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, 2011 Email:2009203024@njau.edu.cn; af-725@163.com Center of Agriculture and Climate Change, Insititute of Resource, Ecosystem and Enviornment of Agriculture. www. climag. com; www.ireea.cn
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; www.ireea.cn
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.
1800 1600 1400 1200 N2O CH4 CO2 1000 800 600 400 200 0 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 ~5500-6000 Mt CO 2 -eq. yr -1 (Smith et al., 2007a&b; Smith et al., 2008).
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
Increase Carbon Sequestration Returning Straw Conservation tillage CO 2 Planting green manure Soil organic matter Improved rotations
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).
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).
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
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
Materials and Methods Biochar was produced from the wheat straw with pyrolysis at 350-550 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 ) (%) 10.4 467.1 5.9 8.9 217 10387.3 6494.6 20.8
Experiment Design Biochar amendment: 0, 10, 20 and 40 t ha -1 in 2009. No more biochar was amended but N fertilizer applied for rice growth in 2010. 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.
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 ) + 298 (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)
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 ) C0 2009 6.53±0.11b 23.2±1.6c 2.07±0.04b 0.99±0.05a 7.72±0.75a 0.82±0.03b 2010 6.53±0.04B 23.5±1.2B 1.98±0.1B 0.94±0.02A 8.94±0.15B 0.35±0.02B C1 2009 6.75±0.08ab 27.1±1.5b 2.19±0.13b 0.96±0.02ab 8.31±0.45a 0.96±0.02a 2010 6.73±0.21AB 25.7±2.0B 1.95±0.14B 0.91±0.03AB 8.49±0.63B 0.45±0.11AB C2 2009 6.77±0.18ab 29.5±0.9b 2.11±0.11b 0.91±0.02b 8.50±1.0a 0.90±0.04a 2010 6.77±0.05AB 28.9±1.6AB 2.16±0.08AB 0.86±0.01C 10.20±0.35A 0.56±0.13A C3 2009 6.77±0.12a 36.0±1.7a 2.54±0.13a 0.89±0.02b 8.32±0.26a 0.94±0.03a 2010 6.89±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
N2O(μgN 2 O-Nm -2 h -1 ) N 2 Oemissions (µgn 2 O-Nm -2 h -1 ) 3500 3000 2500 2000 1500 1000 500 0 2009 year 2010 year F D F M WM F D F M C0 C2 W 300 30 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 ) 250 200 150 100 50 0 30 Jun. 85 30 Jul. 30 Aug. 30 Sept. Date 23 Jun. 14 Jul. 6 Aug. 9 Sept. 11 Oct. 75 65 55 45 35 25 15 5-530 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
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) C0 2009 7.6±0.33b 69.3±7.7c 1.99±0.2a 1107.3±109a 8236.8±406b 1077.1±80ab 2010 7.6±0.19C 28.3±2.6B 4.5±1.0A 1523.7±187.6AB 10770.4±575A 1425.8±74A C1 2009 8.3±0.1a 67.2±9.4c 1.19±0.01b 1179.6±42a 7680.2±432b 924.8±43b 2010 9.7±0.33A 24.5±2.0B 3.1±0.04AB 1306.3±55.1B 8465.7±303B 870.5±2.8B C2 2009 8.4±0.26a 175.1±33a 0.83±0.13c 1074.5±133a 10554.5±882a 1247.3±103a 2010 8.3±0.13BC 43.6±1.9A 2.5±0.5B 1383.4±55.5AB 8908.5±403B 1077.2±65B C3 2009 8.5±0.36a 104.9±10.4b 0.98±0.18bc 1058.9±119a 8438.9±149b 986.1±50b 2010 9.3±1.34AB 39.1±5.0A 2.0±0.4B 1582.5±54.8A 8969.0±48B 982.0±158B GWP (kg CO 2 -equivalent ha -1 ) =CO 2 +25 CH 4 + 298 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
Response ratio of GWP under biochar amendment GWP response ratio (%) 40 30 20 10 0-10 -20-30 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
Response ratio of C intensity of rice production under biochar amendment GHGI response ratio(%) 30 15 0-15 -30 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
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.
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.