ARTICLE

Mitigation of greenhouse gas emission with system of riceintensification in the Indo-Gangetic Plains

Niveta Jain • Rachana Dubey • D. S. Dubey •

Jagpal Singh • M. Khanna • H. Pathak •

Arti Bhatia

Received: 11 January 2013 / Revised: 22 June 2013 / Accepted: 30 July 2013

� Springer Japan 2013

Abstract System of rice intensification (SRI) is an

alternate method of conventional puddled, transplanted,

and continuously flooded rice cultivation for higher yield,

water saving, and increased farmer’s income. The SRI may

also have considerable impact on greenhouse gas emission

because of difference in planting, water and nutrient

management practices. A field experiment was conducted

with three planting methods: conventional puddled trans-

planted rice (TPR), conventional SRI with 12-days-old

seedling (SRI) and modified SRI with 18-days-old seedling

(MSRI) to study their effect on methane and nitrous oxide

emission. Seasonal integrated flux (SIF) for methane was

highest in the conventional method (22.59 kg ha-1) and

lowest in MSRI (8.16 kg ha-1). Methane emissions with

SRI and MSRI decreased by 61.1 and 64 %, respectively,

compared to the TPR method. Cumulative N2O–N emis-

sion was 0.69, 0.90, and 0.89 kg ha-1 from the TPR, SRI,

and MSRI planting methods, respectively. An average of

22.5 % increase in N2O–N emission over the TPR method

was observed in the SRI and MSRI methods. The global

warming potential (GWP), however, reduced by 28 % in

SRI and 30 % in MSRI over the TPR method. A 36 % of

water saving was observed with both SRI and MSRI

methods. Grain yield in the SRI and MSRI methods

decreased by 4.42 and 2.2 %, respectively, compared to the

TPR method. Carbon efficiency ratio was highest in the

MSRI and lowest in the TPR method. This study revealed

that the SRI and MSRI methods were effective in reducing

GWP and saving water without yield penalty in rice.

Keywords System of rice intensification �Transplanted rice � Mitigation � Methane � Nitrous

oxide � Global warming potential

Introduction

Rice (Oryza sativa) is one of the most important cereal crops

of world. Among the rice growing countries in the world,

India has the largest area under rice crop and ranks second in

production next to China. In India, 44.41 million ha (Mha) of

cultivated land is under rice cultivation with the production

of 103.41 million ton (Mt) (MOA 2012). Conventionally,

rice is grown under flooded conditions. Rice needs about

3,000–5,000 L of water to produce 1 kg of grain (Bouman

et al. 2002). At global level, agricultural share for fresh water

is 70–80 % and rice accounts for 85 % of this. Projections

indicate that agriculture’s share in freshwater supplies is

likely to decline by 8–10 % or more. In the Indo-Gangetic

Plains, water is increasingly becoming scarce because of its

other competing use and thus necessitates the development

of alternative irrigated rice systems that require less water

than conventional flooded rice.

Rice fields submerged with water are considered to be

one of the major sources of CH4 emission from soils.

Methane is produced in soil during microbial decomposition

of organic matter under anaerobic conditions. Indian rice

fields emit 3.37 million tons of methane and out of these, 1.84

MTs is the contribution of irrigated rice fields (Bhatia et al.

2013). The strategies for mitigating methane emission from

N. Jain (&) � R. Dubey � D. S. Dubey � J. Singh � H. Pathak �A. Bhatia

Center for Environment Science and Climate Resilient

Agriculture, Indian Agricultural Research Institute,

New Delhi 110 012, India

e-mail: nivetajain@gmail.com

M. Khanna

Water Technology Center, Indian Agricultural Research

Institute, New Delhi 110 012, India

123

Paddy Water Environ

DOI 10.1007/s10333-013-0390-2

rice cultivation could be altering water management, such as

alternate wetting and drying, direct-dry seeding (Tabbal et al.

2002), aerobic rice (Bouman et al. 2005), non-flooded

mulching cultivation, and system of rice intensification

(SRI). The SRI was introduced in irrigated lowland rice in

order to reduce the amount of water used for irrigation

(Uphoff 2003a, 2003b), which includes transplanting of

young seedlings (8–14 days) singly in square pattern keep-

ing paddy field moist by intermittent drying and wetting. It

leads to better plant growth, less use of chemicals and fer-

tilizer, increases productivity of land and economizes use of

water, which helps in maintaining the system productivity as

well as sustainability. Unflooded paddies develop intensive

roots that help in better absorption of water, increased grain

yield, grain-filling rate, and remobilization of carbon

reserves from vegetative tissues to grains (Tuong et al. 2005;

Yang et al. 2007; Zhang et al. 2008, 2009). Although,

methane emission will reduce due to prevailing aerobic

conditions, but considerable amounts of nitrous oxide

emission could occur because of alternate wetting and drying

of rice fields, resulting in the repetition of nitrification and

denitrification processes (Sharma et al. 2008). This effect

will be small when nitrogen fertilizer is not used. As GHG

mitigation practices can affect more than one GHG, it is

important to consider the impact of mitigation options in a

holistic way, and assess the tradeoff relationship between

both N2O and CH4. The objectives of this study were to

evaluate the effect of SRI on methane and nitrous oxide

emission and to evaluate the carbon efficiency ratio (CER)

and global warming mitigation potential of SRI.

Materials and methods

Experimental site and soil

A field experiment was conducted growing rice (var. Pusa

44) in a Typic Ustochrept at the experimental farm of the

Indian Agricultural Research Institute, New Delhi in kharif

2009. The site is located in the Indo-Gangetic alluvial tract

at 28�40N and 77�12E, at an altitude of 228 m above mean

sea level. The climate of the region is subtropical and semi-

arid with mean maximum temperatures varying from 43.9

to 45.0 �C. The mean minimum temperature ranges from 6

to 8 �C with occasional occurrence of frost in January. The

mean summer and mean winter temperatures were 33.0 and

17.3 �C, respectively. The area receives an annual rainfall

of 750 mm, about 80 % of which occurs from June to

September. The rainfall, and minimum and maximum

temperature during crop growing season (July–October)

recorded at the meteorological observatory of Indian

Agricultural Research Institute; New Delhi, India are given

in Fig. 1. The year 2009, had 502 mm of rainfall from July

to October, with 124, 176, and 202 mm (99.8 % of total)

received during July, August, and September months,

respectively. There were 7, 10, and 8 rainy days during

July, August, and September months, respectively.

The soils are well drained with the groundwater table at

6.6 and 10 m deep during the rainy and summer seasons,

respectively. The alluvial soil at the experimental site had a

loamy texture (46 % sand, 33 % silt, and 21 % clay). The

soil of the experimental site characterized before the start

of experiment had a bulk density of 1.49 g cm-3, pH (1:2,

soil to water ratio) of 8.04, electrical conductivity of

0.37 dS m-1, CEC of 7.3 C mol (p?) kg-1, and organic

carbon, total N, Olsen P, and ammonium acetate extract-

able K contents of 5.3, 0.32, 0.008, and 0.14 g kg-1,

respectively.

Treatments and crop management

The treatments consisted of three planting methods: con-

ventional puddled transplanted rice (TPR), conventional

SRI with 12-days-old seedling (SRI), and modified SRI

with 18-days-old seedling (MSRI) having six replica-

tions. The replications were allocated randomly into 18

0

5

10

15

20

25

30

35

40

45

0

20

40

60

80

100

120

7/1/

09

7/8/

09

7/15

/09

7/22

/09

7/29

/09

8/5/

09

8/12

/09

8/19

/09

8/26

/09

9/2/

09

9/9/

09

9/16

/09

9/23

/09

9/30

/09

10/7

/09

10/1

4/09

10/2

1/09

10/2

8/09

Tem

pera

ture

(°C

)

Rai

nfal

l (m

m)

RF TMAX TMIN T MEANFig. 1 Precipitation and mean

and maximum temperature of

the experimental site

Paddy Water Environ

123

experimental plots of size 5.5 m 9 6.0 m. Farmyard

manure (FYM) at the rate of 10 t ha-1 was incorporated

into moist soil 2 weeks before transplanting. The soil was

puddled and P (26.2 kg ha-1) and K (50 kg ha-1) were

incorporated into the soil prior to transplanting using single

super phosphate (SSP) and muriate of potash (KCl),

respectively, in all plots. Nitrogen was applied through

urea at the rate of 120 kg ha-1 in all the plots. The P and K

were applied as basal dose and N in three splits, 50 % as

basal and 25 % each on 32, and 62 days after transplanting

(DAT). Irrigation was given on every alternate day (5-cm

depth) in conventional rice plots to keep saturated condi-

tion and in SRI plots twice a week to keep soil just moist

(3.5 cm). In TPR 2–3 seedlings of 30 days age per hill

were transplanted in the plots. The distance between row to

row and hill to hill was 15 9 20 cm. In SRI and MSRI

plots, one seedling per hill was transplanted with a spacing

of 25 9 25 cm in square pattern. Weeds were controlled as

required.

Soil sampling and analysis

Soil samples from 0 to 15 cm soil layer were collected at

three locations from each plot 0, 36, 70, 90, and 104 DAT

using a core sampler of 8-cm diameter and analyzed for

NO3–N, NH4–N, and organic carbon. The entire volume of

soil was weighed and mixed thoroughly, and 10 g of soil

was weighed and used for making extracts with 2 M KCl.

These extracts were used for estimation of inorganic N viz.

NH4 and NO3 content. Initial soil samples were air-dried,

sieved through a 2-mm screen, mixed, and used to deter-

mine various physico-chemical properties using standard

procedures (Page et al. 1982).

Yield estimation

Rice yields for all the treatments were determined from the

total plot area by harvesting all the hills excluding the hills

bordering the plot. The grains were separated from the

straw, dried, and weighed. Grain moisture was determined

immediately after weighing and subsamples were dried in

an oven at 65 �C for 48 h.

Gas sample collection and analysis

Collection of gas samples for CH4 and N2O was carried out

by the closed-chamber technique. The acrylic chambers of

50 cm 9 30 cm 9 100 cm (length 9 width 9 height)

dimension made of 6-mm sheets were used (Bhatia et al.

2005). Aluminum channels were used with each chamber.

The aluminum channels were inserted 10 cm inside the soil

and were filled with water to make the system airtight. A

battery operated fan was fixed inside the chamber to

homogenize the inside air. A thermometer was also inserted

inside the chamber to monitor the temperature of the

chamber. Gas samples were drawn with 20 ml syringe with

the help of a hypodermic needle (24 ga) at 0, 30 min, and 1 h

for CH4 and N2O. Head space volume and tempera-

ture inside the box was recorded, which was used to calcu-

late flux of methane and nitrous oxide. Gas samples were

collected once in a week throughout the cropping season.

Methane and nitrous oxide (N2O) concentrations in the gas

samples were analyzed by Gas Chromatograph (Schimadzu

8A and HP 5896) fitted with a flame ionization detector (FID)

and electron capture detector (ECD), respectively. A GC–

computer interface was used to plot and measure the peak

area. NIST traceable standards of methane (2 and 5 ppmV)

and N2O (500 and 1 ppmV) obtained from Spectra Gases,

USA were used for calibration.

Samples for GHG analysis were collected between 9.30

and 11 a.m. from each treatment replicate by placing one

box per replicate on, 1, 3, 7, 10, 14, 21, 28, 35, 38, 44, 45,

46, 52, 56, 65, 70, 77, 86, 97, and 104 DAT. The mean

value was taken as the representative value for that method.

Estimation of total N2O and CH4 emissions during the

cropping season was done by successive linear interpola-

tion of average emission on the sampling days assuming

that emission followed a linear trend during the periods

when no sample was taken.

Global warming potential and carbon equivalent

emission

The global warming potential (GWP) is an index and can

be defined as the cumulative radiative forcing between the

present and some chosen later time ‘‘horizon’’ caused by a

unit mass of gas emitted now. It is being used to compare

the effectiveness of each GHG to trap heat in the atmo-

sphere relative to some standard gas, by convention CO2.

The GWP for CH4 (based on a 100-year time horizon) is

25 and N2O is 298 when the value for CO2 is taken as 1.

The GWP of different treatments were calculated using the

following equation (IPCC 2007)

GWP ¼ CH4 � 25þ N2O � 298 ð1Þ

The GWP/unit of yield was calculated by dividing GWP of

a treatment with rice grain yield.

The carbon equivalent emission (CEE) is 27.3 % (12/44)

of the GWP. CER is an index of efficiency of a treatment. It is

a ratio of carbon fixed in terms of grain yield to the carbon

emitted from soil in a particular treatment. The CER, i.e.,

carbon (C) fixed in grain by rice per unit of C emitted from

soil was calculated using the following equation.

CEE ¼ GWP� 12=44ð Þ ð2ÞCER ¼ Grain yield in terms of Cð Þ of the rice=CEE ð3Þ

Paddy Water Environ

123

Irrigation water and water productivity

The irrigation depth of each irrigation event was measured

by using an ordinary scale with in., cm, and mm marking.

In each plot, the depth of water was measured at ten points

randomly after each irrigation and the mean depth of irri-

gation water was taken as representative depth for each

plot. The quantity of water applied during each irrigation

was summed to calculate the total amount of water applied

in a plot throughout the cropping season. The effective

rainfall was estimated using USDA-SCS method. The

evapotranspiration was calculated using CROPWAT model

version 8.0 (FAO 2009). The total inflow and outflow of

water were calculated by water balance equation (Eq. 4).

Water productivity was estimated as grain yield divided by

total water utilized (rainfall and applied) and expressed as

kg m-3.

I þ ER ¼ ETc þ P þ SMS ð4Þ

where I is irrigation water applied, ER is effective rainfall,

ETc is crop evapotranspiration, P is percolation beyond

root zone, and SMS is soil moisture storage.

Data analysis

The data were statistically analyzed using analysis of var-

iance technique as per the factorial RBD with SAS (Sta-

tistical Analysis System) software, i.e., SAS 9.2. The

significance of the treatment was determined using least

significant difference (LSD) at the 5 % probability level.

Results and discussion

Effect of planting methods on methane emission

Flux of CH4 fluctuated between 0.02 and 5.07 kg ha-1

day-1 in conventional transplanting (TPR), -0.11 and

3.92 kg ha-1day-1 in SRI, and -0.10 and 2.83 kg ha-1

day-1 in MSRI methods during the entire rice growing

season (Fig 2a). In TPR treatment, on most days higher

CH4 emissions were observed compared to the SRI and

MSRI methods. The highest flux of 5.07 kg ha-1day-1

CH4 was observed in TPR method on 21 DAT. Whereas in

case of SRI and MSRI methods, the methane flux was high

up to 17 DAT which declined at later stage. The cumula-

tive emission of CH4 during the cropping period was

lowest (8.16 kg ha-1) in the MSRI and the highest

(22.59 kg ha-1) in conventional method of transplanting

method (Table 1). The SRI and MSRI methods reduced the

methane emission by 61.1 and 64 %, respectively. There

was no significant difference in total methane emission

from SRI and MSRI methods. SRI and MSRI methods of

transplanting recorded an average reduction of 62.42 % in

methane flux over conventional method (Fig 2b).

Methane emission throughout the crop growth stages

was dictated by irrigation events. The increased methane

emission in TPR treatment was because of the conducive

anoxic condition due to saturated moisture condition.

Higher rates of methane production in TPR may also be

due to availability of organic substrates in the form of root

exudates and the intensive reducing condition in the rice

rhizosphere (Singh et al. 1998). More over, CH4 production

starts at redox potential (Eh) of a soil below -150 mv. The

Eh of soil gradually decreases after flooding (Jugsujinda

et al. 1996), which may be due to a decrease in the activity

of the oxidized phase and increased activity of the reduced

phase. The higher CH4 emission under flooded rice has

been reported by several researchers (Bhatia et al. 2005;

Zheng-Qin et al. 2007; Kosa et al. 2011). SRI and MSRI

methods recorded 62 % reduction in methane emission.

Relatively low rates of CH4 emission from SRI and MSRI

methods were due to partially aerobic soil conditions

because of intermittent drying and wetting. According to a

study conducted by Hidayah et al. (2009) in Indonesia in

intermittent irrigation and SRI, a reduction of 60 and

1.0-

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

0 10 20 30 40 50 60 70 80 90 100 110

CH

4(k

g h

a-1

d- 1

)

Days after transplanting

TPR

SRI

MSRI

0

5

10

15

20

25

TPR SRI MSRI

CH

4(

kg h

a- 1)

(b)

(a)

Fig. 2 a Temporal emission of CH4 from rice soils under different

planting methods. b Cumulative emission of CH4 from rice soils

under different planting methods

Paddy Water Environ

123

37.5 %, respectively, in methane emission was observed in

comparison with continuous irrigation. Suryavanshi et al.

(2012) have also reported lower methane emissions from

SRI practice. According to Kumaraswamy et al. (2000),

the available organic carbon in the form of increased

root density leads to an increase in methanogen population

in flooding conditions. The intermittent aerobic and

anaerobic conditions in SRI and MSRI methods, reduces

the activity of CH4 producing bacteria resulting in less CH4

production under SRI and MSRI. Hadi et al. (2010) have

suggested that intermittent irrigation and drainage can be a

suitable management option to reduce greenhouse gas

(GHG) emission from paddy soils in Japan and Indonesia.

With every dose of N application, there was a small peak of

methane flux observed in all the treatments. The additional

amount of N provided might have increased the activity of

the microorganisms, involved in the production of methane

(Jain et al. 2000; Pathak et al. 2003) resulting in higher

emission.

Effect of planting methods on nitrous oxide emission

N2O–N emissions varied widely throughout the rice growth

season. Flux of N2O–N ranged among 2.97–13.38,

3.86–20.20, and 4.41–19.86 g ha-1 day-1 from TPR, SRI,

and MSRI methods, respectively, (Fig 3a). First peak flux

of nitrous oxide emission on 3 DAT varied from 13.38 to

20.20 g ha-1 day-1 under different planting methods.

Subsequently, there was lowering of the emission. Highest

N2O–N emission was from SRI method (20.2 g ha-1

day-1) and lowest (1.96 g ha-1 day-1) from conventional

method of planting. The seasonal integrated fluxes of N2O–

N were 0.69, 0.90, and 0.89 kg ha-1 from TPR, SRI, and

MSRI planting methods, respectively. Emission of N2O–N

was increased by 22.5 % in SRI and 23.4 % in MSRI

method over TPR method. There was no significant dif-

ference in total nitrous oxide emission from SRI and MSRI

method (Fig. 3b; Table 1). An average increase of 23.4 %

in N2O–N emission was observed in SRI methods of

transplanting over conventional method.

Initially, flux of N2O–N was high in all treatments which

was preferably due to denitrification of soil NO3-–N. As

NO3-–N in soil decreased due to plant uptake and losses

through denitrification and leaching, N2O–N flux declined

later. First, peak flux of N2O–N was on 3 DAT which

coincided with the first dose of fertilizer application that

supplied the substrate for nitrification (NH4?–N) and sub-

sequently for denitrification (NO3-–N). Later on, the

emission of N2O–N reduced till the next date of fertilizer

application. Emissions of N2O–N from soil in TPR were

lower than intermittent wetting and drying soil conditions

in SRI and MSRI plots which indicated that intermittent

wetting and drying treatments had more supply of NO3-–N

through nitrification as compared to saturated soil moisture

regime. NO3-–N served as a substrate for denitrification by

the denitrifiers and resulted in N2O emission. It could also

be due to the fact that N2O, which was formed during the

process of nitrification and denitrification under saturated

Table 1 Seasonal emissions of

methane, nitrous oxide, and

carbon equivalent emission

from rice soils as influenced by

different methods of rice

cultivation

Method of planting Methane Nitrous oxide GWP (kg

CO2 eq. ha-1)

CEE

(kg C ha-1)

TPR 22.59 0.61 888.1 242.2

SRI 8.81 0.91 644.3 175.7

MSRI 8.16 0.89 620.4 169.2

LSD at 5 % 2.10 0.03 55.75 15.2

0

5

10

15

20

25

N2O

-N (

g h

a-1d

-1)

Days after transplanting

TPR

SRI

MSRI

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

TPR SRI MSRI

N2O

-N (

kg h

a-1

)

(a)

(b)

Fig. 3 a Temporal emission of N2O–N from rice soils under different

planting methods. b Cumulative emission of N2O–N from rice soils

under different planting methods

Paddy Water Environ

123

soil moisture regime, further reduced to N2 when the soils

were anaerobic (Pathak et al. 2002). Alternate anaerobic

and aerobic soil conditions considerably increase N2O

emission relative to constant aerobic and anaerobic con-

ditions (Cai et al. 1997, 2007). N2O emissions during

intermittent irrigation periods, largely depends on, whether

or not the rice fields were water logged. Different water

regimes cause a significant change in N2O emissions from

rice paddies (Zou et al. 2005). Transition in soil water

regime regulates the soil N2O emissions and rice fields are

one of the sources of N2O emission during alternate

flooding and drying (Zheng-Qin et al. 2007).

Effect of planting methods on soil nitrogen

The concentration of NH4?–N in soil varied in the three

planting methods (Fig. 4a). Under TPR method, NH4?–N

concentration was higher compared to both SRI and MSRI

methods of planting and no significant difference was

found between SRI and MSRI methods. The NH4?–N

value ranged from 24.48 to 30.46 kg ha-1 in conventional

method while in SRI and MSRI ranged from 21.14 to

29.19 kg ha-1 and 19.20 to 28.68 kg ha-1, respectively,

during the entire crop growing period (Fig. 4a). A peak was

observed on 36 DAT in all the treatments. The peak

observed on 36 DAT was due to fertilizer application on 32

DAT which increased the availability of NH4?–N in soil.

Subsequently, the NH4?–N in soil decreased probably due

to plant uptake and also its conversion to NO3–N during

the drying phase of soil. At harvesting stage, low NH4?–N

concentrations were observed in all the methods of planting

with minimum in MSRI method and maximum in TPR

method of planting.

The NO3–N concentration fluctuated during the course

of the experiment. The variation in concentration of NO3-–

N among different methods of planting was statistically

significant during the crop growing period. The initial soil

NO3-–N concentration varied between 21.5 and

24.7 kg ha-1 (Fig. 4b). On 36 DAT in SRI and MSRI

methods, NO3-–N was increased by 21 and 26 % than

conventional planting method. Highest concentration of

27.18 and 28.03 kg ha-1 NO3-–N was observed on 70

DAT in SRI and MSRI treatments, respectively. The high

NO3-–N concentration in SRI and MSRI treatments

compared to TPR method may be due to partial anaerobic

and aerobic cycling which considerably increased NO3-–N

concentration relative to constant anaerobic conditions in

TPR method (Cai et al. 1997, 2007). Gradual decrease in

NO3-–N may be attributed to crop uptake at later stages.

Carbon equivalent emissions and carbon efficiency

ratio

A significant variation was observed in carbon equivalent

emission (CEE) amongst the planting methods. CEE was

highest under conventional treatment and lowest in MSRI

treatment. CEE ranged from 169 kg C ha-1 in MSRI to

242 kg C ha-1 in conventional transplanting. The CEE was

lowered by 27.4 % in SRI and 30.1 % in MSRI over

conventional method of planting. The CEE was at par in

SRI and MSRI method. The CEE was highest in TPR

method of planting because CH4 emission was higher

during the entire crop growing period.

The CER i.e., carbon fixed/carbon emitted from soil, is

an index of the efficiency of the particular treatment.

Among the planting methods, CER (11.56) was the lowest

in TPR method and was highest (16.26) in MSRI method

(Table 3). The difference between SRI and MSRI methods

was not significant. The CER of conventional method was

23.7 % lower than SRI and 29.8 % lower than MSRI

method. CER was found to be the lowest in conventional

method of planting which signifies that more C was emitted

and less C was fixed, whereas in case of SRI, the C emitted

15

20

25

30

35

0 20 40 60 80 100 120

NH

4+-N

(kg

ha

-1)

Days after transplanting

TPR

SRI

MSRI

15

20

25

30

35

0 20 40 60 80 100 120

NO

3- -N

(kg

ha

-1)

Days after transplanting

SRI

TPR

MSRI

(a)

(b)

Fig. 4 a Ammoniacal nitrogen in soil under different planting

methods. b Nitrate nitrogen in soil under different planting methods

Paddy Water Environ

123

was significantly reduced as compared to the carbon fixed.

This implies that MSRI and SRI methods are more efficient

since it causes less emission as compared to TPR method

of planting without significant difference in yield.

Reduction in global warming potential with SRI

SRI and MSRI methods of transplanting lowered the GWP

significantly due to low methane emission compared to the

TPR method. In SRI method, the GWP reduced from 888

to 644 and to 620 kg CO2 eq. ha-1 with MSRI method.

This amounted to reduction in GWP by 27.5 % in SRI and

30.2 % in MSRI over TPR method of planting, respec-

tively. Although, nitrous oxide emission was less in TPR

but the overall GWP was higher compared to SRI and

MSRI methods.The average reduction in GWP was 29 %

over TPR method. The GWP per unit of yield ranged from

0.108 kg CO2 eq. ha-1 kg-1 grain in MSRI method to

0.151 kg CO2 eq. ha-1 kg-1 grain in TPR method. The

average GWP per unit of yield of SRI and MSRI was

0.12 kg CO2 eq. ha-1 kg-1 grain.

Grain yield

The methods of planting did not affect the yield. Marginal

decrease in grain yield was observed in SRI (4.42 %) and

MSRI (2.2 %) methods over TPR method (Table 2). Grain

yield was at par in all the methods. Similar results are also

reported by Sheehy et al. (2004). This may be due to

autonomous adjustments between yield components par-

ticularly between number of panicles m-2 as a result of

their phenotypic plasticity (Sumithde et al. 2009).

Although, there are many reports of higher grain yield in

SRI than that of conventional planting (Thakur et al. 2009;

Gujja and Thiyagarajan 2009); however, in our study when

the yield was calculated in terms of seed rate, it indeed

gave higher yield as less seed was used in SRI as compared

to TPR method. Duration of different phonological stages

was not influenced by planting method. But the total crop

duration in SRI methods was reduced by 13 days compared

to TPR method. Days to maturity was less in SRI than

conventional method of planting probably due to trans-

planting of young seedlings which established quickly in

the field and started growing at a faster rate (Krishna et al.

2008).

Water usage and water productivity

Variations in water usage, water saving, and water pro-

ductivity of rice under different planting methods are given

in Table 3. Total number of irrigations given in conven-

tional method of planting were 35 (5-cm depth), whereas in

SRI and MSRI, the number of irrigations were reduced to

28 (3.5 cm) since the field was kept moist. Thus in SRI,

there was a saving of seven irrigations. The total irrigation

water used was 1,750 mm ha-1 in TPR and 980 mm ha-1

in both SRI and MSRI treatments. As all the treatments

received equal amount of rainfall during the growing per-

iod, therefore the effect was nullified. Application of irri-

gation water (3 cm), after formation of hairline cracks

showed considerable water saving besides providing a

better root growing environment in SRI. Total water inflow

was 2,152 mm in TPR and 1,382 mm in SRI and MSRI.

The evapotranspirations were 665, 548, and 593 mm for

TPR, SRI, and MSRI, respectively. The percolation loses

were 23 and 28 % less in SRI and MSRI methods

Table 2 Grain yield, total

carbon fixed, and carbon

efficiency as influenced by

different methods of rice

cultivation

Method of planting Grain yield (t ha-1) Biomass yield (t ha-1) Total C fixed (t ha-1) CER

TPR 5.88 11.86 2.82 11.56

SRI 5.62 14.11 2.70 15.44

MSRI 5.75 14.02 2.76 16.26

LSD at 5 % NS 3.09 NS 3.12

Table 3 Water usage and water productivity of rice as influenced by different planting methods

Method of

planting

No of

irrigation

Total inflow (mm) Total outflow (mm) Water

saving

(mm)

Water

productivity

(kg m-3)Irrigation

water applied

Rainfall Effective

rainfall

Evapotranspiration Percolation Soil

moisture

storage

TPR 35 1,750 502 402 665 1,383 104 0.26

SRI 28 980 502 402 548 685 149 770 (36) 0.38

MSRI 28 980 502 402 593 640 149 770 (36) 0.39

Values in parentheses are percent water saving in SRI and MSRI compared to TPR

Paddy Water Environ

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compared to TPR method. Water saving of 36 % was

observed in SRI and MSRI over TPR. Similar findings

were reported earlier by Thiyagarajan et al. (2002). Water

productivity is defined as the amount of water required per

unit of yield. Grain yield in all the three methods was

statistically at par, but variation in water productivity of

rice under different methods was recorded. Since in SRI

and MSRI, irrigation was given intermittently and yield

was comparable, therefore its productivity was found to be

higher. Total water productivity in conventional method

was 0.26 kg m-3 while in SRI and MSRI methods, it was

0.38 and 3.9 kg m-3, respectively, (Table 3). Water pro-

ductivity in SRI and MSRI was increased by 45.2 and

48.6 % as compared to conventional method of trans-

planting. According to Zhao et al. (2010), compared with

flooding pattern, SRI improves water use efficiency by

91.3 % and irrigation efficiency by 194.9 %. Chapagain

and Yamaji (2010) found 28 % saving of irrigation water,

without reducing grain yield by using alternate wetting and

drying (AWD) practice. Thakur et al. 2011 have reported

water saving of 22 % and water productivity doubled with

AWD-SRI management practices compared with flooded

standard management practice of growing rice.

Conclusions

Rice fields in Southeast Asia are the major source of

atmospheric CH4 and N2O because of large area under

cultivation, more water usage, and high use of resources.

The SRI is an alternate method of rice cultivation leading

to water saving. SRI and MSRI increased the water pro-

ductivity by 45.2 and 48.6 % compared to conventional

planting method. It had considerable impact on GHG

emissions from soil. The study proved that both SRI and

MSRI methods are effective in reducing GWP and saving

irrigation water from rice fields without any reduction in

yield. MSRI method was found equivalent to SRI method

in terms of GHG mitigation, yield, water saving, and also

overcomes the problem of transplanting tender seedlings.

Mitigation of GHG through SRI method can help farmers

in earning carbon credit, for which policy and mechanism

should be developed.

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