1. Supervising Science Research Specialist
2017 Asia Sub-Group Meeting of the Paddy Rice Research Group
And 5th Annual Meeting of MIRSA-2 Project
Tsukuba International Congress Center
( Takezono, Tsukuba, Ibaraki, , Japan)
 02 September 2017
SSPN Paper Summary: Philippines
Evangeline B. Sibayan
Supervising Science Research Specialist

2. Title: Effects of alternate wetting and drying technique on greenhouse gas emissions from irrigated rice paddy in Central Luzon, Philippines Authors: EB. Sibayana, KSPascuala, FS Grospea, MEDCasila, T Tokidac, AT Padreb, K Minamikawac Agencies : PhilRice, IRRI, NIAES-NARO

3. Corresponding author: Kristine S. Pascual, kcsamoy@gmail
Corresponding author: Kristine S. Pascual, Type of contribution: Full-length paper Division: Environment Short running title: AWD feasibility in Philippines

4. Objectives of this study:
to evaluate the feasibility of AWD in reducing CH4 emission during two distinct rice seasons, and
to determine a suitable water management for reducing CH4 and N2O emissions and saving water without compromising grain yields from irrigated rice fields in Central Luzon, Philippines,

5. METHODOLOGY

6. Incorporated rice stubbles*
Table S1. Field management practices during the six season field experiments in Central Luzon, Philippines.
Season
2014DS
2014WS
2015DS
2015WS
2016DS
2016WS
Plowing date
23-Dec-13
12-Jun-14
21-Dec-14
26-Jun-15
18-Oct-15
7-Jun-16
Variety
NSIC Rc238
No. seedlings/hill
2-3
Transplanting date
13-Jan-14
27-Jun-14
12-Jan-15
10-Jul-15
15-Jan-16
29-Jun-16
Harvesting date
21-Apr-14
25-Sep-14
16-Apr-15
8-Oct-15
5-Apr-16
26-Sep-16
Date of Pesticide spraying
16-Jan-14 -
20-Jul-16
Pesticide/Herbicide Application
Pesticide
Herbicide
Total N (kg N ha-1)
120 90
Total K (kg K2O ha-1) 40
total P (kg P2O5 ha-1)
Straw management
Incorporated rice stubbles*
Incorporated rice stubbles

7. RESULTS

8. Figure 1. Methane, Nitrous Oxide Emissions and water level, temperature and rainfall during the 3 DS

9. Figure 2. Methane, Nitrous Oxide Emissions and water level, temperature and rainfall during the 3 WS

10. Methane Emission
CH4 (g m-2)
Cumulative emission

12. Nitrous oxide

13. Global Warming Potential - Season 5

14. Table 2. Seasonal CH4 and N2O emissions, GWP, rice grain yield, yield-scaled GWP, total water use, and water productivity as affected by cropping season and water management
Treatment
CH4
(kg CH4 ha-1)
N2O
(kg N2O ha-1)
GWP
(kg CO2 eq ha-1)
Grain yield
(Mg ha-1)
Yield-scaled GWP
(Mg CO2 ha-1 Mg-1 grain)
Water use
(m-3 ha-1)
Water productivity
(kg m-3) DS WS CF
69.9
328.9
1.60
0.509
2853
11333
6.90
5.41
0.43
2.10
10336
10944
0.77
0.512
AWD
42.2
350.1
3.50
0.633
2476
12093
6.88
5.83
0.37
2.14
5913
9215
1.18
0.645
AWDS
52.8
374.0
2.63
0.528
2578
12874
5.42
0.41
2.46
5012
8949
1.43
0.615
Season mean
54.9
351.5
2.58
0.556
2636
12100
6.89
5.55
0.40
2.23
7087
9702
1.13
0.590
Treatment Means
199.4 A
1.05 B
7093 A
6.16 A
1.27 A
10640 A
0.642 B
196.1 B
2.07 A
7284 A
6.35 A
1.25 A
7564 B
0.914 A
213.4 A
1.58 B
7725 A
1.43 A
6980 B
1.023 A
P value
Source of variation df
Cropping season (CS) 5
***
Dry or Wet (DW)1 1
Dry season (DS)1 2
0.502 ** †
Wet season (WS)1
0.383
0.134
Main plot error 15
Treatment (T) *
0.776
0.666
0.496
T × CS 10
0.297
0.610
0.954
0.585
T × DW2
0.422
0.476
0.457
T × DS2 4
0.562
0.747
T × WS2
0.315
0.769
0.462
0.946
0.434
0.957
Split-plot error 36

15. SUMMARY OF FINDINGS

16. Lower seasonal CH4 emissions were obtained in DS than in WS.
Higher CH4 reduction (60-51%) and GWP reduction (36-22%) relative to CF under AWD during season 5 (2016 DS), was achieved when dry plowing (5cm) was done a few days after harvest of previous crop and earlier drainage was imposed during the crop cycle
Increased N20 fluxes were observed 1-5 days after N fertilizer application under AWD and AWDS during DS representing a significant portion of the total seasonal N2O emissions

17. Higher contribution of N2O emissions to the total GWP in DS.
GWP reduction (at least 35%) was achieved only in 2016 DS by AWD relative to CF due to tillage after harvest of the previous crop and early start of AWD implementation at 10 DAT.
Grain yields were not significantly different among treatments; DS yields were consistently higher than WS yields by %.

18. CONCLUSIONS
Implementation of AWD is only feasible during DS in Central Luzon, Philippines
2. The AWD with the current settings significantly reduced the seasonal total CH4 emission, but the reduction rate against CF was very limited (1.7%). In addition, N2O emission was enhanced and the resultant GWP did not significantly differ among treatments.

19. LEARNINGS
Feasible options that enhance the ability of AWD in reducing GHG emissions:
an earlier rice residue incorporation under dry soil conditions,
an earlier implementation of drainage, and
a proper maintenance of flooded soil condition during/after N fertilizer topdressing.

20. RECOMMENDATION
Further study is necessary to test the quantitative effect of these options under field conditions.

21. Acknowledgements
To the Ministry of Agriculture Forestry and Fisheries (MAFF) of Japan through the International Research Project “Technology development for circulatory food production systems responsive to circulatory food production systems responsive to climate change: Development of mitigation options for greenhouse gas emissions from agricultural lands in Southeast Asia 2 (MIRSA 2) for the funding support, and
To Prof. Kazuyuki Inubushi (Chiba University, Japan), Dr. Reiner Wassmann (IRRI, Philippines), and Dr. Kazuyuki Yagi (NIAES, Japan) for their valuable comments on the earlier version of this manuscript.

22. Thank you for your kind attention!