va nde rWerf ,Februar y1991 .

Contents.

1Objective s ofthi sliteratur e review 2 2Th ehem pplan t 2. 1 Originan d importance 3 2.2 Varieties 4 2. 3 Sexexpressio n 4 2. 4 Anatomy ofth este m 4 2.5 Lengthan ddiamete ro fth e stem 6 3Cultura l practiceso fth ehem pcro p 3. 1 Soilrequirement san dfertilizatio n 7 3. 2 Sowingdat ean ddept h 8 3.3 Sowing rate,plan tdensit yan dro wwidt h 8 3.4 Weeds 9 3.5 Diseasesan dpest s 10 3.6 Harvest timing 10 3.7 Yield componentsan dyiel dleve l 11 4 Discussionan dconclusion s 12 L Objectiveso fthi sliteratur ereview .

Withinth eframewor ko fth eNationa l HempResearc hProgramme ,researc h isconducte d toinvestigat e thepotentia l ofhem pa sa sourc eo ffibr e forth epape r industry inth eNetherlands .Thi sprogramm e startedo n January 1,199 0an dshoul d reacha conclusio no nth eeconomi c feasabilityo fhem pfo rfibr eb yth een do f1992 .Majo r subjectso f research inth eprogra mare : -Breeding -Soil-bornedisease s -Cropphysiolog yan dagronom y -Harvestingan dconservatio n -Pulpan dpape rtechnolog y -Economyan dlogistic s Researcho ncro pphysiolog y isbein gcarrie d outwithi na researc h projecta tCABO ,researc ho nagronom ywithi na join tLUW-PAG Vproject .

Theobjectiv e ofth eresearc hproject sconcernin g cropphysiolog yan d agronomy offibr ehem pi st oanswe r thequestion : Howmuc han dwha tkin d offibr eca nhem pyiel d inth eNetherlands ? Thisliteratur e reviewwil l focuso nth eliteratur e resultsmos t relevantwit hrespec t totha tquestion .Th eobjective so fth eliteratur e revieware :

1.Th e identificationo fresearc hobjective s incro pphysiolog yan d agronomy offibr ehemp ,resultin g ina coheren tprogra mo f experiments serving theobjectives . 2.Relevan t sectionso fthi sliteratur e reviewwil lb euse d ina n article presenting theresult so fth eexperiment s conducted byMeije r andMatthijsse n in198 8an d1989 . 3.Th eliteratur e reviewma yb eusefu l toresearcher s involved inothe r partso fth ehem presearc hprogramme .

Whileconductin g theliteratur e researchan dwritin g thereview , literature oncro pphysiolog y ofhem pturne dou tt ob erare . Consequently thisrevie wmainl ycover s theagronom y ofhem pproduction . 2 THEHEM PPLAN T

2.1Origi nan dimportanc e ofhem p

Theorigi no fhem plie s incentra lAsi ao rChina ;i twa sgrow ni nChin a asearl ya s280 0B C (Derapsey,1975).I nth epas them pwa sa nimportan t fibrecrop ,it simportanc egraduall ydecline d inth ecours eo fth e20t h century (Table 1).Th edeclin ewa smos tpronounce d incountrie shavin ga marketeconomy .

Table 1.Hem pare ai n1,00 0 ha,191 0- 1988 .Dat aFA OYearbooks .

Country Yearo rperio d

1910a 1925b 1948-52 1969-71 1979-81 1988

Africa 1 0 0 0 AmericaN 1 0 0 0 AmericaS 4 4 4 4

Asia 287 171

Bangladesh 7 3 1 China 123 53F India 190F 156 132 90F Japan 4 1 0 0 KoreaN 10F 7 8 15F KoreaS 10 5 1 IF Pakistan 16 10 10 8F Syria 4 1 0 0 Turkey 12 8 9 4F

Europe 275 86 59 63

Austria 23 0 0 0 0 Bulgaria 3 4 21 10 5 1 Czechoslovakia 12 5 2 1 0 France 14 5 5 0 3 IF GermanyE . 4 2 0 0 GermanyW 2 0 0 0 Germany 0 3 6 2 0 0 Hungary 63 14 23 12 7 7F Italy 79 112 58 1 0 0 Poland , 43 14 16 3 3 Romania 6 36 64 26 35 50F Spain 9 7 6 0 0 0 Yugoslavia 15 70 17 4 1

USSR 653 858 558 202 140 100F a:Marquart ,1919 .b :Heuser ,1927 .F :FA Oestimate . 2.2Varietie so fhem p

Mosthem pgrowin gcountrie sgre won eo rmor evarietie swhic hi ngenera l wereselection s from indigenousvarieties .I nEurop e thetw omai ntype s ofhem puse d tob eRussia nhem pan d Italianhem p (Heuser,1927) . Russianhem preache d Europeb ya Norther nroute ,throug hRussia .Italia n hempreache d Europe throughTurke yan dth eMediterranea nregion .Russia n hempha sa goo dearl yvigou r (rapidgrowt h inspring) , isearl ymaturin g andshor t (1.5t o1. 8 m).Th eplan t isstrongl ybranche d andha sa hig h seedyield . Italianhem pha sa poo rgrowt h inspring ,i ti slat ean d tall (3.5m) .Italia nhem pdoe sno tbranc hmuch ,fibr eyiel dan dqualit y arehigh ,see dyiel d ispoo r (Marquart,1919 ;Heuser , 1927). Havellandischer hemp,a nearl yGerma nvariety ,i sbase do nRussia n Material.Kuhnows ehemp ,a lat eGerma nvariety ,i sbase do nItalia nhem p (Heuser, 1927). The so-called Fleischmanno rKompol them pfro mHungar y isbase d onItalia nmateria l (Hoffmann,1957) . Currentlygoo dqualit y seedo f severalmonoeciou s Frenchan ddioeciou s Hungarian (deMeije re tal. , 1990)varietie sca nb eobtaine d commercially.Whe ngrow ni nth eNetherland s theFrenc hvarietie sflowe r inth efirs thal fo fAugust ,th eHungaria nvarietie sflowe r inth e secondhal fo fAugust .Bot hFrenc han dHungaria nvarietie sar e susceptible to Botrytis cinerea and Sclerotinia sclerotiorum. Whether varietiesar eavailabl e frombreedin gand/o r seedproductio nprogramme s inothe rcountrie s isno tknown .

2.3 Sexexpressio no fhem p

Hempi sa dioeciou splant ,monoeciou s individualshoweve rd ooccur . Monoeciousvarietie shav ebee nobtaine d throughbreeding . Themorpholog yo fth einflorescenc e ofhem pma yb eeithe rfeminin : leafy,stocky ,n obranches ,o rmasculin :fe wleaves ,strongl ybranched . Eacho fthes etw otype sma ypresen tonl yfemal eflowers ,onl ymal e flowerso rflower so fbot hsexe si ndifferen tproportions .Hoffman n (1957)present sdenomination s foreac ho fth esi xcombinations .Plant s bearing bothmal ean dfemal e flowersar egrade d intoon eo ffiv eclasse s depending onth eproportio no fmal eflowers . Maleplant sdi eshortl yafte ranthesis .Femal e plantsliv e 2t o4 week s longertha nmal eplants ,unti l thesee d isripe .I na dioeciou scro pth e numbero ffemal eplant s is1 0t o5 0% highe rtha nth enumbe ro fmal e plants (Hoffmann,1957) .

2.4Anatom y ofth este m

The stemo fmatur ehem pma yb edivide d ina vegetativ e anda reproductive section.I nth elowe rvegetativ e partleave sar eopposite , inth euppe rreproductiv e partleave sar ealternate .I nfibr ehem p vegetative internodesar e 3t o4 time slonge r thanreproductiv e internodes (Verzar-Petri etal. , 1981). The stemtissue soutsid e thevascula rcambiu m (henceforward called "bark"i nthi sreview )consis to fth eepidermis ,th ecorte xan dth e phloem. Inth ephloe mar esiev etube san dphloe m fibreso rbas tfibres . Thetissue s insideth evascula rcambiu m ("wood"i nthi sreview )ar eth e pithan dth exylem .Th exyle mconsist so fvesse lmembers ,ra yan d paratracheal parenchyma cellsan dlibrifor mfibres . -5

Hemppresent sbot hprimar yan d secondarybas tfibres .Secondar ybas t fibresar e shorter thanprimar ybas tfibre s (2versu s 20mm )an dar e morelignifie d (Hoffmann, 1957). According toHeuse r (1927)th elengt ho fwoo d fibresi salmos tconstan t at0. 5 mm,th elengt ho fprimar ybas tfibre svarie sfro m1 0t o10 0mm , onaverag e 35t o4 5mm .Bas tfibre sar e1 8t o2 5Jiwide ,bu ti nth e lowerpar to fth este mmuc hwider .Th ediamete ro fth elume ni sabou t 1/3 oftha to fth efibre .Kund u (1942)measure d thelengt ho fprimar y and secondary fibresfro mnea rth ebas eo fa plan twit hnearl ymatur e fruits.Fo rprimar yfibre saverag elengt han dwidt hwer e12. 7m man d 34.2/i .; fo rsecondar y fibresaverag elengt han dwidt hwer e 2.18m man d 16.56/*.Th elengt ho fth eprimar yfibre s increasedwit hth elengt ho f theinternod e (Kundu,1942) . According toBrederaan n(1940 )th elengt ho fprimar ybas tfibre si s largest inth emiddl eo fth estem ,decreasin g toto pan dbasis . Likewise,Bredeman n (1940)state stha tbas tfibr econtent s ishighes ti n themiddl e ofth estem .Bot hHeuse r (1927)an dArnou xe tal . (1969) found thebas tfibr econtent s toincreas efro mth ebasi st oth eto po f theplant .Arnou xe tal . (1969)conclud e thattha ta ste msectio n situatedbetwee n3 0an d4 0% o fth etota lheigh to fth este m (goingfro m baset otop )wil lfor ma goo d sampleo fth este ma si tha sth eaverag e content ofbark ,woo dan dbas tfibre . After 17year so fbreeding ,Bredeman n (1952)increase d theconten to f bastfibr ei nth este mo fa hem ppopulatio nfro m 12t o2 9% . Concomitantly thefractio no fbar ki nth edr ymatte ro fth este m increased from2 9t o4 8% (woo ddecreasin g from 71t o5 2% )an dfibr e content inth edr ymatte ro fth ebar kha dincrease d from4 5t o7 2% . Hoffmann (1957)state stha tbreedin g forhig hbas tfibr etend st ofavou r secondarybas tfibr eove rprimar ybas tfibre ,unles ssecondar ybas t fibre ismonitore ddurin gbreedin g topreven tthis . Bredemanne tal . (1961)foun dbas tfibr econtent si nth edr ymattr ro f theste mt odecreas ewit ha nincreas e inth edr yweigh to fth estem . Withinth ebas tfibr efraction ,th eproportio no fsecondar ybas tfibr e increasedwit ha nincreas e inth edr yweigh to fth estem . Horkay (1982)assesse d thehig hbas tfibr evarietie so fth eHungaria n Kompoltbreedin gprogramme .Sh efoun dlarge rratio so fsecondar yfibr e cellst oprimar yfibr ecell swit hincrease d bastfibr econtents . Bastfibr econten t inth este m increaseswit hplan tdensit y (VonLucke , 1925; Heuser,1927 ;Jakobey , 1965),probabl ya sa resul to fles s secondary thickening inth eplant sa ta hig hdensity .Othe rfactor s influencing theproportion so fbar kan dwoo d inth este mhav eno tbee n found inth eliteratur e onhemp . Inothe rspecie sth efractio no flibrifor m fibersha sbee nfoun dt o decreasewit hth eavailabilit y ofsoi lwate rt oth eplan t(Tobler , 1957).Mechanica l stimulation (e.g.shaking )ma yaffec t thedevelopmen t andgrowt ho fmechanica l tissueso fplant sa swa sshow nfo rcollenchym a byWalke r (1960). Growthregulator sma yaffec tth eproportion s inwhic h xyleman dphloe mar eforme db yth ecambium .Accordin g toBruinsm a (1983) auxinpromote sth eformatio no fxyle man dgibberelli c acidaccelerate s phloemformation .Waise le ta l (1966)howeve rfoun dgiberelli caci dt o increase theproductio no fxylem . -6

2.5Lengt han ddiamete ro fth este m

Hempvarietie sdiffe r inheight :lat evarietie sar etalle rtha nearl y varieties (Heuser,1927 ;Verzar-Petr i etal . 1981). Theheigh to fhem p plants isver y sensitive togrowin g conditions.Poo rcondition s sucha s drought,a ba d soil structure ornutrien tdeficiencie s limitplan t height (Heuser,1927 ;Dempsey , 1975). Plantdensit yals oaffecte dplan t height. Inearl ymaturing ,shor tvarietie splan theigh t increasedwit h plantdensity ; intall ,late-maturin gvarietie splan theigh tdecrease d asplan tdensit y increased (Marquart, 1919).Al lothe rauthor s (Heuser, 1927; vande rSchaaf ,196 3an dJakobey ,1965 )foun d thatplan theigh t decreasedwit hincreasin g plantdensity .Presumabl y theseauthor sdi d not investigate shortvarieties . Stemdiamete rdecrease dwit hincreasin g plantdensity .Th elengt ht o diameterrati oo fth este mincrease dwit hincreasin g plantdensit y (Heuser,1927 ;va nde rSchaaf , 1963). Thediamete ro fa hem pste m islarges ta tabou t 1/3 ofit sheight ; withina ninternod e thediamete r islarges t inth emiddl eo fth e internodean d smallesta tth enodes .Th efor mo fa sectio nthroug ha hempste mi scircula ra tth ebas eo fth eplant ,hexagona l half-wayan d square inth euppe rpar t (Heuser, 1927). According toHeuse r (1927)th ebas tfibr econten to fa hem pplan tha sa strongpositiv e correlationt oit sheight/diamete r ratio.Bredeman n (1927)howeve rdi dno tfin dthi sstron gpositiv ecorrelation .Vo nLuck e (1925)find stha tbas tfibr econten t ispositivel ycorrelate dwit hplan t heightan dnegativel ywit hste mdiameter . -7 -

3CULTURA LPRACTICE SO FTH EHEM PCRO P

3.1 Soilrequirement san dfertilizatio n

Hempgrow sbes to nloos e soils (Marquart,1919 ;Heuser , 1927). In Germanyhem pdi dparticularl ywel lo nth enitrogen-ric hlowlan dbo g ("Niederungsmoor")soil ,especiall y ina rotatio nwit hpotatoes ,a shem p preventeddeterioratio no fth esoi lstructur e (Heuser,1927) .Hem pi s particularly sensitive towate rloggin g (deMeije re tal. , 1990)an di t requiresa well-draine d soil (Friederich,1964 ;Dempsey , 1975). According toHeuse r (1927)hem pi sver ysensitiv e todrought .Dempse y (1975)state d thathem pneed sampl ewate respeciall ydurin g thefirs t6 weekso fit sgrowth .Drough tan dhig htemperature s towardsth een do f thegrowin g seasonhaste nth ematurit yan dlea dt oshor tplants .

Marquart (1919)stresse d theimportanc eo fN an dK fo rHemp .Heuse r (1927)an dDempse y (1975)bot hstresse d thathem prequire smuc hCa . Bredemann(1945 )an dMathie u (1980)presen tdat ao nth euptak eo f nutrients.Th enutrien t contenta tflowerin g ismuc hhighe rtha na tsee d maturity (Table2) .

Table 2.Nutrient s inhem pcrop s (kg/ha). Acro pyieldin g 6.6 tonneso f stera+leavesdr ymatte ran d0. 7 tonneso fsee ddr ymatte r (Bredemann, 1945).A cro pyieldin g 10tonne so fstem+leave sdr ymatte r (Mathieu, 1980).

Nutrient Highestnutrien t Nutrientsharveste d contenti n shoot+ roo t Bredemann Mathieu kg/ha (Bredemann) kg/ha kg/tonned m kg/tonne dm

N 211 111 15.2 9.0 K2O 241 124 17.0 15.0 CaO 259 108 14.8 15.0 MgO 43 22 3.0 1.5 p2o5 62 36 4.9 2.5

Rivoiraan dMarra s (1975)foun d thehighes t stemyiel da t15 0k go fN/h a aftera dr ysprin gan da t22 5k go fN/h aafte ra we tspring . Bastfibr eyield showeve rwer ehighes ta t 75k go fN/h a inbot hyears . Plantdensit ya tharves tdecrease dwit hincrease d levelso fN fertilization. ForFrance ,a soi lp Ho fa tleas t 5wa srecommende d (Anonymous,1982) .A yield of1 0tonnes/h ao fste mdr ymatte rwoul d require 1000t o150 0 kg/hao flime ,8 0t o12 0kg/h ao fN ,8 0t o12 0kg/h ao fP 205an d 160t o 200kg/h ao fK 20. InDenmark ,Nordestgaar d (1976)obtaine dmaximu mbas tfibr eyield sa t thehighes tN rat eapplie d (140kg/ha) . Forth eNetherlands ,Friederic h (1964)recommende d 120k go fN/ha ,8 0k g ofP20 5/haan d16 0t o18 0k go fK 20/ha. Insi xtrial s inth eNetherland sAukem aan dFriederic h (1957)compare d 100,15 0an d 200k go fN/ha .Bot hste man dbas tfibr eyiel dwer ehighes t at20 0kg/ha .Bas tfibr econten t inth este mhoweve rdecrease dwit h increasingN-fertilizatio n

3.2Sowin gdat ean ddept h

Thousand kernelweigh to fhem p seedrange dbetwee n9 an d2 5g (Marquart , 1919).Accordin g toHoffman n (1957)th ethousan dkerne lweigh twa s between 18an d 22g ;fo rmonoeciou svarietie s itwa sabou t 16g . ForGermany ,Heuse r (1927)advise d toso wi nth esecon dhal fo fApri lo r inth efirs thal fo fMay . Inhi strials ,earlie r sowingreduce dyields , 'probablydu et oa lowe rplan tdensit ycause d byfros tdamage .Provide d thatth esoi lmoistur e contentwa ssufficient ,th ecro pemerge d in3 t o 5days . For Italy,Rivoir aan dMarra s (1975)foun d sowing inearl yApri l tob e better thansowin g inearl yMay .Th eforme r sowingdat eextende dth e durationo fth ebiologica l cyclewit h1 0t o1 5days . Tschaneff (1959)advise d sowing inearl yMarc hfo rBulgaria . Inth eNetherlands ,hem pshoul db esow naroun d the15t ho fApri l according toFriederic h (1964). Earlier sowingma ycaus emor ewee d problems.

Onno ncrust-formin g soilshem pshoul db esow na ta dept ho f4 t o5 c m (Heuser,1927) . Spaldonan dLasko s (1964)advise da sowin gdept ho fa t least4 cm ,u pt o6 c mi ndr yyear san dfo rlat esowing .

3.3Sowin grate ,plan tdensit yan dro wwidt h

Heuser (1927)investigate d theeffec to ffiv e sowingrate srangin gfro m 42t o17 4kg/h ao nhem pyield .Th eyiel do fabove-groun d plantdr y matterwa smaxima la t8 2kg/ha .Ste myiel dhoweve rwa smaxima la tth e highest seedrate ,a sbot hth efractio no fleave san dsee d inth eabove - groundplan tdr ymatte rwer enegativel ycorrelate dwit hsee drate .Bas t fibrefractio ni nth este m increasedwit hsee drate .Unfortunatel yn o datao nplan tdensit ywer egive nfo rthi sexperiment .Heuse rdoe sstat e however,tha t8 0k go fseed/h aresulte d ina plan tdensit ya tharves to f about260/m ^o na minera l soilan dabou t 160/m^o na moo r soil.Thi s difference isattribute d toth emor erapi dgrowt ho nth enitrogen-ric h moorsoi lwhic h enhances inter-plantcompetition . Areductio ni nth enumbe ro fplant sfailin g toreac hmaturit yca nb e obtainedb ypromotin ghomogeneou scondition s forgerminatio nan dearl y growth.Marquar t (1919),sowin gth esam eamoun to fsee da tro wwidth s rangingfro m8 t o3 0cm ,foun dplan tdensitie sa tharves tt oincreas e withdecreasin g rowwidth . Inthes eexperiment sa reductio no fro wwidt h probablyle dt oa mor ehomogeneou sdistributio no fplants ,thu sreducin g inter-plant competition.Broadcas t sowingo fth esam eamoun to fsee dle d toa ver ylo wplan tdensity ,probabl ya sa resul to fclusterin go f plantso ro flarg edifference s ingerminatin g conditionsan dmomen to f emergence. InItaly ,Rivoir aan dMarra s (1975)use d 60k go fseed/h a insevera l experiments.Plan tdensitie sa tharves tvarie d from4 0t oove r20 0 plants/m^.On eo fth efactor saffectin gplan tdensit ywa snitroge n fertilization.Particularl y intrial s inwhic hnitroge ncause da larg e 9- yield increase,plan tdensitie sa tharves tdecrease dwit ha nincreas ei n nitrogenapplied .Castellin i (1962)gav ea commo nsee drat efo r Italyo f 40t o5 0kg/ha ,thi syielde dabou t 200plants/m ^a temergence ,bu ta t harvestonl y 120t o15 0plants/m ^wer epresent . InFrance ,th eus eo f5 0t o7 0k go fseed/ha ,i srecommende d (Anonymous, 1982), resulting inabou t 250plant/m ^ (probably shortlyafte r emergence). InHungary ,Jakobe y (1965)compare d 11initia l plantdensitie srangin g from 1.6 to40 0plants/m ^i nthre eyears .Stra wweigh twa smaximu m between20 0an d40 0plants/r a ,bas tfibr eyiel dan dbas tfibr econten t weremaximu m at40 0plants/m ^i n2 ou to f 3years . InHungar y 80t o9 0 kgo fseed/h a isrecommended ,yieldin ga ninitia lplan tdensit yo fove r 300plants/m^ .A tharves tplan tdensit ywil lb eabou t 150plants/m ^(d e Meijere tal. , 1990). InDenmark ,Nordestgaar d (1976)use d 100k go fseed/ha .Th enumbe ro f plants/m^decrease d from42 0a temergenc e to36 0a tharvest . Danell (1965), comparing seedrate so f40 ,60 ,8 0an d 100kg/h ai n Swedenfoun d thehighes tyield so fste man dbas tfibr ewhe nrespectivel y 100an d8 0k go fseed/h awer eapplied . Inth eNetherlands ,Aukem aan dFriederic h (1957)teste d seedrate sfro m 60t o13 0kg/h a infou rtrials .The yfoun dn oconsisten t effectso nth e yieldo fbas tfibr eo rabove-groun d drymatter .Va nde rSchaa f (1963) compared 50,7 0an d9 0k go fseed/h a inon etrial .Yiel do fbas tfibr e washighes ta t 50k gseed/ha .D uBoi s (1984)conducte d 3trial so n different soiltype sdurin gon eyear ,comparin gsee drate so f20 ,40 ,6 0 and8 0kg/ha .A see drat eo f2 0kg/h aresulte d in7 4plants/m ^a t harvest,o fwhic h2 1% wer ediseased ;8 0k go fseed/h aresulte d in21 4 plants/m^a tharvest ,o fwhic h3 9% wer ediseased .Th elowes tsee drat e resulted inth ehighes tste myield .

Marquart (1919)indicate d thata ro wwidt ho f2 5c mo rmor ema ycaus e weed problems,unles sth ecro pi scultivated . Heuser (1927)recommende d amos t suitable rowwidt ho f2 0cm .A ro w widtho fu pt o3 0c mcoul db euse dwithou t significantlyreducin gth e quantityan dqualit yo fbas tfibr eyield .Rivoir aan dMarra s (1975) adviseda ro wwidt ho f1 5t o1 8cm ,whil ea ro wwidt ho f 15t o1 7c mwa s recommended inFranc e (Anonymous 1982). Inth eNetherlands ,Aukem aan dFriederic h (1957)foun d botha highe r stemdr ymatte ryiel dan da highe rbas tfibr econten ta t1 0c mro wwidt h compared to2 0c mro wwidth .

3.4Weed s

Underfavourabl e circumstanceshem pwil lgro wrapidl yan dsuffocat ewee d plants (Heuser, 1927). Sowna t4 t o5 c mdepth ,lightl yharrowin ga dr ysoi l shortlyafte r emergencekille dweed swithou tharmin g thecro p (Heuser,1927) . Lotze tal . (1991)foun dtha them preduce d growthan dreproductio no f thewee d Cyperus esculentus toa muc hlarge rexten ttha nothe rcrop s sucha smaiz eo rwinte rbarle y 10

3.5Disease san dpest s

Marquart (1919)state d thatdisease san dpest shav ebee nrar ei nGerman y sofar . Heuser (1927)mentione d thatdisease san dpest sar ever yrar e inhemp . Hoffmann (1957)mentioned : Alternaria sp., Rhizoctonia solani Khn., Pythium debaryanum (=P. ultimum Trow.), Botrytis cinerea and Sphaerella cannabis (= Mycosphaerella cannabis (Wint.)Roeder) . Of these, the latter twoals odamag e fullygrow nplants . Sclerotinia sclerotiorum causes similardamage .A sbot h B. cinerea and S. sclerotiorum damageth e bastfibre ,an d B. cinerea inparticula r occursmor ean dmor e frequently,Hoffman nrecommende d totak e thesetw odisease s intoaccoun t inbreedin gprogrammes . Hoffmannfurthe rmentione d thestrongl y increased incidenceo fa hem p anthracnosiswhic hreduce dqualit yan dyiel do fhemp .Thi santhracnosi s wascause db y Colletotrichum atramentarium (Berk& Broome )Taubenhau s (= C. coccodes (Wallr.Hughes) . Hoffmannmentione d twoinsects : Psyloides attenuata, thehem pfle a beetlean d Pirausta nubilalis, theEuropea ncor nborer ,whic hma ycaus e damage inhemp . Copperdefficienc yma ycaus ea diseas e called "gummi"-hemp:th exyle mi n theplant sha slos t itsrigidity ,causin g theplant s tolodg eseverely . Friederich (1964)mentione d thata larg ero wwidt ho rth eus eo fto o muchsee dwil lcaus ea larg enumbe ro fsmal lbackwar d plantswhic hwil l lodgean db einfeste d by B. cinerea, forminga sourc eo finfestation . According toFriederich , B. cinerea wasth ewors tdiseas e inhem pi nth e Netherlands. Meijeran dd eMeije r (1990)reporte d severeyiel dlosse s inhem pgrow n inth eNetherland s causedb y B. cinerea and S. sclerotiorum. Infiel d trialsa frequen t (at10 -o r14-da yintervals )applicatio no f fungicideskep tth ecro pdiseas efree . NBA nextensiv e reviewo fth eliteratur e concerningdisease so fhem pi s beingprepare d byA .Termorshuize n (IPO).

3.6Harves ttimin g

According tobot hMarquar t (1919)an dHeuse r (1927)lodgin g isver yrar e inhemp ,s oi tshoul dno tcomplicat eharvesting .Marquar t (1919)advise d tomo whem pfo rfibr ewhe nth este man dth elowe rleave so fth efemal e plantsbegi nt oyellow ,whil eth elowe rleave so fth emal eplant sar e alreadyfalling .Heuse r (1927)doe sno tgiv ea clea rdefinitio no fth e optimumharves t stage.H ementione d thatafte rflowerin gfemal eplant s continued toincreas e indiamete r (+7 t o3 4% )an d inbas tfibr e content (secondary fibre).Lignificatio no fbas tfibre soccure ddurin g andafte rripenin g ofth e seed.Hoffman n (1957)mentione d thatharves t forfibr egenerall yoccur sa tth een do ffemal eflowering . According toSpaldo nan dLasko s (1964)i nCzechoslovaki a thehighes t yieldo flon gbas tfibr ei sb eobtaine dwhe nth ecro pi sharveste dwhe n 75t o10 0% o fth emal eplant sar e sheddingpolle ni nhal fo rmor eo f theirinflorescences . Insouther nHongari amal eflowerin gbegin s inearl yJuly ,technica l maturity (=harves tfo rfibre )i sreache d inth ebeginnin go fAugus t (Jakobey, 1965). 11

InItal yflowerin g startsa tth ebeginnin g ofJul yan d thehighes tbas t fibreyiel d isattaine ddurin g thelas tdecad e ofJul yo ri nth e beginningo fAugust .Hem pfo rfibr e isharveste ddurin gful lflowering . Thesee di srip eon emont hlate ran dth ecro pca nb eharveste d forbot h seedan dfibr e (Rivoiraan dMarras ,1975) . InFrance ,harves tfo rfibr etake splac eb ymowin g thecro pa tth een d offlowering .Th een do fflowerin goccur saroun dAugus t 20o rlater , depending onth evariety .Th ecro pthe nlie so na 5 cm-lon g stubblean d reachesa humidit y of1 4t o1 8% i n4 t o8 days .A cro pmow nwit ha mowercrushe rwil ldr ymor erapidly .Whe nth ecro pi ssufficientl ydr y iti sbaled .Harves t forbot hfibr ean dsee doccur swhe nth esee di s ripe,thi swil lb ebetwee nSeptembe r 5an d30 ,dependin go nth evariet y (Anonymous, 1982). Inon etria l inth eNetherlands ,va nde rSchaa f (1963)harveste d Fibrimon2 1o nAugus t 10an d2 4an do nSeptembe r7 . Highest steman dbas tfibr eyield swer eobtaine d onSeptembe r7 .

3.7Yiel dcomponent s andyiel dleve l

Marquart (1919)analyse dwhol eplan tdr ymatte ro fsevera l indigenous varietieso fhemp .A cro po f Italianhem pconsistin g ofplant swit ha meanheigh to f29 8c myielde d 12tonne so fwhol eplan tdr ymatter/ha . Thecro pconsiste d for 10% o froot ,7 2% o fstems ,1 4% o fleave san d4 %o fseed .Simila rdat aar egive nfo rothe rvarieties . Ina see drat e trial,4 2k go fsee dyielde d plantswit ha mea nheigh to f 185c man da nabove-groun d drymatte ryiel do f7. 8 tonnes/ha.Th ecro p consisted for6 3% o fstems ,2 2% o fleave san d1 5% o fseed . Inth e sametria l17 4k go fseed/h ayielde dplant swhic hwer e 176c mhigh , yielding 7.7 tonnes/haabove-groun ddr ymatte ran dconsistin g for 72% ofstems ,1 5% o fleave san d 13% o fsee d (Heuser,1927) . OnJul y2 5a hem pcro pi nwhic hfemal eplant s started flowering consisted for4 0% o fleaves+inflorescense s andfo r6 0% o fstems .O n September9 whe nfemal eplant sstarte dt omature ,th ecro pconsiste dfo r 37% o fleaves+inflorescense s andfo r6 3% o fstems ;whe nth ecro pwa s readyt ob emowed ,o nth e 251-"o fSeptember ,i tconsiste d for2 3% o f leaves+inflorescences andfo r 77% o fstem s (Bredemann, 1945).

According toMarquar t (1919)yield so fdr yhem pste mvarie d from 3t o1 0 tonneso fdr ymatter/h a inGermany . InItal ya hem pcro pyielde d11. 5 tonneso fste mdr ymatte rwhe nharveste da tth een do fJul y (Rivoiraan d Marras, 1975).Average d over1 1trial sconducte dfro m 1959t o196 3i n Sweden,Fibrimo n2 1yielde d 8.7 tonneso fste mdr ymatter/h a(Danell , 1965).Average d over8 trial sconducte d from 1965t o196 9i nDenmark , Fibrimon2 1yielde d 8.9 tonnes/hao fste mdr ymatte r (Nordestgaard, 1976). Inth eNetherland sAukem aan dFriederic h (1957)obtaine d 11tonnes/h ao f above-grounddr ymatte ro nsand ypea tsoils .O ncla ysoil sabove-groun d drymatte ryield srange dfro m9 t o1 4tonne sdr ymatter/ha .Friederic h (1964)obtaine d 10tonne so fstraw/h awit hFibrimo n56 . Fortrial sconducte d from 1987t o198 9Meije ran dd eMeije r (1990) reportedyield srangin gfro m8 t o1 3tonne so fste mdr ymatter/ha . -1 2

4Discussio nan dconclusion s

Theeconomica l importanceo ffibr ehem pha sbee ndiminishin gsteadil y inth ecours e ofthi scentury .Withi nEurope ,hem pbarel y survivesa sa cropi nFranc ean dHungar ywher ea fe wthousan dhectare sar egrown .I n Romaniaan dth eUSS Rhem p ismor e important (50,000an d 100,000hectare s respectively). Thecurrentl yavailabl eFrenc han dHungaria nvarietie sd ono tperfor m satisfactorilyi nth eNetherlands ,a sthe yar eto oearl yan dto o susceptible todiseases .Hem pgrow ni nTh eNetherland s forpape rpul p doesno tnecessaril yhav et ob eharveste dearl yo rt oproduc eseed . Latervarietie sma yyiel dmor estem ,a slea fare aduratio nwil lb e longeran dn oassimilate s arediverte d toth einflorescenses .Th e potential oflat evarietie sma yb e investigated infiel dtrial si nwhic h thevarietie scurrentl yuse dar eprevente d fromflowerin gb ymean so fa longda ytreatment .Lat ediseas eresistan tvarietie sma yb eobtaine d throughbreeding . Theanatom yo fth este mo fi sth eke yt oa definitio no fqualit yo f hemp stemmateria la sa sourc eo ffibre .Hem pstem scontai nthre etype s offibre :primar ybas tfibre swhic har elon gan dlo wi nlignin , libriformfibre swhic har eshor tan dhig hi nligni nan dsecondar ybas t fibreswhic har eo f intermediatelengt han dligni ncontent .Variabilit y offibr echaracteristic swithi neac ho fth ethre etype so ffibr edoe s not seemt ob elarg erelativ e toth edifference s infibr e characteristicsexistin gbetwee ntype so ffibre .Qualit yo fhem pste m thereforewil ldepen dmainl yon : a)th esiz eo fth efibr efractio ni nth edr ymatte ro fth este m b)th eproportio no feac htyp eo ffibr ei nth etota lfibr efractio n Atth ecro pleve lgenotyp ean dplan tdensit y seemt ob eth emai nfactor s determiningth esiz eo fth efibr efractio nan dth eproportio no feac ho f thethre etype so ffibr ei nth estem .Literatur eresult so nothe r factorsdeterminin g theproportion s ofth ethre etype so ffibr e (primary bastfibre ,secondar ybas tfibr ean dlibrifor mfibre )i nth este mar e scarce.A bette runderstandin g offactor sgovernin gth einitiatio no f fibrecell si nth eape xan d inth evascula rcambiu ma swel la so f factorsdeterminin g thedistributio no fassimilate s tobas tan d libriform fibres seemsindispensable .Thi styp eo fknowledg ema yb e obtained throughbot hfiel dexperiment s (plantdensit ytrials )an d experiments ina controlle d environment investigatingth eeffect so f factorssuc ha s :temperature ,ligh t (quantityan dquality) ,mechanica l stimulationan dplan tgrowt hregulators . Literaturedat ao nfertilizatio no fhem par eno tsufficien tt o formulatea fertilizatio nadvic ewhic hwoul d taketh esoi lfertilit y statusan dothe rcrop si nth erotatio nint oaccount .Fo rth etim ebein g itseem sbes tt ofertiliz ehem paccordin g toth euptak eo fminerals . Considering thedat acollecte db yBredeman nan dMathieu ,nutrient s harvestedpe rtonn eo fabove-groun d drymatte rca nb eestimate d at:1 5 kgo fN ,5 k go fP 205,1 7k go fK 20, 3k go fMg Oan d1 5k go fCaO . Fertilizationtrial smigh tallo wa mor eaccurat efertilizatio nstrategy , thistyp eo fresearc hhoweve rdoe sno tsee mt ob ea priority . Sowingdate srecommende d inth eliteratur evary .Optimu m sowingdat e willdepen dmuc ho nth especifi c springwheathe rcondition s ineac h country.Yield sobtaine d sofa ri nTh eNetherland srang efro m8 t o1 3 tonneso fste mdr ymatter/ha .Thes eresult swer eobtaine dwit hcrop s 13 sowni nth esecon do rthir ddecad eo fapril .A shem pshow sgoo dgrowt h atlo wtemperatures ,earlie r sowingmigh t result inearlie rcro p establishment andhighe ryields .Sowin gdat etrial sshoul db econducte d inth eresearc ho nagronom y ofhem pa sthe ywil l reveal thepotentia l andhasard so fearlie rsowing . Theliteratur e has showna hig hplan tdensit y tob edesirable . Althoughth eeffec to fplan tdensit y onwhol eplan tdr ymatte ryiel d generallywa s insignificant,a hig hplan tdensit ydecrease d thefractio n ofleave san dinflorescence s inth eplant ,thu sincreasin g theste m fraction.Furthermore ,a hig hplan tdensit yresulte d ina highe r fractiono fth emor evaluabl ebas tfibr e inth edr ymatte ro fth estem , thusimprovin g thequalit yo fste mdr ymatter .Literatur edat afro m Germany, Italy,Hungar yan dFranc eal lindicat e thatplan tdensit y shortlyafte remergenc egenerall ywa sa tleas ttwic ea shig ha splan t densitya tharvest .Dat aobtaine d inTh eNetherland s showeve nmor e severe selfthinning .Th eplant swhic hdi edurin g thegrowin g seasonno t onlyrepresen ta los so fdr ymatter ,bu tma yals ohaste nth eoccurenc e offunga ldisease s inth ecrop . Ina hem pcrop ,th eindividual swhic hdi edurin g thegrowin gseaso n areth esmal l ones.An ymeasur e reducingvariabilit y inplan tsiz ewil l thereforeprobabl ycontribut e toa reduce dmortality .A mor ehomogeneou s plantsiz ema yb eobtaine d eitherthroug hbreedin go rb yagronomi c measures.Bot happroache s seemwort hpursuing .Apar tfro mreducin g mortality,les svariabilit y inplan tsiz ewoul dprobabl y bebeneficia l aswel ldurin gharvestin gan dprocessin g (betterseparatio no fleave s andinflorescence s fromste mmaterial) .T owhic hexten ta reduce d variability inplan t sizewil l reducemortalit y (selfthinning )ma yb e investigated infiel dtrial sb ycreatin ghem pcrop sdifferin g inplan t sizevariabilit y throughhan d thinning,th eus eo fprecisio nsowin g versusconventiona l sowingan db yvaryin g inter-plantdistance sthroug h avaryin gro wwidth . Weedcontro ldoe sno tsee mt ob ea proble m inhemp .Herbicide sar eno t needed,provide d thecro pha sa hig hplan tdensity .Researc hi nthi s field thereforedoe sno tsee mt ob ea priority . Diseaseso rpest swer eno ta larg eproble m inhem paccordin g toth e literature.I ngenera l thisma yb edu et oth emor econtinenta l climate ofth ecountrie s inwhic hhem pwa san di sbein ggrown . B. cinerea and S. sclerotiorum areles so fa proble m ina dr ysummer .Furthermore ,i nth e Netherlands croprotation sar eshorte rtha ni nmos them pgrowin g countries. Ingenera ldiseas eproblem sar emor efrequen t inshorte rcro p rotations.Finally ,statement s inth eliteratur eo nth elac ko fdisease s inhem pma yb eth eresul to fa lac ko fthoroug hinvestigation s intoth e statuso fdisease s inhemp .Funga ldisease sar ea nimportan t problemi n hempi nth eNetherlands .Hopefull ymor edisease-resisten t varietiesca n bebre dt osolv ethi sproblem .A tth eagronomica l levelth eeffec to f applyinga fungicid e onceo rtwic ewil lb einvestigated . Theplan tdevelopmen t stage inwhic hfibr ehem pi sharveste dvarie s fromon ecountr yt oanother ,i tlie sbetwee nflowerin gan dsee d maturity.Fibr eyiel dcontinue st oincreas eafte rflowering .Whe n varietiesbecom eavailabl ewhic hflowe rver ylat eo rno ta tall ,th e development stagea twhic hth ecro pi sharveste dwil lb ebefor eo ra t flowering.Therefore ,a nextensiv e investigation intoth eoptimu m harveststag eo ffibr ehem pi nth eNetherland sdoe sno tsee ma priorit y atthi smoment . 14

Yieldsobtaine d sofa r infiel dexperiment s inth eNetherland srang e from 8t o1 3tonne so fste mdr ymatter/ha .Yield sobtaine d inothe r Europeancountrie sar e somewhatless .Perspectiv e forincreasin gyiel d level seemspresent .Measure s thatma ycontribut e toincrease dste m yieldsare :earlie r sowing,lat evarietie san dles svariabilit y inplan t sizeresultin g inles ssel fthinning .

Itma yb econclude d fromth eliteratur e reviewed thatth efollowin g experimentsar emos tlikel yt ocontribut e toa nanswe rt oth equestion : Howmuc han dwha tkin do ffibr eca nhem pyiel d inth eNetherlands ?

Fieldexperiments : * Sowingdat ean dyiel dan dqualit yo fhem p * Plantdensit yan dyiel dan dqualit yo fhem p * Thepotentia l ofa non-flowerin g hempcro p * Inter-plantvariabilit y andsel fthinnin g * Reductiono fdamag eb y B. cinerea and S. sclerotiorum using fungicides

Greenhouse orgrowt hroo mexperiments : * Plantgrowt hregulator san dqualit yo fhem p * Temperature andligh t intensityan dqualit yo fhem p * Levelo fred/far-re dligh tan dqualit yo fhem p

Acknowledgement

Theautho rwoul dlik et othan kA.J .Haverkort ,P.W.M ,va nde nBrink ,M . tenCate ,W .Meije ran dA .Termorshuize nfo rthei rconstructiv e comments onth emanuscript . 15

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