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Qin X.,Chinese Academy of Agricultural Sciences | Qin X.,Agriculture and Agri Food Canada | Li Y.,Chinese Academy of Agricultural Sciences | Wang H.,Agriculture and Agri Food Canada | And 6 more authors.
Science of the Total Environment | Year: 2016

To evaluate long-term effect of biochar application on yield-scaled greenhouse gas emissions (YSGE) in a paddy rice cropping system, a 4-year field experiment by static chamber - gas chromatograph method was conducted in South China. Principal component analysis and terminal restriction fragment length polymorphism (T-RFLP) and real-time qPCR was used to unravel the microbial mechanisms of biochar addition. Six treatments were included: control (CK), application of 5tha-1 biochar (BC1), application of 10tha-1 biochar (BC2), application of 10tha-1 biochar (BC3), rice straw return at 2400kgha-1(RS) and inoculated rice straw return at 2400kgha-1(RI). The results indicated that biochar amendment significantly decreased methane (CH4) and gross greenhouse gas (GHG) emissions. This may primarily be ascribed to the stimulated biodiversity and abundance of methanotrophic microbes, increased soil pH and improved aeration by reducing bulk density after biochar incorporation. Compared with CK, RS and RI, 26.18%, 70.02%, 66.47% of CH4 flux and 26.14%, 70.16%, 66.46% of gross GHG emissions were reduced by biochar (mean of three biochar treatments), respectively. Furthermore, biochar significantly increased harvest index of double rice production (p <0.05). In comparison with CK, RS and RI, 29.14%, 68.04%, 62.28% of YSGE was reduced by biochar, respectively, and the highest biochar addition rate (20tha-1) contributed most to the mitigation of GHG emissions (36.24% decrease compared to CK) and improvement of rice yield (7.65% increase compared to CK). Results of our study suggested that long-term application of biochar should be the potential way to mitigate GHGs emissions and simultaneously improve rice productivity in the paddy rice system. © 2016 Elsevier B.V. Source


Qin X.,Chinese Academy of Agricultural Sciences | Li Y.,Chinese Academy of Agricultural Sciences | Wan Y.,Chinese Academy of Agricultural Sciences | Shi S.,Chinese Academy of Agricultural Sciences | And 3 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

To investigate the effects of straw mulching on greenhouse gas intensity (GHGI) under the no tilling conditions, a two-year (2008-2009) observation of greenhouse gas emissions with different treatments of NWS (no till + no residue), HN (no till + high stubble) and SN (no till + straw mulching) was conducted by using the static chamber-GC (gas chromatography) method. The results indicated that the two treatments of HN and SN at the same rate of straw mulching had no difference in rice yield and increased GHGI compared to the NWS treatment. The GHGI of SN was lower than that of HN, which indicated that the HN treatment enhanced the ability of GHGI transportation by rice aerenchyma. On a 20-year scale, the average GHGI of methane was 109 times and 14 times greater than nitrous oxide for early and late rice, respectively, while on a 20-year scale, the value was lower, but still was 35 times and 3.77 times. In conclusion, the GHGI of the double-rice field will be affected by different practices of retaining rice residue determined. Compared with the HN treatment, straw mulching (SN) will be a reasonable choice for straw mulching. This study provides references for the enhancement of carbon sequestration and mitigation of GHGI emissions in a double-rice field in the Central China Region. Source


Qin X.,Chinese Academy of Agricultural Sciences | Li Y.,Chinese Academy of Agricultural Sciences | Wang H.,Agriculture and Agri Food Canada | Li J.,Chinese Academy of Agricultural Sciences | And 7 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

The resource utilization of organic materials in China cropland is a great challenge we are facing now. To study the ecological effects of biochar utilization, and explore the response of carbon emission intensity (GHGI) to biochar amendment for the long term in a double rice field in South China, two-year field measurements of greenhouse gases based on a static chamber-gas chromatography method were conducted. Six experimental treatments were set up, including 1) CK (famer traditional operation), 2) BC1 (biochar amendment at 5 t/hm2), 3) BC2 (biochar amendment at 10 t/hm2), 4) BC3 (biochar amendment at 20 t/hm2), 5) RS (raw rice straw residue return) and 6) RI (composted rice straw residue return). As a result, compared to CK, all of the biochar treatments inhibited the emission peaks of greenhouse gases from the double rice field. During the four rice growing seasons, the three biochar treatments decreased the 100 yr-scaled carbon dioxide emission equivalents by 27.53%, 58.65%, and 63.43%, respectively, compared with CK, RS, and RI. The biochar treatments significantly reduced methane emissions (P<0.05) at an average reduction rate of 50.84%. Among the three biochar and two rice straw residue treatments, BC3 had the lowest methane emission potential (2.75 mg/(m2 h)), while RS had the highest (10.05 mg/(m2·h)). For the nitrous oxide emissions, the average value of the three biochar treatments was lower than CK but higher than the two rice straw residue return treatments (P>0.05). Furthermore, there was no statistical significant yield increase effect found in the biochar treatments (P>0.05), compared with CK, RS, and RI, as the four-season average rice yields of the three biochar treatments were increased by 3.21%, 5.11%, and 2.29%, respectively. A significant higher yield in BC3 was observed than that in RS (P<0.05). Additionally, on a 100-year horizon, the GHGI of the three biochar treatments (average at 0.33 kg/kg) were 30.57%, 61.00%, and 64.82% lower than CK (0.48 kg/kg), RS (0.86 kg/kg), and RI (0.48 kg/kg), respectively. By the correlation matrix and principal component analysis, the biochar amendment controlled the distribution of rice yield, harvest index, soil organic matter, total carbon content, and chlorophyll content, while the rice straw residue return treatments dominated the distribution of the methane flux and GHGI. In summary, based on the present study, the application of the regression tree analysis offered a quantitative alternative to decision-making in analyzing the effects of biochar amendment on ecological environment. The results of this study indicated that the biochar amendment in soils has the potential to enhance soil carbon sequestration, increase rice yield, and mitigate the carbon emission intensity and the impact of climate change by optimization of the field managements and biochar return in an appropriate amount. This research could be used as a successful case study of scientific utilization of crop straw residue in China's agriculture. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source


Qin X.,Chinese Academy of Agricultural Sciences | Qin X.,The Key Laboratory for Agro environment and Climate Change | Qin X.,Agriculture and Agri Food Canada | Li Y.,Chinese Academy of Agricultural Sciences | And 11 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012

To investigate the regression relationships between greenhouse gas (GHG) emissions and soil microbes in a double-rice paddy soil under various management practices, a two-year study was conducted to observe the seasonal variation of GHG emissions and activities of soil microbes (SMA) as well as their populations (SMP) using the closed static chamber-GC (gas chromatography) and the most probable number methods. There were seven management practices (or treatments), including CWS (Conventional Tillage + Without Straw Residues + Urea), NWS (No Tillage + Without Straw Residues + Urea), SCU (Conventional Tillage + Without Straw Residues + Controlled-Release Urea), HN (High Stubbles + No Tillage + Urea), HC (High Stubbles + Conventional Tillage + Urea), SN (Straw Cover + No Tillage + Urea) and SNF (Straw Cover + No Tillage + Urea + Continuous Flooding). The average values of seven treatments′ daily fluxes of GHGs and SMA as well SMP were used for the analysis in this study. Regression analysis was conducted using the R statistical software. Similar seasonal variations of methane flux and SMA as well as the amount of soil methanogens (MET) were found in the rice growing season of 2008-2009; and same regularity occurred in the temporal distribution of nitrous oxide flux and the amount of soil nitrifiers and denitrifiers. Furthermore, there was a strong correlation between methane flux and SMA as well as the population of MET. The relationships of methane flux vs. SMA and methane flux vs. MET can be represented by using the exponential and quadratic polynomial models, respectively. Simple regression indexed that the quantity of MET could explain individually at least 96. 96% of variance of methane flux (R 2 =0. 969, P<0. 001), but the fitting precision of multiple nonlinear regression of methane flux with two factors of SMA and MET (R 2 =0. 975, P< 0. 001) was higher than the univariate regression analysis. Besides, the pronounced positive dependency of nitrous oxide flux with soil nitrifiers and denitrifiers has also been found (P<0. 05). The mixed binary nonlinear regression of nitrous oxide flux with the SMP of the two types of microbes can explain at least 70. 4% of variance of nitrous oxide flux (R 2 ≥ 0. 704, P<0. 001), and of course the fitting precision of multiple nonlinear regression was higher than the simple regression using the SMP of either nitrifiers or denitrifiers. However, as we know, GHG emissions from paddy soils are affected by many factors, of which SMA and SMP are the most direct influential variants. In order to reasonably reveal the interactions between GHG emissions and environmental variables, the multivariate nonlinear regression analysis should be carried out based on data derived from the extensive field experiments rather than few laboratory trials. Source


Qin X.B.,Chinese Academy of Agricultural Sciences | Li Y.E.,Chinese Academy of Agricultural Sciences | Wan Y.F.,Chinese Academy of Agricultural Sciences | Gao Q.Z.,Chinese Academy of Agricultural Sciences | And 5 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013

To investigate the effect of soil oxygen availability (SOA) on greenhouse gas (GHG) emissions from a double- rice cropping field, a two-year observation of greenhouse gas emissions of seven treatments from a rice paddy field was conducted by using the static closed-chamber method. There were seven management practices (or treatments), including CWS (Conventional Tillage+Without Straw Residues+Urea), NWS (No Tillage+Without Straw Residues+Urea), SCU (Conventional Tillage+Without Straw Residues+Controlled-Release Urea), HN (High Stubbles+No Tillage+Urea), HC (High Stubbles+Conventional Tillage+Urea), SN (Straw Cover+No Tillage+Urea) and SNF (Straw Cover+No Tillage+ Urea+Continuous Flooding). Three SOA factors, i.e., soil redox potential (Eh), pH and field water level (H) of each treatment was determined simultaneously. Our results indicated that methane emissions was sensitive to all of the three SOA factors. The critical values at which the higher methane fluxes were observed, for Eh, pH and H was -100-0mV, 5-6 and 1-5cm, respectively, and therefore the proportions of methane emitted from these three ranges were 48.8%, 61.1% and 77.0%, respectively. The determination coefficient of linear or quadratic polynomial regression models of the methane fluxes and the individual three SOA factors ranged from 0.04 to 0.38 (P<0.05). Among of them, H was attributed to the most important influence on methane emissions, explaining 37.8% of the variance of methane emissions from paddy field (P<0.05). While for nitrous oxide (N2O), large amount of negative fluxes occurred, If only positive N2O emissions considered, most of them were observed under conditions of 0mV Source

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