Estimation of methane and nitrous oxide emissions from paddy fields in Taiwan
Shang-Shyng Yang
a
,b
,*
, Chao-Ming Lai
c
, Hsiu-Lan Chang
b
, Ed-Huan Chang
b
, Chia-Bei Wei
b
aDepartment of Biochemical Science and Technology, National Taiwan University, Taipei 10617, Taiwan bInstitute of Microbiology and Biochemistry, National Taiwan University, Taipei 10617, Taiwan cDepartment of Agricultural Chemistry, National Taiwan University, Taipei 10617, Taiwan
a r t i c l e
i n f o
Article history:
Available online 20 January 2009 Keywords: Methane Nitrous oxide Paddy field Intermittent irrigation IPCC
a b s t r a c t
To investigate the greenhouse gases emissions from paddy fields, methane and nitrous oxide emissions were estimated with the local measurement and the IPCC method during 1990–2006 in Taiwan. Annual methane emission ranged from 9001 to 14,980 ton in the first crop season for 135,314–242,298 ha of paddy fields, and it was between 16,412 and 35,208 ton for 101,710–211,968 ha in the second crop season with the local measurement for intermittent irrigation. The value ranged from 31,122 to 55,729 ton of methane emission in the first crop season, and it was between 29,493 and 61,471 ton in the second crop season with the IPCC guideline for continuous flooding. Annual nitrous oxide emission from paddy fields was between 371 and 728 ton in the first crop season, and the value ranged from 163 to 365 ton in the second crop season with the local measurement. Methane emission from paddy fields in Taiwan for intermittent irrigation was only 26.72–28.92%, 55.65–57.32% and 41.19–43.10% with the IPCC guidelines for continuous flooding and mean temperature of transplanting stage in the first crop, the second crop and total paddy fields, respectively. The values were 53.44–57.84%, 111.29–114.55% and 82.38–86.20% with the IPCC guidelines for single aeration and mean temperature of transplanting stage, respectively; and the values were 133.60–144.61%, 282.56–286.62% and 205.96–215.49% with the IPCC guidelines for multiple aeration and mean temperature of transplanting stage, respectively. Intermittent irrigation in paddy fields reduces methane emission significantly; appropriate application of nitrogen fertilizer and irrigation in paddy fields also decreases nitrous oxide emission.
Ó 2008 Published by Elsevier Ltd.
1. Introduction
Global warming induced by increasing greenhouse gases
concentrations in the atmosphere is a matter of great
environ-mental concern. Methane, carbon dioxide, nitrous oxide and
chlo-rofluorocarbons (CFCs) are the greenhouse gases, which have strong
infrared absorption bands and trap part of the thermal radiation
from the earth’s surface. Concentrations of carbon dioxide,
methane, nitrous oxide and CFCs increased from 337 to 360, 1.50 to
1.72, 0.302 to 0.320, and 4.68 10
4to 7.69 10
4g m
3,
respec-tively, during last decade in the atmosphere
[1]
.
About 80% of methane is produced biologically and the major
source sites are rice paddy, wetland, sediment, enteric
fermenta-tion, animal wastes treatment, agricultural waste burning,
savannah burning, landfill and sewage treatment under low redox
potential conditions by obligate anaerobes
[2–12]
. The release of
nitrous oxide was increasing in recent years due to more intensive
agricultural practices. Denitrification of heterotrophic microbes in
oxygen deficient environments, nitrification of autotrophic and
heterotrophic nitrifying microbes and dissimilate nitrate to
ammonium of heterotrophic microbes in aerobic conditions
produced nitrous oxide
[13]
. The contribution of agriculture to the
global annual nitrous oxide emission was estimated at
approxi-mately 35%
[14]
.
In Taiwan, there were 263,188 ha of paddy fields and more than
4 million tons of crop residues in 2006. Rice was cultivated with
intermittent irrigation in Taiwan, while continuous flooding was
used in other countries. There are two crop seasons in Taiwan, the
first crop season is cultivated in February and harvested in July, and
the second crop season is cultivated in August and harvested in
December. Estimation of methane and nitrous oxide emissions
from paddy fields during 1990–2006 with the country-specific
emission factors were used, whereas the local data were
unavail-able and the emission factors recommended by the IPCC guideline
[15,16]
were used.
*Corresponding author. Department of Biochemical Science and Technology,
National Taiwan University, Taipei 10617, Taiwan. E-mail address:ssyang@ntu.edu.tw(S.-S. Yang).
Contents lists available at
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j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / r e n e n e
0960-1481/$ – see front matter Ó 2008 Published by Elsevier Ltd. doi:10.1016/j.renene.2008.12.016
2. Materials and methods
2.1. Cultivation area
Cultivation areas of paddies in Taiwan from 1990 to 2006 are
adapted from the Taiwan Agriculture Yearbook from 1991 to 2007
[17,18]
.
2.2. Measurement of methane and nitrous oxide emissions
Methane and nitrous oxide emissions were measured by
home-made acrylic chamber (length 40 cm, width 40 cm and height
65 cm, about 96 l)
[19]
. Methane and nitrous oxide were analyzed
by gas chromatograph using FID and ECD, respectively
[20]
.
2.3. Methane and nitrous oxide emission factors of paddy fields
Methane and nitrous oxide emission factors from paddy fields of
Taiwan were measured by the local measurement and listed in
Table 1
. Other emission factors were recommended by the IPCC
guidelines
[15]
. Most of the paddies were applied chemical
fertil-izers; only the organic paddies production used organic fertilizers.
2.4. Estimation of methane and nitrous oxide emissions
Methane and nitrous oxide emissions from paddy fields were
calculated from the experimental data and estimated by the
following equation at each growth stage
[7,32]
.
F [ ðV=AÞð
D
C=
D
tÞ
Where F is the methane or nitrous oxide emission rate
(mg m
2h
1), V is the volume of chamber above the soil (m
3), A is
the cross-section of chamber (m
2),
D
C is the concentration
difference between zero time and time t (mg m
3), and
D
t is the
time duration between two sampling period (h). The total
methane or nitrous oxide emission from paddy fields was the
summation of methane and nitrous oxide emissions in all growth
stages of crops.
Table 1
Greenhouse gas emission from paddy fields.
Location Treatment Methane emission Nitrous oxide emission
1st crop 2nd crop 1st crop 2nd crop Full year
g m2
NTU Exper. Station Inter. irrigation 2.55–11.70k 13.73k 0.30–0.39g 0.07–0.75g –
Cont. flooding – 28.85k – – –
Taoyuan Dist. AIS Inter. irrigation 1.73–5.23k 10.54–10.56k 0.44–0.54g 0.06–0.40g –
W/green manure 5.55k 14.43–30.12k – 1.22g –
Miaoli farm Inter. irrigation 9.82k 39.50k – – –
NCHU Exper. Station Inter. irrigation 8.18j 1.18j
0.11–0.60a 0.11–0.50a 0.22–1.25a
0.61b
Huatan-CH farm Inter. irrigation 9.00–19.80c,l 12.03–33.11c,l 0.32h 0.48–0.52h,l –
Inter. irrigation – 4.76l – 0.27l
Chihu-CH farm Inter. irrigation 0.15j 10.45j – – 0.05–1.11a
Chihu-CH farm Inter. Irrigation 23.06c – – – –
Tachen-CH farm Inter. Irrigation 0.94g – – – –
Tienwei-CH farm Inter. Irrigation 0.59b
Chiayi farm Inter. irrigation 3.48j 10.17j – – 0.24–0.99a
Lutsao-Chiayi Inter. Irrigation 4.78d 35.27d – – 0.44b
Inter. Irrigation 9.20e 49.00e
W/burned rice straw 4.10d 41.79d
W/rice straw 5.72d 80.62d
W/chicken manure 66.90e
W/soybean cake 46.65e
W/rice bran 14.89e
Cont. flooding 55.80e 84.50e
Kaohsiung Dist. AIS Inter. irrigation 2.36j 8.47j – – 0.05–1.14a
Inter. Irrigation 0.49e
Hwalien-Lotung AIS Inter. irrigation 2.92k 24.64k 0.35–0.78g 0.0–0.06g –
Hwalien-Chian AIS Inter. irrigation 1.42–2.42i 0.26–2.33i – – –
W/rice straw 2.77–2.85i 3.13–7.60i – – –
Hwalien-Fuli AIS Inter. irrigation 7.40–13.10i 12.50–24.30i – – –
W/high N fertile. 11.60–19.73i 21.14–48.37i – – –
IPCC Cont. flooding 23f 29f – – –
Single drain 11.50f 14.50f Multiple drains 4.6f 5.8f aChao[21]. b Chao[22]. c Chen et al.[23]. d Huang et al.[24]. e Huang et al.[25]. f IPCC[15]. g Lai[26]. hLai et al.[27]. i Huang et al.[28]. j Wang and Shieh[29]. k Yang and Chang[6,30].
3. Results and discussion
3.1. Methane emission from paddy fields
There are two crop seasons for paddy rice in Taiwan. Total
growth period of paddy rice in the first crop season (February to
July) was between 122 and 149 days, and it ranged from 112 to 135
days in the second crop season (August to December). The daily
temperature increased gradually during rice cultivation in the first
crop season, and it was reversed in the second crop season. The
mean temperature in the first crop season (February to July) was
19.17–26.25
C, and the value was 19.54–26.56
C in the second
crop season (August to December). While the mean temperature
during the transplanting stages of rice cultivation was 16.27–
24.10
C in the first crop season (February to April), and the value
was 21.20–28.37
C in the second crop season (August to October).
Most of mean temperatures in the second crop were higher than
those in the first crop except in 1991 and some areas in 1994, 1999,
2001, 2002, 2003 and 2004. This is different from the single crop
season countries such as Japan, Korea, USA and Italy
[33–36]
.
Therefore, the methane emission patterns of the two crop seasons
in Taiwan were also different from other locations with single crop
season. Methane emission was high at the active tillering, booting,
flowering and ripening stages for the active degradation of organic
Table 2
Methane emission from paddy fields in Taiwan with local measurement from 1990 to 2006 (ton).
Year Taipei, Keelung I-lan Taoyuan, Hsinchu Miaoli Taichung, Changhua, Nantou Yuanlin, Chiayi, Tainan Kaohsiung, Pingtung Taitung, Hwalien Total 1990 1st crop 265.9 319.2 989.4 1,327.8 6,161.8 4,510.8 496.0 908.6 14,979.5 2nd crop 240.4 1,371.9 3,823.0 5,372.3 6,058.6 15,009.1 1,702.5 1,631.1 35,208.4 Sub-total 506.3 1,691.0 4,812.4 6,700.1 12,220.3 19,519.9 2,198.5 2,539.7 50,187.9 1991 1st crop 206.1 286.0 934.1 1,219.0 5,800.0 4,357.4 435.7 862.9 14,101.2 2nd crop 198.8 1,272.1 3,778.9 4,828.2 5,950.1 14,104.4 1,502.4 1,526.7 33,161.6 Sub-total 404.9 1,558.1 4,712.9 6,047.1 11,750.1 18,461.8 1,938.1 2,389.7 47,262.8 1992 1st crop 167.1 288.5 909.9 1,136.3 5,648.2 3,641.9 390.9 851.5 13,034.3 2nd crop 131.1 819.7 3,587.5 4,711.2 5,675.3 13,303.0 1,233.1 1,496.0 30,956.9 Sub-total 298.2 1,108.3 4,497.3 5,847.5 11,323.5 16,944.9 1,623.9 2,347.6 43,991.2 1993 1st crop 142.1 276.7 862.7 1,079.7 5,337.4 4,272.2 357.4 798.8 13,127.0 2nd crop 96.9 754.9 3,468.9 4,388.4 5,448.4 12,952.9 1,053.0 1,451.5 29,614.9 Sub-total 239.0 1,031.5 4,331.6 5,468.1 10,785.8 17,225.1 1,410.4 2,250.3 42,741.9 1994 1st crop 99.6 278.3 723.2 1,055.4 5,077.6 3,808.2 375.3 816.4 12,234.0 2nd crop 84.4 480.4 3,185.6 4,270.2 5,187.7 12,377.6 988.7 1,457.0 28,031.6 Sub-total 184.0 758.7 3,908.8 5,325.6 10,265.3 16,185.8 1,364.0 2,273.4 40,265.6 1995 1st crop 106.2 270.2 782.5 982.6 4,923.9 4,033.6 329.4 799.0 12,227.4 2nd crop 76.8 301.5 3,239.9 4,264.1 4,985.1 12,182.0 895.9 1,543.7 27,489.0 Sub-total 182.9 571.7 4,022.3 5,246.8 9,909.0 16,215.6 1,225.3 2,342.7 39,716.4 1996 1st crop 76.0 267.5 655.9 951.3 4,777.2 3,540.9 316.5 870.2 11,455.5 2nd crop 71.9 264.7 3,115.5 3,994.9 4,875.2 12,400.8 925.8 1,632.9 27,281.7 Sub-total 147.9 532.2 3,771.4 4,946.2 9,652.4 15,941.7 1,242.3 2,503.1 38,737.2 1997 1st crop 86.5 282.6 783.1 960.1 4,923.3 4,205.9 303.7 963.9 12,509.1 2nd crop 64.4 207.3 3,231.5 4,102.1 4,787.6 11,886.0 813.4 1,728.0 26,820.3 Sub-total 150.9 489.8 4,014.5 5,062.2 9,710.9 16,091.9 1,117.1 2,691.9 39,329.4 1998 1st crop 72.0 275.2 792.5 956.0 4,782.2 4,260.3 305.5 977.0 12,420.7 2nd crop 60.7 29.1 3,108.1 3,886.5 4,624.2 11,759.0 720.2 1,677.9 25,865.7 Sub-total 132.7 304.3 3,900.7 4,842.4 9,406.4 16,019.3 1,025.8 2,654.9 38,286.4 1999 1st crop 67.1 272.7 747.1 897.7 4,680.9 4,174.5 303.5 970.9 12,114.4 2nd crop 53.2 76.5 2,821.6 3,776.8 4,639.2 11,910.1 789.2 1,745.6 25,812.2 Sub-total 120.3 349.2 3,568.7 4,674.6 9,320.1 16,084.6 1,092.7 2,716.5 37,926.6 2000 1st crop 62.7 268.0 710.4 904.0 4,518.1 4,252.0 317.7 978.6 12,011.5 2nd crop 50.0 42.6 2,461.2 3,245.3 4,449.9 11,095.6 695.9 1,693.3 23,734.7 Sub-total 112.7 310.6 3,171.6 4,149.3 8,968.0 15,347.6 1,013.6 2,671.9 35,745.3 2001 1st crop 56.8 258.9 667.6 853.1 4,499.4 4,078.3 307.3 917.8 11,639.2 2nd crop 49.7 8.5 2,325.6 2,889.6 4,485.3 11,304.4 656.4 1,726.6 23,446.1 Sub-total 106.6 267.4 2,993.2 3,742.7 8,984.8 15,382.7 963.8 2,644.5 35,085.3 2002 1st crop 50.9 236.3 538.6 723.1 4,430.7 3,939.3 289.8 946.0 11,154.7 2nd crop 43.8 7.2 1,714.6 2,790.9 4,257.3 10,354.1 518.1 1,587.6 21,273.6 Sub-total 94.7 243.5 2,253.2 3,514.0 8,688.1 14,293.4 807.9 2,533.6 32,428.3 2003 1st crop 42.0 234.0 269.5 743.7 4,309.1 3,637.1 286.5 900.3 10,422.2 2nd crop 40.1 0.3 1,136.9 2,305.3 3,843.3 9,000.5 425.5 1,476.0 18,227.9 Sub-total 82.1 234.3 1,406.4 3,049.0 8,152.4 12,637.6 712.0 2,376.3 28,650.1 2004 1st crop 39.6 215.9 133.9 546.4 4,181.3 2,733.4 270.9 879.8 9,001.1 2nd crop 43.4 0.8 944.0 2,039.3 3,760.0 7,786.7 323.6 1,514.0 16,411.7 Sub-total 83.0 216.7 1,077.8 2,585.7 7,941.3 10,520.1 594.4 2,393.8 25,412.8 2005 1st crop 38.2 215.2 342.9 654.6 4,247.0 3,560.0 268.9 879.7 10,206.5 2nd crop 39.1 0.3 1,103.2 2,305.7 3,866.4 9,133.9 295.9 1,544.3 18,288.8 Sub-total 77.3 215.5 1,446.1 2,960.3 8,113.4 12,693.9 564.7 2,424.0 28,495.3 2006 1st crop 33.0 215.1 287.8 620.7 4,188.9 3,591.1 243.5 906.4 10,086.5 2nd crop 33.6 0.5 886.5 2,135.1 3,730.0 9,357.3 219.0 1,580.0 17,942.0 Sub-total 66.6 215.6 1,174.3 2,755.8 7,918.9 12,948.4 462.5 2,486.4 28,028.5 Average 1st crop 94.8 262.4 654.8 918.3 4,852.2 3,917.5 329.3 895.8 11,924.6 2nd crop 81.1 331.7 2,584.3 3,606.2 4,742.6 11,524.6 809.3 1,589.0 25,268.8 Sub-total 175.9 594.1 3,239.1 4,524.5 9,594.8 15,442.1 1,138.6 2,484.8 37,193.4
matter and high concentration of root secretes
[6,7]
. However,
drainage was practiced at the flowering and ripening stages in the
intermittent irrigation system, and the methane emission rate
decreased at these stages. Methane emission was high at the
flooding and the transplanting stages in the second crop season for
organic matter degradation with high temperature. While methane
emission was low at the flooding and the transplanting stages in the
first crop season for low temperature, and it was also low at the
flowering and the ripening stages for the intermittent irrigation
and high redox potential repressed methane emission. Therefore,
methane emission from paddy field in the second crop season was
higher than those in the first crop season.
Methane emission was between 0.15 and 19.80 g m
2with
intermittent irrigation in the first crop season, and it ranged from
1.18 to 49.00 g m
2in the second crop season. Methane emission
increased with green manure, burn rice straw, rice straw, rice bran,
soybean cake and chicken manure amendment. It was 1.06–3.20,
0.86, 1.18–1.95, and 1.62 times higher than those with intermittent
irrigation and convention chemical fertilizer application for green
manure, burn rice straw, rice straw and rice bran amendment in the
first crop season, respectively; and the value was 1.36–2.85, 1.18,
1.34–3.26, 1.37, and 0.95 times higher than those with intermittent
irrigation for green manure, burn rice straw, rice straw, chicken
manure and soybean cake amendment in the second crop season,
respectively
[6,24,25,28,30]
. High nitrogen fertilizer application
also enhanced 1.51–1.57 and 1.69–1.99 times of methane emission
higher than those with convention nitrogen chemical fertilizer
application in the first and second crop seasons, respectively
[28]
.
Green manure amendment stimulated methane emission rate and
it also increased the soil organic matter content
[6,30]
. Similar
results were also found in rice cultivated during dry and wet crop
seasons in the Philippines paddy fields
[37]
.
Methane emission factors of paddy fields at different locations
in Taiwan with the local measurement were the average of the local
measurement at different years and different paddy fields in each
location. Methane emission in the second crop season was 1.15–
12.94 times higher than those in the first crop season with
inter-mittent irrigation; the reverse was true in the pot cultivation with
continued flooding
[6,38]
. There was a 10–15 cm depth of flooding
in the soil surface during the rice cultivation in Italian, Louisiana
and California paddy fields
[4,37]
. However, the intermittent
irri-gation system was very popular in the late stage of paddy rice
cultivation in Taiwan to reduce the water resource for rice growth,
to increase the rice yield and to eliminate toxic substances in the
rice root. The accumulative methane emission was around 47–58%
lower with intermittent irrigation than with continuous flooding
treatment. Miaoli area had high methane emission due to the high
soil organic matter content
[7]
.
Cultivation area of paddy fields in the first crop was 1.14 times
higher than that of the second crop in 1990, the value increased
gradually to 1.45 times in 2003, and then the value slightly
decreased to 1.44 in 2006. Cultivation area of paddy fields in the
first crop was higher than the second crop due to the cultivation of
vegetable and upland crop, and the low rice productivity (71–91%
of the first crop) in the second crop season. Cultivation area of
paddy fields was also decreased because of the change of culture
system and agriculture policy in Taiwan. The first crop, second crop
and total cultivation area were 242,298, 211,968 and 454,266 ha in
1990, respectively and the cultivation areas decreased to 155,248,
107,940 and 263,188 ha in 2006. Taichung, Changhua, Nantou,
Yuanlin, Chiayi, and Tainan in the central Taiwan are the major
cultivation area. It had 59.06–67.71%, and 60.48–71.49% of total
paddy cultivation area in the first and the second crop, respectively,
and the ratio increased gradually due to the change of land use and
culture system in the northern and southern Taiwan.
Annual methane emission from paddy fields was calculated
with the emission factors and cultivation area at each location and
the results are illustrated in
Table 2
. Annual methane emission
decreased with the decreasing of cultivation area of rice. Total
methane emissions were 14,980 and 35,208 ton at the first and the
second crop seasons in 1990, respectively, and it decreased to
10,087 and 17,942 ton in 2006. Although the cultivation area of the
first crop was higher than that of the second crop, however,
methane emission of the second crop season was higher than that
of the first crop season. Methane emission of the second crop
season was 2.35 times higher than that of the first crop season in
1990, and the value decreased to 1.78 times in 2006 due to the
cultivation of vegetable and upland crop and the decreasing of
cultivation area of rice paddy in the second crop.
Table 3
Methane emission from paddy fields in Taiwan calculated with local measurement and IPCC guidelines from 1990 to 2006(ton).
Year Local measurement IPCC continuous IPCC single aeration IPCC multiple aeration 1990 1st crop 14,979.5 55,728.9 27,864.3 11,145.7 2nd crop 35,208.4 61,470.7 30,735.4 12,294.1 Sub-total 50,187.9 117,199.6 58,599.7 23,439.8 1991 1st crop 14,101.2 52,305.2 26,152.6 10,461.0 2nd crop 33,161.6 58,399.3 29,199.7 11,679.9 Sub-total 47,262.8 110,704.5 55,352.3 22,140.9 1992 1st crop 13,034.3 48,178.1 24,089.1 9,635.6 2nd crop 30,956.9 54,424.3 27,212.2 10,884.9 Sub-total 43,991.2 102,602.4 51,301.2 20,520.5 1993 1st crop 13,127.0 48,711.7 24,355.9 9,742.3 2nd crop 29,614.9 51,949.7 25,974.9 10,389.9 Sub-total 42,741.9 100,661.4 50,330.7 20,132.3 1994 1st crop 12,234.0 45,152.9 22,576.5 9,030.6 2nd crop 28,031.6 49,160.8 24,580.4 9,832.2 Sub-total 40,265.6 94,313.7 47,156.9 18,862.7 1995 1st crop 12,227.4 45,441.3 22,720.7 9,088.3 2nd crop 27,489.0 48,113.3 24,056.7 9,622.7 Sub-total 39,716.4 93,554.6 46,777.3 18,711.0 1996 1st crop 11,455.5 42,045.6 21,022.8 8,409.1 2nd crop 27,281.7 47,837.0 23,918.5 9,567.4 Sub-total 38,737.2 89,882.6 44,941.3 17,976.5 1997 1st crop 12,509.1 46,462.3 23,231.2 9,292.5 2nd crop 26,820.3 47,038.3 23,519.1 9,407.7 Sub-total 39,329.4 93,500.6 46,750.3 18,700.2 1998 1st crop 12,420.7 46,327.5 23,163.8 9,265.5 2nd crop 25,865.7 45,316.3 22,658.1 9,063.3 Sub-total 38,286.4 91,643.8 45,821.9 18,328.8 1999 1st crop 12,114.4 45,338.3 22,669.1 9,067.7 2nd crop 25,812.2 45,223.2 22,611.6 9,044.6 Sub-total 37,926.6 90,561.5 45,280.8 18,112.3 2000 1st crop 12,011.5 44,862.7 22,431.3 8,972.5 2nd crop 23,734.7 41,918.3 20,959.2 8,383.7 Sub-total 35,746.2 86,781.0 43,390.5 17,356.2 2001 1st crop 11,639.2 43,367.2 21,683.6 8,673.4 2nd crop 23,446.1 41,489.1 20,744.6 8,297.8 Sub-total 35,085.3 84,856.3 42,428.2 16,971.3 2002 1st crop 11,154.7 40,913.3 20,456.7 8,182.7 2nd crop 21,273.6 37,397.2 18,698.6 7,479.4 Sub-total 32,428.3 78,310.5 39,155.3 15,662.1 2003 1st crop 10,422.2 37,072.3 18,536.2 7,414.5 2nd crop 18,227.9 32,172.6 16,086.3 6,434.5 Sub-total 28,650.1 69,244.9 34,622.5 13,849.0 2004 1st crop 9,001.1 31,122.2 15,561.1 6,224.4 2nd crop 16,411.7 29,493.3 14,746.6 5,898.7 Sub-total 25,412.8 60,615.5 30,307.7 12,123.1 2005 1st crop 10,206.5 36,444.0 18,222.0 7,288.8 2nd crop 18,288.8 32,065.6 16,032.8 6,413.1 Sub-total 28,495.3 68,509.6 34,254.8 13,701.9 2006 1st crop 10,080.5 35,707.0 17,853.5 7,141.4 2nd crop 17,944.1 31,302.9 15,651.4 6,260.6 Sub-total 28,024.6 67,009.9 33,504.9 13,402.0 Average 1st crop 11,924.6 43,834.1 21,917.1 8,766.8 2nd crop 25,268.8 44,398.3 22,199.2 8,879.7 Sub-total 37,193.4 88,232.4 44,116.3 17,646.5
Average methane emission factors from paddy fields with 52
samples in 11 locations of the world except Taiwan were
26.00 g m
2. Hour et al.
[39]
reported the average methane
emis-sion factors from the Japan, Korea, Philippines, Thailand and Texas
were 20 g m
2. The methane emission factors were 20 and
26 g m
2in northern and southern Taiwan at the first crop season,
respectively; while the values were 25 and 30 g m
2at the second
crop season, respectively. From the mean temperature of the first
and the second crop growth season, it showed that the average
temperatures of 7 locations from 1990 to 2006 were 23.93 and
24.43
C during the growth period at the first crop (February to
July) and the second crop (August to December) season,
respec-tively. While the mean temperatures during the flooding and the
transplanting stage at the first crop (February to April) and the
second crop (August to October) were 20.41 and 26.53
C,
respec-tively. Methane emission from paddy fields is high at the flooding
and the transplanting stages for the organic matter degradation
and the submerged state
[30,38]
. A positive linear correlation
between
methane
production
(Y)
and
temperature
(X)
(Y ¼ 0.22X 3.94) (r
2¼ 0.93) between 15 and 37
C was described
in previous paper
[30]
. Therefore, the methane emission factors
calculated with the IPCC guideline and mean temperature of the
flooding and the transplanting stages are estimated as 23 and
29 g m
2.
Annual methane emissions from the paddy fields in Taiwan with
the IPCC guideline from 1990 to 2006 are calculated in
Table 3
.
Table 4
Nitrous oxide emission from paddy fields in Taiwan with local measurement from 1990 to 2006 (ton).
Year Taipei, Keelung I-lan Taoyuan, Hsinchu Miaoli Taichung, Changhua, Nantou Yuanlin, Chiayi, Tainan Kaohsiung, Pingtung Taitung, Hwalien Total 1990 1st crop 16.05 80.49 187.87 76.85 147.54 120.96 22.99 74.93 727.68 2nd crop 1.54 1.54 57.12 24.31 116.01 99.87 60.80 3.87 365.06 Sub-total 17.59 82.03 244.99 101.16 263.55 220.83 83.79 78.80 1,092.72 1991 1st crop 12.44 72.12 177.37 70.55 138.87 116.85 20.19 71.16 679.55 2nd crop 1.27 1.42 56.46 21.85 113.94 93.85 53.66 3.63 346.08 Sub-total 13.71 73.54 233.83 92.40 252.81 210.70 18.11 74.79 1,025.63 1992 1st crop 10.09 72.76 172.77 65.76 135.24 97.66 44.04 70.22 668.54 2nd crop 0.84 0.92 53.60 21.32 108.68 88.52 62.15 3.55 339.58 Sub-total 10.93 73.68 226.37 87.08 243.92 186.18 106.19 73.77 1,008.12 1993 1st crop 8.58 69.76 163.81 62.49 127.80 114.56 16.56 65.87 629.43 2nd crop 0.62 0.85 51.82 19.86 104.33 86.19 37.61 3.45 304.73 Sub-total 9.20 70.61 215.63 82.35 232.13 200.75 54.17 69.32 934.16 1994 1st crop 6.01 70.18 137.32 61.08 121.58 102.12 17.39 67.32 583.00 2nd crop 0.54 0.54 47.59 19.33 99.34 82.36 35.31 3.46 288.47 Sub-total 6.55 70.72 184.91 80.41 220.92 184.48 52.70 70.78 871.47 1995 1st crop 6.41 68.15 148.58 56.87 117.90 108.16 15.27 65.89 587.23 2nd crop 0.49 0.34 48.40 19.30 95.46 81.06 32.00 3.67 280.72 Sub-total 6.90 68.49 196.98 76.17 213.36 189.22 47.27 69.56 867.95 1996 1st crop 4.59 67.45 124.55 55.06 114.38 94.95 14.67 71.76 547.41 2nd crop 0.46 0.30 46.54 18.08 93.35 82.51 33.06 3.88 278.18 Sub-total 5.05 67.75 171.09 73.14 207.73 177.46 47.73 75.64 825.59 1997 1st crop 5.22 71.26 148.69 55.57 117.88 112.78 14.07 79.49 604.96 2nd crop 0.41 0.23 48.28 18.56 91.68 79.09 29.05 4.10 271.40 Sub-total 5.63 71.49 196.97 74.13 209.56 191.87 43.12 83.59 876.36 1998 1st crop 4.35 69.40 150.49 55.33 114.50 114.24 14.16 80.57 603.04 2nd crop 0.39 0.03 46.43 17.59 88.55 78.24 25.72 3.99 260.94 Sub-total 4.74 69.43 196.92 72.92 203.05 192.48 39.88 84.56 863.98 1999 1st crop 4.05 68.77 141.87 51.96 112.08 111.94 14.06 80.06 584.79 2nd crop 0.34 0.09 42.15 17.09 88.84 79.25 28.19 4.15 260.10 Sub-total 4.39 68.86 184.02 69.05 200.92 191.19 42.25 84.21 844.89 2000 1st crop 3.79 67.57 134.89 52.32 108.18 114.02 14.72 80.70 576.19 2nd crop 0.33 0.05 36.77 14.69 85.21 73.83 24.85 4.02 239.75 Sub-total 4.12 67.62 171.66 67.01 193.39 187.85 39.57 84.72 815.94 2001 1st crop 3.43 65.29 126.77 49.37 107.73 109.36 14.24 75.69 551.88 2nd crop 0.32 0.01 34.74 13.08 85.89 75.22 23.44 4.10 236.80 Sub-total 3.75 65.30 161.51 62.45 193.62 184.58 37.68 79.79 788.68 2002 1st crop 3.07 59.59 102.27 41.85 106.09 105.63 13.43 78.01 509.94 2nd crop 0.28 0.01 25.62 12.63 81.52 68.89 18.51 3.77 211.23 Sub-total 3.35 59.60 127.89 54.48 187.61 174.52 31.94 81.78 721.17 2003 1st crop 2.53 59.02 51.17 43.04 103.18 97.53 13.28 74.24 443.99 2nd crop 0.26 0.00 16.99 10.43 73.59 59.89 15.20 3.51 179.87 Sub-total 2.79 59.02 68.16 53.47 176.77 157.42 28.48 77.75 623.86 2004 1st crop 2.39 54.45 25.42 31.62 99.07 73.30 12.55 72.55 371.36 2nd crop 0.28 0.01 14.10 9.23 72.00 51.84 11.56 3.60 162.60 Sub-total 2.67 54.46 39.52 40.85 171.07 125.14 24.11 76.15 533.96 2005 1st crop 2.31 54.28 65.10 37.89 100.63 95.46 12.46 72.55 440.67 2nd crop 0.25 0.01 16.48 10.43 74.04 60.81 10.57 3.67 176.25 Sub-total 2.56 54.29 81.59 48.32 174.66 156.28 23.03 76.22 616.92 2006 1st crop 1.99 54.25 53.50 35.93 99.25 96.30 11.28 74.74 427.24 2nd crop 0.22 0.01 13.24 9.66 71.43 62.30 7.82 3.76 168.43 Sub-total 2.21 54.26 66.74 45.59 170.68 158.60 19.10 78.50 595.67 Average 1st crop 5.72 66.16 124.26 53.15 115.99 105.05 16.79 73.87 560.99 2nd crop 0.52 0.37 38.61 16.32 90.82 76.69 29.97 3.78 257.07 Sub-total 6.14 66.53 162.87 69.47 206.81 181.74 46.76 77.65 818.06
Methane emission from the paddy fields in Taiwan that were
proposed by the IPCC guidelines ranged from 31,122.2 to 55,728.9,
29,493.3 to 60,615.5 and 69,244.9 to 117,119.6 ton with continuous
flooding at the first crop, the second crop and the total paddy field
during 1990 to 2006, respectively. Methane emission from the
paddy fields with the local measurement were 26.72–28.11%,
55.65–57.32% and 41.19–43.10% of those calculated with the IPCC
guideline for continuous flooding method at the first crop,
the second crop and total paddy field, respectively. However, the
intermittent irrigation management at the latter stage of rice
growth was used in Taiwan to decrease the toxic substances
accumulation in the flooding soil and the water requirement for
rice growth. Methane emissions from the paddy fields with
continuous flooding for single aeration and continuous flooding for
multiple aerations were 50% and 20% of that with continuous
flooding
[15]
. Sass et al.
[40]
also reported that the paddy fields of
Houston with midseason drain and three aerations were 52.46%
and 12.4% of that continuous flooding, respectively. Methane
emissions from the paddy fields with the local measurement were
53.44–57.84%, 111.29–114.07% and 82.38–86.20% of those calculated
with the IPCC guidelines for continuous flooding and single
aera-tion at the first crop, the second crop and total paddy fields,
respectively. However, the values were 133.60–144.61%, 278.32–
286.62% and 205.96–215.49% of those calculated with the IPCC
guidelines for continuous flooding and multiple aerations at the
first crop, the second crop and total paddy fields, respectively. The
differences among these paddy fields might be due to the different
irrigation managements. Paddy fields in Taiwan had multiple
aerations (more than three aerations) during the flowering and
ripening stages. However, the temperature was low in the flooding
and transplanting stages at the first crop season with continuous
flooding and temperature was high in the flowering and ripening
stages with drain; while the temperature was high in the flooding
and transplanting stages at the second crop season and the
temperature was low in the flowering and ripening stages.
There-fore, methane emission from the paddy fields in Taiwan was lower
than that with continuous flooding and single aeration treatments
in the first crop season, while the value was reversed in the second
crop season. Methane emission from the paddy fields in Taiwan was
lower than those with continuous flooding or continuous flooding
with single aeration, but the value was higher than those with
continuous flooding and multiple aerations by the IPCC guideline in
both crop seasons.
3.2. Nitrous oxide emission from paddy fields
Agriculture is the main source of most nitrous oxide emissions.
Nitrous oxide was produced from soil processes as an intermediate
product of microbial nitrification and denitrification. Nitrous oxide
emission was between 0.11 and 0.78 g m
2with intermittent
irrigation in the first crop season, and it ranged from 0.11 to
0.75 g m
2in the second crop season (
Table 1
)
[21,26,31]
. Nitrous
oxide emission also increased with green manure amendment
[26]
.
It was 3 to 20 times higher than those with convention chemical
fertilizer. Green manure amendment stimulated nitrous oxide
emission rate due to the increase of soil organic matter and
nitrogen content. Nitrous oxide emission increased with the
increasing of nitrogen fertilizer application and decreased with
the nitrification inhibitor added
[41]
.
Nitrous oxide emission coefficient of paddy field at different
locations in Taiwan was between 0.038 and 0.174 mg m
2h
1in the
first
crop
season,
and
the
value
ranged
from
0.010
to
0.105 mg m
2h
1in the second crop season. Nitrous oxide
emis-sion coefficient in the first crop season was higher than those in the
second crop season because of the intermittent irrigation and high
temperature at the later growth stage. Slow-release N fertilizer
application reduced nitrous oxide emission
[40]
. Annual nitrous
oxide emission from paddy fields was calculated with the local
emission factors at each location and cultivation area, and the
results are also presented in
Table 4
. Annual nitrous oxide emission
decreased with the decreasing of cultivation area of paddy. Total
nitrous oxide emission was 1092 ton in 1990 and the value
decreased to 596 ton in 2006. Nitrous oxide derived from N
fertil-izer in paddy field was between 0.05 and 0.28% in the central and
southern Taiwan
[41]
. Appropriate fertilization could reduce the
nitrous oxide emission from the paddy fields.
Acknowledgements
The author thanks Professors H. P. Wu, C. C. Chao, S. N. Huang, R.
M. Liou, J. J. Horng, U. Hegde, and I. C. Lin for their helpful
assis-tances and comments, National Science Council and Environmental
Protection Administration of Taiwan for financial supports.
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