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Fertilizer application often significantly affects soil quality and crop productivity, thus, can affect soil greenhouse gas (GHG) emissions and nitrogen use efficiency (NUE) as well. However, the impacts have not been well documented under double maize cropping system in subtropical China. Based on a thirty-year field experiment with five fertilization treatments (i.e. no fertilizer (CK), organic manure (OM), N, NPK and NPK plus OM (NPKM)), maize cultivar (Yedan 13) was planted both at the early maize season and late maize season, we assessed the impacts of different fertilizer application on nitrous oxide (N 2 O) and methane (CH 4 ) emissions, grain yield and NUE. Compared to the NPK, manure application (i.e. OM and NPKM) significantly increased N 2 O emissions, and maize yield. Nevertheless, there was no significant difference in yield–scaled global warming potential (GWP) among NPK, OM, and NPKM. Manure application increased soil pH, soil organic carbon, and soil total N, suggesting it can improve soil quality. The NPKM treatment had the highest N uptake, but in terms of NUE, it was lower than OM, due to double N application. Our results suggest that manure application can compensate its negative impacts on N 2 O emission through improving soil quality, maize yield and N use efficiency. [ABSTRACT FROM AUTHOR]

China is the largest country in grain production and consumption with the greatest emission of greenhouse gas (GHG) in the world. To learn the historical changes and regional differences in GHG emission of the major grain crop production can provide important references to the mitigation of GHG emission in the country and other similar countries. Therefore, we quantified the carbon footprints of rice ( Oryza sativa L.), wheat ( Triticumaestivum L.) and maize ( Zea mays L.) production based on agricultural inputs in the country over the period of 1978–2012. The results showed that area-scaled carbon footprint of rice, wheat and maize production increased gradually from 1286, 937 and 895 kg carbon dioxide equivalent (CO 2 -eq) ha −1 in 1978–2682, 2978 and 2294 kg CO 2 -eq ha −1 in 2012, respectively, and the average increase rates for the three crops were correspondingly 41, 60 and 41 kg CO 2 -eq ha −1 a −1 . During the last ten years, however, all the average yield-scaled carbon footprints of rice, wheat and maize decreased by 0.11 kg CO 2 -eq kg −1 10a −1 . Chemical fertilizer contributed the largest ratio to the total GHG emission by 66, 68 and 76% for rice, wheat and maize, respectively. Significant increasing contribution ratio to the carbon footprint was found in the electricity used for crop irrigation. There were large differences in both the area- and yield-scaled carbon footprints among the cropping regions with the lowest GHG emission occurring in the major cropping regions. Our findings indicate a great potential to reduce GHG emission of grain production through optimizing the spatial layout of cropping region and enhancing chemical fertilizer use efficiency. Further efforts also need to be made on water-saving irrigation to decrease the electricity usage. [ABSTRACT FROM AUTHOR]

As pressure on water resources increases, alternative practices to conserve water in paddies have been developed. Few studies have simultaneously examined the effectiveness of different water regimes on conserving water, mitigating greenhouse gases (GHG), and maintaining yields in rice production. This study, which was conducted during the drought of 2013, examined all three factors using a split-plot experiment with two rice varieties in a no-till paddy managed under three different water regimes: 1) continuous flooding (CF), 2) flooded and wet intermittent irrigation (FWI), and 3) flooded and dry intermittent irrigation (FDI). The Methane (CH 4 ) and nitrous oxide (N 2 O) emissions were measured using static chamber-gas measurements, and the carbon dioxide (CO 2 ) emissions were monitored using a soil CO 2 flux system (LI-8100). Compared with CF, FWI and FDI irrigation strategies reduced CH 4 emissions by 60% and 83%, respectively. In contrast, CO 2 and N 2 O fluxes increased by 65% and 9%, respectively, under FWI watering regime and by 104% and 11%, respectively, under FDI managed plots. Although CO 2 and N 2 O emissions increased, the global warming potential (GWP) and greenhouse gas intensity (GHGI) of all three GHG decreased by up to 25% and 29% ( p < 0.01), respectively, using water-saving irrigation strategies. The rice variety also affected yields and GHG emissions in response to different water regimes. The drought-resistance rice variety (HY3) was observed to maintain yields, conserve water, and reduce GHG under the FWI irrigation management compared with the typical variety (FYY299) planted in the region. The FYY299 only had significantly lower GWP and GHGI when the yield was reduced under FDI water regime. In conclusion, FWI irrigation strategy could be an effective option for simultaneously saving water and mitigating GWP without reducing rice yields using drought-resistant rice varieties, such as HY3. [ABSTRACT FROM AUTHOR]

Abstract: Agricultural soils are main sources and sinks of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The source–sink function depends on soil characteristics, climate and management. Emission measurements usually quantify the net result of production, consumption and transport of these gases in the soil; they do not provide information about the depth distributions of the concentrations of these gases in the soil. Here we report on concentrations of CO2, CH4 and N2O in air of 300cm deep soil profiles, at resolutions of 30–50cm, over a full year. Gas samples were taken weekly in a long-term field experiment with an irrigated winter wheat–summer maize double cropping system, and four fertilizer N application rates (0, 200, 400 and 600kgNha−1 year−1). The results showed distinct differences in CH4, CO2 and N2O concentrations profiles with soil depth. The concentrations of CO2 in soil air increased with soil depth and showed a seasonal pattern with relatively high concentrations in the warm and moist maize growing season and relatively low concentrations in the winter-wheat growing season. In contrast, CH4 concentrations decreased with depth, and did not show a distinct seasonal cycle. Urea application did not have a large effect on CH4 or CO2 concentrations, neither in the topsoil nor the subsoil. Concentrations of N2O responded to N fertilizer application and irrigation. Application of fertilizer strongly increased grain and straw yields of both winter wheat and summer maize, relatively to the control, but differences in yield between the treatments N200, N400 and N600 were not statistically significant. However, it significantly increased mean N2O concentrations peaks at basically all soil depths. Interestingly, concentrations of N2O increased almost instantaneously in the whole soil profile, which indicates that the soil had a relatively high diffusivity, despite compacted subsoil layers. In conclusion, the frequent measurements, at high depth resolutions, of concentrations of CH4, CO2 and N2O in soil air under a winter wheat–summer maize double crop rotation provide detailed insight into the production, consumption and transport of these gases in the soil. Concentrations of CH4, CO2 and N2O responded differently to management activities and weather conditions. [Copyright &y& Elsevier]

Abstract: Increasing atmospheric greenhouse gas concentrations are expected to induce significant climate change over the next century and beyond, but the impacts on society remain highly uncertain. This work examines potential climate change impacts on the productivity of five major crops in eastern China: canola, corn, potato, rice, and winter wheat. In addition to determining domain-wide trends, the objective is to identify vulnerable and emergent regions under future climate conditions, defined as having a greater than 10% decrease and increase in productivity, respectively. Data from the ICTP RegCM3 regional climate model for baseline (1961–1990) and future (2071–2100) periods under A2 scenario conditions are used as input for the EPIC agro-ecosystem simulation model in the domain [30°N, 108°E] to [42°N, 123°E]. Simulations are performed with and without the enhanced CO2-fertilization effect. Results indicate that aggregate potential productivity (i.e. if the crop is grown everywhere) increases 6.5% for rice, 8.3% for canola, 18.6% for corn, 22.9% for potato, and 24.9% for winter wheat, although with significant spatial variability for each crop. However, without the enhanced CO2-fertilization effect, potential productivity declines in all cases ranging from 2.5 to 12%. Interannual yield variability remains constant or declines in all cases except rice. Climate variables are found to be more significant drivers of simulated yield changes than changes in soil properties, except in the case of potato production in the northwest where the effects of wind erosion are more significant. Overall, in the future period corn and winter wheat benefit significantly in the North China Plain, rice remains dominant in the southeast and emerges in the northeast, potato and corn yields become viable in the northwest, and potato yields suffer in the southwest with no other crop emerging as a clear beneficiary from among those simulated in this study. [Copyright &y& Elsevier]