IJERD – International Journal of Environmental and Rural Development (2017) 8-1

Research article
erdComparative Study of Methane Emission and StructuralDevelopment of Rice Plants from SRI and non-SRI Methods
in a Lysimeter Experiment
ISHWAR PUN*
Graduate School of Frontier Science, The University of Tokyo, Chiba, Japan
Email: punisr@gmail.com

EIJI YAMAJI
Graduate School of Frontier Science, The University of Tokyo, Chiba, Japan
Received 16 December 2016

Accepted 5 May 2017(*Corresponding Author)

Abstract Mitigating greenhouse gas (GHG) emission is a challenging issue in context ofcoping with the ongoing climate change. Rice farming is considered as the major emitter ofCH4 along with gaseous N2O. There are several methods of irrigation management that reduces
the amount of CH4 and N2O gases produced, such as intermittent irrigation and mid-season
drainage. SRI (System of Rice Intensification) is one of the new methods known to increase theyield while mitigating GHGs by applying one of key elements intermittent irrigation, and is amethod which is now disseminating in many tropical countries. This study was conducted tomeasure the effectiveness of SRI method by measuring rice plant development, yieldcomponent, and methane emission using a lysimeter facility. The transplanted nursery waskoshihikari, a Japanese rice variety. The study compared between two plots with different
water treatments. The results showed that a plant growth characteristics were better in aContinuous plot than in a Intermittent plot, while grain yield was not significantly different.
Methane gas was almost 50% less in the Intermittent plot than in the Continuous plot. Total
global warming potential from methane emission for Intermittent plot and Continuous plot
were 50.41 g CO2/m2 and 100.53 g CO2/m2, respectively. The results suggest that SRI
methodology could be an effective method for mitigating methane emission without reducing
the grain yield.
Keywords methane, water management, system of rice intensification, climatic variability

INTRODUCTION
Mitigating greenhouse gases is a challenging issue in the present world. Exponential growth in world
population against a linear growth of food supply, coupled with a decrease in agricultural land, aremajor problems for the world. To overcome the problems, several technologies are being applied toincrease food supply to support the growing population. The development of rice technology isbeneficial for both the environment and rice production. In rice production, technologies like SRI(System of Rice Intensification), and an irrigation management method called intermittent (AlternativeWetting and Drying) irrigation, are being practiced in areas with limited resources to adapt to theongoing climate changes. SRI was originated in Madagascar in 1983, developed by Father Henri deLaulanı´e and later disseminated by Cornel University to more than 50 countries. SRI is broadly
defined as an agro-ecological methodology for increasing the productivity of irrigated rice by changing
the management of plants, soil, water, and nutrients (Cornell International Institute for Food,
Agriculture and Development, CIIFAD). Moreover, SRI method is a single transplanting method that
reduces seed requirement by 90%, increases yield by 20-100%, and saves water by 50%, according toⒸ ISERD

20

IJERD – International Journal of Environmental and Rural Development (2017) 8-1

the CIIFAD report. However, several issues are also known in implementation of SRI within local
farming practices from region to region, because the rice production largely depends on the topography,
climate conditions, and soil nutrients. Nonetheless, SRI method has shown positive synergies. Sato etal., (2005) reported that it is a method that saves water and costs, while also producing high yields inIndonesia. SRI method in India resulted in higher yields by almost 67% than a conventional method(Singh and Talati, 2006). Similarly, SRI method can save up to 25-50% water compared toconventional practices in Japanese rice farming (Chapagain and Yamaji, 2010). A study of the rice
plant development in China (Defeng et al., 2002) under a wider space transplanting method resulted ina higher root number than a close transplanting method. SRI method itself is a single transplanting
method of baby nursery with wider spacing. Chapagain et al., (2011) showed that the SRI method
results in a higher development of roots, where root number was greater by 30% and tillering and early
flowering increased by 25% during the paddy field experiment in Japan. Similarly, an experiment inIndia with the SRI method observed a significantly higher development in terms of physiological andplant development characteristics (Thakur et al., 2009).
Yet there are still a lack of reports for SRI adoption, particularly in Japan, since there arechallenges that needs to be overcome against local methods. Therefore, a comparative study of SRI andnon-SRI methods was conducted with a lysimeter facility of the University of Tokyo in Kashiwa,
Chiba, Japan. The objectives of the study were to examine the structural development of rice plant andmethane emission by two methods: the SRI method (intermittent irrigation) and non-SRI method(continuous flooding). The hypothesis was that the SRI method would perform better in comparison to
the non-SRI method. In particular, the SRI method was expected to result in higher grain yield,
biomass, and longer roots elongation, as reported in other countries. The experiment was conducted in
the lysimeter with transplantation of single seedling in two plots, where the intermittent plot wasirrigated by intermittent irrigation, and non-SRI method plot by continuous flooding. how high yields
are achieved through SRI’s key principles through a range of environmental factors and agronomic
management practices including variety selection.
METHODOLOGY
Study Area and Experimental Set Up
The experiment was conducted on the lysimeter situated in the University of Tokyo in Chiba
Prefecture during the rice growing season, from May to the end of October, in 2014. The lysimeter area
was 500 x 160 cm, soil depth 25 cm, was equipped with a drainage system on the right border andirrigation tap on the left border (Fig. 1). The soil was puddled homogeneously at the time of soil
preparation. 800 g of organic fertilizer was applied homogeneously. The composition of fertilizer was
1.3% nitrogen, 0.6% phosphorus, and 1.8% potassium, with C/N ratio of 22. The lysimeter was divided
into two plots by along the center by a plastic sheet. Plot A was named Intermittent plot and plot B wasnamed Continuous plot. Two water tubes of 25 cm length and 13.5 cm diameter were installed tomonitor the ponding depth of the plots. The water tubes featured a fixed measuring scale made ofaluminum to observe the water level in the lysimeter. Twelve days-old single nursery of Japanese rice
variety (koshihikari) was transplanted. The nurseries were prepared by the local farmers under ourrequest. Thirty-two nurseries were transplanted on May 23. The space between each hill was (30 x 30)
cm. The Soil Eh (ORP) sensors were set up for both plots at 5 cm and 10 cm depths. Soil Eh data wererecorded by EH-120 (Fujiwara Scientiﬁc Co. Ltd., Tokyo, Japan).
Management MethodⒸ ISERD

21

IJERD – International Journal of Environmental and Rural Development (2017) 8-1

Two types of water management were applied in the experiment. One was intermittent irrigation for
the Intermittent plot, and the other was continuous flooding for the Continuous plot. For the first twoweeks after the transplantation, shallow ponding condition was maintained in both plots until theyoung rice nurseries became stronger. Intermittent plot was then managed by intermittent irrigation
method (Fig. 2). Water was drained by a pumping tube in case of excess rainfall. Continuous plot wasponded continuously during the vegetative phase. The first weed was removed from both plots three
weeks after the transplantation. The plots were maintained by periodical weeding thereafter. The weeds
removed from the plots were buried under the soil as practiced in the SRI method. The first floweringof the rice plant was observed on August 9th. The lysimeter was covered by a net on August 29th toprevent damage by birds. The rice was harvested on October 3, 2014. Lysimeter was kept dry for thelast two weeks to prepare for the harvest.

Fig. 1 Layout of lysimeter

Fig. 2 Ponding condition in lysimeter
RESULTS AND DISCUSSION
Rice Plant Development
The rice plant development in this study is divided into three phases. The day from the transplantation
to panicle formation is the vegetative phase. From panicle formation to the fertilization is thereproductive phase. The final phase is the ripening phase, which includes maturity of rice grains.
During the vegetative phase, rice plant height was similar in growth (Fig. 3a). After the vegetativephase, plant height grew significantly higher in the Continuous plot, suggesting that plant height growsⒸ ISERD

22

IJERD – International Journal of Environmental and Rural Development (2017) 8-1

more favorably without water stress. The development of rice tillers during the first three weeks after
the transplantation was similar. Afterwards, a significant increase in the number of tillers was observedin the Continuous plot (p<0.01). Higher number of tillers was observed in Continuous plot DAT (DaysAfter Transplant) 49 and 56. Intermittent plot showed a higher number of tillers in DAT 70 (Fig. 3c).
After DAT 70, tiller number decreased as the lower parts of small tillers decayed in both plots, which
was not included in counting. Higher number of leaves was observed in DAT 70 in both plots (Fig. 3b).
Average number of leaves for the Intermittent plot and Continuous plot were 51.90 and 66.06,
respectively. In the reproductive phase, similar cases of descending number of leaves were observed
after the dry leaves were excluded from the count. The first panicle was counted on DAT 78. Lower
number of panicles was recorded in Intermittent plot because of lower tiller number compared to theContinuous plot. The number of panicles and tillers were same at the time of harvest (Fig. 3d).

Fig. 3 Rice plant development: (a) plant height, (b) number of leaves,(c) number of tillers, and (d) number of flowerings
Rice Yield and Root Development
Table 1 Comparisons between number of grain, branch, rice root, and methane
Measurement indicators
Number of grains
Grain weight (gram)
Panicle branches (number)Panicle weight without grain (gram)
Root length (centimeter)
Dry root weight (gram)
Methane flux (mg/m2/hr.)

Significantlevel
**
****
**

Intermittent plot
MeanSD†1086.10395.49Continuous plot
MeanSD†
1198.30
383.15

21.03
95.50
1.09
19.20
5.07
0.82

21.97
117.30
1.34
20.60
7.62
1.77

6.82
36.08
0.41
2.53
2.21
0.73

5.95
39.19
0.49
2.63
3.23
1.70

* Significant level at 0.1, ** Significant level at 0.05, *** Significant level at 0.01, - Not Significant† Standard deviation

To study the yield component, ten rice plants were selected from both plots. The rice plants wereselected from both sides of the plot borders in order to make the sampling process uniform. Larger
panicles were observed in rice plants from borders than from the middle of the plot. The number ofgrains, panicle branches, and roots were measured from the same rice plant samples. Everymeasurement indicators are an average of ten plants from each plot. The average grains number andⒸ ISERD23IJERD – International Journal of Environmental and Rural Development (2017) 8-1

weight were higher in the Continuous plot, but without significant difference compared to theIntermittent plot. A significant difference was observed in panicle branches. Higher number of panicle
branches were found in the Continuous plot than in the Intermittent plot (Table 1). In terms of dry root
weight, Continuous plot had a higher weight of total root than the Intermittent plot, but there was nodifference between root lengths. Thakur et al., (2009) reported a higher elongation and betterdistribution of root system by SRI method, and several other studies from outside Japan has also
reported of high yield and water savings by SRI. In this study, however, no significant difference wasobserved in terms of the yield and grain numbers.
Methane Emission
The methane gas emission from the Intermittent plot was typically lower than the Continuous plot. The
methane gas reduction process by intermittent irrigation is already known by many researchers (Hadi etal., 2010; Kudo et al., 2014). The pattern of methane emission in both plots were increasing during thevegetative phase and decreasing during the reproductive phase. The rapid development of rice plants
during the vegetative phase and longer application of irrigation caused the higher emission of methane.
Soil Eh was measured as an indicator of methane gas emission from both plots. A significantly positive
correlation between methane flux and soil water content was found in the lysimeter experiment in 2013
(Pun et al., 2013).

Fig. 4 Methane gas emission in Intermittent plot and Continuous plot

Fig. 5 Relation between methane flux and soil EhⒸ ISERD24

IJERD – International Journal of Environmental and Rural Development (2017) 8-1

Moreover, to understand the mechanism of methane gas flux with soil layer condition, depth-wisemeasurements of soil Eh were taken. In both plots at 10 cm depth, positive correlation was observed
between methane flux and soil Eh in Figs. 5a and 5b. However, Intermittent plot showed a negative
correlation at 5 cm depth in Fig. 5a. In the Intermittent plot, the soil surface was alternatively kept wetand dry by intermitttent irrigation, resulting in a soil Eh fluctuation and low level of methane formation.
The aerobic condition of the soils kept the emission low in the Intermittent plot. In case of theContinuous plot with continuous water ponding, soil Eh was lower at both 5 cm and 10 cm depths withhigher methane flux. During the continuous flooding, the soil was under a reducing condition and thus
emitted the methane gas. Cumulative methane flux during the rice growing season was reduced bynearly 50% in the Intermittent plot compared to the Continuous plot. Total methane flux emitted fromthe Intermittent plot and the Continuous plot were 50.41 g CO2/m2 and 100.53 g CO2/m2 per rice
growing season, respectively. Another anthropogenic gas, N2O emission, occurred when the flooding
water disappeared from paddy field and fertilizer was applied (Cai et al., 1997).
CONCLUSION
The experiment was conducted to measure methane emission and the structural development of rice
plant by SRI and non-SRI methods. The structural development of rice plant in the Continuous plot
was significantly greater than the Intermittent plot. Young single seedlings were used in both plots, andthere was no difference in grain yield. Dry root weight was greater in the Continuous plot but nodifference was observed for root length. The methane flux in Intermittent plot was significantly lower
than the Continuous plot, with almost 50% reduction in emission. The methane flux peak was mainly
observed during the vegetative and pre-reproductive phases. If the water could be managed without
stress to the plant, then SRI method can be the appropriate method for reducing global warming
potential. The higher correlation between soil Eh and methane flux were found at 10 cm depth in bothplots. The experiment was conducted on concrete made Lysimeter, and the heat from the concrete may
have affected the measurements for soil temperature and Eh. To clearly understand soil Eh in relation
to depth, tests in real paddy fields are needed. SRI method itself is a new environment-friendly method,
and while several researchers produced higher yields than a conventional rice cultivation method, theresults from this study was different. The dissemination of SRI method is still a work in progress,
where key basic elements are being identified by particular local areas, since different areas havedifferent climate conditions and resource availability. The difference in result was because the same
number of rice seedling was transplanted in both plots. In other to further understand the structuraldevelopment in SRI and non-SRI methods, an experiment is needed to test by seedling densities.
REFERENCES
Cai, Z., Xing, G., Yan, X., Xu, H., Tsuruta, H., Yagi, K. and Minami, K. 1997. Methane and nitrous oxide emissions
from rice paddy ﬁelds as affected by nitrogen fertilisers and water management. Plant and Soil, 196, 7-14.
Chapagain, T. and Yamaji, E. 2010. The effects of irrigation method, age of seedling and spacing on cropperformance, productivity and water-wise rice production in Japan. Paddy Water Environ, 8 (1), 81-90.
Chapagain, T., Yamji, E. and Riseman, A. 2011. Assessment of system of rice intensification (SRI) andconventional practices under organic and inorganic management in Japan. Rice Science, 18 (4), 311-320.
Defeng, Z., Shibua, C., Yuping, Z. and Xiaqing, L. 2002. Tillering patterns and the contribution of tillers to grain
yield with hybrid rice and wide spacing. In Assessments of the System of Rice Intensification: Proceedings ofInternational Conference, Sanya, China, 1-4 April 2002, 125-131. Eds N. Uphoff et al. Ithaca, New York:Cornell International Institute for Food, Agriculture and Development. Retrieved from http://ciifad.cornell.edu/sri/proc1/sri_28.pdf.
Hadi, A., Inubushi, K. and Yagi, K. 2010. Effect of water management on greenhouse gas emissions andmicrobial properties of paddy soils in Japan and Indonesia. Paddy Water Environ, 8, 319-324.
Ⓒ ISERD25

IJERD – International Journal of Environmental and Rural Development (2017) 8-1

Kudo, Y., Noborio, K., Shimoozono, N. and Kurihara, R. 2014. Effects of water management practices formitigating gas emission and maintaining rice yield in central Japan. Agriculture, Ecosystem and Environment,
186, 77-85.
Pun, I, Yamaji, E. and Ches, S. 2015. Effect of INTERMITTENTI Practices on methane gas emission in a small
scale lysimeter. Paper presented at: The THA 2015 International Conference on “Climate Change and Water& Environment Management in Monsoon Asia”, Bangkok, Thailand.
R Core Team. 2014. R: A language and environment for statistical computing. R foundation for statisticalcomputing, Vienna, Australia. Retrieved from https://www.R-project.org/
Sato, S. 2005. 3 years experience of SRI (System of Rice Intensification) under SSIMP-DISIMP in easternIndonesia. Paper presented at: Integrated Citarum Water management Project, 4-5 July, 2005, Jakarta.
Sato, S., Yamaji, E. and Kuroda, T. 2010. Strategies and engineering adaptations to disseminate SRI methods inlarge-scale irrigation systems in Eastern Indonesia. Paddy water environ, 9, 79-88.
Singh, S.K. and Talati, J. 2006. Productivity impacts of the system of rice intensification (SRI), A case study inWest Bengal, India. Agricultural Water Management, 87, 55-60.
Thakur, A.K., Uphoff, N. and Antony, E. 2009. An assessment of physiological effects of system of riceintensification (SRI) practices compared with recommended rice cultivation practices in India. Expl. Agric.,
46 (1), 77-98. Doi: 10.1017/S0014479709990548Ⓒ ISERD26