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Water-saving techniques: potential, adoption and empirical evidence for mitigating greenhouse gas emissions from rice production


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This book provides experiences from studies on agricultural water management under climate change as references for agriculture and irrigation planners, decision makers, researchers and students. Chapters 2 and 3 provide an overview of global assessment of climate change impacts and water requirement for future agriculture. Chapters 4-7 provide analyses of crop water requirements in four case studies in developing countries. Chapters 8 and 9 are studies of irrigation management under sea-level rise in Vietnam's Mekong Delta. Chapters 10-12 discuss examples of adaptation alternatives such as water-saving techniques and groundwater exploitation, and related policy settings. The last chapter links the dominant approach of uncertainty presented in the climate change discourse with policy discussions on climate adaptation strategies.
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© CAB International 2015. Climate Change and Agricultural Water Management in
Developing Countries (eds C.T. Hoanh et al.) 193
* Corresponding author, e-mail:
Mitigating Greenhouse
Gas Emissions from Rice
Production through Water-saving
Techniques: Potential, Adoption
and Empirical Evidence
Bjoern Ole Sander,* Reiner Wassmann and Joel
D.L.C. Siopongco
Crop and Environmental Sciences Division, International Rice
Research Institute (IRRI), Los Baños, Philippines
Flooded rice  elds are a large anthropogenic source of the greenhouse gas (GHG) methane (CH4). Aeration of the
paddy  eld can reduce methane emissions and at the same time save water. Di erent forms of water saving tech-
niques (WST), e.g. alternate wetting and drying (AWD) and midseason drainage (MSD), have been developed and
disseminated.  is article gives an overview on adoption of AWD in the Philippines and assesses prospects and
constraints. It also explains the Clean Development Mechanism (CDM) methodology for rice production and anal-
yses the mitigation potential of WST in the form of a literature review.
e adoption rate of AWD strongly depends on the incentive for the farmer. While direct monetary incentives
are limited to areas where saving water is directly linked to reduced costs (e.g. pump irrigation systems), indirect
incentives (e.g. improved crop development) have not yet been scienti cally assessed.  e literature meta-analysis
proves the great mitigation potential of WST. Methane emissions can be reduced by an average of 36.5% with a
single drainage and by 43% with multiple aerations. Nitrous oxide emissions increase under all WST but this
increase does not o -set the reduction in CH4 emissions.  is study also shows that the amount of GHG emissions
can vary drastically between di erent regions.  is poses a challenge for the transfer of mitigation strategies from
one region to another.
12.1 Water-saving Strategies
12.1.1 Principles of alternate wetting and
drying and midseason drainage
Producing rice with less irrigation water
requirements has been one of the core
research objectives of natural resource man-
agement at IRRI and other research institu-
tions. Midseason drainage is one strategy
that has been widely adopted in China and
Japan over the past decades.  e principle is
to expose the rice  eld to a dry period of
about 7 days towards the end of the vegeta-
tive stage. Although water saving might be
low under this strategy, grain yield tends to
increase ( ompson, 2006) due to suppres-
sion of unproductive tillers, which translates
to a higher water use e ciency.
While previous in-depth research
focused on the identi cation of thresholds
for reducing water use without compromising
194 B.O. Sander et al.
rice yield, this work has developed into a
concise water-saving technology for rice
farmers in irrigated lowlands called ‘alter-
nate wetting and drying’ (AWD) starting in
the early 2000s (Bouman etal., 2007).  e
term AWD has been coined at IRRI and is
synonymous with a variety of terms, such as
controlled or intermitted irrigation as well
as multiple aeration, that are used to
describe alternatives to farmers’ conven-
tional practice of continuous  ooding (CF).
e intervals of non- ooded conditions
from 1 day to more than 10 days depend on
soil type and weather. In this technology,
the farmers are taught to monitor the depth
of the water table in the  eld using a perfo-
rated water tube that is inserted into the soil
(Lampayan etal., 2013).  e practice which
commences at 1 to 2 weeks after transplant-
ing involves draining the  eld until the water
level reaches 15 cm below the soil surface
after which the  eld is re- ooded to a depth
of around 5 cm.  is irrigation scheme is
done throughout the cropping season except
during the  owering stage.  e threshold of
water at a 15 cm level below soil surface is
called ‘safe AWD’, as this will not cause any
yield decline because the roots of the rice
plant will still be able to capture water from
the saturated soils (Lampayan etal., 2009).
e AWD technology can reduce the number
of irrigations signi cantly compared to
farmer’s practice, thereby lowering irriga-
tion water consumption by 15–30%.
Adoption of alternate wetting and drying
Estimating the number of adopters of AWD
is di cult. For the Philippines, the best esti-
mation based on survey responses from
national institutions is that around 100,000
farmers have adopted AWD (Lampayan,
2013).  is number is based on the number
of trainings and demonstration trials in dif-
ferent regions and the level of involvement
of farmers and promotion of the technology.
However, response may vary from those
who practised AWD in the Philippines, e.g.
in Canarem (Tarlac Province) the majority of
the farmer-cooperators had positive feed-
back about the e ectiveness of AWD as a
water-saving technology as follows: (i) no
yield di erence with farmer’s practice of
continuous  ooding; (ii) saves water; (iii)
saves time and labour, thus, less expensive;
(iv) heavier and bigger grains, and good
shape; (v) more tillers; and (vi) less insect
pests and diseases (Palis etal., 2004).
Another example of AWD practised in
the Philippines was in Bohol Island. In the
face of declining rice production due to
insu cient water supply and unequal water
distribution, NIA (the National Irrigation
Association of the Philippines) established
the Bohol Integrated Irrigation System
(BIIS) with: (i) the construction of a new
dam (Bayongan Dam); and (ii) the imple-
mentation of AWD, which was imposed on
the whole island by periodic water supply.
e adoption of AWD facilitated an opti-
mum use of irrigation water, so that the
cropping intensity increased from ca. 119%
to ca. 160% (related to the maximum of
200% in these double-cropping systems)
(UNFAO, 2010).
e adoption of AWD strongly depends
on the incentive for the farmer. In many
parts of the Philippines, this incentive is
directly linked to the irrigation system. In a
pump system where farmers can achieve
direct  nancial savings due to reduced diesel
use for pumping under AWD, it is easily
adopted and properly implemented. In irri-
gation systems where farmers pay seasonal
fees independent of the actual water usage
as currently employed in most of NIA-ser-
viced areas, farmers were found to be reluc-
tant to use water-saving techniques and
AWD was not carried out properly.
With the development and improve-
ment of irrigation canals by NIA as part of
their nationwide medium-term plan, the use
of pumps would become gradually less
important. In turn, this – genuinely positive
development – may decrease the incentive
to adopt AWD as long as there are no policies
from the local government units on water
savings to support the practice of AWD by
other means. As one example, adoption of
meter-based (volumetric consumption-
based) water rates instead of  xed area-
based rates would promote practices of
water saving. Volumetric pricing of irriga-
tion water should induce incentive for better
Mitigating Greenhouse Gas Emissions from Rice Production 195
collective action toward saving water
resources, than does area-based pricing in
which marginal cost of using water is zero
(Tsusaka etal., 2012).
Potential and constraints
In the perception of farmers, AWD means
inadequate soil-water during the dry period,
thus carries the risk of drought stress to the
crop. However, studies have shown that
thoroughly implemented AWD, speci cally
‘safe AWD’, does not lead to any yield
declines because the roots of the rice plant
can still capture enough water. Flooding of
soils over many years triggers the develop-
ment of a hardpan at 15–30 cm depth which
acts as a mechanical barrier for roots and
water. Although this sealing may not be
complete in terms of percolation losses, it
reduces seepage so that roots can acquire
enough water even after several days with-
out surface water. It is di cult to convince
farmers that the absence of standing water
does not automatically imply absence of soil
water.  us, the perforated tube serves a
dual purpose: (i) measuring the water table
below the soil surface; and (ii) acting as
visual assurance to the farmer that the roots
still have access to water at the subsurface.
One requirement for successful dissemina-
tion of AWD, however, is a reliable irrigation
source to enable farmers to irrigate when-
ever it is needed. If irrigation water is scarce
sometimes and farmers cannot be sure to
have su cient water, they would prefer to
irrigate soon and not wait for a recom-
mended level of drainage to avoid possible
drought stress.
Another barrier for adoption of any
water-saving strategy by farmers within a
wider irrigation system is the physical sepa-
ration of adopter and bene ter. Farmers
near the source of irrigation water
(‘upstream farmers’) who have the potential
of saving water have no need to save water.
It is the farmers who are far from the irriga-
tion source (‘downstream farmers’) who
would bene t from water saving because
those farmers potentially face water scarcity
but, as a result, have not much potential to
save water themselves.
On the positive side, there is anecdotal
evidence through farmers’ claims that prac-
tising AWD not only saves water but also
increases rice yields.  is observation may
be the exception rather than the rule but it
should be followed up for further improving
the attractiveness of AWD. Several potential
mechanisms have been reported as a means
to increase yields under AWD but this needs
further investigation:
lodging resistant culms;
profuse tillering;
reduced pests and diseases; and
better soil conditions at harvest.
Even if the practised AWD management
is ‘slightly unsafe’, i.e. the water level drops
below 15 cm below soil surface and yields
slightly decrease, the economic yield tends
to be higher in AWD (Sibayan etal., 2010)
because the cost of irrigation has decreased
(in pump systems).
Water savings and greenhouse gas emission
Moreover, AWD technology has a proven
potential to mitigate CH4 emission. Meth-
ane is a potent GHG with a global warming
potential (GWP) of 25 (IPCC, 2006), which
means that it is 25 times more e ective in
trapping heat inside the Earth’s atmosphere
than CO2. Cultivated wetland rice soils emit
signi cant quantities of CH4 (Smith et al.,
2008). Methane is produced anaerobically
by methanogenic bacteria, which thrive well
in paddy rice  elds. Hence, flooded rice fields
are a large source of CH4 emissions contrib-
uting about 10–14% of total global anthro-
pogenic CH4 emissions. Because periodic
aeration of the soil inhibits CH4-producing
bacteria, AWD can reduce CH4 emissions.
Various studies on GHG emissions under
AWD and other water-saving strategies have
been conducted to quantify the mitigation
potential of those water management strat-
egies.  e results will be further discussed in
Section 12.3.
e capability of AWD to reduce CH4
emissions is also re ected in the IPCC meth-
odology (IPCC, 2006) which is used for com-
puting GHG emissions in the ‘National
Communications’ submitted by countries to
196 B.O. Sander et al.
the UNFCCC. ‘Multiple aeration’, the cate-
gory AWD falls in, is presumed to reduce CH4
emissions by 48% compared to continuous
ooding of rice  elds (IPCC, 2006). A single
aeration of the  eld, commonly referred to as
‘midseason drainage’, reduces CH4 emissions
by 40%, as IPCC guidelines suggest.
However, AWD adoption may also have
pitfalls in terms of higher emissions of
nitrous oxide (N2O), a GHG even more
potent than CH4 with a GWP of 298 (IPCC,
2006). Nitrous oxide emissions are generally
very low to negligible in continuously
ooded systems, so that the IPCC guidelines
assign a lower emission factor to rice as com-
pared to non- ooded crops. Under water-
saving strategies, N2O emissions tend to
increase due to increased nitri cation and
denitri cation activities with the soil condi-
tions constantly changing between anaero-
bic and aerobic and related changes in the
redox potential. Data on N2O emissions
under di erent water management regimes
is limited and varies drastically as discussed
in Section 12.3.  e available data, however,
suggest that the incremental N2O emission
through AWD is insigni cant as long as the
N fertilization remains within a reasonable
range.  us, the combination of AWD with
e cient fertilization techniques, such as
Site-Speci c Nutrient Management, is the
best way to avoid excessive N levels in the
soil and thus, negative trade-o s in terms of
mitigation potentials.
12.2 Clean Development Mechanisms
12.2.1 Defi nition and criteria
e CDM is one of the  exibility mecha-
nisms introduced by the Kyoto Protocol (KP)
in 1997. It is a project-based mechanism of
emissions trading involving non-Annex 1
parties (developing countries) that do not
have any stipulated obligation to reduce
their GHG emissions.  e idea behind this
cooperative mechanism is that reduced GHG
emissions will slow global warming – irre-
spective of the location of the savings.
Annex 1 (industrialized) countries can take
advantage of a CDM project implemented in
a developing country by purchasing Certi-
ed Emission Reduction Units (CERs) to
meet their targets or emission caps.  is
mechanism adds more choices and  exibility
to comply with the targets and o ers eco-
nomically sound solutions.  e non-Annex 1
countries in turn receive capital for invest-
ments in projects and clean technologies to
reduce their emissions and enhance socio-
economic well-being.
us, the CDM has two key goals: (i) to
promote sustainable development (SD)
objectives in the host country (i.e. non-
Annex 1 countries); and (ii) to assist Annex
1 parties to meet their GHG reduction tar-
gets. A CDM project activity in a non-Annex
1 country produces certi ed emission reduc-
tions that can be used towards partial com-
pliance of their emission reduction targets.
According to Section 12.5 of the KP, a
CDM project has to satisfy the following cri-
teria: (i) parties involved in the project activ-
ity do so voluntarily and both approve the
project; (ii) the project must produce real,
measurable and long-term bene ts to the
mitigation of climate change; and (iii) the
emission reductions should be additional to
any that would occur without the project
activity (commonly known as the ‘addition-
ality’ criterion).
Moreover, article 12.2 of the KP states
that the purpose of the CDM is to assist non-
Annex 1 parties in achieving SD.  is is inter-
preted to suggest that the project activities
should be compatible with the SD require-
ments of the host country. However, neither
the KP nor the subsequent Conference of
Parties (COPs) have provided guidance on
de ning sustainability, leaving the decision
to the host countries. COP 7 in Marrakech in
2001 stipulated that all participating coun-
tries have to establish a ‘Designated National
Authority’ (DNA) to assess if any CDM pro-
posal complies with their own sustainability
criteria (Bhattacharyya, 2011). Figure 12.1
gives an overview over the application and
approval process of a CDM project.
However, applying CDM projects in rice
production faces many challenges.  e Bohol
case (see ‘Adoption of alternate wetting and
drying’ above) is an example of water
Mitigating Greenhouse Gas Emissions from Rice Production 197
savings possessing new technologies that
increase the income of poor farmers while
decreasing GHG emissions. Yet, it is not eli-
gible for CDM because of missing addition-
ality, i.e. AWD was introduced for the
purpose of water saving without the incen-
tive of CER generation and would have been
introduced even if no GHG saving would
have been achieved.
12.2.2 The rice clean development
mechanism methodology
e eligibility of projects reducing in situ
emissions from land use such as CH4
emissions from rice remains intricate (Was-
smann, 2010). However, in 2011 a CDM
methodology for ‘Methane emission reduc-
tion by adjusted water management practice
in rice cultivation’ was approved by the
UNFCCC (2012).  e methodology has been
modi ed and is in its third version since
August 2012. It now de nes default CH4
emission reduction values for di erent man-
agement practices in rice production. For
applying AWD, for example, a reduction of
1.8 kg C H4 ha1 day1 can be claimed under a
certi ed CDM project.  is translates to a
saving of 4.5 t CO2-eq ha1 season1 assum-
ing a 100-day growing period (GWP
(CH4) = 25) or 4.5 CERs.
Payment for CERs
Transfer of CERs
Annex 1
Entity #2
Entity #1
Letter of
Design. Nat. Authorities:
Non-Annex 1 + Annex 1
Baseline Meth
Design. Nat. Authority:
Non-Annex 1 Letter of
‘no objection’
Fig. 12.1. Schematic presentation of the CDM Pipeline (Meth, methodology; Design. Nat. Authority,
Designated National Authority; Docum., document).
198 B.O. Sander et al.
12.3 Literature Review
For this study we have surveyed peer-
reviewed articles on CH4 and N2O emissions
under di erent water management tech-
niques in rice  elds.  e objective was a
proof of concept as to what extent water
management can be used to mitigate GHG
emissions from rice  elds. Using an online
search engine for scienti c literature, ISI
Web of Knowledge, we identi ed 24 articles
on  eld measurements encompassing GHG
emission changes as a function of water
management of a rice  eld.  e initial num-
ber of results of the search was much higher,
but many articles on this topic reported
mechanistic studies without comparative
emission rates under di erent water man-
agement strategies.  ese 24 articles com-
piled a total number of 96 experimental
comparisons, i.e. one comparison corre-
sponds to one season with adjacent  eld
plots of CF and WST, which can be either
multiple aeration (MA) or single aeration
(SA).  ese two WST include AWD and mid-
season drainage, respectively, as their most
common forms. Moreover, we also included
three articles on pot experiments that emu-
lated di erent water management practices;
these articles encompassed four compari-
sons between CF and WST. For comparing
relative emission di erences between CF
and WST, the pot experiments were included
in the analysis. For a comparison of absolute
emission di erences, however, pot experi-
ments were excluded because of the di er-
ent environmental e ects of ‘ eld’ and
‘greenhouse’. To assess the e ect of di erent
kinds of WST, these 106 comparisons were
further classi ed according to two types of
WST: SA and MA.
12.3.1 Results
e emission rates obtained from the di er-
ent publications are shown in Tables 12.1–
12.4 separated by countries/regions (for
eld measurements) and in Table 12.5 for
the pot experiments. In these tables – as
well as in the narrative – percentages given
are relative GHG emissions of an applied
WST as compared to a continuously  ooded
(CF)  eld (e.g. a relative emission of 60%
shown in these tables translates into a
reduction e ect of 40%). We recognize that
many readers will primarily be interested in
the reduction e ect, but we felt that the con-
sistent use of relative emission rates will
provide a more comprehensive presenta-
tion. In some instances in the text, we have
given absolute values for reduction in units
of kilograms per hectare per day.
ese tables list emission rates per day
as well as per season. Typically, the articles
provided only one of these values, but we
computed the corresponding value by using
the number of days for one season, which
was also obtained from the article. In some
articles, emission rates were given as hourly
rates and we multiplied it with a factor of 24
for daily emissions (assuming that hourly
values provide daily averages).
e articles on  eld comparisons were
sorted according to the location of the
experiments into  ve groups: China (Table
12.1), India (Table 12.2), Japan and South
Korea (Table 12.3) and Indonesia and the
Philippines (Table 12.4).
As an initial observation, the published
studies from South-east Asia are older than
10 years, whereas many studies were con-
ducted in India, China and Japan in more
recent years. Emission rates from rice  elds
in India are much lower than from other parts
of Asia, i.e. only 10% of the emission rates
observed in  eld studies in China, Japan and
South Korea. One exception is the study by
Yue etal. (2005) that reports emissions from
a CF  eld in China as low as 24.8 kg CH4 ha1
season1, but the authors explain the low
emission by very low soil temperature in the
region of the experiment.
Methane emissions
In total, 19 articles report comparative CH4
emissions from a continuously  ooded  eld
or pot with a  eld/pot under MA
Relative CH4 emissions in the MA plots
as given in these 19 articles (compiling 60
experimental observations) were found in
Mitigating Greenhouse Gas Emissions from Rice Production 199
Table 12.1. Compilation of fi eld studies on GHG emissions as affected by water-saving techniques
conducted in China.
Methane Nitrous oxide
EF under
rel. CH4
EF under
rel. N2O
Citation Location
kg1 ha1
(kg ha1
g N ha1
(g N ha1
(%) Remarks
Zhang et al.
China, Jiangsu 185 (1.48) 30.89
Wang et al.
China, Jiangsu 221 (1.77) 33.89160 (1.28) 137.5
278 (2.22) 22.89550 (4.40) 123.6
548 (4.38) 38.99130 (1.04) 153.8
515 (4.12) 52.79280 (2.24) 121.4
Qin et al. (2010) China, Jiangsu 127 (1.04) 43.89180 (1.48) 194.5
105 (0.88) 41.09 50 (0.42) 1390.5
Jiao et al. (2006) China, Liaoning 230 (1.56) 75.77 296 (2.00) 123.72 4 aerations
Yue et al. (2005) China, Liaoning 24.8 (0.20) 67.74 382 (3.05) 133.33 2 aerations, low
soil temperature
Zou et al. (2005) China, Jiangsu 85 (0.72) 35.29 60 (0.51) 2583.3
220 (1.86) 64.09 30 (0.25) 4766.7
Wang et al.
China, Beijing 503 (3.73) 41.2976.59Automated system
Lu et al. (2000) China, Zheijang 565 (4.25) 38.9956.19Automated system
Wang et al.
China, Beijing 748 (7.48) 41.69
145 (1.18) 74.69Automated system
EF, emission factors given per season and per day, respectively; CF, continuous fl ooding; MA, multiple aeration; SA,
single aeration.
Table 12.2. Emission factors of methane and nitrous oxide under continuous fl ooding and relative emis-
sions under multiple aeration (MA) from different studies in India.
Methane Nitrous oxide
Citation Location
EF under CF kg1
ha1 season1 (kg
ha1 day1)
rel. CH4
MA (%)
EF under CF g
N ha1 season1
(g N ha1 day1)
rel. N2O
MA (%) Remarks
Khosa et al.
62.3 (0.53) 46.4
36.8 (0.31) 36.2
Pathak et al.
(2002, 2003)
India, New
24.3 (0.27) 34.2 323 (3.63) 95.0 N2O reported 2002,
CH4 reported 2003,
rice/wheat system
28.1 (0.32) 52.0 735 (8.26) 126.4
45.4 (0.51) 61.0 593 (6.66) 120.4
20.2 (0.23) 47.5 483 (5.43) 111.8
Adhya et al.
15.7 (0.16) 84.6 Automated system
30.5 (0.32) 75.0
Jain et al.
India, New
39.8 (0.41) 81.4
34.8 (0.37) 86.2
22.7 (0.23) 42.8
.23 (0.23) 77.8
16.6 (0.17) 78.0
200 B.O. Sander et al.
the range between 19.9% and 86.2% of the
emissions of the corresponding CF plot.  e
arithmetic mean is 56.9% (CV: 36%). For
single aeration, a total of 40 experiments in
13 articles were identi ed. One out of four
eld comparisons in Wassmann etal. (2000)
was disregarded for this analysis because of
non-achievement of the drainage.  e rela-
tive CH4 emissions of the remaining 40
experiments varied between 17.9% and
152.6% with an arithmetic mean of 63.5%
(CV: 47%) compared to a continuously
ooded paddy  eld/pot.
e absolute CH4 reduction (in kilo-
grams per hectare per day) has also been
assessed for SA and MA. For this
assessment, however, only  eld experiments
were considered as explained above. Figures
12.2 and 12.3 show the absolute CH4 emis-
sions (in CO2-equivalents) of CF and WST
elds for SA and MA, respectively. For fur-
ther analysis of the absolute mitigation
potential, only  eld experiments with sea-
sonal emissions of 80 kg CH4 ha1 or more
were considered because low-emission  elds
might not give potential for further emis-
sion reduction. For all 42  eld experiments
on MA, the arithmetic mean of CH4 reduc-
tion was 1.26 kg ha1 day1 with a CV of
69%. For SA the arithmetic mean of reduc-
tion of the 26  eld experiments was 1.15 kg
CH4 ha1 day1 (CV: 94%).
Table 12.3. Compilation of fi eld studies on CH4 emissions as affected by water saving techniques con-
ducted in Japan and South Korea (no studies comparing N2O emissions from this region could be identi-
ed; abbreviations, see Table 12.1).
EF under CF rel. CH4 emission
Citation Location
kg1 ha1
season1 (kg
ha1 day1) MA (%) SA (%) Remarks
Itoh et al. (2011) Japan, Nagaoka 307 (2.38) 48.19Average of 3 observations
318 (2.50) 25.59
662 (5.25) 977.0
1044 (8.92)9968.7
Japan, Koshi 965 (0.58) 938.0
952 (0.44) 102.6
270 (2.48) 129.6
Minamikawa and
Sakai (2006)
Japan, Tsukuba 139 (1.03) 947.3 Aeration after EH control
142 (1.06) 51.44
227 (1.79) 30.77
252 (1.98) 25.60
Yagi et al. (1996) Japan, Ryugasaki 148 (1.19) 58.31 Automated system
94.9 (0.65).54.58
Kwun et al. (2003) S Korea, Milyang 503 (4.70) 85.19Assumed growth period: 107 days
Park and Yun
S Korea, Suwon,
Iksan, Milyang
257 (2.40) 62.59Average of 7 observations,
assumed growth period: 107 days
599 (5.60) 64.39Average of 5 observations,
assumed growth period: 107 days
396 (3.70) 62.29Average of 3 observations,
assumed growth period: 107 days
289 (2.70) 63.09Average of 4 observations,
assumed growth period: 107 days
175 (1.40) 81.89Average of 4 observations,
assumed growth period:125 days
Mitigating Greenhouse Gas Emissions from Rice Production 201
Nitrous oxide emissions
Only nine di erent studies comprising 23
experiments could be identi ed that mea-
sured N2O emissions from rice  elds under
di erent water management practices. N2O
emissions were generally higher under
water-saving strategies as compared to con-
tinuously  ooded elds. However, the
Table 12.4. Compilation of fi eld studies on GHG emissions as affected by water saving techniques
conducted in Indonesia and the Philippines (abbreviations, see Table 12.1).
Methane Nitrous oxide
EF under
rel. CH4
EF under
rel. N2O
Citation Location
kg1 ha1
(kg ha1
g N ha1
(g N ha1
(%) Remarks
Suratno et al.
West Java
249 (1.98) 134.94 Water level down to
‘0 cm’ only; assumed
growth periods of 91
days and 112 days,
254 (2.02) 158.10
514 (4.08) 95.28
622 (4.93) 143.41
716 (5.69) 78.69
713 (5.66) 117.84
Husin et al.
West Java
437 (3.06) 43.1
381 (2.95) 61.7
Corton et al.
89 (0.91) 57.1 Automated system
75 (0.73) 63.0
348 (3.75) 92.5
272 (3.23) 55.1
et al. (2000)
251 (2.51) 17.93 Automated system
35 (0.35) 31.43
10 (0.10) 80.00
28 (0.28) 121.43 Rain in SA, no drainage
Bronson et al.
17.3 (0.20).38.5 259 (3.05) 246.33Automated system
371 (4.36) 57.2 28 (0.33) 589.29
Table 12.5. Compilation of pot studies on GHG emissions as affected by water saving techniques
(abbreviations, see Table 12.1).
Methane Nitrous oxide
EF under
CF rel. CH4 emission
EF under
CF rel. N2O emission
Citation Location
kg ha1
season1MA (%) SA (%)
g N ha1
season1MA (%) SA (%) Remarks
Katayanagi et al.
1580.7 27.2110.19 32,476.2
Minamikawa and
Sakai (2005)
13531. 19.9155.61Int. irrigation only
after 81 DAT
19261. 29.7169.51
Mishra et al.
43.80 59.65 BL: 6.393 mg/
202 B.O. Sander et al.
variation of the results was also higher than
for CH4 results.
For multiple aeration, 12 experiments
were analysed and the arithmetic mean of
the relative N2O emissions was found to be
120% (CV: 19%) compared to CF. For SA, 11
relevant experiments were found and the
relative N2O emissions were between 121%
and 4767% with an arithmetic mean of
907% (CV: 171%) as compared to a CF refer-
ence  eld.  e high coe cient of variation is
mainly caused by results of one study (Zou
et al., 2005) that reports very high N2O
emission increases for SA. Due to this fact, it
might be more meaningful to use another
statistical measure, namely the median,
which is 176% for relative N2O emissions
under SA.  e median for relative N2O emis-
sions under MA is 122%.
Global warming potential
Only seven  eld studies were identi ed mea-
suring both CH4 and N2O emissions, as
a ected by di erent water management
strategies (Fig. 12.4). In all of the studies
CH4 emissions decrease under WST while
N2O emissions increase.  e total GWP,
however, decreases in all of them (between
18% and 59%).  e contribution of N2O to
the total GWP of continuously  ooded  elds
is between 0.6% and 2.4% for the  ve stud-
ies with a GWP higher than 1 t CO2-eq ha1
season1. For the other two studies with a
very low GWP, Yue etal. (2005) and Pathak
etal. (2002, 2003), contribution of N2O is
22% and 25%, respectively. In the WST
plots, the contribution of N2O increased
from 3.8% to 6.4% for Wang et al. (2012),
Qin etal. (2010), Jiao etal. (2006) and Bron-
son etal. (1997), to 25% for Zou etal. (2005)
and to 36% and 44% for Yue etal. (2005) and
Pathak etal. (2002, 2003), respectively.  e
increase of N2O emissions by switching from
CF to WST, however, in all the studies
(except Zou etal., 2005) is between 17% and
180%, while Zou et al. report an N2O
increase of 3300%.
Fig. 12.2. Methane emissions from studies comparing continuous fl ooding (black) and single aeration
(grey). Values are arithmetic means of all experiments in the respective article. GWP (CH4) = 25.
CH4 emission (t CO2-eq ha–1 season–1)
Mitigating Greenhouse Gas Emissions from Rice Production 203
Taking the average of all these seven
studies, the GWP decreases from 4.2 t CO2-
eq ha1 season1 under CF to 2.4 t CO2-eq
ha1 season1 under a WST with the contri-
bution of N2O increasing from 3% to 11%.
12.3.2 Discussions
Derived from this meta-analysis,  eld drain-
age in irrigated rice production can be
deemed a promising mitigation option with
the potential to substantially reduce GHG
emissions. Although N2O emissions increase
under WSTs, this increase does not o -set
the reduction in CH4 emissions.
e CH4 reduction potentials of SA and
MA are at similar levels – which is a some-
how unexpected result. SA was found to
reduce CH4 emissions by 36.5% in average,
MA by 43.1%.  e explanation for this could
be how the drainage is carried out in detail.
In studies with only one dry period in the
growing season, this drainage might be exe-
cuted more accurately and maybe even lon-
ger (i.e. a lower water level) than the
drainages in studies on MA. Hence, this one
dry period would have a higher mitigation
e ect than one dry period in a  eld managed
under MA. Also, the stronger increase of
N2O emissions in SA (median: 176%) than
in MA (median: 122%) supports this
Furthermore, CH4 emissions tend to
increase slowly in the beginning of the
growth period.  e highest  ux rates are
found towards the middle of the season
(Yagi et al., 1996; Hou et al., 2000).  us,
practising a WST in the beginning of the sea-
son has a lower mitigation e ect than prac-
tising it around the middle of the season.
After a dry period, CH4 ux only slowly
increases again (Cai etal., 1997).
e relative CH4 emission levels of plots
treated with SA and MA, respectively, as
assessed in this literature study are in good
agreement with what the IPCC suggests
Fig. 12.3. Methane emissions from studies comparing continuous fl ooding (black) and multiple aeration
(grey). Values are arithmetic means of all experiments in the respective article. GWP (CH4) = 25.
CH4 emission (t CO2-eq ha–1 season–1)
204 B.O. Sander et al.
using the default values given in its 2006
guidelines (IPCC, 2006). For SA the IPCC
guidelines recommend a ‘scaling factor’ of
0.6, i.e. a relative CH4 emission level of 60%
compared to continuous  ooding.  e aver-
age emission level for SA as found in this
study is 63.5%. For MA, the IPCC suggests a
default scaling factor of 0.52 (i.e. relative
CH4 emissions in a MA  eld are 52% of those
in a CF  eld) while the average emissions as
assessed in this study are 56.9%. It should
be noted that the IPCC scaling factors were
also founded on a literature survey that
probably in large parts is included in this
study. But this analysis shows that the IPCC
factors still represent good default means
even if articles from after 2006 are included
in the assessment.
Comparing the absolute values of CH4
reduction as found in the available litera-
ture with what the CDM methodology for
rice production gives as standard values, it
can be said that for both practices, SA and
MA, the CDM standard values are higher
than was found in the available literature.
e CDM methodology suggest a reduction
of 1.8 kg CH4 ha1 day1 for shifting to
intermittent  ooding with MA and the
arithmetic mean of CH4 reduction as found
in the literature is 1.26 kg ha1 day1. For
midseason drainage, the CDM methodol-
ogy suggests a reduction of 1.5 kg CH4 ha1
day1 while the arithmetic mean of all liter-
ature  ndings for SA is 1.15 kg CH4 ha1
e share of N2O emissions to the total
GWP is higher under an applied WST than
under continuous  ooding. Nitrous oxide
contributions under both management
strategies, CF and WST, are generally below
10% except when CH4 emissions are very
low as e.g. found in India. Only in one study
(Zou et al., 2005) did N2O emissions
exceeded 0.3 t CO2-eq ha1 season1.
Fig. 12.4. Global warming potential of different water management practices as derived from articles
comparing both methane and nitrous oxide emissions. Values are arithmetic means of all experiments in
the respective article. GWP (CH4) = 25, GWP (N2O) = 298 (CF, continuous fl ooding; SA, single aeration;
MA, multiple aeration).
Global warming potential (t CO2– eq ha–1season–1)
Mitigating Greenhouse Gas Emissions from Rice Production 205
12.4 Conclusions
AWD and MSD as representative forms of
MA and SA, respectively, are potent mitiga-
tion options for irrigated rice production
systems.  e average relative CH4 emission
under SA and MA are at similar levels
according to the  ndings in this literature
study.  is could have implications on the
dissemination of water-saving strategies as
mitigation options. Farmers adopt the AWD
technology primarily because of the water
saved, yet maintained yields. While in areas
with pump irrigation AWD is easily adopted
because of the direct monetary pay-out, in
areas with improved canal irrigation facili-
ties with more than adequate water supply
farmers are more reluctant to the adoption
of AWD. Instead of introducing AWD, which
might require more e ort for a farmer to
accurately practise and could be considered
as too harsh with its alternating dry phases
(thus, has a high adoption barrier), the
entry point in those areas could be a single
MSD.  e mitigation potential of MSD is
similar to AWD but it only requires water
control during approximately 1 week of the
growth period.  us, farmers might be more
willing to adopt this water management
strategy and might even practise it more
accurately. After adoption of MSD, introduc-
tion of AWD could follow.  e clean develop-
ment mechanism may serve as additional
incentive if properly coordinated. Aside
from this, it is important that other indirect
bene ts from AWD (e.g. less crop lodging,
reduced pest damage, better soil conditions)
are further explored and scienti cally
is study further shows that the IPCC
scaling factors represent good average val-
ues according to the articles analysed.
However, CH4 emissions are very low in
India compared to other parts of Asia (e.g.
China or Japan), which shows that disag-
gregation for any mitigation strategies is
important. Moreover, this  nding shows
limits for the transfer of any mitigation
option from one region to another. Assess-
ment of region-speci c characteristics is
B.O. Sander thanks GIZ (Deutsche Gesell-
schaft fuer Internationale Zusammenarbeit)
and CCAFS (the CGIAR Research Program
on Climate Change, Agriculture and Food
Security) for funding his position at IRRI in
2012 and 2013, respectively.
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... Regarding total GHG emissions (GWP of CH 4 and N 2 O), AWD has been shown to reduce CH 4 emissions by up to 90% (Lagomarsino et al., 2016). On average, reported CH 4 emissions are approximately halved with the reduction highly dependent on local site conditions (Jiang et al., 2019;Sander et al., 2015). Likewise, the effect of AWD on N 2 O emissions is highly variable. ...
... While some studies report increased emissions of N 2 O under AWD treatment of up to 500% (Lagomarsino et al., 2016), others found no significant change (Setyanto et al., 2018;Tran et al., 2018). In a review, Sander et al. (2015) report mean increases of N 2 O emissions by 20%, but with high variability due to differences in environmental conditions and field management. ...
... According to the simulations, the introduction of AWD at national scale, that is, the Philippines, has the potential to reduce national CH 4 emissions from rice systems by about −23%. This reduction is lower than that has 15 of 20 been observed for the site-scale studies reviewed by Sander et al. (2015) (−43%, range: −80% to −14%). The discrepancy between simulated regional and observed site results is a consequence of AWD being less effective in terms of CH 4 emissions during the WS since abundant precipitation can prevent fields from draining. ...
Full-text available
Worldwide, rice production contributes about 10% of total greenhouse gas (GHG) emissions from the agricultural sector, mainly due to CH4 emissions from continuously flooded fields. Alternate Wetting and Drying (AWD) is a promising crop technology for mitigating CH4 emissions and reducing the irrigation water currently being applied in many of the world's top rice‐producing countries. However, decreased emissions of CH4 may be partially counterbalanced by increased N2O emissions. In this case study for the Philippines, the national mitigation potential of AWD is explored using the process‐based biogeochemical model LandscapeDNDC. Simulated mean annual CH4 emissions under conventional rice production for the time period 2000–2011 are estimated as 1,180 ± 163 Gg CH4 yr⁻¹. During the cropping season, this is about +16% higher than a former estimate using emission factors. Scenario simulations of nationwide introduction of AWD in irrigated landscapes suggest a considerable decrease in CH4 emissions by −23%, while N2O emissions are only increased by +8%. Irrespective of field management, at national scale, the radiative forcing of irrigated rice production is always dominated by CH4 (>95%). The reduction potential of GHG emissions depends on, for example, number of crops per year, residue management, amount of applied irrigation water, and sand content. Seasonal weather conditions also play an important role since the mitigation potential of AWD is almost double as high in dry as compared to wet seasons. Furthermore, this study demonstrates the importance of temporal continuity, considering off‐season emissions and the long‐term development of GHG emissions across multiple years.
... For example in SA 2012 the yield loss was over 120 tons. [6] [18], who develop yield response curves from a meta-analysis of published crop simulations [4] Climate changes as increasing temperature, it made evaporation and drought, the Figure 1 shows the yield change with increasing temperatures. Maize and rice are more temperature resistant than wheat, both decrease only a little bit with increasing temperature. ...
... [17] Flooded rice fields emit significant amounts of methane, recent work suggests that flooded rice contributes about 10-12% of the human induced emissions from agriculture. AWD can reduce the CH 4 by 48% compared to continuously flooded irrigated rice systems [18]. Unfortunately, AWD (multiple aeration) emits more N 2 O than continuously flooded ( Figure 3). ...
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Vietnam is one of the countries most suffered by climate change, as a result, the water resources is also significantly affected. As a developing country, extreme weather events such as floods and droughts have caused considerable damage to agricultural production and hydropower. Different strategies for agriculture and hydropower are analyzed to adapt to climate change. Alternative wetting and drying (AWD) is a water saving technology. It reduces the water use up to 30%. In addition, it reduces CH 4 emissions up to 48%. Hydropower plants contribute about 40% to the electricity demand in Vietnam. Furthermore, the reservoirs play an important role to prevent flooding and to ensure water supply. Multi-objective deterministic and stochastic optimization was used. This method can mitigate flooding and increase the hydropower production by 7%. Building a hydropower dam is a big encroachment into the environment. Different scenarios are investigated to reduce hydrological alteration and to increase the hydropower production at the same time. One scenario was able to increase the hydropower production by 4% and decreased the hydrological alteration by 27%.
... Annual emission rates of CH 4 from individual plots were positively correlated with the content of readily mineralizable carbon (RMC) in paddy soils (Yagi & Minami, 1990) and were derived from inherent and exogenous sources Yagi & Minami, 1990). In the later growth period in AWD, CH 4 emissions were reduced owing to periodic aeration of the soil inhibiting CH 4 -producing bacteria (Ly et al., 2013;Sander et al., 2015;Yagi et al., 1996). Wang et al. (2012) andZou et al. (2005) stated that the CH 4 emissions from rice fields were influenced by water management and reduced CH 4 by 29 and 45% in single and multiple drainage, respectively (Wang et al., 2018). ...
To assess the effect of different organic manures and rice cultivars on methane emissions, a pot experiment was conducted at the Yezin Agricultural University, Nay Pyi Taw, Myanmar during the wet season of 2016. Organic manures (control, compost, and cow dung) and two rice cultivars (Manawthukha and IR 50) were tested. For both rice cultivars, high grain yield was observed in the control, and the minimum grain yield was observed in the cow dung treatment. The rate and cumulative CH4 emissions in Manawthukha were higher than those in IR 50, in accordance with the yield, because of the longer growth duration. Although not significant, the lowest methane emissions were observed in the cow dung manure treatment (0.808 g CH4 kg‐1 soil) against the control (0.893 g CH4 kg‐1 soil) and compost (0.951 g CH4 kg‐1 soil) treatments. Based on these results, a field experiment was conducted at Madaya Township, Mandalay region, Myanmar during the dry and wet seasons of 2017 to determine the effects of water management and different rates of cow dung manure on methane emission and yield of IR 50. Higher methane emissions were recorded for continuous flooding (CF) than for alternative wetting and drying (AWD). In both seasons, higher grain yields (1.8% in dry and 7.6% in wet) were recorded for AWD than for CF. Higher methane emissions were recorded from OM3 and lower emissions from OM0 in both water management practices. In AWD, methane emissions were restricted under aerated soil conditions, although a higher amount of manure was added. This article is protected by copyright. All rights reserved.
... Soil carbon storage strategies include peatland restoration, forest agriculture, residue retention and cover cropping, and increased photosynthesis [8]. Emissions reductions strategies in landscapes often focus on non-CO 2 greenhouse gases such as N 2 O (via nutrient management [9]) and CH 4 (through modified rice irrigation [10][11][12] or changes in cattle management [13]). Whole-farm and life-cycle or supply-chain approaches extend these concerns to reduce fuel use or otherwise limit CO 2 emissions, though the variety of implementation strategies and paucity of data means that realistic depictions of NbCS in life cycle assessments remain challenging [14]. ...
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Nature-based Climate Solutions are landscape stewardship techniques to reduce greenhouse gas emissions and increase soil or biomass carbon sequestration. These mitigation approaches to climate change present an opportunity to supplement energy sector decarbonization and provide co-benefits in terms of ecosystem services and landscape productivity. The biological engineering profession must be involved in the research and implementation of these solutions—developing new tools to aid in decision-making, methods to optimize across different objectives, and new messaging frameworks to assist in prioritizing among different options. Furthermore, the biological engineering curriculum should be redesigned to reflect the needs of carbon-based landscape management. While doing so, the biological engineering community has an opportunity to embed justice, equity, diversity, and inclusion within both the classroom and the profession. Together these transformations will enhance our capacity to use sustainable landscape management as an active tool to mitigate the risks of climate change.
... The different management practices in rice field such as water regimes, fertilizer application, and other crop rotation are known to be an important factor for emissions of CH 4 and N 2 O, and soil carbon sequestration (Cai et al., 1997;Towprayoon et al., 2005;Cha-un et al., 2017). Several water-saving irrigation technologies such as alternate wetting and drying (AWD), surface water level control (SWL) and drip irrigation (DI) have been identified and developed depending on the availability of water in order to increase rice yield and GHG mitigation (Sander et al., 2015;Rao et al., 2017;Tran et al., 2018;Chidthaisong et al., 2018;Sibayan et al., 2018). ...
Conference Paper
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This study aimed to evaluate the feasibility and suitability of water-saving irrigation technologies to investigate the rice yield, water use and GHG emissions for Thai Hom Mali rice production. Drip irrigation (DI) technology was conducted and compared with alternate wet and dry (AWD), surface water level control (SWL) and continuous flooding (CF) management practices. The pot experiment was laid out in plastic greenhouse and planted Khao Dok Mali 105 (KDML 105) variety in the oval shape plastic pots of wide 70 cm, long 90 cm and depth 30 cm. Rice was planted by the dry direct seeding method by three hills per pot, three to five seeds per hill with a spacing of 20 cm. The irrigation system was given through PVC pipe and dripping pipeline. Our study showed that the water use under DI was significantly smaller by 64% than that under CF. Rice grain yield in DI was significantly greater among treatments. The lowest CH 4 emission was found in DI. The combined GWP in DI was 60, 68 and 72% smaller than that in AWD, SWL and CF, respectively. The yield-scaled GWP in DI was 64, 77 and 79% lower than that in AWD, CF and SWL, respectively. While, the highest water productivity was found in DI.
... Another main benefit of AWD is that it has proven to reduce CH 4 emissions by as much as 80% (Sander et al., 2016). However, there is growing evidence that N 2 O emissions from intermittent flooding may be higher than those of permanent flooding regimes (Kritee et al., 2018). ...
Technical Report
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Water and climate change are intricately linked. Global warming is changing the water cycle, affecting water availability and quality and extreme weather events such as droughts and floods. At the same time, sustainable water management and energy-efficient wastewater treatment play an important role in mitigating greenhouse gas emissions. This state-of-the-art report encapsulates the main impacts of climate change on the water cycle and highly water-dependent sectors. The Gesellschaft für Internationale Zusammenarbeit (GIZ), adelphi and Potsdam Institute for Climate Impact Research (PIK) explore relevant models, projections and uncertainties, discuss global trends and evaluate regional case studies. On this basis, the study develops recommendations for future action and enables a better understanding of how the water sector and water-related activities can contribute towards the goals of climate mitigation and adaptation. The report primarily targets water professionals, water-sector decision-makers and the water expert community. Yet, as a comprehensive knowledge base, the report also provides evidence-based information for climate experts and professionals.
... This could partly be explained by their access to natural resources, such as water reservoirs, which could play an important role in their production. Previous research has shown that access to natural resources may influence farmers' behavior and perceptions (Sander et al., 2016). Since aquaponics production has been considered to be of greater value in water-and land-scarce areas , farmers' differing access to water reservoirs raises questions regarding the competitive advantages of aquaponics among production systems. ...
Several adoption models have been developed to explain the dynamics behind the uptake of new technologies in food-production systems. However, the literature has yet to consider a range of external forces that affect farmers' decision-making processes. We argue that climate change and institutions are latent explanatory variables that require attention in the literature on aquatic-based innovations. Our aim is to conduct an ex-ante analysis focusing on these two external forces in the context of aquaculture and the adoption of aquaponics technology in Colombia. We use an embedded case-study design incorporating a qualitative and exploratory approach and employ two categories of fish-farming production systems as units of analysis. We triangulate our findings using non-probability sampling techniques and use our findings as a benchmark to discuss the potential adoption of aquaponics technology. Our findings suggest that fluctuations in rainfall and drought are the most important climate variables influencing negatively fish farming activities. Furthermore, we find that the complex institutional structures involved create unequal informal mechanisms among fish-farming production systems. We argue for context-specific designs when considering the adoption of aquaponics and conclude that, while fish-farming production systems encounter these external forces differently, heterogeneity also exists within systems, revealing intricacies worth considering.
... Methane emission mainly contributes to the GWP from paddy production. Many studies [39,54,[78][79][80][81][82] reported that N 2 O emissions contribute much less to the global warming potential than those of CH 4 . Therefore, the water regime in paddy production is the main factor controlling CH 4 emissions from rice fields [39, 54,83]. ...
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The study is focused on impact of manure application, rice varieties and water management on greenhouse gas (GHG) emissions from paddy rice soil in pot experiment. The objectives of this study were a) to assess the effect of different types of manure amendments and rice varieties on greenhouse gas emissions and b) to determine the optimum manure application rate to increase rice yield while mitigating GHG emissions under alternate wetting and drying irrigation in paddy rice production. The first pot experiment was conducted at the Department of Agronomy, Yezin Agricultural University, Myanmar, in the wet season from June to October 2016. Two different organic manures (compost and cow dung) and control (no manure), and two rice varieties; Manawthukha (135 days) and IR-50 (115 days), were tested. The results showed that cumulative CH4 emission from Manawthukha (1.084 g CH4 kg-1 soil) was significantly higher than that from IR-50 (0.683 g CH4 kg-1 soil) (P
... Water management technique, mitigating greenhouse gas emissions from rice production [14] Drum seeder Plants rice seeds, preferably pre-germinated, directly in neat rows Sustainable mechanization, efficient cropping process ...
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Farmer adoption of sustainable rice farming technologies and practices is critical for climate change adaptation and mitigation. Often adoption is investigated in isolation focusing on factors influencing farmer decision making and overlooking the effects of technology adoption on farmers’ livelihoods and perceptions of change. Therefore, the present study investigated technology adoption and its effects on farmers with a special focus on additional revenue allocation and perception of social, economic and environmental change. Using a digital survey platform, 153 farmers (21.6% female) were interviewed in three sub-districts of Yogyakarta, Indonesia. On average, farmers adopted two technologies or practices, adopted high-yielding rice varieties, and increased their revenue from US$105 to US$122 per hectare per season. Barriers to adoption included time constraints, unsuitability for field conditions and incompatibility with cropping systems. Farmers invested the extra income in farming business and improved diets. Furthermore, farmers perceived changes in social and human capital and also poverty reduction due to technology adoption. This study highlights the importance of including an analysis of social impact in agricultural research.
Few studies have simultaneously evaluated the impact of alternate wetting and drying (AWD) on profit and life cycle greenhouse gas (LC-GHG) emissions based on a farm survey for all rice (Oryza sativa L.)-cropping seasons in a year. This study explores whether AWD allows farmers to increase profits and reduce LC-GHG emissions compared with conventional water management. To achieve this objective, survey data were collected by a structured interview from two groups of farmers in An Giang Province in Vietnam: one group was defined as AWD farmers who attended a training course and answered that they conducted AWD, and the other was defined as non-AWD farmers who did not attend the course and answered that they did not conduct AWD. The survey data were analysed by a regression approach and cradle-to-farm gate life cycle assessment. The results showed that the impact of AWD on profit varied depending on the season. The impact of AWD on profit was significant and positive for the early wet season (p < 0.05) and throughout the year (p < 0.1), but the impact was not significant for the dry and late wet seasons. In contrast, LC-GHG emissions by AWD farmers were significantly lower for all seasons when compared to non-AWD farmers. Although few studies have analysed the impacts of AWD on profits in the early wet season, AWD farmers may obtain higher profits than non-AWD farmers due to water from precipitation, which may reduce severe water stress and alleviate some of the adoption constraints. Based on these results, this study recommends implementing AWD throughout the year in An Giang Province if irrigation and drainage systems are available. The results on seasonal variations in impacts and the overall annual impact of AWD on profits and LC-GHG emissions will help farmers make decisions and help to achieve mitigation targets in the nationally determined contribution under the Paris Agreement.
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Worldwide, about 79 million ha of irrigated lowlands provide 75% of the total rice production. Lowland rice is traditionally grown in bunded fields that are continuously flooded from crop establishment to close to harvest. It is estimated that irrigated lowland rice receives some 34–43% of the total world’s irrigation water, or 24–30% of the total world’s freshwater withdrawals. With increasing water scarcity, the sustainability, food production, and ecosystem services of rice fields are threatened. Therefore, there is a need to develop and disseminate water management practices that can help farmers to cope with water scarcity in irrigated environments. This manual provides an overview of technical response options to water scarcity. It focuses on what individual farmers can do at the field level, with a brief discussion on response options at the irrigation system level. The manual is meant as a support document for training on water management in rice production. It combines scientific background information (with many literature references for further reading) with practical suggestions for implementation. The target audience is people involved in agricultural extension or training with an advanced education in agriculture or water management, who wish to introduce sound water management practices to rice farmers (such as staff of agricultural colleges and universities, scientists, irrigation operators, and extension officers). Introductory chapters analyze the water use and water balance of rice fields, and water movement in the plant-soil system, and discuss the concepts of water scarcity and water savings. Consequences of water scarcity for sustainability, environmental impacts, and ecosystem services of irrigated rice fields are discussed at the end. An appendix introduces two simple instruments to characterize the water status of rice fields that can help farmers in applying water-saving technologies. This manual was developed through the Water Work Group of the Irrigated Rice Research Consortium (which is co-funded by the Swiss Agency for Development and Cooperation). The sections on aerobic rice were co-developed by the CGIAR Challenge Program on Water and Food through the project “Developing a System of Temperate and Tropical Aerobic Rice in Asia (STAR).” Many partners from national agricultural research and extension systems in Asia have contributed to the work described in this manual. The manual was reviewed by Dr. Ian Willet (Australian Centre for International Agricultural Research) and Dr. Mohsin Hafeez (CSIRO Land and Water).
Conference Paper
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Safe alternate wetting and drying (AWD) irrigation in rice is a mature technology that saves water by 15-30% without reducing yields. It entails an irrigation scheduling in which the field is allowed to dry for a number of days before re-irrigation, without stressing the rice plants. This technology is becoming a recommended practice in water-scarce irrigated areas in South and Southeast Asia. In the Philippines, the adoption of safe AWD started in 2002 with farmers using deep-well pump systems in Tarlac Province. The technology was simplified by using a simple perforated field water tube installed at 15 cm deep from the soil surface to help farmers implement the technology. This paper presents results of adoption studies in the deep-well pump systems, farmers’ perceptions, current course of action, including widespread training and dissemination. Insights from lessons learned in the impact-pathway networks will also be presented. As the project unfolds, it revealed a pattern of research-development-extension which follows a process of technology adaptation rather than “transfer”, following the concept of participatory learning and action. Our expanding impact-pathway networks (both the scaling out and scaling up) have been driven by widespread training activities, while building on necessary outscaling mechanisms, including documenting evidence from local success stories and increasing buy-in from local R&D partners.
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Safe alternate wetting and drying (AWD) irrigation in rice is a mature technology that saves water by 15-30% without reducing yields. It entails an irrigation scheduling in which the field is allowed to dry for a number of days before re-irrigation, without stressing the rice plants. This technology is becoming a recommended practice in water-scarce irrigated areas in South and Southeast Asia. In the Philippines, the adoption of safe AWD started in 2002 with farmers using deep-well pump systems in Tarlac Province. The technology was simplified by using a simple perforated field water tube installed at 15 cm deep from the soil surface to help farmers implement the technology. This paper presents results of adoption studies in the deep-well pump systems, farmers' perceptions, current course of action, including widespread training and dissemination. Insights from lessons learned in the impact-pathway networks will also be presented. As the project unfolds, it revealed a pattern of research-development-extension which follows a process of technology adaptation rather than "transfer", following the concept of participatory learning and action. Our expanding impact-pathway networks (both the scaling out and scaling up) have been driven by widespread training activities, while building on necessary outscaling mechanisms, including documenting evidence from local success stories and increasing buy-in from local R&D partners.
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Intermittent irrigation is an important option for mitigating CH4 emissions from paddy fields. In order to better understand its controlling processes in CH4 emission, CH4 fluxes, CH4 production and oxidation potentials in paddy soils, and 13C-isotopic signatures of CH4 were observed in field and incubation experiments. The relative contribution of acetate to total CH4 production (fac) and fraction of CH4 oxidized (fox) in the field was also calculated using the isotopic data. At the beginning of the rice season, the theoretical ratio of acetate fermentation: H2/CO2 reduction = 2:1 was reached, however, in the late season H2/CO2-dependent methanogenesis became dominant. Compared to continuous flooding, intermittent irrigation significantly reduced CH4 production potential and slightly decreased fac-value, indicating methanogens, particularly acetate-utilizing methanogens, were inhibited. CH4 oxidation was very important, especially in paddy fields under intermittent irrigation where 19–83% of the produced CH4 was oxidized. Intermittent irrigation enhanced CH4 oxidation potential slightly and raised fox-value significantly relative to continuous flooding. Intermittent irrigation significantly decreased CH4 flux creating a more positive δ13C-value of emitted CH4 by 12–22‰. A significant negative correlation was found between CH4 fluxes and values of δ13CH4 suggesting that the less the CH4 oxidation, the higher the CH4 emission, and the lower the δ13C-value of emitted CH4. Collectively, the findings show that intermittent irrigation reduced the seasonal CH4 production potential by 45% but increased the fraction of CH4 oxidized by 45–63%, thus decreasing the seasonal CH4 emission from the paddy fields by 71%, relative to continuous flooding.
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Methane (CH4) emissions were measured with an automated system in Central Luzon, the major rice producing area of the Philippines. Emission records covered nine consecutive seasons from 1994 to 1998 and showed a distinct seasonal pattern: an early flush of CH4 before transplanting, an increasing trend in emission rates reaching maximum toward grain ripening, and a second flush after water is withdrawn prior to harvesting. The local practice of crop management, which consists of continuous flooding and urea application, resulted in 79–184 mg CH4 m-2 d-1 in the dry season (DS) and 269–503 mg CH4 m-2 d-1 in the wet season (WS). The higher emission in the WS may be attributed to more labile carbon accumulation during the dry fallow period before the WS cropping as shown by higher % organic C. Incorporation of sulfate into the soil reduced CH4 emission rates. The use of ammonium sulfate as N fertilizer in place of urea resulted in a 25–36% reduction in CH4 emissions. Phosphogypsum reduced CH4 emissions by 72% when applied in combination with urea fertilizer. Midseason drainage reduced CH4 emission by 43%, which can be explained by the influx of oxygen into the soil. The practice of direct seeding instead of transplanting resulted in a 16–54% reduction in CH4 emission, but the mechanisms for the reducing effect are not clear. Addition of rice straw compost increased CH4 emission by only 23–30% as compared with the 162–250% increase in emissions with the use of fresh rice straw. Chicken manure combined with urea did not increase CH4 emission. Fresh rice straw has wider C/N (25 to 45) while rice straw compost has C/N = 6 to 10 and chicken manure has C/N = 5 to 8. Modifications in inorganic and organic fertilizer management and water regime did not adversely affect grain yield and are therefore potential mitigation options. Direct seeding has a lower yield potential than transplanting but is getting increasingly popular among farmers due to labor savings. Combined with a package of technologies, CH4 emission can best be reduced by (1) the practice of midseason drainage instead of continuous flooding, (2) the use of sulfate-containing fertilizers such as ammonium sulfate and phosphogypsum combined with urea; (3) direct seeding crop establishment; and (4) use of low C/N organic fertilizer such as chicken manure and rice straw compost.
Since its modest beginning in the 1970s, the academic and research focus on energy has grown substantially and energy has established itself as an independent, interdisciplinary subject area. It attracts attention from people in a range of different fields including engineers, scientists, geologists, environmentalists, bankers, investors, policy makers and politicians. Energy Economics introduces the basic concepts of energy economics and explains how simple economic tools can be used to analyse contemporary energy issues. Energy Economics is organised into six parts that give the reader a thorough grounding in various key aspects of the subject: •basic demand-related concepts and ideas used in energy economics; •supply-side economics; •energy markets, with specific emphasis on oil, gas and coal; •the application of simple economic principles in analysing contemporary energy issues; •environmental aspects of energy use; and •regulatory and governance issues. Energy Economics is an easily accessible reference book for students of energy economics at the postgraduate level, as well as for a wider interdisciplinary audience. It provides readers with the skills required to understand and analyse complex energy issues from an economic perspective.
Artefactual field experiments, spatial econometrics, and household surveys are combined in a single study to investigate the neighborhood effects of social behaviors. The dictator and public goods games are conducted among rice farmers in irrigated and non-irrigated areas in the Philippines. We find the neighborhood effects but the magnitude and statistical significance of endogenous social effects vary with the irrigation availability, type of social behavior, and type of neighborhood. Altruistic and cooperative behaviors are significantly influenced by the behaviors of neighbors only in the irrigated area, where social ties are strengthened through collective irrigation management. Through this effect, irrigated farmers’ social behaviors become similar to those of one another. Neighborhood effects for cooperative behavior are stronger among farm plot neighbors than among residential neighbors, which may reflect their interactions in irrigation management. Although non-dynamic, these findings are consistent with the theory of social norm evolution through common pool resource management.
Methane fluxes from Beijing ricefields as affected by organic amendment, water regime, crop establishment method, and rice cultivar were measured with a closed chamber method in 1990, 1991, 1995, and 1996. Total fluxes from plots receiving high organic amendment always exceeded those from the low-input plots. Compared with continuous flooding, intermittent irrigation (there were a few days of no standing water between two irrigations) and constant moisture (the field had no standing water, but remained saturated) reduced methane emission rate by 25.4 and 58.4%, respectively. Methane flux from a dry-seeded rice field was 75.2% lower than from a transplanted ricefield although both dry-seeded rice plots and transplanted ricefields were initially flooded at the same time. Rice cultivars differed in methane emission rates by 9.0–55.7%. Emission rates were positively correlated with aboveground dry matter production and root weight, but not grain yield. Intermittent irrigation and rice cultivar seem to be the most promising methods for mitigating methane emission from ricefields; they do not affect rice yield and are easily implemented at the farm level.
Methane (CH4) and nitrous oxide (N2O) emissions from an irrigated rice field under continuous flooding and intermittent irrigation water management practices in northern China were measured in situ by the static chamber technique during May to October in 2000. The intermittent irrigation reduced total growing‐season CH4 emission by 24.22% but increased N2O emission by 23.72%, when compared with the continuous flooding. Soil Eh and four related bacterial groups were also measured to clarify their effects on gaseous emissions. Three ranges of soil redox potential were related to gas emissions: below −100 mV with vigorous CH4 emission, above +100 mV with significant N2O emission, and +100 to −100 mV with little CH4 and N2O emissions. Intermittently draining the field increased soil oxidation, with a decrease in CH4 emission and an increase in N2O emission. In general the mid‐season drainage slightly increased the populations of methanotrophs, nitrifiers, and denitrifiers but decreased that of methanogens.
The effect of differing water management schemes on the emission of methane (CH4) from rice paddies to the atmosphere was studied in a Japanese paddy field. Using an automated sampling and analyzing system, the test site was divided into two plots: a continuously flooded plot which was maintained flooded by constant irrigation from May to August, and an intermittently drained plot in which short-term draining practices were performed several times during the flooding period. The draining practice had a strong effect on CH4 emission. A large flush of CH4 emission was observed in the intermittently drained plot immediately after each drainage. It was followed by a rapid decrease in CH4 flux in most of the cases. A large flush of CH4 was observed after the final drainage at the end of August in the continuously flooded plot, accounting for about 7% of the total CH4 emitted in the plot. Total emission rates of CH4 during the cultivation period were 14.8 and 8.63 gm-2 for 1991 and 9.49 and 5.18 gm-2 for 1993 in the continuously flooded and intermittently drained plots, respectively. Companion N2O flux measurements showed that almost no N2O was emitted from either plot until the final drainage. These results indicate that short-term draining practices strongly reduce CH4 emission from rice paddy fields, and that improvement in water management can be one of the most important mitigation strategies for CH4 emission from rice paddy fields.