Search

Two-year field experiments were conducted at Tamil Nadu Rice Research Institute, Aduthurai, Tamil Nadu, India, to evaluate the effect of continuous flooding (CF) and alternate wetting and drying (AWD) irrigation strategies on rice grain yield and greenhouse gas emissions from double-cropping paddy rice. Field observation results showed that AWD irrigation was found to reduce the total seasonal methane (CH4) emission by 22.3% to 56.2% compared with CF while maintaining rice yield. By using the observed two-year field data, validation of the DNDC-Rice model was conducted for CF and AWD practices. The model overestimated rice grain yield by 24% and 29% in CF and AWD, respectively, averaged over the rice-growing seasons compared to observed values. The simulated seasonal CH4 emissions for CF were 6.4% lower and 4.2% higher than observed values and for AWD were 9.3% and 12.7% lower in the summer and monsoon season, respectively. The relative deviation of simulated seasonal nitrous oxide (N2O) emissions from observed emissions in CF were 27% and −35% and in AWD were 267% and 234% in the summer and monsoon season, respectively. Although the DNDC-Rice model reasonably estimated the total CH4 emission in CF and reproduced the mitigation effect of AWD treatment on CH4 emissions well, the model did not adequately predict the total N2O emission under water-saving irrigation. In terms of global warming potential (GWP), nevertheless there was a good agreement between the simulated and observed values for both CF and AWD irrigations due to smaller contributions of N2O to the GWP compared with that of CH4. This study showed that the DNDC-Rice model could be used for the estimation of CH4 emissions, the primary source of GWP from double-cropping paddy rice under different water management conditions in the tropical regions., Peer Reviewed

Two-year field experiments were conducted at Tamil Nadu Rice Research Institute, Aduthurai, Tamil Nadu, India, to evaluate the effect of continuous flooding (CF) and alternate wetting and drying (AWD) irrigation strategies on rice grain yield and greenhouse gas emissions from double-cropping paddy rice. Field observation results showed that AWD irrigation was found to reduce the total seasonal methane (CH4) emission by 22.3% to 56.2% compared with CF while maintaining rice yield. By using the observed two-year field data, validation of the DNDC-Rice model was conducted for CF and AWD practices. The model overestimated rice grain yield by 24% and 29% in CF and AWD, respectively, averaged over the rice-growing seasons compared to observed values. The simulated seasonal CH4 emissions for CF were 6.4% lower and 4.2% higher than observed values and for AWD were 9.3% and 12.7% lower in the summer and monsoon season, respectively. The relative deviation of simulated seasonal nitrous oxide (N2O) emissions from observed emissions in CF were 27% and −35% and in AWD were 267% and 234% in the summer and monsoon season, respectively. Although the DNDC-Rice model reasonably estimated the total CH4 emission in CF and reproduced the mitigation effect of AWD treatment on CH4 emissions well, the model did not adequately predict the total N2O emission under water-saving irrigation. In terms of global warming potential (GWP), nevertheless there was a good agreement between the simulated and observed values for both CF and AWD irrigations due to smaller contributions of N2O to the GWP compared with that of CH4. This study showed that the DNDC-Rice model could be used for the estimation of CH4 emissions, the primary source of GWP from double-cropping paddy rice under different water management conditions in the tropical regions., Peer Reviewed

Climate change is a vital environmental issue for the twenty-first century, which may significantly affect rice productivity and accelerate greenhouse gas emissions from paddy ecosystem, which is of great environmental concern which is of great environmental concern. Methane (CH4) and nitrous oxide (N2O) are the most important greenhouse gases due to their radiative effects as well as global warming potentials (GWPs). CH4 and N2O gases are simultaneously emitted from rice fields to the atmosphere due to their favorable production, consumption, and transport systems. The intensive rice farming system has been creating excessive pressure on rice fields to produce more rice for the expanding world population, thereby deteriorating soil fertility status and rice paddy ecosystem balance by stimulating more CO2, CH4, and N2O fluxes to the atmosphere. The extreme climatic variables such as high light intensity, high water vapor or relative humidity, high temperature, and drought stress may badly suppress beneficial microbial activity, soil nutrients, and water availability to rice plant; eventually, rice yield may be decreased drastically, and simultaneously, greenhouse gas emissions could be increased significantly. In this situation, conservation tillage, water saving irrigation technique such as alternate wetting and drying, soil amendments with biochar, vermicompost, azolla-cyanobacterial mixture, recommended silicate slag, and phospho-gypsum with minimum NPKSZn fertilizer (IPNS) should be introduced to the field level farmers for sustainable rice production and mitigating greenhouse gas emissions.

Climate change is a vital environmental issue for the twenty-first century, which may significantly affect rice productivity and accelerate greenhouse gas emissions from paddy ecosystem, which is of great environmental concern which is of great environmental concern. Methane (CH4) and nitrous oxide (N2O) are the most important greenhouse gases due to their radiative effects as well as global warming potentials (GWPs). CH4 and N2O gases are simultaneously emitted from rice fields to the atmosphere due to their favorable production, consumption, and transport systems. The intensive rice farming system has been creating excessive pressure on rice fields to produce more rice for the expanding world population, thereby deteriorating soil fertility status and rice paddy ecosystem balance by stimulating more CO2, CH4, and N2O fluxes to the atmosphere. The extreme climatic variables such as high light intensity, high water vapor or relative humidity, high temperature, and drought stress may badly suppress beneficial microbial activity, soil nutrients, and water availability to rice plant; eventually, rice yield may be decreased drastically, and simultaneously, greenhouse gas emissions could be increased significantly. In this situation, conservation tillage, water saving irrigation technique such as alternate wetting and drying, soil amendments with biochar, vermicompost, azolla-cyanobacterial mixture, recommended silicate slag, and phospho-gypsum with minimum NPKSZn fertilizer (IPNS) should be introduced to the field level farmers for sustainable rice production and mitigating greenhouse gas emissions.

Nitrogen (N) supply is a major factor controlling the yield and quality of vegetables. The purpose of the present study was to determine the effects of different rates of controlled-release N fertilizers (CRFs) and urea applications with cow manure on a) yield (Brassica napa L.), b) nitrate leaching from soil, and c) N2O flux in surface soil. The fertilizers were applied according to the following 6 type-rate combinations: 1) CM-CDU 450 (kg ha-1), 2) LP 450, 3) urea 450, 4) CM-CDU 360, and 5) LP 360, and 6) control (no fertilizer). Yield was significantly higher in theCM-CDU 450 and LP 450 whereas other fertilizer treatments did not show significant differences. The total amounts of leaching nitrate from soils were significantly higher in the urea treatment than in the CM-CDU and LP. Total amount of nitrous oxide (N2O) emission in the urea treatment was highest among the treatments during three cropping seasons. Emission factor (EF) in every treatment ranged from 0.2 to 0.3%.

Nitrogen (N) supply is a major factor controlling the yield and quality of vegetables. The purpose of the present study was to determine the effects of different rates of controlled-release N fertilizers (CRFs) and urea applications with cow manure on a) yield (Brassica napa L.), b) nitrate leaching from soil, and c) N2O flux in surface soil. The fertilizers were applied according to the following 6 type-rate combinations: 1) CM-CDU 450 (kg ha-1), 2) LP 450, 3) urea 450, 4) CM-CDU 360, and 5) LP 360, and 6) control (no fertilizer). Yield was significantly higher in theCM-CDU 450 and LP 450 whereas other fertilizer treatments did not show significant differences. The total amounts of leaching nitrate from soils were significantly higher in the urea treatment than in the CM-CDU and LP. Total amount of nitrous oxide (N2O) emission in the urea treatment was highest among the treatments during three cropping seasons. Emission factor (EF) in every treatment ranged from 0.2 to 0.3%.

To evaluate spatial variability of nitrous oxide (N2O) emissions and to elucidate their determining factors on a field-scale basis, N2O fluxes and various soil properties were evaluated in a 100- x 100-m onion (Allium cepa L.) field. Nitrous oxide fluxes were determined by a closed chamber method from the one-hundred 10- x 10-m plots. Physical (e.g., bulk density and water content), chemical (e.g., total N and pH), and biological (e.g., microbial biomass C and N) properties were determined from surface soil samples (0–0.1 m) of each plot. Geostatistical analysis was performed to examine spatial variability of both N2O fluxes and soil properties. Multivariate analysis was also conducted to elucidate relationships between soil properties and observed fluxes. Nitrous oxide fluxes were highly variable (average 331 µg N m-2 h-1, CV 217%) and were log–normally distributed. Log-transformed N2O fluxes had moderate spatial dependence with a range of >75 m. High N2O fluxes were observed at sites with relatively low elevation. Multivariate analysis indicated that an organic matter factor and a pH factor of the principal component analysis were the main soil-related determining factors of log-transformed N2O fluxes. By combining multivariate analysis with geostatistics, a map of predicted N2O fluxes closely matched the spatial pattern of measured fluxes. The regression equation based on the soil properties explained 56% of the spatially structured variation of the log-transformed N2O fluxes. Site-specific management to regulate organic matter content and water status of a soil could be a promising means of reducing N2O emissions from agricultural fields.

To evaluate spatial variability of nitrous oxide (N2O) emissions and to elucidate their determining factors on a field-scale basis, N2O fluxes and various soil properties were evaluated in a 100- x 100-m onion (Allium cepa L.) field. Nitrous oxide fluxes were determined by a closed chamber method from the one-hundred 10- x 10-m plots. Physical (e.g., bulk density and water content), chemical (e.g., total N and pH), and biological (e.g., microbial biomass C and N) properties were determined from surface soil samples (0–0.1 m) of each plot. Geostatistical analysis was performed to examine spatial variability of both N2O fluxes and soil properties. Multivariate analysis was also conducted to elucidate relationships between soil properties and observed fluxes. Nitrous oxide fluxes were highly variable (average 331 µg N m-2 h-1, CV 217%) and were log–normally distributed. Log-transformed N2O fluxes had moderate spatial dependence with a range of >75 m. High N2O fluxes were observed at sites with relatively low elevation. Multivariate analysis indicated that an organic matter factor and a pH factor of the principal component analysis were the main soil-related determining factors of log-transformed N2O fluxes. By combining multivariate analysis with geostatistics, a map of predicted N2O fluxes closely matched the spatial pattern of measured fluxes. The regression equation based on the soil properties explained 56% of the spatially structured variation of the log-transformed N2O fluxes. Site-specific management to regulate organic matter content and water status of a soil could be a promising means of reducing N2O emissions from agricultural fields.

To evaluate spatial variability of nitrous oxide (N2O) emissions and to elucidate their determining factors on a field-scale basis, N2O fluxes and various soil properties were evaluated in a 100- x 100-m onion (Allium cepa L.) field. Nitrous oxide fluxes were determined by a closed chamber method from the one-hundred 10- x 10-m plots. Physical (e.g., bulk density and water content), chemical (e.g., total N and pH), and biological (e.g., microbial biomass C and N) properties were determined from surface soil samples (0–0.1 m) of each plot. Geostatistical analysis was performed to examine spatial variability of both N2O fluxes and soil properties. Multivariate analysis was also conducted to elucidate relationships between soil properties and observed fluxes. Nitrous oxide fluxes were highly variable (average 331 µg N m-2 h-1, CV 217%) and were log–normally distributed. Log-transformed N2O fluxes had moderate spatial dependence with a range of >75 m. High N2O fluxes were observed at sites with relatively low elevation. Multivariate analysis indicated that an organic matter factor and a pH factor of the principal component analysis were the main soil-related determining factors of log-transformed N2O fluxes. By combining multivariate analysis with geostatistics, a map of predicted N2O fluxes closely matched the spatial pattern of measured fluxes. The regression equation based on the soil properties explained 56% of the spatially structured variation of the log-transformed N2O fluxes. Site-specific management to regulate organic matter content and water status of a soil could be a promising means of reducing N2O emissions from agricultural fields.

We conducted pot and field experiments to examine the effects of amendments of two types of microbial material solution on methane emission from submerged paddy soil and rice field. The microbial material solution (MMS) containing mainly lactic acid bacteria and yeasts (MMS type1) was used in the pot experiment, while the other solution containing mainly purple nonsulfer bacteria (MMS type2) was also used in the field experiment. In this study, we used organic fertilizer named "Bokashi", which was made of rice bran, rapeseed oil mill sludge and fish meal and incubated with or without MMS type1. Pot experiment showed significant increase in methane emission by application of Bokashi with MMS typel (B+M) to compare with that with Bokashi only (B). Total methane emission during cultivation was 77.4 g carbon m^<-2> and 49.0 g carbon m^<-2> in B+M and B, respectively. Soil Eh decreased rapidly both in B+M and B pots. These results suggest that application of MMS type1 increase methane emission due to decomposition of organic matter in pot experiment, indicating that Bokashi provided substrates and also reductive conditions suitable for methanogens. Field experiment showed, on the other hand, suppression effect on methane emission by increasing application rate of MMS type2 as 0 to 20 mL m^<-2>, probably due to decrease of substrate by competition between methanogens and purple nonsulfer bacteria. In contrast, brown rice yield was increased by application of MMS type2.