Biochar amendment decreased C intensity of rice production in a Chinese rice paddy: a

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Biochar amendment decreased C intensity of rice production in a Chinese rice paddy: a field study of 2 consecutive rice growth cycles in Tai Lake plain, China Afeng Zhang, Genxing Pan, Rongjun Bian

1 Biochar amendment decreased C intensity of rice production in a Chinese rice paddy: a field study of 2 consecutive rice growth cycles in Tai Lake plain, China Afeng Zhang, Genxing Pan, Rongjun Bian Nanjing Agricultural University Sept. 19, @njau.edu.cn; af-725@163.com Center of Agriculture and Climate Change, Insititute of Resource, Ecosystem and Enviornment of Agriculture. www. climag. com;

2 Contents Introduction Objective Materials and Methods Results Conclusions Center of Agriculture and Climate Change, Insititute of Resource, Ecosystem and Enviornment of Agriculture. www. climag. com;

3 Global anthropogenic GHG emissions Agriculture 5.1 to 6.1 GtCO 2 -eq/yr in 2005 (13.5% of total global anthropogenic emissions of GHGs) CH 4 and N 2 O contributes to 3.3 and 2.8 GtCO 2 -eq/yr, respectively; accounts for about 50% and 60% of global anthropogenic emissions in 2005.

4 N2O CH4 CO Cropland management Grazing land management Restore cultivated organic soils Restore degraded -200 lands Rice management Livestock Bioenergy (soils component) Water management Setaside, LUC & agroforestry Manure management Mt CO 2 -eq. yr -1 Mitigation measure The global technical mitigation potential from agriculture (excluding fossil fuel offsets from biomass) by 2030 is estimated to be ~ Mt CO 2 -eq. yr -1 (Smith et al., 2007a&b; Smith et al., 2008).

5 Improved timing and application rates Decrease N 2 O Emissions Improved placement N 2 O Water and fertilizer management NH 4 NO 3 SOM N Plant N Nitrification inhibitors/ slow release fertilizer

6 Increase Carbon Sequestration Returning Straw Conservation tillage CO 2 Planting green manure Soil organic matter Improved rotations

recommended as an effective soil amendment

7 Withdraw CO 2 from the atmosphere Recently, biochar has been strongly recommended as an effective soil amendment to improve soil fertility and mitigate climate change (Lehmann,2007) through increasing soil carbon storage (Lehmann et al., 2006; Fowles, 2007), decreasing direct GHGs emission and improving crop productivity (Major et al.,2010).

8 Introduction Wide variations in the rates of CO 2 emissions from soils treated with biochar have been reported in literatures (Karhu et al., 2011;Kimetu and Lehmann, 2010; Zimmerman et al., 2011 ). The effects of biochar amendment on non-co 2 GHGs emission may also vary with soil types, site condition as well as properties of biochar used (Spokas and Reicosky, 2009).

9 Objective The long-term effect of biochar amendment on greenhouse gases emissions from paddy soil Overall C intensity of rice production between the two rice cycles following biochar amendment

10 Materials and Methods The site for field experiment with rice paddy is located in Yixing municipality, Jiangsu Province, China. Biochar as soil amendment Closed chamber method GC detection

11 Materials and Methods Biochar was produced from the wheat straw with pyrolysis at at Sanli New Energy Company, Henan, China. Basic properties and components of the biochar ph OC Total N Surface area CEC Ca Mg Ash content (H 2 O) (g kg -1 ) (g kg -1 ) (m 2 g -1 ) (cmol kg -1 ) (mg kg -1 ) (mg kg -1 ) (%)

12 Experiment Design Biochar amendment: 0, 10, 20 and 40 t ha -1 in No more biochar was amended but N fertilizer applied for rice growth in The N fertilizer as urea was applied at 300 kg N ha 1 in both of years Rice seeds were sowed in a nursery bed for seedlings on 15 May, 2009 but directly sowed to plots on 5 June, 2010 respectively. Water regime was consistently managed for the two cycles under an alternating flooding and drainage cycle of F-D-F-M mode (flooding- drainage- reflooding- moist), except for moist before tillering stage in the 2 nd cycle.

13 Calculation A total gross GWP in CO 2 -e per hectare (GWP t ) was calculated using the following equation (Watson et al., 1996; IPCC, 2007): GWP t = (CO 2 ) + 25 (CH 4 ) (N 2 O)... (1) C intensity of rice production (GHGI) = GWPt /Y (2) Here, we used a response ratio for highlighting the biochar effect over another factors, like planting patterns, water regime and so on. Response ratio (%) = (GWP(BC)-GWP(CK))/GWP(CK) 100 (3)

14 Results Soil ph (H 2 O), SOC, total N, bulk density, LOC and HWEC (mean ± S.D., n=3) of topsoil (0-15 cm) following biochar amendment during 2-rice growing season Treatment Rice cycle ph (H 2 O) SOC (g kg -1 ) Total N (g kg -1 ) Bulk density (g cm -3 ) LOC (mg g -1 ) HWEC (mg g -1 ) C ±0.11b 23.2±1.6c 2.07±0.04b 0.99±0.05a 7.72±0.75a 0.82±0.03b ±0.04B 23.5±1.2B 1.98±0.1B 0.94±0.02A 8.94±0.15B 0.35±0.02B C ±0.08ab 27.1±1.5b 2.19±0.13b 0.96±0.02ab 8.31±0.45a 0.96±0.02a ±0.21AB 25.7±2.0B 1.95±0.14B 0.91±0.03AB 8.49±0.63B 0.45±0.11AB C ±0.18ab 29.5±0.9b 2.11±0.11b 0.91±0.02b 8.50±1.0a 0.90±0.04a ±0.05AB 28.9±1.6AB 2.16±0.08AB 0.86±0.01C 10.20±0.35A 0.56±0.13A C ±0.12a 36.0±1.7a 2.54±0.13a 0.89±0.02b 8.32±0.26a 0.94±0.03a ±0.11A 36.1±5.6A 2.27±0.24A 0.88±0.02BC 9.47±0.87AB 0.53±0.05A Different lowercase in a single column indicate difference between the treatments at p<0.05 Different capital letter in a single column indicate difference between the treatments at p<0.05 Labile oxidation carbon (LOC) was measured by a KMnO 4 (333 mm) oxidation procedure

15 N2O(μgN 2 O-Nm -2 h -1 ) N 2 Oemissions (µgn 2 O-Nm -2 h -1 ) year 2010 year F D F M WM F D F M C0 C2 W Jun. 30 Jul. 30 Aug. 30 Sept. 23 Jun. 14 Jul. 17 Aug. 20 Sept. 20 Oct. C1 C3 CO 2 emissions (mgco 2 -Cm -2 h -1 ) CO 2 (mg m -2 h -1 ) CH 4 emissions(mgch 4 -Cm -2 h -1 ) CH 4 (mg m -2 h -1 ) Jun Jul. 30 Aug. 30 Sept. Date 23 Jun. 14 Jul. 6 Aug. 9 Sept. 11 Oct Jun. 30 Jul. 30 Aug. 30 Sept. Date 23 Jun. 14 Jul. 6 Aug. 9 Sept. 11 Oct. Fig.1 Dynamic of N 2 O, CO 2 and CH 4 emissions from the rice paddy under water regime of F-D-F-M and M- F-D-F-M during the rice growing season

16 Rice yield (t ha -1 ) and total emissions (kg ha -1 )(mean ± S.D., n=3) of CO 2, CH 4 and N 2 O over the WRGS from the rice paddy and their total CO 2 -e as affected by biochar amendment Treatment Rice cycle Yield (t ha -1 ) CH 4 -C (kg ha -1 ) N 2 O-N (kg N ha -1 ) CO 2 -C (kg ha -1 ) GWP (kg ha -1 ) GHGI (kg CO 2 -e t 1 production) C ±0.33b 69.3±7.7c 1.99±0.2a ±109a ±406b ±80ab ±0.19C 28.3±2.6B 4.5±1.0A ±187.6AB ±575A ±74A C ±0.1a 67.2±9.4c 1.19±0.01b ±42a ±432b 924.8±43b ±0.33A 24.5±2.0B 3.1±0.04AB ±55.1B ±303B 870.5±2.8B C ±0.26a 175.1±33a 0.83±0.13c ±133a ±882a ±103a ±0.13BC 43.6±1.9A 2.5±0.5B ±55.5AB ±403B ±65B C ±0.36a 104.9±10.4b 0.98±0.18bc ±119a ±149b 986.1±50b ±1.34AB 39.1±5.0A 2.0±0.4B ±54.8A ±48B 982.0±158B GWP (kg CO 2 -equivalent ha -1 ) =CO CH N 2 O ( Watson et al., 1996; IPCC, 2007) GHGI (kg CO 2 -e t -1 productions)=gwp/rice yield (Mosier et al., 2006; Shang et al., 2011; Zhang et al., 2010, 2011) Different lowercase in a single column indicate difference between the treatments at p<0.05 Different capital letter in a single column indicate difference between the treatments at p<0.05

17 Response ratio of GWP under biochar amendment GWP response ratio (%) A A 2009 year 2010 year A C1 C2 C3 B B B Biochar amendment GWP response ratio (%)=(GWP(BC)-GWP(CK))/GWP(CK) 100 A, B indicated the GWP response ratio difference (p<0.01) between two years at the same rate of biochar amendment

18 Response ratio of C intensity of rice production under biochar amendment GHGI response ratio(%) A A 2009 year 2010 year C1 C2 C3 A B -45 B Biochar amendment B GHGI response ratio(%)=(ghgi(bc)-ghgi(ck))/ GHGI(CK) 100 A, B indicated the GHGI response ratio difference (p<0.01) between two years at the same rate of biochar amendment

19 Conclusions Biochar amendment increased rice productivity, soil ph, soil organic carbon, total nitrogen but decreased soil bulk density in two cycles. Biochar amendment seemed no effect on soil respiration in two cycles, there was a consistent effect of biochar amendment on decreasing nitrous oxide emission but increasing methane emission from the paddy over two cycles of rice production. While methane emissions significantly decreased in the second cycle compared to that of in the first cycle.

20 Conclusions Both of the global warming potential and C intensity of rice production under biochar amendment tended decreased significantly in the 2 nd cycle though not seen in the 1 st cycle. Biochar amendment could have residual effect on decreasing overall greenhouse gas emissions from agriculture, which could be very brilliant for low carbon technology in China s agriculture.

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