1996.Methane Emissions From Rice Cultivation Flooded Rice Fields

7/31/2019 1996.Methane Emissions From Rice Cultivation Flooded Rice Fields

1/23

4 A G R I C U L T U R E

R e v i s e d 1 9 9 6 I P C C G u i d e l i n e s f o r N a t i o n a l G r e e n h o u s e G a s I n v e n t o r i e s : R e f e r e n c e M a n u a l 4 . 5 3

4 .3 Met hane Emi ssions f rom Rice C u l t ivat ion :F looded Rice F i e lds

4 . 3 . 1 O v e r v i e w

A nae r ob i c dec om pos i t i on o f o r gan i c m a t e r i a l i n f l ooded r i c e f i e l ds p r oduc es m e t hane(C H 4 ) , w h i c h esc apes t o t he a t m o sphe r e p r i m a r i ly by d i f fus iv e t r anspo r t t h r ough t he r i c ep lan ts dur ing the gro w ing season. U p land r i ce f ie lds , w h ich are no t f l oo ded and ther e for edo no t p r o duc e s ign if ic an t quan t it i e s o f C H 4 , a c c oun t f o r app r ox i m a t e l y 10 pe r c en t o ft he g loba l r i c e p r od uc t i on and abou t 15 pe r c en t o f t he g loba l r i c e ar ea unde r c u l t i va t ion .The remain ing area i s g rown fo r wet land r i ce , cons is t ing o f i r r i ga ted , ra in fed , anddeepw ater r i ce . T he globa l wet land r i ce area harves ted annua l ly in the ear l y 1980 s w asabout 123.2 m i l l i on hec tares ( to ta l harves ted area inc lud ing up land r i ce i s 144 Mha) , over90 pe r c en t o f w h i c h w as i n A s i a ( N eue e t a l., 1990 ) .1 4

O f t he w i de v ar i e t y o f s ou r c es o f at m os phe r i c C H 4 , r i ce paddy f ie lds a re cons idered oneo f t he m o s t im po r t an t . The I n t e r gov e r nm en t a l Panel on C l im a t e C hange ( IPC C , 1996 )es t imated the g loba l em iss ion ra te f rom paddy f ie lds a t 60 Tg/y r , w i th a range o f 20 to100 Tg / y r . Th i s is abou t 5 - 20 pe r c en t o f t he t o t al em i ss ion f r om al l an t h r opo gen i csour ces . T h is f i gur e i s m a in ly based on f ie ld measur em ents o f C H 4 f l u x es f r om paddyf ie lds in the U ni t ed States, Spain, I ta ly, C hina, India, A ustr al ia, Japan and T hai land .

The m eas u r em en t s a t v a r i ous l oc a t i ons o f t he w o r l d s how t ha t t he r e a r e l a r ge t em po r a lv a r i a t i ons o f C H 4 f l u x es and t ha t t he f l u x d i f f e r s m a r k ed l y w i t h s o i l t y pe and t ex t u r e ,app l ica t ion o f o r gan ic m at te r and m iner a l fe r t i l ise r (N eue and Sass , 1994) . T he w ide

var ia t ions in CH 4 f l uxes a lso ind ica te tha t the f l ux i s c r i t i ca l l y dependent upon severa lfactors including c l imate, character is t ics of soi ls and paddy, and agr icul tural pract ices,par t i cu la r l y w ater reg ime. T he par ameter s tha t af fec t met hane em iss ion s vary w ide lybo th spat ia ll y and tem po ra l l y . M u l t i p le year da ta se ts near the same loca t ion and und ersimi lar condi t ions can lead to substant ia l d i f ferences in seasonal methane emission levels,m ak ing i t d i f f i cu l t t o es tab l i sh a s ingle num ber as the m ethane em iss ion leve l fro m a f ie ld ,le t alone a t a reg iona l o r co unt ry leve l . T hus , a t the cur r en t l eve l o f unders tand ing , arepor ted range in methane em iss ion leve ls fo r a count ry i s more rea l i s t i c than a s ing len u m b e r .

Methane production processes

The m a j o r pa t hw ay s o f C H 4 p r oduc t i on i n f l ooded s o i l s a r e t he r educ t i on o f C O 2 w i t h

H 2 , w i th fat t y ac ids o r a lcoho ls as hydr ogen do no r , and the t r ansm ethy la t ion o f ace t i c ac idor m ethano l by methane-pr od uc ing bac ter ia (T akai , 1970; Co nr ad 1989) . In paddy f ie lds,the k ine t i cs o f the reduc t ion processes are s t rong ly a f fec ted by the compos i t i on andt ex t u r e o f so i l and i t s c on t en t o f ino r gan ic el ect r on acc ep t o r s. The pe r i od be t w eenf lood ing o f the so i l and the onset o f methanogenes is can apparent l y be d i f fe ren t fo r thevar ious so i l s . H ow ever , i t i s unc lear i f so i l t ype a lso a f fec ts the r a tes o f met hanogenesisan d C H 4 emiss ion when s teady s ta te cond i t i ons have been reached (Conrad, 1989) .

1 4 The te rm "harves ted area" has a d i f fe ren t mean ing f rom "cu l t i va ted area" in tha t thef o r m e r ac coun t s f o r do ub l e and t r i p le c r opp i ng. Fo r ex am p l e , i f a c oun t r y has 10 m i l li onhec tares o f l and under r i ce cu l t i va t ion , a l l o f wh ich are doub le-c ropped ( i .e . , two c rops o fr i c e a r e g r ow n o n each hec t a r e eac h y ea r ) , t hen t h i s c oun t r y has 20 m i ll ion hec t ar es o f

r ice area harvested annual ly .


2/23

A G R I C U L T U R E

4 . 5 4 Re v i s e d 1 9 9 6 I P C C G u i d e l i n e s f o r N a t i o n a l G r e e n h o u s e G a s I n v e n t o r i e s : R e f e r e n c e M a n u a l

T h e r e d o x 1 5 p o t e n t i al i s o n e i m p o r t a nt f ac t o r f o r p r o d u c t i o n o f C H 4 in so i ls. T he Eh, o re lec t ro n ac t i v i t y , o f the so i l g radua ll y decr eases a fte r f l oo d ing . Pat r i ck ( 1981 )

dem o ns t r a t ed t hat t he r edox po t en t i al o f a so i l m us t be bel ow app r ox i m a t e ly - 150 m V i no r d e r t o h av e C H 4 p r o duc t i on . Y am ane and Sat o ( 1964 ) al so s how ed t ha t t he ev o l u t i ono f C H 4 f r om f loo ded paddy so i l s d i d no t c om m enc e un t i l t he Eh f e ll be low - 150 m V .

C arbo n subs t r a te and nu t r ien t avai lab i l it y ar e also impo r tan t fac to rs . A pp l i cat io n o f r i ces t raw to paddy f ie lds s ign i f i can t l y inc reases the CH 4 em i s s i on r a t e c om pa r ed w i t happ li c at i on o f c om po s t p r epa r ed w i t h r i c e st r aw o r c hem i c al fe r t i l i se r .

So i l t em pe r a t u r e i s k no w n t o be an i m po r t an t f ac t o r i n a ff ect i ng t he ac t iv i t y o f s o i l m i c r o -o r gan is m s. Th i s is t o a c e r t a in ex t en t r e l at ed t o t he s o i l m o i s t u r e c o n t en t bec ause bo t ht he hea t c apac i t y and t he hea t c onduc t i v i t y a r e l ow e r f o r a d r y s o i l t han f o r a w e t s o i l .Yamane and Sato (1961) have a l ready found tha t CH 4 f o r m a t i on r eac hed a m ax i m um a t3 5

oC in w ater lo gged al luv ia l so i l s. T he ra te o f met hane fo r mat io n w as very smal l be low

20oC .

B ec aus e t he c onv e r s i on r a t e o f s ubs t r a t e t o C H 4 depends on t he t em pe r a t u r e , i t i sgene r a l l y obs e r v ed t ha t t he m om en t a r y l oc a l em i s s i on o f C H 4 f r o m t h e s o i l t o t h ea t m o sphe r e depends on t he t em pe r a t u r e . H ow ev e r , t he dependenc e o f t he s easona l lyin tegra ted em iss ions o f CH 4 on t em pe r a t u r e i s m uc h w eak e r . Th at em i s si on dependsp r i m a r i l y on t he t o t a l i npu t o f o r gan i c s ubs t r a t e : a l t hough t he t em pe r a t u r e de t e r m i nest he t i m e i t t a k es t o c onv e r t t he s ubs t r a t e t o C H 4 , tha t t ime i s genera l l y shor t comparedto a season . T hus the met ho do logy pr op osed here w i l l be based on t he season a ll yi n t eg r a t ed C H 4 emiss ion , whose tempera ture dependence can be neg lec ted in f i r s tapp r ox i m a t i on .

I t i s gener a ll y reco gn ised tha t C H 4 f o r m a t i on i s on l y e f f i c i en t i n a na r r ow pH r angea r ound neu t r a l it y ( pH f r om 6 .4 t o 7 . 8 ) . T he e ff ect o f f loo d i ng i s t o i n c r ease t he pH i n

ac id so i l , w h i le it decr eases the pH in alka line so i l . T he inc r ease o f pH in ac id so i l s ismain ly due to the reduc t ion o f ac id ic Fe 3 + t o F e 2 + wh ich s imu l taneous ly reduces the Eh.The add i t i on o f n i t ra te as chemica l fe r t i l i se r to f l ooded so i l s may suppress the produc t iono f C H 4 , because ni t r ate acts, as w el l as Fe 3 + , M n 4 + , as a te rm ina l e lec t ron acceptor in theabsence o f mo lecu la r oxygen dur ing anaerob ic resp i ra t ion , and po ises the redox po ten t ia lo f so i l s a t values such tha t the ac t i v it y o f st r i c t anaero bes is p r evented . T he add i t i o n o fsu lphate may a lso inh ib i t methane produc t ion fo r s im i la r reasons as n i t ra te .

T he r e a r e t h r ee p r oc es ses o f C H 4 r e lease in to t he atm ospher e f ro m r i ce fi e lds. D i f fus ionl os s o f C H 4 across the w ater sur face i s the leas t im po r t an t p ro cess . M ethane loss asbubb les (ebu l l it i on ) f ro m paddy so i l s i s a com mo n and s ign if i can t m echan ism, espec ial l y i fthe so i l tex tu r e is no t c layey . D ur ing land pr epara t ion and in i t i a l g ro w th o f r i ce , ebu l l i t i onis the major r e lease m echan ism. T he th i rd p r ocess i s C H 4 t r ans po r t t h r ough r i c e p l an t s ,

w h i c h has been r epo r t ed as t he m o st i m po r t an t phenom enon ( Se i le r e t a l ., 1984 ; Sc h t zet a l . , 1989b).

M a n y r e se ar c h e r s r e p o r t e d t h a t m o r e t h a n 9 0 p e r c e n t o f t o t a l C H 4 em i t t ed du r i ng t hecropp ing season i s re leased by d i f fus ive t ranspor t th rough the aerenchyma sys tem o f ther i ce p lan ts and no t by d i ffusion o r ebu l l i t i on . Em iss ion t h r ou gh r i ce p lan t , may beexpec t ed t o show grea t seasona l var ia t ion s as a func t ion o f changes in so i l cond i t i ons andv ar i a t i ons in p l an t g r ow t h .

1 5 R edox ( E h ) r e f e r s t o ox i da t i on - r educ t i on , t w o p r oc es s es t ha t t ak e p l ac es im u l taneous ly . O x ida t ion i s the loss o f an e lec t ro n by an ato m , and reduc t ion i s the gain

o f an e lec t r o n by an a t om .


3/23



Methane em iss ion ra tes a re a lso a func t ion o f the par t ia l p ressure o f CH 4 in th e soi l . Par to f t h e C H 4 p r o duc ed i n t he so i l i s c ons um ed i n t he o x i d i sed r h i z os phe r e o f r i c e r oo t s o r

i n t he ox i d ised so i l - fl ood w a t e r i n t e r f ac e . I t i s k no w n t ha t so i l m e t hano t r oph i c bact e r i ac a n g r o w w i t h C H 4 as the i r so le energy source , and o ther so i l bac ter ia , such asN i t r o s o m o n a s spec ies a re a lso ab le to con sume C H 4 (C on rad, 1993) . M ethane i s a lsoleached to g ro und w ater , as a smal l par t d i sso lves in water . T her e for e a red uc t io n in so i lmethane does no t necessar i l y mean tha t a l l th i s CH 4 has been em i t t ed i n t o t hea t m os phe r e .

Global emissions from rice fields

The t o t a l har v es t ed a r ea o f r i c e has inc r eased f r o m 86 M ha i n 1935 t o 144 M ha i n 1985 ,w h ich m eans an annua l average inc r ease o f 1 .05 per cen t . T he average annua l i nc reasew as 1 .23 per c en t be t w een 1959 and 1985 . H ow ev e r , i n t he l ast f ew y ear s , t he r at e o fexpans ion o f the t o t a l r i ce acreage has decr eased (M inam i , 1994) .

Tab le 4 -9 p rov ides a summary o f measured em iss ions a t a number o f spec i f i c researchsi t es a r ound t he w o r l d . I t s hou l d be no t ed t ha t m e t hane fl u x es f r om paddy r i c e fi e ldsvary substant ia l ly f ro m day to d ay, and dur ing a day (e.g., day and night) . T he datap r es en t ed he r e a r e bas ed on f r equen t m eas u r em en t s w h i c h c ap t u r e t he d i u r na lvar iat io ns , and var iat io ns over t he gro w ing season. Based on area and pro duc t ions ta t i s t i cs , w i th average em iss ion va lues , a number o f researchers have es t imated g loba lem iss ions f rom r i ce .


4/23



TABLE 4-9REPRESENTATIVE METHANE EMISSIONS FROM RICE PADDY FIELDS IN VARIOUS LOCATIONS OF THE W ORLD

C o u n t r y Lo cat io n Ran ge o f C H 4f lux

mg/m 2/ h r

Season to ta l

g/m 2

Exper imen ta l

T r e a t m e n t

Re fe rence

Australia G r iffi t h 2 .8 1 0 - N G G IC , 1 9 96

China Beijing 14 .6 - 48 .9 2 7 - 9 1 O M , W M C h en et al., 1 99 3

Beij ing 9 .4 - 26 .8 1 2 - 3 9 M F, O M , W M Y ao and C h en , 1 99 4a,

1 9 9 4 b

Beij in g 1 .9 - 4 8 .9 5 .3 - 1 00 .9 M F, O M , SO , W M Shao , 1 99 3

H an gzh o u , Z hejian g 6 .9 - 50 .6 14 - 8 2 M F, O M , SE W assm an n et al., 1 99 3a

N an j ing, Jian gsu 2 .6 - 1 4 .3 6 - 3 4 M F, O M , W M C h en et al., 1 99 3

T ao yu an , H u nan 6 .5 - 5 6 .2 1 2 - 11 5 M F, O M , SE W assm an n et al., 1 99 3b

T u zh u , Sich uan 58 .0 16 7 K hal i l e t al ., 19 91

W ux ian , Jiangsu 3 .2 - 6 .2 10 - 1 9 C U , M F, O M , SE, W M C ai e t al., 19 94

India A llahab ad , U t t ar Pr ad esh 0 .2 0 .5 N A V M it r a, 19 92

B ar r ac k p o r e , W e st

Benegal

0 .7 , 20 .2 1 .8 , 6 .3 N A V M it r a, 19 92

C u t t ack , O r issa 2 .7 -7 .2 7 -1 9 C U M it r a, 19 92

Faizab ad , U t t ar Pr ad esh 0 .8 2 N A V M it r a, 19 92G aragacha, W est

Benegal

1 1 29 N A V M it r a, 19 92

Jo r h at , A ssam 1 8 .1 4 6 N A V M it r a, 19 92

K alyan i, W est Ben gal 4 .1 1 0 .8 N A V M it r a, 19 92

K o ir apu r , W est Bengal 6 .1 19 N A V M it r a, 19 92

M ad r as, T am il N ad u 5 .8 11 N A V M it r a, 19 92

N ew D elh i 0 .0 2 -0 .21 0 .06 -0 .58 M F M it r a, 19 92

Pu r u lia, W est Ben gal 4 .2 11 N A V M it r a, 19 92

T r ivan d r um , K er ala 5 .1 9 N A V M it r a, 19 92

Indonesia T am an Bo go , Lam p un g 18 .0 - 2 7 .1 3 1 - 4 7 M F, O M N u gr o h o et al., 1 9 94 a

T am an Bo go , Lam p un g 17 .9 - 3 1 .7 3 0 - 5 0 M F, O M N u gr o h o et al., 1 9 94 b

Su k am an d i, W est Java 8 .7 - 2 0 .2 19 - 4 4 W M , C U H u sin e t al., 1 9 95

Italy V er cel l i 5 - 2 8 1 8 - 7 5 M F, O M Sch t z e t al., 19 89 a


5/23



TABLE 4-9 (CONT .)

REPRESENTATIVE METHANE EMISSIONS FROM RICE PADDY FIELDS IN VARIOUS LOCATIONS OF THE W ORLD

C o u n t r y L o cat io n Ran ge o f C H 4f lux

mg/m 2/ h r

Season to ta l

g/ m 2

Exper imen ta lT r e a t m e n t

Re fe rence

Japan K aw ach i 1 6 .3 4 5 Y agi an d M inam i, 19 90 a;

M inam i , 1994

M it o 1 .2 - 4 .1 4 - 1 3 M F, O M Y agi an d M inam i, 199 0a;M inam i , 1994

Ryugasak i 2 .8 - 1 5 .4 11 - 28 M F, O M Y agi an d M inam i, 199 0a;Minami , 1994 ,

Ryugasak i 1 .9 - 7 .9 7 - 12 W M Y agi an d M inam i, 199 0a;

M inam i , 1994

T aya 7 .0 26 Y agi and M in am i, 1 99 0a;

M inam i , 1994

T su k ub a 0 .2 - 0 .4 < 1 .1 O M Y agi an d M inam i, 199 0a;

M inam i , 1994

Korea Su w o n 0 .66 - 4 .5 5 9 - 6 0 O M , W M Sh in et al., 1 99 5

Philippines Lo s Ban o s 0 .8 - 1 8 .5 2 - 4 2 M F, O M N eu e et al., 19 94

Lo s Ban o s 3 .3 - 7 .9 7 - 1 9 SE W assm an n et al., 1 99 4

Spain Savil la 4 1 2 Seiler e t al., 19 84

Thailand A yu t t haya 3 .3 - 7 .9 13 - 2 0 C U , O M , W M Sir ir at p ir aya, 1 990

Ban g K h en 4 .3 - 2 1 .7 16 - 55 SE M in am i, 1 994 ;

Yagi e t a l . , 1994 b

C hai N at 1 .6 4 M inam i, 1 99 4Yagi e t a l . , 1994 b

C h ian g M ai 3 .7 - 5 .5 9 - 1 3 M F, O M Jer m saw at d ip o ng et al.,

1 9 9 4

C h ian g M ai 9 .0 - 9 .5 20 - 21 C U Sir ir at p ir iya et al 19 95

K h lo ng Luang 3 .8 8 M in am i, 19 94

Yagi e t a l . , 1994 b

K h o n K aen 2 3 .0 7 6 M inam i, 1 99 4 ; Y agi e t al.,

1 9 9 4 b


6/23



TABLE 4-9 (CONT.)REPRESENTATIVE METHANE EMISSIONS FROM RICE PADDY FIELDS IN VARIOUS LOCATIONS OF THE W ORLD

C o un t r y Lo cat io n Ran ge o f C H 4f lux

mg/m 2/ h r

Season to ta l

g/ m 2

Exper imen ta l

T r e a t m e n t

Re fe rence

Thailand

(con t . )

N ak o m pat ho m 9.4 -1 2 .0 2 5-3 2 SE T o m pr ayo o n et al., 1 99 1

Pat hu m t h an i 1 .9 - 4 .6 5 - 1 1 M F, O M Jer m saw at d ip o n g e t al., 1 99 4

Ph it san u lo k 6 .6 - 7 .2 1 7 - 1 8 SE K at o h e t al, 19 9 5

Ph r ae 16 .6 - 22 .2 5 1 - 6 9 SE M in am i, 1 99 4 ; Y agi e t al., 1 99 4b

Rat chabu r i 3 .2 - 42 .5 9 - 1 1 7 M F, O M Jer m saw at d ip o ng et al., 19 94

San Pa T o ng 1 0 .4 - 1 6 .1 25 - 40 SE M in am i, 19 9 4 ; Y agi e t al., 1 99 4b

Sur in 15 .0 - 2 4 .5 4 1 - 6 6 M F, O M Jer m saw at d ip o n g e t al., 1 99 4

Su r in 1 3 .3 4 1 Jer m saw at d ip o ng et al., 1 994

Sup han Bu r i 1 9 .5 - 32 .2 5 1 - 75 SE M in am i, 19 94 ; Y agi e t al., 19 94 b

USA Beau m o nt , T ex as 2 .5 - 23 .5 5 - 36 O M , SO Sass et al., 1 99 0 , 19 91 a, 19 9 1b

Beaum o nt , T ex as 0 .6 - 6 .3 1 -1 5 W M Sass et al ., 1 99 2

C r o w ley , Lo u isian a 10 .2 - 1 7 .9 2 1 - 3 7 M F L in d au et al ., 1 99 1

C r o w ley , Lo u isian a 1 2 .6 - 8 5 .0 22 - 14 9 M F, O M , SE L in d au an d Bo ll ich , 19 93

C r o w ley , Lo u isian a 27 - 9 9 6 0 - 2 2 0 M F L in d au , 1 9 94

D av is, C alifo r n ia 3 .4 - 10 .4 1 8 C icer o n e et al., 19 83 , 1 99 2

Knights Landing,

Ca l i fo rn ia

0 .5 - 1 8 .8 1 - 5 8 M F, O M C icer o n e et al., 19 9 2

Exper iment a l t r ea tment : C U - cu l t i vars, M F - fe r t i l ise rs, O M - o rgan ic mat te r s, SE - seasons (ear l y and late r i ces, o r d r y and ra iny seasons) , SO

- so i l t yp e s , W M - w a t e r m a n a ge m e n t .

N A V = n o t a vai la b le

So u r ce : M o d i f ie d f r o m K M i n am i (1 9 9 5 )

Globa l em iss ions o f CH 4 f r om r i c e padd i es r epo r t ed by s ev e r a l r es ea r c he r s a r esumm ar ised in Tab le 4 -10 . Ex t r apo la t ion o f em iss ion r a tes to a globa l sca le i s veryd i f f i cu l t , because the e f fec ts o f var ia t ions in agr i cu l tu ra l p rac t i ces , number o f c rops peryear , so i l t yp es and o ther fac to rs d iscussed above ar e uncer ta in .

T he I PC C ( I PC C , 1996 ) p r es en t ed a c and ida t e l ist o f C H 4 s ou r c es t o t he a t m os phe r e asannua l re lease ra tes . T he to ta l annua l sour ce is cons t r a ined by the obser ved ra te o fa t m o sphe r i c i n c r ease o f c onc en t r a t i ons and by t he est i m a t ed a t m os phe r i c l i fe t i m e t o be

5 3 5 T g C H 4/ yr . R ic e pad d ie s ar e li st ed as a so u r ce o f 60 4 0 T g C H 4/ yr .


7/23



TABLE 4-10

REPRESENTATIVE GLOBAL ANNU AL METHAN E EMISSIONS

FROM RICE FIELDS AS ESTIM ATED BY DIFFERENT AUT HO RS

*

Refer en ce Est im at e (T g C H 4/y r )

K o y ama (1 9 6 4 )

Ehhal t and Schmid t (1978)

C i c ero n e a n d Sh e t t e r (1 9 8 1 )

Khal i l and Rasmussen (1983)

Sei ler e t a l (1984)

B lake and Row land (1988)

C ru t z e n (1 9 8 5 )

H o lzap fe l -Pschorn and Se i ler (1986)

C i c ero n e an d O re m l an d (1 9 8 8 )

Scht z et a l . (1989a)

A s el ma n an d C ru t z e n (1 9 8 9 )

Schtz et a l . (1990)

W ang e t a l . (1990)

N eue e t a l. (1990)

B o u w ma n (1 9 9 0 )

Yagi and M inam i (1990b)I PC C (1 9 9 0 )

M i n a mi (1 9 9 4 )

Sass (1994)

Parashar et a l (1994)

I PC C (1 9 9 6 )

1 90

2 80

5 9

9 5

35-59

1 4 2 -1 9 0

1 2 0 -2 0 0

7 0 -1 7 0

6 0 -1 7 0

5 0 -1 5 0

6 0 -1 4 0

5 0 -1 5 0

6 0 -1 2 0

25-60

5 3 -1 1 4

22-732 5 -1 7 0

1 2 -1 1 3

25-54

2 0

2 0 -1 0 0

So u r ce : M o d i f ie d f r o m K . M i n a m i (1 9 9 4 )


8/23



4 .3 .2 M e th o d s F o r E s t im a t in g E m is s io n s

Em iss ion s o f meth ane fro m r i ce fi e lds can be repr esented as fo l l ow s:

EQUATION 1

Fc = EF A 1 0 -1 2

w h e r e :

Fc = e st i m at e d an n ual e m issio n o f m e t h an e fr o m a par t i cu larr i ce water reg ime and fo r a g iven organ ic amendment , i nTg pe r y ea r ;

EF = m et hane em issio n fact o r in t egr at ed o ver in t egr at edcropping season, in g/m 2;

A = ann ual har vest ed ar ea cu lt ivat ed und er c o nd it io ns d efinedabove. I t i s g iven by the cu l t i vated area t imes the num berof cropping seasons per year, i .e. , in m 2/y r .

The seasona l l y in tegra ted em iss ion fac to r i s eva lua ted f rom d i rec t f i e ld measurements o fm ethane f luxes fo r a sing le c ro p .

In p rac t i ce , i t w i l l be necessary to ca lcu late t he t o t a l annua l em issions f ro m a count ry as as um o f t he em i s si ons ov e r a num be r o f c ond i t i ons. To t a l r i c e p r o duc t i on c an be d i vi ded

in to subcategor ies based o n d i f fe ren t b io lo g ica l, chemical and phys ica l fac to r s tha t con t r o lm ethane em issions fro m r i ce f i elds . In la rge cou nt r ies, th i s may inc lude d i ffe ren tgeograph ic reg ions . T o accoun t fo r the d i f fe ren t co nd i t i o ns , F is de f ined as the sum o f Fc(see Equat ion 1) . T h is appro ach to em iss io ns es t imat ion can be repr esented as fo l l ow s:

EQUATION 2

F = i j k EFij k x 10 - 1 2

w h e r e :

i j k : a re ca tegor ies under w h ich m ethane em issions f ro m r i ce f i e lds may vary .

For instance, i m ay repr esent w ater leve ls in t he r i ce f ie lds such as fi e lds inundated fo r the

du r a t i on o f t he g r ow i ng s eas on ( f l ooded r eg i m e ) o r f i e l ds unde r w a t e r on l yi n t e r m i t t en t l y . Th i s oc c u r s e i t he r unde r m anaged ir r i ga t ion w hen w a t e r i s no t r ead i lyav a i l ab l e o r w hen r a i ns do no t m a i n t a i n f l ooded c ond i t i ons t h r oughou t t he g r ow i ngseason ( in te rm i t ten t r eg im e) as g iven in Tab le 4 -12 . j , k , may r epr esent w ater r eg imesmodi f ied by o ther fac to rs l i ke o rgan ic inpu ts , so i l tex tu res , fe r t i l i sa t ion reg imes undereac h o f t he c ond i t i ons r ep r esen t ed by t he index i , and so o n . A s m o r e f ac t o r s ar eident i f i ed , m or e categor ies need to b e inc luded. Inc lusion o f add i t i o na l paramet ers sho u ldl ead t o an im p r ov em en t o f t he est i m a t e o f t he t o t a l em i ssi ons . The s um m at ion s hou l dinclude al l cropping seasons.

The fac to rs c lear l y iden t i f i ed by f i e ld exper iments as be ing most impor tan t a re (1 ) waterreg ime w i th inorgan ic fe r t i l i se rs (except su lphate-conta in ing inorgan ic fe r t i l i se rs wh ichi nh i b i t C H 4 produc t ion) ; (2 ) o rgan ic fe r t i l i se r app l i ca t ions ; (3 ) so i l t ype , and so i l tex tu re ;

(4 ) cu l t i var ; and (5 ) agr i cu l tu r a l p r ac t i ces such as d i rec t seed ing or t ransp lan t ing . D ata


9/23



show tha t i n con t inuous ly f l ooded f ie lds , some types o f o rgan ic fe r t i l i se rs and cer ta inc u l t i v a r s l ead t o h i ghe r em i s s i ons c om pa r ed t o r i c e g r ow n w i t hou t o r gan i c am endm en t s

o r i n t e r m i t t en t o r m anaged i r r i ga t i on i n w h i c h t he f i e l ds a r e no t c on t i nuous l y i nunda t edand on ly w here ch emica l fe r t i l iser s are u sed.

A t p r esen t t he r e ar e i nsu f fi c ien t da t a t o i nc o r po r a t e m o s t o f t hes e f ac t o r s . N one t he l ess,t he es t i m a t es c an be i m p r ov ed s ubs t an t i a l l y by i nc o r po r a t i ng t he c u r r en t k now l edge onw ater reg imes, o r gan ic am endm ents and so i l t ypes e tc . For som e count r ies the e f fects o fo r gan ic fe r t i l i se r can be inc luded.

4 . 3 . 3 Su m m a r y of R e co m m e n d e d M e t h o d

Basic Method

D ata on r i ce cu l t i va t ion und er d i f fe ren t w ater m anagement t echn iques shou ld be avai lab lef r om m o st o f t he im p o r t an t r i c e- p r o duc i ng c oun t r i es. The r e f o r e , t he basi c m e t hod f o res t imat ing em iss ions f rom each count ry inc ludes es t imates based on r i ce ecosys tems( K us h ,1984 ; N eue , 1989 ) r e l at i ng t o w at e r r eg i m e ( T ab l e 4 - 12 ) , nam e l y :

Upland: Fie lds a re never f l ood ed fo r a sign i f ican t per iod o f t ime.

Lowland: Fie lds a re f l oo ded fo r a sign i f ican t per iod o f t ime.

Irrigated: W a t e r r egi m e i s f u ll y c on t r o l l ed .

Continuously flooded: Fie lds have s tand ing water th roughout

t he r i c e gr o w i ng season and m ay on l y d r y f o r ha r v est .

Intermittently flooded : Fie lds have a t l eas t one aera t io n per iod o fm o r e t han 3 d ay s du r i ng t he c r o pp i ng season .

Single aeration: Fields have a s ingle aerat ion dur ing thecro pp ing season a t any gr ow th s tage.

Multiple aeration: Fie lds have more than one aera t ionpe r i od du r i ng t he c r opp i ng season .

Rainfed: W at e r r eg im e depends so l e l y on p r ec ip i t at i on .

Flood prone: T he w at e r l e ve l m ay r i s e up t o 50 c m du r i ng t hecro pp ing season .

Drought prone: D r o ugh t pe r i ods oc c u r du r i ng ev e r y c r opp i ngseason.

Deep water rice: Fl oo dw a t e r r i ses t o m o r e t han 50 c m f o r a si gn i fi c an tpe r i od o f t i m e du r i ng t he c r opp i ng seas on .

F ie l ds i nundat ed w i t h w a t e r dep t h f r om 50 - 100 c m .

F ie l ds i nundat ed w i t h w a t e r dep t h > 100 c m .

T he d iscuss ion r e fe rs to a sing le invento ry (o r b ase) year , (e.g. , 1990 ) bu t an aver age o verth ree years a round the base year (e .g . , 1989-1991) i s recommended fo r the ac t i v i t y da ta ,i f po ssible.


10/23



Fo r t he i nv en t o r y y ea r , a num be r o f inpu t da t a ar e r equ i r ed .

A r ea o f r i c e c u l t i v a t i on by w a t e r m anagem en t r eg i m e i n s qua r e m e t r es ( m 2 ) . A s

d iscussed abo ve, tha t a rea i s m u l t i p l i ed by the num ber o f c ro ps per year . Th isinc ludes areas counted fo r each c rop .

Season a ll y in tegra ted f l ux (EF) em iss ion va lues fo r a reas o f d i f fe r en t r i ce ecosystem s( w at e r r eg im es ) w i t ho u t o r gan i c am endm en t s .

o f enhanc em en t f ac t o r s f o r o r gan ic am endm en t s.

Th e r es u lt i s m e t hane em i ss ions f o r eac h c at ego r y . The t o t a l em i ss ions f o r t he c o un t r y i sthe sum o f the ind iv idual resu l t s fo r each categor y .

Default data

In many cases , espec ia l l y a t the beg inn ing o f the process , there w i l l be impor tan t r i ce-gro w ing areas fo r w h ich spec if i c f l uxes w i l l no t be avai lab le . In such cases the r eg ion a land count ry -spec i f i c de fau l t da ta p rov ided in Tab les 4-12 and 4-13 can be used to car ryou t f ir s t o r der es t imates . T hese da ta m ay a lso be used by nat io na l exper ts fo rcom par iso n . Severa l on go ing ac t i v it i es to im pr ove com parab le m easur emen t da ta havebeen iden t i f ied . See A ppend i x f o r f u r t he r i n f o r m a t i on .

Area Statistics

Tab l e 4 - 11 c on t a ins in f o r m a t ion on ha r v est ed a r ea o f r i c e ac c o r d i ng t o s t a t i st i c s fr o m t heFA O Y ea r boo k ( U N , 1992 ) , C h i na A g r i c u lt u r a l Y ear bo ok ( 1990 ) , IR R I RI C E A l m anac( IRR I, 1994) and W or ld R ice Sta t i s t i cs ( IRR I, 1993) . A l loca t ion o f areas to ca tego r ies , e .g .,i r r i ga ted , ra in fed ( f l ood prone and low land ra in fed) and up land r i ce fo r ma in r i ce-

p r oduc i ng c oun t r i es w e r e bas ed on t he I R R I R i c e A l m anac ( I R R I , 1994 ) and f o r o t he rr i c e - p r oduc i ng c oun t r i es t hes e c a t ego r i es w e r e bas ed on I R R I ( 1990 ) , H uk e ( 1982 ) andG r is t (1986) . A c tua l per centage o f the i r r i ga ted , ra in fed , and floo d pro ne ar eas w h ich ar ec on t i nuous l y f l ooded o r hav e an ae r a t i on pe r i od g r ea t e r t han 3 day s o r m u l t i p l eaer a t i ons , a r e t o be o b t a ined f r o m t he c o un t r y s peci fi c dat a .

Seasona l ly In tegra ted f lux va lues

Tab les 4-12 and 4-13 prov ides de fau l t EF va lues fo r var ious ca tegor ies o f water reg imesand m ul t ip l i cat io n fac to r s fo r o rgan ic amendm ents . Em iss ion s f ro m up land r i ce a reassumed t o be 0 and igno red in the em iss ion ca lcu lat io ns .

For con t inuous ly f l ooded r i ce , a mode l average seasona l l y in tegra ted em iss ions fo r r i ce-

g r ow i ng c oun t r i es o f t he w o r l d w as es t i m a t ed f r om ex i s t i ng da t a ( Tab l e 4 - 13 ) t o be20 g /m 2 . T hese f lux values are repr esenta t i ve o f f l ood ed r i ce fi e lds w her e or gan icfe r t i l ise r i s no t used.

Fo r i n t e r m i t t en t l y fl ood ed r i c e , a si m p l e c o r r ec t i on i s app li ed . F lux es ar e t ak en t o be 50pe r c en t o f t he f l oo ded ( no n - o r gan i c ) v al ue o f 20 g /m 2 fo r s ing le aera t ion and 20 per cen tf o r m u l t i p l e ae r a t i on . Fo r o t he r w a t e r r egi m es new de f au l t v al ues a r e gi v en i n T ab l e 4 - 2 .For i r r i ga ted and cont inuous ly f l ooded, low land r i ce ecosys tems, the de fau l t seasona l l yin tegra ted methane em iss ion i s 20 g /m 2 (see Tab le 4 -13) fo r so i l s w i thout o rgan icam endm en t s . Fo r c onv e r s i on t o m e t hane em i s si ons f r om so i l s w i t h o r gan i cam endm en t s , a de fau lt c o r r ec t i on f act o r o f 2 ( R ange 2 - 5 ) is app l ied t o t he c o r r espond i ngr i ce ecosys tems fo r t he w i th ou t o r gan ic am endm ent categor y . T h is i s because or gan icamendments o f f l ooded r i ce padd ies inc rease methane em iss ion to the a tmosphere

(Yagi and Min ami, 199 0a; Sass et a l ., 199 1a, 199 1b; N eue et a l ., 199 4). A co m pr ehen sive


11/23



r ev i ew o f m e t hane f l u x m eas u r em en t s ov e r t he pas t dec ade f r om a v a r i e t y o f c oun t r i esand w i th d i f fe ren t o rgan ic amendments and inorgan ic fe r t i l i se r t rea tments , i s p resented by

M inami (1995) . T he am ou nt o f met hane tha t i s em i t ted as a resu l t o f o r gan ic so i lamendments depends grea t l y on the amount and cond i t i on o f read i l y ava i lab ledeco m po sab le carbo n con ta ined in the t rea tm ent . Schtz et al (1989a) ob servedincreases f rom a cont ro l va lue o f 28 .6 g CH 4 m 2/y r t o 68 .4 g C H 4 m 2/ yr w it h ad ded r ic es t raw , (a fac to r o f 2 .4 ) . C icero ne e t al . (1992) o bserved inc reases f ro m a con t r o l value o f1 .4 g CH 4 m 2/ y r t o u p t o 58 .2 g C H 4 m 2/ yr w it h ad d ed st r aw , a fact o r o f o ver 40 t im esh igher . In fi e ld s tud ies in the Ph i l ipp ines , D en ier van der G on and N eue (1995) foun dt ha t f ie l ds t r eat ed w i t h g r een m anu r e app l ied a t a r a t e o f 22 t onnes / ha em i t t ed ov e r t w i c eas m uch m ethane as f i elds in w h ich the app l i cat io n r a te w as 11 t on nes /ha.

M ethane em ission ra tes ar e h igh ly sens it i ve to w ater m anagement . Per iod ic d r a inage o fi r r igated r ice paddies resul ts in a s igni f icant dec r ease in m eth ane emission s. Yagi andMinami (1990a) repor ted a decrease in methane em iss ion ra tes as a resu l t o f a

m id-seaso n dr ainage in Japanese r ice f ie lds. Sass et a l . (199 2) fo und th at a singlem idseason dra in reduced seasona l em iss ion ra tes by 50 per cen t ( f rom 9 .27 g /m 2 t o4.86 g/m 2 ) . In add i t i on , mu l t i p le sho r t per iods o f d ra inage (2 -3 days) appro x im ate ly everyth r ee weeks dur ing the gro w ing season reduced m ethane em issions to an ins ign if i can tamount (1 .15 g /m 2 ) w i t ho ut decr easing r i ce g ra in y ie ld . Yagi e t al . (1996) co m pared ac on t i nuo usl y f loo ded p l o t w i t h c ons t an t i r r i gat i on w i t h an in t e r m i t t en t l y d r a i ned p l o t w i t hshor t - t e rm dr a in ing per iods severa l t im es dur ing the r i ce g ro w ing season. T o t a l seasona lm e t hane em i s s i on r a t es du r i ng t he c u l t i v a t i on pe r i od w e r e 14 . 8 g / m 2 and 8.6 g/m 2 fo r1991 and 9 .5 g /m 2 and 5.2 g/m 2 f o r 1993 i n t he c on t i nuous l y f l ooded and i n t e r m i t t en t l ydr a ined p lo t s , respec t i ve ly . Sca ling fac to r s in T ab le 4 -12 have been deve lop ed us ing theda t a f r om t he l it e r a t u r e .

D efau l t va lues in Tab les 4 -12 and 4-13 can be used fo r i n i t i al ca lcu lat io n w her e loca l

m easu r em en t s a r e no t adequa t e . H ow ev e r , nat i ona l ex pe r t s ar e enc ou r aged t o us elocal ly avai lable data i f avai lable. I f th is is do ne i t is im po r tant t o ensur e that th esecoef f i c ien ts a re based on a su f f i c ien t number o f measurements to capture the var iab i l i t yand produce a representa t i ve seasona l average va lue , wh ich i s needed fo r i nventoryca lcu lat io ns (see A ppend ix ) .

Possible Refinements

N a t iona l ex pe r t s ar e enc ou r aged t o go bey ond t he basi c m e t ho d , and add as m uc h de t a ilas can be sc ien t i f i ca l l y j us t i f i ed , based on labora tory and f ie ld exper iments on var iousamendments and theore t i ca l ca lcu la t ions , to a r r i ve a t the es t imate o f em iss ions f rom r i cec u l t iv at i on i n t he i r c oun t r y . Thes e de t ai ls shou l d be i nc o r po r a t ed i n t o s ubc at ego r i es( ind ices j ,k i n Equat ion 2) under each o f the main water m anagement ca tegor ies in

Equa t ion 2 s o t ha t t hey c an be c om pa r ed a t t hat l e v e l w i t h da t a fr o m o t he r c o un t r i es.

Fo r ex am p l e :

W her e em iss ion da ta ar e avai lab le fo r d i f fe ren t fe r t i l i se r t ypes , th i s may beincor po ra ted in to t he calcu lat io ns . Each ca tegor y , (e .g ., con t inuou s ly fl oo ded) w ou ldbe fu r ther d iv ided as fo l l ows:

F ( c on t i nuous l y fl ood ed ) = F ( f loo ded c hem i c al ) + F ( fl oo ded / o r gan i c am endm en t )

Th is p rocedure wou ld then be repeated fo r as many separa te subcategor ies as have been

def ined. Each amendm ent may be incor po ra ted in the same m anner .


12/23



In al l cases, the em iss ion invento r y must be fu l ly docum ented. T he docum enta t ion hastw o aspec ts . F irs t , metho d o f calcu lat io n mu st be spec i f ied as in Equat ion 2 . M at r i ces o f

amendm ents must be de l inea ted . Second , a ll data and or iginal sou rces must bere fer enced, i f no t i nc luded exp l i c it l y as par t o f the invento ry r epo r t . I t i s des i rab le in al lc as es t o r e l y on pub l is hed i n f o r m at i on , w he t he r f r om t he c o un t y s gov e r nm en t / sc i en t i f icins t i tu t io ns an in te r na t iona l o r gan isa t ion such as the U N -FAO , or the scien t i f i c l i t e ra tu r e .


13/23



TABLE 4-11

DEFAULT ACTIVITY DAT A - H ARVESTED RICE

C o u n t r y o r Regio n 1 99 0 A r ea

(1000s ha)

I r r iga teda

(%)

U p land R ice

(%)

Rainfed b

(%)

Americas

U SA 11 14 1 00 0 0

Belize 2 1 0 90 0

C o st a R ica 5 3 1 0 90 0

C u ba 1 50 1 0 0 0 0

D o m in ican Rep 9 3 9 8 2 0

El Salvad o r 15 10 90 0

G uat em ala 15 10 90 0

H ait i 5 2 4 0 60 0

H o n d u r as 19 10 90 0

Jam aica 0 4 0 60 0

M ex ico 1 23 4 1 59 0

N icar agua 48 10 90 0

Panam a 9 2 5 95 0

Pu er t o R ico 0 7 5 25 0T r in id ad & T o bago 5 45 55 0

A r gen t ina 10 3 100 0 0

Bo liv ia 11 0 25 75 0

Br azil 39 45 19 75 6 (0 + 6 )

C h ile 35 79 21 0

C o lum b ia 43 5 67 23 1 0 (0 + 1 0 )

Ecuad o r 2 66 4 0 10 50

G u yan a 6 8 9 5 5 0

Par aguay 34 5 0 50 0

Per u 1 85 8 4 16 0

Sur inam 5 8 1 00 0 0

U r u gu ay 1 08 1 00 0 0

V enezuela 11 9 90 10 0


14/23



TABLE 4-11 (CONT.)DEFAULT ACTIVITY DAT A - H ARVESTED RICE

C o u n t r y o r Regio n 1 99 0 A r ea(1000s ha)

I r r iga teda

(%)U p land R ice

(%)Rainfed b

(%)

Asia

Br unei 1 79 21 0

H o ng K o n g 0 1 00 0 0

Syr ia 0 100 0 0

T ur k ey 52 1 0 0 0 0

In d ia 42 32 1 5 3 (1 6 + 3 7 ) 15 3 2 (1 6 + 1 6 )

Pak ist an 21 13 10 0 0 0

Ban glad esh 1 04 35 22 8 7 0 (23 + 47 )

M yanm ar 4 76 0 18 6 76 (2 4 + 5 2 )

N ep al 14 45 2 3 3 7 4 (8 + 66 )

A fghan ist an 17 3 10 0 0 0

Bh u t an 2 5 5 0 4 4 6 (42 + 4 )

C h i n a 3 33 2 65 93 2 5 (0 + 5 )

In d o n esia 1 05 0 2 7 2 (22 + 5 0 ) 1 1 1 7 (1 0 + 7 )

Ir an 5 70 1 0 0 0 0

Ir aq 7 8 1 0 0 0 0

Jap an 2 07 4 9 9 (2 + 9 7 ) 1 0

M alaysia 63 9 6 6 1 2 2 2 (1 + 2 1 )

Ph il ipp ines 3 31 9 6 1 2 3 7 (2 + 3 5 )

Sr i Lank a 82 8 37 7 56 (3 + 53 )

T aiw an 7 00 9 7 3 0

T hailan d 9 65 0 7 1 92 (7 + 85 )

K am p uchea 1 80 0 8 2 9 0 (4 2 + 4 8 )

Lao s 6 38 2 37 6 1 (0 + 6 1 )

V iet n am 6 02 8 53 8 3 9 (1 1 + 2 8 )

D e mo c ra t i c R e p u b li c o fK o r e a

6 7 0 67 13 2 0

Rep ub lic o f K o r ea 1 24 2 1 00 (9 + 9 1 ) 0 0


15/23



TABLE 4-11 (CONT .)


C o un t r y o r Regio n 19 90 A rea

(1000s ha)

I r r iga teda

(%)

U p land R ice

(%)

Rainfed b

(%)

Europe

A lban ia 2 1 0 0 0 0

Bu lgar ia 11 1 00 0 0

Fr ance 20 1 00 0 0

G r eece 1 5 10 0 0 0

H un gar y 1 1 10 0 0 0

It aly 2 0 8 1 00 0 0

Po r t ugal 33 10 0 0 0

Ro m an ia 37 1 00 0 0

Spain 8 1 1 0 0 0 0

Fo r m er U SSR 6 24 10 0 0 0

Fo r m er Y u go slavia 8 1 00 0 0

Pacific

A u st r alia 1 02 1 00 0 0

Fij i 1 3 5 0 50 0

Africa

A lger ia 1 1 0 0 0 0

A ngo la 18 1 00 0 0

Ben in 7 10 90 0

Bu r k in a Faso 19 8 9 11 0

Bur und i 12 25 7 5 0

C am er o o n 15 2 5 7 5 0

C A fr ican Rep 10 2 5 75 0

C h ad 3 9 25 75 0

C o m o r o s 1 3 1 0 0 0 0

C o n go 4 2 5 75 0

Egyp t 4 36 10 0 0 0

G abo n 0 25 75 0

G am b ia 1 4 90 10 0

G h an a 8 5 24 76 0

G u inea B issau 5 7 25 75 0

G u inea 6 08 8 47 45


16/23



TABLE 4-11 (CONT.)


C ou n t r y o r Regio n 19 90 A rea

(1000s ha)

I r r iga teda

(%)

U p land R ice

(%)

Rainfed b

(% )

Ivo r y C o ast 58 3 6 8 7 7

K en ya 15 25 7 5 0

L iber ia 1 68 0 94 6

M ad agascar 1 16 0 10 1 4 76 (2 + 74 )

M alaw i 29 25 7 5 0

M ali 2 22 25 75 0

M au r it an ia 14 10 0 0 0

M o r o cco 6 1 0 0 0 0

M o zam b iqu e 1 09 25 75 0

N iger 2 9 3 5 65 0

N iger ia 15 67 16 51 33 (3 3 + 0 )

Rw and a 3 25 7 5 0

Senegal 73 25 7 5 0

Sier r a Leo n e 33 9 1 6 7 3 2

So m alia 5 5 0 5 0 0

So u t h A fr ica 1 10 0 0 0

Sud an 1 5 0 5 0 0

Sw aziland 0 2 5 7 5 0

T an zan ia 37 5 3 2 2 75 (0 + 7 5 )

T o go 21 4 9 6 0

U gan d a 37 25 75 0

Z air e 3 93 5 90 5

Z am b ia 1 1 25 75 0

Z im b abw e 0 25 75 0

aN u m b e r s i n b ra cke t s in d i cat e co n t i n u o u s ly f l o o d e d a n d i n t e rm i t t e n t l y f lo o d e d r e sp ec t i ve ly .

b N u m b e r s in b ra cke t s i n d ica t e co n t i n u o u s ly f lo o d -p ro n e an d d ro u g h t -p ro n e r e sp ec t i ve ly .

c Values are curren t l y be ing updated .

So u r ce s : D e D a t t a (1 9 7 5 ) , H u ke , (1 9 8 2 ) , G r i s t ( 1 9 8 6 ) , I R R I (1 9 9 0 ) , N G G I C (1 9 9 6 ) .

Notes: A r e as w e re t a ke n f ro m FA O Y e a rb o o k (U N , 1 9 9 2 ) , C h i n a A g r i cu l t u ra l Y e a rb o o k (1 9 9 0 ) , W o r l d R ice St a t i st i cs (I R R I, 1 9 9 0 )

and IRRI R ice A lmanac 1993-1995 ( IRRI , 1993) .


17/23



TABLE 4-12

SCALING FACTORS FOR METHANE EMISSIONS FOR RICE ECOSYSTEMSRELATIVE TO CONTINUOUSLY FLOODED FIELDS

(W ITHOUT ORGANIC AMENDMENTS)

C at ego r y Sub -C at ego r y a Scal ing Factors (re la t ive to emissionfac to rs fo r con t inuous ly f looded f ie lds )

U p lan d N o ne 0

Lo w land Ir r igat ed C o n t inu o usly flo o d ed 1 .0

I n t e rm i t t e n t l yf l o o d e db

Single aer at io n 0 .5 (0 .2 -0 .7 )

Mu l t i p l eae ra t ion

0.2 (0 .1-0.3)

Rain fed Flo o d p r o n e 0 .8 (0 .5 -1 .0 )

D r o u gh t p r o n e 0 .4 (0 -0 .5 )

D eep w at er W at er d ep t h 5 0 -10 0 cm 0 .8 (0 .6 -1 .0 )

W at er d ep t h > 1 0 0 cm 0 .6 (0 .5 -0 .8 )

a O ther r i ce ecosystem ca tegor ies, l i ke swamps and in land, sa l ine or t i da l w et lands may be d i scr im ina ted wi t h in each sub-ca tegory accor d ing to l oca l

e m i sso n m e a su re m e n t s .

b

D ef ined as > 3 days aera t ion dur ing the vegeta t i ve per iod .

Note: For i r r i ga ted and cont inuously f l ooded, l owland r i ce ecosystems, the de fau l t seasona l l y i n tegra ted methane emission i s 20 g /m 2 ( se e Ta b l e 4 -1 3 )

f o r so i l s w i t h o u t o r g an i c am e n d m e n t s . Fo r co n ve rs io n t o m e t h a n e e m i ss io n s f r o m so i ls w i t h o rg a n ic a m e n d m e n t s , ap p l y a d e fa u lt co r r e c t i o n f ac t o r o f

2 (R a n ge 2 -5 ) t o t h e co r re sp o n d i n g r i ce eco syst e m f o r t h e w i t h o u t o r g an i c am e n d m e n t cat e g o ry .


18/23



TABLE 4-13SEASONALLY INTEGRATED METHANE EMISSION FACTORS FOR CONTINUOUSLY FLOODED RICE W ITHOUT ORGANIC FERTILISER

IN VARIOUS LOCATIONS OF THE W ORLD

C o u n t r y Seaso nally In t egr at ed Em issio n

Fac to r , EFa

(g/m 2 )

L i t e ra t u re / R e ma rk s

A ust r alia 22 .5 N G G IC , 1 9 96

C h ina 13 (10 -22 ) W assm an et al ., 1 9 93 a

Ind ia 1 0 (5 - 15 ) M it r a, 19 96

Par ashar et a l ., 1996

Ind o nesia 1 8 (5 - 4 4 ) N u gr o h o et al., 1 9 94 a,b

It aly 36 (1 7 -5 4 ) Sch t z et al., 1 98 9 aJap an 1 5 M in am i, 1 99 5

Repu b lic o f K o r ea 1 5 Sh in et al., 1 99 5

Ph il ip p ines (2 5 - 30 ) N eue et al., 19 9 4 ; W assm an et al., 19 9 4

T hailand 1 6 (4 - 4 0 ) T o w p r yao o n et al., 1 99 3

U SA (T ex as) 25 (15 - 3 5 ) Sass an d Fisher , 1 9 95

A r i t h m e t ic M e an b 20 (12 -28 ) -

a I t i s reco gn ised tha t the emission facto r s p r esented in T ab le 4 -13 w i l l need to b e per io d ica l ly updated as be t t e r da ta becom e avai lab le . H ow ever , th i s

da tase t represents the best ava i l ab le i n fo rmat ion a t the t ime o f compi la t i on .

b T he ar i t hm et i c mean o f the seasona l l y in tegra ted em ission facto r , EF, i s der i ved fro m t he va lues sho w n in Tab le 4 -13 . Th e range o f emission facto rs

i s de f ined as the standard devia t i on about the mean.


19/23



Appendix

In te rcomparab i l i ty o f Methane Emiss ionD a t a f r o m R ice Cu l t i v at io n

Chamber measurements

E ac h l abo r a t o r y s hou l d p r ov i de a s t anda r d i s ed em i s s i on p r og r am o f c on t r o l f l u xm easu r em en t s t o ensu r e t he i n t e r c om pa r i b il t y and i n t e r c a li b r a t i on o f ex t ended da t a se t s .

An em iss ion s tandard isa t ion programme w i l l cons is t o f a spec i f i ed exper imenta l p lan fo rseason a l and annual f lux m easur em ents a lon g w i th spec i fi c accom pany ing data o n lo ca t ionand c l imate , so i l , water management , p lan t charac ter i s t i cs , fe r t i l i se r t rea tment and adeta i led c r op p ing calendar .

M et hane f l u x m eas u r em en t s s hou l d be r ec o r ded a t l eas t t w i c e pe r w eek ov e r an

ent i r e season. Exper im ents shou ld be con t inued dur ing fal l ow and/or a l te r na tecro pp ing t imes as w e l l as dur ing the en t i r e no rm al loca l r i ce gro w ing season inc lud ingland prep ara t ion . In ar eas w her e doub le o r t r i p le c ro pp ing i s p r ac t i sed , da ta shou ldbe co l lec ted fo r a ll g row ing season s .

Since em issions are s t r on g ly in f luenced by da i l y tem pera tur e changes , the d ie l pa t te r no f em i ssi on ( 6 - 12 f l u x r a t es w i t h i n a 24 hou r pe r i od ) s hou l d be de t e r m i ned a t l eastth ree t imes dur ing the season.

A data log of a l l agr icul tural events should be kept . , e.g. , t ransplant date, panic lein i t iat io n, heading, anthe sis, harve st , etc. as w el l as fer t i l isat io n, w ater m anagem entschedu le , w eed ing schedu le , herb ic ide and pes t i c ide t rea tm ents .

A t t he t i m e o f eac h f l u x m eas u r em en t , one s hou l d a l s o c o l l ec t t he a i r t em pe r a t u r e ,

f loo d w a t e r t em pe r at u r e , and t he so i l t em pe r a t u r e .

Fer t i l i sa t ion t rea tment in the s tandard isa t ion (cont inuous i r r i ga t ion) p lo ts shou ld beacco rd ing to loca l p r act i ces , bu t l im i ted t o ino rgan ic fe r t i l i se r . T he app l ica t ion r a te ask g N h a-1 and num be r and t i m i ng o f app l ic at i ons s hou l d be r epo r t ed .

Fer t i l i sa t ion t rea tment in o ther exper imenta l a reas , i nc lud ing organ ic fe r t i l i se rs ,shou ld re f lec t l oca l p r ac t i ces . A m ou nts , t ype , and t im ing o f app l i cat io ns sho u ld berep or ted fo r each phase o f the c r op p ing sequence a t a ll sca les .

S t anda r d i s a t i on c ham be r p l o t s a r e t o be k ep t f l ooded f r om s ho r t l y be f o r et r ansp l an t i ng un t i l m a t u r i t y . D u r i ng fl oo d , t he w a t e r s hou l d be k ep t a t a 5 cmm i n i m um c o nst an t dep t h . A da il y l og shou l d be k ep t o f t he am o un t o f w a t e r addedand w hen .

O t he r w at e r m anagem en t r eg im es shou l d be i nv est i gat ed w hen t hey a r e p r act i sedloca l ly . A d a il y l og sho u ld be kept o f t im es and dura t io ns o f d ra in ing , the amo unt s o fw ater added and o t her app l i cab le da ta.

F o r f u r t h e r i n f o r m a t i o n , see G lo b a l M e a su r em e n t s St a n d a r d s o f m e t h a n e e m iss io n s f o r i r r iga ted r ice cu l t i va t ion , I G A C ( 1 9 9 4 ).


20/23


21/23



4.4 G r eenhouse G as Em issions fr omAgr icu l tu ra l Burn ing

4 . 4 . 1 I n t r o d u c t i o n

W her e t he r e i s open bu r n i ng ass oc ia t ed w i t h agr i c u l t u r a l p r ac t i ces, a num be r o fgr eenho us e gas es ( G H G s) ar e em i t t ed fr o m c om bus t ion . A l l bu r n i ng o f b i om assproduces subs tan t ia l CO 2 emissions . H ow ever , i n agr i cu l tu ra l bur n ing , the C O 2 re leasedi s no t c ons i de r ed t o be net em iss ion . T he b iom ass bur ned i s genera l ly rep laced byr eg r o w t h ov e r t he subs equen t y ear . A n equ iv al en t am o un t o f c ar bo n i s r em ov ed f r o mt he a t m os phe r e du r i ng t h i s r eg r ow t h , t o o f f s e t t he t o t a l c a r bon r e l eas ed f r omc om bus t ion . The r e fo r e t he l ong t e r m ne t em i ssi ons o f C O

2a r e c ons i de r ed t o be z e r o .

Agr i cu l tu ra l burn ing re leases o ther gases in add i t i on to CO 2 w h i c h a r e by - p r oduc t s o fi nc om p l e t e c om bus t i on : m e t hane , c a r bon m onox i de , n i t r ous ox i de , and ox i des o fn i t r o gen , am ong o t he r s . Th ese non - C O 2 t race gas em iss ions f rom b iomass burn ing arene t t r ansf e r s f r om t he b i osphe r e t o t he a t m o sphe r e . I t i s i m po r t an t t o est i m a t e t heseemissions in na t io na l i nventor ies.1 6

There are two major t ypes o f agr i cu l tu ra l burn ing addressed in th i s sec t ion savannabur n ing and f ie ld burn ing o f c ro p r es idues . T he appro ach is essent ia l ly the sam e as tha tu se d f o r n o n - C O 2 t r ace gases fo r a ll bur n ing o f unpr ocessed b iom ass , inc lud ing t r ad i t i ona lb iom ass fue ls and open bu rn ing o f c lear ed fo r es ts. For a ll these ac t i v i t i es, there i s ac om m on app r oac h i n t he p r opos ed m e t hodo l ogy , i n t ha t c r ude es t i m a t es o f non - C O 2t r ace gas em iss ion s can be based on r a t ios to the t o t a l carbo n re leased. T he carb on

trace gas releases (CH 4 and C O ) a r e t r eat ed as d i r ec t r at i os t o t o t a l c ar bo n r e l eased .N on - m e t hane v o l at i l e o r gan i c com pounds ( N M V O C s) c an be t r eat ed i n a si m i l ar w ay .H ow ev e r , no de f au l t v al ues f o r N M V O C a r e p r o v i ded i n t h is v e r s ion o f t he Guide l ines .To hand l e n i t r ogen t r ac e gas es , n i t r ogen t o c a r bon r a t i os a r e us ed t o de r i v e t o t a ln i t rogen re leased and then em iss ions o f N 2O an d N O x a r e est i m a t ed based o n r at i os o fthese gases to to ta l n i t ro gen re leased. T ab les 4 -15 and 4-16 p r ov ide sugges ted de fau l tv a l ues f o r non - C O 2 t r ace gas em ission r a t ios . T hese are p r esented w i th r anges , w h ich

1 6

Fo r b i om as s c om bus t i on , C O 2 emiss ions are f requent l y no t cons idered netemissions , and t h i s is the case fo r agr i cu l t u r a l burn ing . O ne co u ld a rgue, in such cases ,t ha t t h i s bu r n i ng c ou l d be c ons i de r ed a s ho r t t e r m s i nk o f C O 2 . Tha t i s , a po r t i on o fcarbon in b iomass is being released as net emiss ions o f CH 4 an d C O , w h i le r e gr o w t h i sr em ov i ng t he f u l l am oun t o f t he o r i g i na l c a r bon f r om t he a t m os phe r e i n t he nex t c y c l e .Eac h y ear p l an t s t ak e up a ce r t a i n am o un t o f c ar bo n f r om t he a t m o sphe r e . W hen t heyar e b u r n e d s o m e o f t h at c ar b o n i s c o n v e r t e d t o C O , an d C H 4 , so tha t an amount lesst han t he t o t a l C O 2 which was taken up by the p lan ts i s re -em i t ted as CO 2 . See H ow denet a l . (1996) , fo r a more de ta i led d iscuss ion o f th i s p roposa l . T rea t ing em iss ions o f COan d C H 4 t o t he a t m o sphe r e , as a si nk f o r at m os phe r i c C O 2 , ho w ever , is incon s is ten t w i tht he p r o pos ed IPC C em i ssi ons m e t hod o l ogy . I n par t i c u lar , t he o t he r c a r bon c om poundsem i t t ed a r e c onv e r t ed bac k i n t o C O 2 i n t he a t m os phe r e ov e r pe r i ods o f day s up t o adec ade o r s o . Thus , ov e r t he t i m e ho r i z ons o f i n t e r es t f o r C O 2 , ( i . e . more than 100

y ear s ) t he r e i s no s ink o f C O 2 .


22/23



em phasise the i r uncer t a in ty . H ow ever , the basic ca lcu lat io n meth od o lo gy requ i res tha tusers select a best est imate value.1 7

The ca lcu la t ion o f immedia te t race gas em iss ions , based on the de fau l t em iss ion ra t iosprov ided in Tab les 4-15 and 4-16 , p roduces re la t i ve ly c rude es t imates w i th subs tan t ia luncer ta in t ies .1 8 U se o f spec if i c em iss ion ra t io s wh ich vary by t ype o f burn ing , reg ion , e tc .m ay a llow fo r m or e pr ec ise ca lcu lat io ns . T he calcu lat io ns descr ibed here igno re th econ tem po rar y f lux es assoc iated w i th past bur n ing ac t i v it i es . T hese de layed re leases arek no w n t o ex i st , bu t ar e poo r l y under s t o od at p r es en t . Th i s and o t he r pos si b lere f inem ents a re d iscussed a t the en d o f th i s sec t ion .

4.4.2 Prescr ibed Burning of Savannas

Background

The t e r m s av anna r e f e r s t o t r op i c a l and s ub t r op i c a l v ege t a t i on f o r m a t i ons w i t h apredominant l y con t inuous grass cover , occas iona l l y in te r rup ted by t rees and shrubs(Bou l ie r e and H ad ley 1970) . T hese fo r m at ions ex ist i n A f r i ca , La t in Am er ica , A s ia , andA ust r a lia. T he gro w th o f vegeta t io n in savannas i s con t ro l led by al te r na t ing w et and drys easons : m os t o f t he g r ow t h o c c u r s du r i ng t he w e t s eason ; m an - m ade and / o r na t u r a l fi r esare f requent and gener a ll y occur d ur ing the dr y season . T he g loba l area o f savannas i suncer ta in , i n par t du e to lack o f da ta and in p ar t d ue t o d i f fe r ing ecosys tem c lass if i ca t ions .Es t imates o f the area l ex ten t o f savannas range f rom 1300-1900 m i l l i on hec tares wor ld -w i de , abou t 60 pe r c en t o f w h i c h ar e hum i d savannas ( annua l r a i n fal l o f 700 m m o r m o r e )and 40 p er cen t a re a r id savannas (annua l ra in fal l o f l ess than 70 0 m m ) (Bo l in e t a l ., 1979;W hi t t aker and L ikens , 1975; Lan ly , 1982; Lacey e t al ., 1982 ; and H ao e t a l ., 1990) . Large-scale burning takes place pr imar i ly in the humid savannas because the ar id savannas lack

suff i c ien t g rass cover to susta in fi re . H um id savannas are burn ed every on e to fou r yearson aver age w i th th e h ighes t f requency in t he hum id savannas o f A f r i ca (as c ited in H ao e tal ., 199 0).

1 7 Emiss ions inventory deve lopers a re encouraged to p rov ide es t imates o f uncer ta in tya l ong w i t h t hes e bes t es t i m a t e v a l ues w he r e pos s i b l e o r t o p r ov i de s om e ex p r es s i on o fthe leve l o f con f idence assoc ia ted w i th var ious po in t es t imates prov ided in the inventory .P r oc edu r es f o r r epo r t i ng t h i s unc e r t a i n t y o r c on f i denc e i n f o r m a t i on a r e d i s c us s ed i nV o lu m e 1 : Re p o r t i n g I n st r u c t i o n s .

1 8

Emiss ion ra t ios used in th i s sec t ion and presented in the tab les a re der i ved f romC ru tzen and And r eae (1990) , D e lmas (1993) , D e lmas and Ah u ja (1993 ) and Lacaux , e t a l.(1993) . They are based on measurements in a w ide var ie ty o f f i res , i nc lud ing fo res t andsavanna f i res in the t rop ics and labora tory f i res us ing grasses and agr i cu l tu ra l was tes asfuel . In many cases these rat ios are general averages for a l l b iomass burning. Research w i l lneed to be conduc ted in the fu tu re to de term ine i f more spec i f i c em iss ion ra t ios , e .g . ,spec if i c to t he type o f b iom ass and burn ing cond i t i ons , can be ob t a ined. A lso , em issionr a t ios vary s ign i f ican t l y be tw een th e f l am ing and smo u lder ing phases o f a fi re . C O 2 , N 2 O ,an d N O x are main ly em i t ted in the f l am ing s tage, wh i le CH 4 and C O a r e m a in l y em i t t eddur ing the smou lder ing s tage (Lober t e t a l . , 1990) . The re la t i ve impor tance o f these twos tages w i l l vary be tween f i res in d i f fe ren t ecosys tems and under d i f fe ren t c l imat i ccond i t i ons , and so the em iss ion ra t ios w i l l vary . As inventory methodo log ies a re re f ined ,em iss ion ra t ios shou ld be chosen to represent as c lose ly as poss ib le the ecosys tem type

be ing burn ed, as we l l as the charac ter i s t i cs o f the f i re .


23/23

1996.Methane Emissions From Rice Cultivation Flooded Rice Fields

Documents

Transcript of 1996.Methane Emissions From Rice Cultivation Flooded Rice Fields