Effect of land-use changes on nitrous oxide (N2O) emission from tropical peatlands

E�ect of land-use changes on nitrous oxide (N2O) emissionfrom tropical peatlands

Abdul Hadi a, K. Inubushi a,*, E. Purnomo b, F. Razie b, K. Yamakawa a,H. Tsuruta c

a Faculty of Horticulture, Chiba University, Matsudo, Chiba 271-8510, Japanb Faculty of Agriculture, Lambung Mangkurat University, Banjarbaru 70714, Indonesia

c National Institute of Agro-Environmental Sciences, Kan-nondai, Tsukuba 305-8604, Japan

Received 15 June 1999; accepted 30 March 2000

Importance of this paper: The e�ect of land-use changes on nitrous oxide (N2O) emission from tropical peatlands in

Indonesia and Malaysia was studied in the ®eld and in the laboratory. The amount of N2O emitted from the peatland varied

widely according to the land-use management, water contents, addition of fertilizer or organic waste and location of the site.

Changing natural peatland to cultivated land can have a signi®cant impact of either increasing or decreasing N2O emission

to the atmosphere depending on the land-use management and environmental conditions.

Abstract

Tropical peatlands could be a potential source of nitrous oxide (N2O) which has a signi®cant impact on global

warming. To reduce N2O emission and develop best management practices for peatlands, the formation and emission

rates of N2O as a�ected by land-use management (i.e., changing peatland into agricultural land) and the factors af-

fecting the process must be understood. Therefore, one ®eld and three laboratory incubation experiments were carried

out during 1998±99 using peatland soils from 12 sites in South Kalimantan (Indonesia) and one site in Sarawak

(Malaysia) to quantify the N2O emission and the factors a�ecting it. The results from the ®eld experiment showed that

land-use managements, changing water table and locations had a signi®cant impact on N2O emission. Changing

peatland into cultivated lands (cultivated upland and paddy ®eld) enhanced the N2O emission. For example, cultivated

upland Cassava crop resulted in the highest amounts of N2O emission (1.04 mg N mÿ2 hÿ1) compared to other

treatments. The N2O emission during 1998 was higher than those during 1999 because of the changing water table and

dry season in 1998. The laboratory experiments showed that the N2O emission was also strongly in¯uenced by land-use

management, soil moisture contents, addition of ammonium fertilizer or rice straw and soil depths. For example, the

¯ooded conditions stimulated the N2O emission compared to that at 60% moisture contents. Similarly, the addition of

ammonium fertilizer suppressed the N2O emission compared to control treatments because of the high ammonium

contents that inhibit nitri®cation. Nevertheless, incorporation of rice straw to soil samples from 20 to 40 cm soil depth

stimulated N2O emission. Ó 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Denitri®cation; Land-use change; Nitri®cation; Nitrous oxide; Peat soil; Tropical peatlands

1. Introduction

Peatlands include soils which contain 30% or more

organic matter in the top 40 cm and cover 80% of the

area (FAO, 1988). Approximately 29 million ha is

Chemosphere ± Global Change Science 2 (2000) 347±358

* Corresponding author. Fax: +81-47-308-8720.

E-mail address: [email protected] (K. Inu-

bushi).

1465-9972/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved.

PII: S 1 4 6 5 - 9 9 7 2 ( 0 0 ) 0 0 0 3 0 - 1

tropical peatland worldwide (Takai, 1997). A large

portion of this tropical peatland exists in the Borneo

Island (Driesen, 1981; Takai, 1997), which belongs to

three countries (i.e., Indonesia, Malaysia and Brunei).

Recently, large areas of peatland have been con-

verted by constructing drainage ditches into agricultural

and aquacultural lands in South Kalimantan (Indone-

sia) and in Sarawak (Malaysia) because of the intensi-

®cation of agriculture due to growing population in

those areas (Moehansyah, 1988; MacKinnon et al.,

1996). For example, oil palm and rice crop have been

grown on most peatland in Sarawak (nearly 1 million

ha) and South Kalimantan (about 200,000 ha), respec-

tively (Ismunadji and Soepardi, 1984; Ahmad et al.,

1986; Radjagukguk, 1990).

Both natural and converted peat soils may act as a

potential source of N2O of which the global emission

rate approximately 15 Tg N yÿ1 (Bouwman, 1990).

Large amounts of ammonium �NH�4 � and nitrate �NOÿ3 �accumulate when organic matter in peat soil undergoes

either aerobic or anaerobic decomposition (Driesen,

1981; Ismunadji and Soepardi, 1984). This could pose a

great threat to the environment by emitting various

gases like nitrous oxide (N2O), methane (CH4) and

carbon dioxide (CO2). However, there is a lack of

quantitative information regarding the emission of N2O

from natural and converted peatland (Terry et al.,

1981a,b; Agustin et al., 1998). Therefore, the present

study was designed to investigate the formation and

emission of N2O from natural and converted tropical

peatlands and the factors a�ecting the process of N2O

emission.

2. Materials and methods

Four experiments (i.e., one ®eld experiment and three

laboratory incubation experiments) were carried out to

determine the impact of land-use management (i.e.,

converting natural peatland into agricultural land) and

Fig. 1. Map of the sampling sites.

348 A. Hadi et al. / Chemosphere: Global Change Science 2 (2000) 347±358

Tab

le1

Sit

elo

cati

on

,d

escr

ipti

on

an

dp

hysi

coch

emic

al

pro

per

ties

of

the

soil

su

sed

Lo

cati

on

Sit

eco

de

GP

SL

an

du

sem

an

agem

ent

Pea

tth

ick

nes

s

(cm

)

Sam

ple

dep

th

(cm

)

pH

(1:5

)T

ota

lo

rg-C

(gk

gÿ1

)

To

tal

N

(gk

gÿ1

)

CE

C

(cm

ol

(+)

kgÿ1

)

Ga

mb

ut

G-1

3°2

50 S

Un

cult

iva

ted

up

lan

d®

eld

70±100

0±10

3.8

612.5

15.0

75.8

11

4°4

00 E

10±20

3.4

620.2

12.8

92.0

20±30

3.2

615.6

8.9

103.2

G-2

3°2

50 S

Un

cult

iva

ted

up

lan

d®

eld

10±40

0±10

3.8

485.5

9.6

132.8

11

4°4

00 E

10±20

3.6

306.0

4.8

70.6

20±30

3.8

338.3

5.9

72.7

G-3

3°2

50 S

Sec

on

da

ryfo

rest

100±200

0±10

3.2

485.7

15.9

103.4

11

4°4

00 E

10±20

3.0

368.3

10.1

71.0

20±30

3.3

506.3

9.7

108.1

Jel

ap

at

J-4

Pa

dd

y®

eld

(1yea

rru

nn

ing)

5±20

0±10

3.3

192.2

10.8

40.5

10±20

3.6

47.1

4.1

40.8

20±30

3.2

0.0

1.6

30.3

J-5

Sec

on

da

ryfo

rest

15±25

0±10

3.4

240.6

11.8

62.4

10±20

3.2

73.3

3.6

30.1

20±30

3.3

79.4

2.1

34.6

Ba

ram

ba

iB

-63°0

00 S

Pa

dd

y®

eld

(3yea

rsru

nn

ing)

40±50

0±10

3.3

123.7

5.1

49.2

11

4°4

20 E

10±20

3.2

235.2

7.1

68.9

20±30

3.6

246.9

7.0

52.3

B-7

3°0

00 S

Cu

ltiv

ate

du

pla

nd

®el

d(c

ass

ava

cro

p,

3y

ears

run

nin

g)

70

0±10

3.4

140.8

5.7

43.2

11

4°4

20 E

10±20

3.4

146.6

3.9

44.6

20±30

3.2

142.9

5.3

44.7

B-8

2°5

90 S

Sec

on

da

ryfo

rest

5±15

0±10

3.6

139.7

5.4

56.6

11

4°4

30 E

10±20

3.4

27.5

4.1

32.2

20±30

3.5

50.4

4.3

41.3

Ma

rgasa

riM

-92°5

60 S

Sec

on

da

ryfo

rest

20±60

0±10

4.3

237.6

9.2

61.6

11

5°0

10 E

10±20

4.6

163.2

9.1

54.3

20±30

4.7

140.4

3.9

25.6

Am

un

tai

A-1

02°2

60 S

Ric

e±so

yb

ean

rota

tio

n®

eld

(6yea

rs

run

nin

g)

20±40

0±15

a4.6

574.3

13.2

103.7

11

5°2

30 E

A-1

12°1

90 S

Pa

dd

y®

eld

(2yea

rsru

nn

ing)

100±200

0±10

4.7

458.6

15.0

38.0

11

5°2

10 E

10±20

4.3

507.1

15.3

26.1

20±30

4.1

556.4

15.6

29.3

A. Hadi et al. / Chemosphere: Global Change Science 2 (2000) 347±358 349

other environmental factors on the emission of N2O

during 1998±99, using peatland soils from 12 sites in

South Kalimantan (Indonesia) and one site in Sarawak

(Malaysia) (Fig. 1). The details of each experiment is

given below.

2.1. Field experiment: emission of N2O from natural and

converted tropical peatlands

This study was conducted in December 1998 and

December 1999, using 11 natural and converted peat-

land sites in South Kalimantan. Out of one million ha

peatland area, 500,000 ha were surveyed and then 11

sites were selected for this study. The 11 peatland sites

comprised of ®ve secondary forests, three converted

paddy ®elds, one converted upland ®eld grown with

cassava and two converted uncultivated uplands. Sites in

Barambai and Jelapat are in¯uenced by daily tidal

movement. The sites codes, position and chemical

properties are given in Table 1. The soil depths varied

and ranged from 10 to 200 cm. In most sites, peat soils

were derived from a mixture of wood and grass, except

G-1, G-2 and G-3 in Gambut where peat soils were

derived from grass only (Sabiham, 1988, 1989).

Nitrous oxide (N2O) was measured by inserting a gas

chamber made up of PVC pipe (21 cm diameter and 14

cm long). The gas chamber was closed from the upper

end, having a septum port in the center, which was at-

tached to a rubber tube. Gas samples were collected by

inserting a 35 ml syringe into the tube and then sucking

the air. Four gas samples were collected from each

chamber at time 0, 5, 10 and 15 min after the enclosure.

Gas samples were then transferred into a vacuum vial

(22 ml) and analyzed for N2O using a Shimadzu GC-7A

gas chromatograph with 63Ni electron-capture detector.

Nitrous oxide (N2O) was separated on a Porapak Q

column (0.002 ´ 2 m) by keeping oven and detector

temperatures at 40°C and 350°C, respectively. The N2O

had a retention time of 2.9 min at a ¯ow rate of 20 ml

minÿ1 of CH4 and Ar gas mixture (volume ratio 5:95).

The emission rate of N2O was calculated from the in-

crease in N2O concentration in the chamber head space

per unit time multiplied by the height of the gas

chamber.

Redox potential (Eh) in the ®eld was measured by

inserting a platinum electrode in three soil depths (i.e.,

10, 20 and 30 cm) as described by Hesse (1971). Ground

water table was measured by inserting a pizometer into

the soil. Water samples from soil-pore were collected by

inserting a porous cup (Daiki Physicochemical Compa-

ny, Japan) and sucking water into a 50 ml syringe.

Water samples were analyzed for Fe2� concentration

using Merck RQ ¯ex plus (Merck, Germany; Maruo

et al., 1998).

Soil samples were taken during 1998 and 1999 from

three soil depths (0±10, 10±20 and 20±30 cm) andTab

le1

(Co

nti

nu

ed)

Lo

cati

on

Sit

eco

de

GP

SL

an

du

sem

an

agem

ent

Pea

tth

ick

nes

s

(cm

)

Sam

ple

dep

th

(cm

)

pH

(1:5

)T

ota

lo

rg-C

(gk

gÿ1

)

To

tal

N

(gk

gÿ1

)

CE

C

(cm

ol

(+)

kgÿ1

)

A-1

22°1

80 S

Sec

on

da

ryfo

rest

>200

0±10

4.1

471.9

20.8

37.6

11

5°2

10 E

10±20

4.9

410.5

13.7

65.8

20±30

4.3

513.6

19.0

53.0

Sara

wa

kS

2°4

90 N

Oil

pa

lmp

lan

tati

on

100±200

0±10

4.4

11

1°5

40 E

10±20

4.0

715.8

15.9

20±40

4.1

917.4

16.2

40±60

3.4

835.7

11.2

60±80

4.0

946.9

7.7

aO

nly

on

eso

ild

epth

(i.e

.,0

±1

5cm

)w

as

tak

enfr

om

site

A-1

0,

on

Feb

ruary

1998.


analyzed for NH�4 and NOÿ3 by using the methods de-

scribed by Anderson and Ingram (1989) and Hayashi et al.

(1997), respectively. A composite soil sample from each

site and soil depth was taken in 1999, air dried, sieved

<2 mm and analyzed for various soil chemical properties

(i.e., pH, organic carbon and total N) (Table 1).

2.2. Laboratory incubation experiment 1: e�ect of

ammonium fertilizer on N2O emission

A laboratory incubation was carried out to investi-

gate the in¯uence of ammonium fertilizer (NH4)2SO4 on

N2O emission. During 1998, soil samples were collected

from three soil depths (0±10, 10±20 and 20±30 cm) of the

converted paddy ®eld site B-6. Five grams soil on oven

dry basis was amended with (NH4)2SO4 at the rate of

100 kg N haÿ1. The soil samples were then transferred

into 60 ml serum bottles and incubated at 28°C for 14

days. The controls (soil only) were treated in similar

way. The emission of N2O was carried out on daily basis

for the ®rst 6 days and then on day 14. All analyses were

carried out in triplicate.

In another set of soil sample, three control soil

samples were extracted on day 0 and analyzed for NH�4and NOÿ3 as described earlier. Then additional soil

samples (three amended with (NH4)2SO4 and three

controls) were incubated under similar conditions and

analyzed for NH�4 and NOÿ3 contents after 7 days.

2.3. Laboratory incubation experiment 2: e�ect of mois-

ture contents and land-use management on N2O emission

A laboratory incubation was carried out to determine

the e�ect of soil water contents on the emission of N2O

from tropical peatlands. Soil samples were collected

from rice±soybean rotation ®eld (six years running

A-10), paddy ®eld (two years running A-11) and forest

(A-12) and had a moisture content of 31%, 63% and

71%, respectively, because of the drought weather in

1997 and early 1998. To measure the emission of N2O at

60% H2O level, deionized H2O was added to soils from

rice±soybean rotation ®eld; while those samples of

paddy ®eld and forest were dried to bring them to 60%

moisture level. Soil samples were transferred into 120 ml

serum bottles and incubated at 28°C for 100 days. An-

other set of soil samples were prepared similarly and

incubated under ¯ooded condition (i.e., 2 cm water

depth) by adding deionized water. N2O emission was

carried out at 2, 5, 13, 46, 60 and 100 days of incubation.

The NH�4 and NOÿ3 concentrations were measured at

day 0, 5, 60 and 100 days of incubation.

To determine the optimum moisture level for opti-

mum N2O emission, soil samples from paddy ®eld site

A-11 were ®rst brought to 70%, 80% and 100% moisture

levels and submerged condition, and were then taken

into 120 ml serum bottles. These soil samples were in-

cubated at 28°C for 2 days and analyzed for N2O

emission.

2.4. Laboratory incubation experiment 3: e�ect of rice

straw and ammonium fertilizer on N2O emission

A laboratory incubation was conducted to determine

the e�ect of rice straw and ammonium fertilizer on

emission of N2O from soil samples taken from di�erent

depths. Soil samples were collected from ®ve soil depths

(0±10, 10±20, 20±40, 40±60 and 60±80 cm) in Sarawak

(Malaysia). Ten grams moist soils were placed in 60 ml

Table 2

Emission of N2O from di�erent land-use management in South Kalimantan (Indonesia)

Site code Land-use management N2O emission (mg N mÿ2 hÿ1)

1998 1999

Average values SD Average values SD

G-1 Uncultivated upland 0.12 0.01 )0.03 0.01

G-2 Uncultivated upland 0.01 0.18 0.02 0.01

G-3 Secondary forest 0.04 0.02

J-4 Paddy ®eld (1 year running) 0.03 0.05

J-5 Secondary forest 0.02 0.04

B-6 Paddy ®eld (3 years running) 0.08 0.06 0.04 0.03

B-7 Cultivated upland ®eld (cassava

crop 3 years running)

1.04 0.10 0.16 0.07

B-8 Secondary forest 0.10 0.08

M-9 Secondary forest )0.02 0.02

A-11 Paddy ®eld (2 years running) 0.14 0.13

A-12 Secondary forest 0.03 0.01


Tab

le3

Gro

un

dw

ate

rle

vel

,E

hv

alu

es,

NH� 4

,N

Oÿ 3

an

dF

e2�

con

cen

trati

on

so

fp

eatl

an

din

So

uth

Kali

man

tan

du

rin

g1998±99

Sit

eco

de

La

nd

-use

ma

na

gem

ent

19

98

1999

Gro

un

d

wa

ter

(cm

)

NH� 4

(lg

Ngÿ1

soil

)

NOÿ 3

(lg

Ngÿ1

soil

)

Eh

(mV

)F

e2�

(mg

Lÿ1

)

Gro

un

d

wate

r(c

m)

NH� 4

(lg

Ngÿ1

soil

)

NOÿ 3

(lg

Ngÿ1

soil

)

Eh

(mV

)F

e2�

(mg

Lÿ1

)

G-1

Un

cult

ivate

du

pla

nd

10

34

.4a

11.0

352

3.4

15.1

788.3

31.3

358

<0.5

14

.5b

15.7

214

0.7

1150.1

20.7

7<

0.5

8.7

c10.9

102

2.2

633.8

18.8

157

<0.5

G-2

Un

cult

ivate

du

pla

nd

)4

4.1

8.5

124

14.7

)2.1

396.6

46.6

124

1.3

1.9

2.5

)310

8.2

219.8

10.5

)10

1.0

)168

14.6

121.3

11.9

)81

1.2

G-3

Sec

on

da

ryfo

rest

10

571.3

24.9

323

0.5

637.0

24.0

60

<0.5

1361.9

29.0

185

<0.5

J-4

Pa

dd

y®

eld

(1y

ear

run

nin

g)

)5.1

281.6

57.6

)30

97.0

5.8

)90

43.8

6.4

55

J-5

Sec

on

da

ryfo

rest

)6.4

182.9

19.2

)72

40.4

11.6

29

45.2

9.6

)15

B-6

Pa

dd

y®

eld

(3y

ear

run

nin

g)

08

3.5

1.7

56

200

)5.8

367.6

20.6

)88

<0.5

87

.93.3

130

135

347.6

26.1

)120

<0.5

58

.74.4

22

43

269.1

52.8

)156

<0.5

B-7

Cu

ltiv

ate

du

pla

nd

®el

d

(ca

ssa

va

cro

p3

yea

rs

run

nin

g)

25

15.0

164.8

15.9

)130

1.6

142.2

9.6

)6

125

312.8

17.1

)47

98

B-8

Sec

on

da

ryfo

rest

25.5

141.6

10.9

36

<0.5

66.2

18.2

)133

10.5

44.9

4.0

55

24

M-9

Sec

on

da

ryfo

rest

)3.7

612.0

15.2

)171

0.7

158.3

19.1

)155

<0.5

68.8

3.3

)174

2.1

A-1

1P

ad

dy

®el

d(2

yea

rs

run

nin

g)

)2.7

328.9

17.1

15

1.0

512.2

41.3

96

1.1

69.1

23.7

80

1.0

A-1

2S

eco

nd

ary

fore

st0

520.6

50.2

43

854.0

83.9

48

<0.5

751.1

72.2

22

<0.5

aS

oil

dep

th0

±1

0cm

.b

So

ild

epth

10

±20

cm.

cS

oil

dep

th2

0±

30

cm.


serum bottles. Soil samples were then amended with

recommended doses of rice straw powder (4 ton haÿ1) or

ammonium sulfate (100 kg N haÿ1). The head space was

replaced with air and evacuated several times. The serum

bottles were sealed by using butyl rubber stopper and an

aluminum crimp and incubated at 28°C for 28 days.

Nitrous oxide emission was carried out on weekly basis

and quanti®ed as described earlier.

At the end of incubation, soils treated with rice straw

were analyzed for water-soluble organic carbon, using

Total Organic Carbon analyzer 5000 (Shimadzu, Japan),

ammonium and nitrate concentrations.

3. Results and discussion

3.1. Characteristics of peatlands

Most of the peat soils considered in this study are

classi®ed as shallow peat soils because the peat depths

were <100 cm except in sites G-3, A-11, A-12 and S,

where the peat depth ranged from 100 to 200 cm or more

(medium to deep) (Radjagukguk, 1990). The peat soils

were strongly acidic having a pH value less than 5. The

organic carbon contents varied with locations and soil

depths and ranged from 0 to 947 g C kgÿ1 soil. The total

nitrogen also showed variation with locations and soil

depths and were in the ranged of 2±21 g N kgÿ1 soil

(Table 1).

3.2. Field experiment: emission of N2O from natural and

converted tropical peatlands

The emission of N2O was signi®cantly a�ected by

land-use management (Table 2). During 1998, the N2O

emission was the highest (i.e., 1.04 mg N2O-N mÿ2 hÿ1)

in the cultivated upland peat soils (site B-7) followed by

uncultivated upland (site G-1) and then paddy ®eld (site

B-6); while uncultivated upland (site G-2) resulted in the

lowest N2O emission (0.01).

The N2O emission during 1999 followed similar

pattern and exhibited variations with di�erent land-use

management, but the N2O emission rates were lower

than those observed during 1998 (Table 2). The N2O

emission was the highest (i.e., 0.16 mg N2O-N mÿ2 hÿ1)

in cultivated upland peat soils (site B-7) followed by

paddy ®eld (site A-11) and secondary forest (site B-8).

The N2O emission in other sites were lower and were in

this order: paddy ®eld (B-6) and secondary forest (site

G-3) > paddy ®eld (site J-4) and secondary forest (site A-

12) > secondary forest (site J-5) and uncultivated upland

(site G-2). The uncultivated upland (site G-1) and sec-

ondary forest (site M-9) resulted )0.03 and )0.02 mg

N2O-N mÿ2 hÿ1, respectively. The di�erence in N2O

emission from di�erent sites was probably due to the

di�erent land-use managements, environmental condi-

tions (i.e., groundwater table) and other soil chemical

properties (which will be discussed later).

The groundwater levels measured during 1998 and

1999 were a�ected by land-use management (Table 3).

During 1998, groundwater was generally low except at

site G-2 which was ¯ooded. Low groundwater in 1998

was caused by the unusual long drought season in 1997

and 1998. Contrary to that, during 1999, most of the

experimental sites were water ¯ooded except G-1, G-3,

B-7 and B-8.

The variations in N2O emission could also be due to

the changing groundwater levels. The highest amount of

N2O emission from site B-7 compared to the lowest N2O

emission at site G-2 clearly indicates that the N2O

emission was maximum at non-¯ooded conditions. The

¯uctuation of groundwater due to the tidal movement in

site B-7 may also have contributed to the high N2O

emission in this site. These results have some practical

implication in the management of N2O emission from

peatland; the emission will be more at sites where the

water table ¯uctuated. In contrast, the ¯ooded condi-

tions at site G-2 was not favorable for the nitri®cation,

resulting in the lowest N2O emission. The presence of

supernatant water at ¯ooded sites might have also

Table 4

E�ect of ammonium fertilizer on emission of N2O, soil pH, NH�4 and NOÿ3 concentrations in paddy ®eld soil (site B-6) in South

Kalimantan

Sample

depth

(cm)

Treatments N2O emission (ng N2O-N gÿ1 dry soil) pH NH�4(lg N gÿ1 soil)

NOÿ3(lg N gÿ1 soil)

Day 1 Day 2 Day 3 Day 4 Day 6 Day 14 Day 0 Day 14 Day 0 Day 7 Day 0 Day 7

0±10 Control

(NH4)2SO4

0.00 6.07 9.17 13.48 25.19 25.05 3.40 3.40 83.5 105.1 1.7 3.09

3.90 2.41 0.00 0.00 0.00 0.00 3.36 1111.3 145.3 19.15

10±20 Control

(NH4)2SO4

5.48 8.30 9.80 5.45 0.00 0.00 3.49 3.70 87.9 119.7 3.3 2.71

5.44 3.54 0.00 0.00 0.00 0.00 3.45 1115.9 151.9 15.91

20±30 Control

(NH4)2SO4

0.00 3.90 6.29 6.90 11.15 8.43 3.49 3.40 28.7 73.2 4.4 4.35

0.00 0.00 0.00 0.00 0.00 0.00 3.41 1086.9 197.4 14.90


Tab

le5

E�

ect

of

mo

istu

reco

nte

nt

an

dla

nd

-use

ma

na

gem

ent

on

the

emis

sio

ns

of

N2O

,N

H� 4

an

dN

Oÿ 3

con

cen

trati

on

sin

top

ical

pea

tlan

dso

ilsa

Da

ys

Tre

atm

ent

N2O

(ng

Ngÿ1

soil

hÿ1

)N

H� 4

(ug

gÿ1

soil

)N

Oÿ 3

(ug

gÿ1

soil

)

Sit

ebA

-10

A-1

1A

-12

A-1

0A

-11

A-1

2A

-10

A-1

1A

-12

0C

on

tro

l157.0

143.0

190.0

0.5

20.0

32.8

2C

on

tro

l2

.4(1

.7)

1.9

(1.2

)0.2

(0.0

1)

Flo

od

ed6

.7(2

.0)

347.4

(18.8

0)

163.0

(13.1

)

5C

on

tro

l0

.4(0

.03

)0

.3(0

.05)

0.4

(0.1

)147.0

39.0

19.0

16.1

7.2

23.3

Flo

od

ed0

.2(0

.1)

1.0

(0.3

)0.2

(0.0

2)

8.3

152.0

189.7

05.3

10.0

13

Co

ntr

ol

0.1

(0.0

7)

0.0

7(0

.05)

0.1

(0.0

3)

Flo

od

ed0

.02

(0.0

3)

0.0

0(0

.00)

0.0

0(0

.00)

46

Co

ntr

ol

0.3

(0.0

2)

0.3

(0.0

2)

0.1

(0.0

2)

Flo

od

ed0

.4(0

.02

)0

.1(0

.03)

0.1

(0.0

1)

60

Co

ntr

ol

77.5

9.4

14.1

2.5

42.2

38.0

Flo

od

ed25.6

59.4

201.0

017.2

22.0

10

0C

on

tro

l0

.2(0

.02

)0.7

3(0

.61)

0.2

(0.0

4)

8.1

7.0

7.6

5.0

15.2

19.0

Flo

od

ed0

.6(0

.60

)1

6.4

1(1

.27)

22.1

(14.5

)14.0

21.2

218.0

40.2

38.0

44.0

aN

um

ber

sin

pa

ren

thes

isin

dic

ate

sta

nd

ard

dev

iati

on

of

trip

lica

tes

mea

sure

men

ts.

bA

-10

:ri

ce±

soy

bea

nro

tati

on

®le

d,

A-1

1:

pa

dd

y®

eld

,A

-12

:se

con

dary

fore

st.


provided less di�usivity of soil in emitting N2O from

¯ooded sites (Terry et al., 1981a; Keller and Reiners,

1994; Mosier and Delgado, 1997).

The di�erences in groundwater level may have also

resulted in the signi®cant di�erence in N2O emission

measured during 1998 and that measured during 1999.

The emission during 1998 was enhanced by the drier

®eld, hence resulted in higher N2O emission.

Soil ammonium concentration varied with di�erent

peatland sites and soil depths (Table 3). The soil NH�4concentration during 1998 ranged from 2 to 89 lg NH�4gÿ1 soil, while the soil NH�4 concentration during 1999

was signi®cantly higher than that of 1998 and ranged

from 40.4 to 1362 lg NH�4 gÿ1 soil. Soil nitrate con-

centration during 1998 and 1999 followed similar trend

of changing with sites and were in similar range (i.e.,

2±16 in 1998 and 3.3±83 in 1999) (Table 3).

Redox potentials (Eh) measured during 1998 and

1999, indicated that they changed with experimental

sites and were generally higher, where the groundwater

level was lower (Table 3). The Fe2� concentration in

pore water during 1998 was higher (i.e., 200 mg Fe2� Lÿ1

in site B-6), than that during 1999.

3.3. Laboratory incubation experiment 1: e�ect of

ammonium fertilizer on N2O emission

The addition of (NH4)2SO4 to soil signi®cantly re-

duced the emission of N2O compared to the control

treatments (Table 4). The N2O emission in the fertilizer

treated soils was very fast during the ®rst 2 days of in-

cubation and became slow for the remaining period of

incubation. The higher NH�4 and lower NOÿ3 concen-

trations measured on day 7 indicated that nitri®cation

was much slower which could have lowered the rate of

N2O emission from ammonium fertilizer treated soils.

This is supported by Heynes (1986) and Zaman et al.

(1999) who reported slower nitri®cation rate due to high

ammonium concentration and anaerobic condition.

Fig. 2. Emission rate of N2O at di�erent water content of soil

taken from paddy ®eld site B-6 in South Kalimantan. Bars in-

dicate standard error of two replicates.

Fig. 3. Changes in nitrous oxide concentrations in head space

of (A) unamended, (B) ammonium sulfate-amended and (C)

rice straw-amended peat soils from Sarawak. Data with coef-

®cient of variance more than 100% were excluded from these

graphs because the big variations may be due to experimental

errors.


3.4. Laboratory incubation experiment 2: e�ect of mois-

ture contents and land-use management on N2O emission

The N2O emission was strongly in¯uenced by soil

water contents and land-use managements (Table 5).

Incubating soil samples at ¯ooded condition, resulted in

signi®cantly higher amounts of N2O emission than those

at 60% water contents, indicating that the moisture

content of 60% limited the N2O formation. It can be

through retarding the proliferation of N2O producing

microorganism by an insu�ciency of water (Paul and

Clark, 1996). These results are contrary to our ®eld

measurements, where ¯ooded conditions resulted in

lower N2O emission. These could be due to the variable

®eld conditions plus some other variables which were

not considered in this study. On day 2 of the incubation

period, the paddy ®eld soils (A-11) resulted in signi®-

cantly higher amount of N2O (347.4 ng gÿ1 soil hÿ1)

than that from secondary forest soil (A-12) (162.6) at

¯ooded conditions; while the rice±soybean rotation ®eld

(A-10) resulted in the lowest N2O emission rate (6.4) at

the same moisture content. These variations are proba-

bly due to di�erence in land-use managements as dis-

cussed earlier in ®eld experiment. The N2O emission

during the remaining incubation period reduced except

on day 100, when secondary forest soils (A-12) resulted

in a high N2O emission followed by paddy ®eld (A-11) at

¯ooded conditions.

The NH�4 and NOÿ3 concentrations changed with

land-use management and soil water contents (Table 5).

The soil NH�4 concentration in paddy ®eld (A-11) and

secondary forest (A-12) did not decrease quickly when

the soils were incubated under ¯ooded conditions; while

those at 60% water contents disappeared at a faster rate.

This might be due to the fast nitri®cation at 60% water

content than that at ¯ooded condition because all nit-

ri®ers are strictly aerobes (McLaren and Cameron, 1996;

Paul and Clark, 1996). The NOÿ3 concentration de-

creased quickly during the ®rst 5 days of incubation and

increased afterward when the soils were incubated under

¯ooded condition indicating fast denitri®cation rates at

¯ooded conditions than at 60% moisture content. These

results con®rm previous studies that denitri®cation

proceeds at faster rate under ¯ooded conditions

(Bouwman, 1990; Paul and Clark, 1996).

The amount of N2O emitted from soil taken from

paddy ®eld site B-6 was signi®cantly a�ected by soil

water content (Fig. 2). The N2O emission rate was

highest from 100% water content followed by that from

¯ooded soil, 80% and 70% moisture contents in this

order. This indicates that 100% moisture content fa-

vored the N2O emission. Flooding the soil resulted in the

lower N2O emission than that incubated under 100%

moisture level for the same reason explained for the ®eld

experiment (Section 3.2).

3.5. Laboratory incubation experiment 3: e�ect of rice

straw, ammonium fertilizer and soil depths on N2O

emission

The emission of N2O during the 28 days of incu-

bation was strongly in¯uenced by soil samples from

di�erent depths and by the addition of rice straw and

(NH4)2SO4 (Fig. 3). During the ®rst 7 days, the

(NH4)2SO4 or rice straw amended soils suppressed the

N2O emission in soil samples from all ®ve depths ex-

cept (20±40 cm). This could have been due to the in-

hibitory e�ect of NH�4 on nitri®cation which provides

substrate (i.e., NOÿ3 ) for denitri®cation (Haynes, 1986;

Zaman et al., 1999). This is con®rmed when the sur-

face soil layer (0±10 cm) of the unamended soils re-

sulted in higher N2O than the same layers of amended

soils during the ®rst two weeks of incubation. In

amended soils, soil samples from (20±40 cm) produced

more N2O than other soil depths. The denitri®cation

Table 6

Changes in NH�4 and NOÿ3 concentrations and water soluble organic carbon (SOC) during 28 days after addition of rice straw to

tropical peatland soil from Sarawak (site S)

Soil depth (cm) Incubation time (day) NH�4 (ug N gÿ1 soil) NOÿ3 (ug N gÿ1 soil) SOC (mg C gÿ1 dry soil)

0±10 0 ± 2.2 6.4

28 ± 0.0 2.2

10±20 0 291.2 0.0 5.5

28 5.7 0.0 1.9

20±40 0 286.4 4.3 4.9

28 5.4 3.3 1.1

40±60 0 68.4 4.6 5.1

28 4.4 3.3 1.7

60±80 0 37.2 5.5 4.9

28 10.9 5.1 1.7


in soil depth 20±30 cm of rice straw-amended soil was

enhanced by the presence of high water-soluble carbon

(i.e., rice straw powder). The water-soluble carbon

coupled with wet conditions might have resulted in the

highest N2O emission from soil depth 20 to 40 cm of

rice straw-amended soil. The N2O emission from both

amended and unamended treatments in subsoil layers

(below 40 cm) were very low (less than 0.5 lg N gÿ1

soil). This could be due to the low availability of

carbonaceous materials (Table 6) and low microbial

activity (Inubushi et al., 1998).

4. Conclusions

The results from the ®eld experiment showed that

land-use managements, changing water table and loca-

tions had a signi®cant impact on N2O emission.

Changing peatland into cultivated lands (cultivated up-

land and paddy ®eld) enhanced the N2O emission. For

example, cultivated upland Cassava crop resulted in the

highest amounts of N2O emission (1.04 mg N mÿ2 hÿ1)

compared to other treatments. The N2O emission during

1998 was higher than those during 1999 because of the

changing water table and dry season in 1998. The lab-

oratory experiments showed that the N2O emission was

also strongly in¯uenced by land-use management, soil

moisture contents, addition of ammonium fertilizer or

rice straw and soil depths. For example, the ¯ooded

conditions stimulated the N2O emission compared to

that at 60% moisture contents. Similarly, the addition of

ammonium fertilizer suppressed the N2O emission

compared to control treatments because of the high

ammonium contents that inhibit nitri®cation. Never-

theless, incorporation of rice straw to soil samples from

20 to 40 cm soil depth stimulated N2O emission indi-

cative of favorable conditions for both nitri®cation and

denitri®cation.

Acknowledgements

We acknowledge H. Ari®n (professor of Soil Science

at Lambung Mangkurat University) for his valuable

comments, suggestions and help. The ®eld work in

South Kalimantan was possible by the help of Messrs.

Hairil Ifansyah, Sudirman and Tau®k Fadilah (sta� and

students of Lambung Mangkurat University) and Mu-

hammad Haridi (sta� of Agricultural Extension Station

in Amuntai). The help of Dr. Mohammad Zaman

(Lincoln University, New Zealand) during the prepara-

tion of this manuscript is highly acknowledged. This

work was partly supported by the Grant from the En-

vironmental Agency, Japan.

References

Agustin, J., Merbach, W., Sre�ens, L., Snelinski, B., 1998.

Nitrous oxide ¯uxes of disturb mineratrophic peatlands.

Agribiol. Res. 51, 47±57.

Ahmad, Md.S., Kamarudin, A., Ismail, A.B., 1986. Agronomic

consideration on peatland development: A Malaysian

experience. In: Proceedings of the Second International Soil

Management Workshops. Thailand/Malaysia, pp. 195±211.

Anderson, J.M., Ingram, J.S.I., 1989. Colorimetric determina-

tion of ammonium. In: Tropical Soil Biology and Fertility.

ISSS, CAB International, Wallingford, pp. 42±43.

Bouwman, A.F., 1990. Introduction. In: Bouwman, A.F. (Ed.),

Soils and the Greenhouse E�ect. Wiley, New York, pp. 25±

35.

Driesen, P.M., 1981. Peat soil. In: IRRI (Ed.), Soil and Rice.

IRRI, Los Ba~nos, Philippines, pp. 763±779.

FAO, 1988. Revised legend of the FAO-Unesco soil map of the

world. World Soil Resources Report No. 60, Rome, p. 109.

Hayashi, A., Sakamoto, K., Yoshida, T., 1997. A rapid method

for determination of nitrate in soil by hydrazine reduction

procedure. Jpn. J. Soil Sci. Plant Nutr. 68, 322±326 (in

Japanese).

Hesse, P.R. (Ed.), 1971. A Text Book of Soil Chemistry

Analysis. William Clower, London, pp. 464±476.

Heynes, R.J., 1986. The decomposition process: mineralization,

immobilization, humus formation, and degradation. In:

Heynes, R.J. (Ed.), Mineral Nutrition in the Plant±Soil

System. Academic Press, Orlando, pp. 52±125.

Inubushi, K., Hadi, A., Okazaki, M., Yonebayashi, K., 1998.

E�ect of converting wetland forest to sago palm plantations

on methane ¯ux and organic carbon dynamics in tropical

peat soil. Hydrological Processes 12, 2073±2080.

Ismunadji, Soepardi, G., 1984. Peat soil: problems and crop

production. In: IRRI (Ed.), Organic Matter and Rice.

IRRI, Los Ba~nos, Philippines, pp. 489±502.

Keller, M., Reiners, W.A., 1994. Soil±atmosphere exchange of

nitrous oxide, nitric oxide and methane under secondary

succession of pasture to forest in the Atlantic lowland of

Costa Rica. Global Biogeochem. Cycle 8, 399±409.

MacKinnon, K., Hatta, G., Halim, H., Mangalik, A. (Ed.),

1996. The Ecology of Kalimantan. Periplus Editions (HK)

Ltd, Singapore, pp. 802.

Maruo, T., Nomura, K., Shinohara, Y., Hajo, M., Ito, T., 1998.

Studies on the method of determination of inorganic ion

concentration in nutrient solutions for hydroponics using a

simple re¯ection photometer system. Tech. Bull. Fac. Hort.

Chiba Univ. 52, 1±6.

McLaren, R.G., Cameron, K.C., 1996. Soil, plant and fertilizer

nitrogen. Soil Science. Oxford University Press, Auckland,

pp. 192±206.

Moehansyah, 1988. Capability of tidal swampy area of South

Kalimantan for housing. Faculty of Agriculture, Lambung

Mangkurat University, pp. 1±11 (in Indonesian).

Mosier, A.R., Delgado, J.A., 1997. Methane and nitrous oxide

¯uxes in grasslands in western Puerto Rico. Chemosphere

35, 2059±2082.

Paul, E.A., Clark, F.E., 1996. Soil Microbiology and Biochem-

istry. Academic Press, San Diego, pp. 273.

Radjagukguk, B., 1990. Management of peatland productivity

for lowland rice. In: Taher, et al. (Eds.), Pengelolaan Sawah


Bukaan Baru Menunjang Swasembada Pangan dan Pro-

gram Transmigrasi. Faperta, University Prasakti/Balittan

Sukarami, pp. 217±235 (in Indonesian with English sum-

mary).

Sabiham, S., 1988. Studies on peat in the coastal plains of

Sumatra and Borneo, physiography and geomorphology of

the coastal plains. Southeast Asian Studies 26, 308±335.

Sabiham, S., 1989. Studies on peat in the coastal plains of

Sumatra and Borneo, micromorphological study of peat in

coastal plains of Jambi, South Kalimantan and Brunei.

Southeast Asian Studies 27, 339±351.

Takai, Y., 1997. Environmental characteristic and management

in peat/acid sulfate soils of Southeast Asia. MAB Report,

Japan, 1996±1997, pp. 31±49.

Terry, R.E., Tate III, R.L., Duxbury, J.M., 1981a. The e�ect of

¯ooding on nitrous oxide emission from an organic soil. Soil

Sci. 132, 228±232.

Terry, R.E., Tate III, R.L., Duxbury, J.M., 1981b. Nitrous

oxide emissions from drained, cultivated organic soils of

south Florida. J. Air Pollution Control Assoc. 31, 1173±

1177.

Zaman, M., Di, H.J., Cameron, K.C., Frampton, C.M., 1999.

Gross nitrogen mineralization and nitri®cation rates and

their relationship to enzyme activities and the soil microbial

biomass in soils treated with dairy shed e�uent and

ammonium fertilizer at di�erent water potentials. Biol.

Fertil. Soils 29, 178±186.

Abdul Hadi is a sta� member of Lambung Mangkurat Uni-versity, Banjarmasin (Indonesia) and is now a Ph.D student atChiba University (Japan). His research interest is on the man-agement of wetlands. So far, he has published ®ve papers onthis topic.


Effect of land-use changes on nitrous oxide (N2O) emission from tropical peatlands

Documents

Transcript of Effect of land-use changes on nitrous oxide (N2O) emission from tropical peatlands