Global warming impacts of the process to utilize digested slurry from methane fermentation as a fertilizer: Case Study of the Yamada Biomass Plant

Greenhouse gas (GHG) emissions from the process to utilize digested slurry from methane fermentation as a fertilizer were calculated with actual operational data from a methane fermentation plant and the effects were verified by introducing the process into a field system. The results indicated that the total emissions from the utilization of digested slurry as a fertilizer were 8.1 kg-CO₂ eq. per 1 ton of digested slurry and transportation was the major source of GHG emissions, accounting for 67 % of the total emissions. Shortening the transportation distance by using digested slurry in farmlands near the methane fermentation plant is the most effective to reduce GHG emissions. The results also indicated that GHG emissions from the wastewater treatment process for digested slurry were much larger than GHG emissions from the utilization of digested slurry as a fertilizer. In conclusion, CH₄ as an energy source and digested slurry as a fertilizer can be effectively utilized and reduce GHG emissions by introducing the methane fermentation processes to the use of digested slurry as a fertilizer.     

Spatial-uniform application method of methane fermentation digested slurry with irrigation water in the rice paddy field

Promoting biomass utilization, the objectives of this study were to clarify the spatial distribution of nitrogen, one of the most important fertilizer components in the methane fermentation digested slurry (i.e., the digested slurry), and to establish an effective method to apply spatial-uniformly digested slurry with irrigation water in the rice paddy field. A numerical model describing the unsteady two-dimensional flow and solution transport of paddy irrigation water was introduced. The accuracy of this model was verified with a field observation. The tendencies of the TN simulated in inlet and outlet portions had good agreement with the measured data and the accuracy of the numerical model could be verified. Using the numerical model, scenario analyses were conducted to determine the method for spatial-uniform application of the digested slurry with irrigation water. The simulated results indicated that drainage of the surface water and trenches at the soil surface were effective for spatial-uniform application of the digested slurry with irrigation water in the rice paddy fields. The effect of the trenches was maximized when the surface water of the rice paddy field was drained adequately.     

Effect of organic,inorganic and slow-release urea fertilisers on CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O emissions from rice paddy fields

Vietnam is one of the world’s top two rice exporting countries. However, rice cultivation is the primary source of agriculture’s greenhouse gas (GHG) emissions in Vietnam. In particular, strategies are required to reduce GHG emissions associated with the application of organic and inorganic fertilisers. The objective of this study was to assess the effects of various combinations of biochar (BIOC), compost (COMP) and slow-release urea (SRU) on methane (CH₄) and nitrous oxide (N₂O) emissions. In total, 1170 gas samples were collected from closed gas chambers in rice paddies at Thinh Long commune and Rang Dong farm in northern Vietnam between June and October 2014. The gas samples were analysed for CH₄-C and N₂O-N fluxes using gas chromatography. The application of BIOC alone resulted in the lowest CH₄ emissions (4.8–59 mg C m^?2 h^?1) and lowest N₂O emissions (0.15–0.26 µg N m^?2 h^?1). The combined application of nitrogen–phosphorus–potassium (NPK) + COMP emitted the highest CH₄ (14–72 mg C m^?2 h^?1), while ½NPK + BIOC emitted the highest N₂O (1.03 µg N m^?2 h^?1 in the TL commune), but it was the second lowest (0.495 µg N m^?2 h^?1) in the RD farm. Green urea and orange urea reduced N₂O emissions significantly (p < 0.05) compared to white urea, but no significant differences were observed with respect to CH₄ emissions. SRU fertilisers and BIOC alone measured the lowest greenhouse gas intensity, i.e. <2.5 and 3 kg CO₂ eq. kg^?1 rice grain, respectively. Based on these results, application of fertilisers in the form of BIOC and/or orange or green urea could be a viable option to reduce both CH₄ and N₂O emissions from rice paddy soils.     

Dry direct-seeding of rice for mitigating greenhouse gas emission: field experimentation and simulation

Conventional puddled transplanted rice (TPR) is a major source of greenhouse gas (GHG), particularly methane, causing global warming. Direct-seeded rice (DSR) is a feasible alternative to mitigate methane emission, besides saving water and labor. A 2-year field experiment was carried out to quantify GHG mitigation and water- and labor-saving potentials of the DSR crop compared to TPR in three villages in Jalandhar district of Punjab, India. The InfoRCT simulation model was used to calculate the emission of CO₂ besides CH₄ and N₂O in different districts of Punjab, India. Total global warming potential (GWP) in transplanted rice in various districts of Punjab ranged from 2.0 to 4.6 t CO₂ eq. ha^?1 and in the DSR it ranged from 1.3 to 2.9 t CO₂ eq. ha^?1. Extrapolation analysis showed that if the entire area under TPR in the state is converted to DSR, the GWP will be reduced by 33 %, and if 50 % area is converted to DSR the GWP will be reduced by 16.6 % of the current emission. The DSR crop saved 3–4 irrigations compared to the transplanted rice without any yield penalty. Human labor use also reduced to 45 % and tractor use to 58 % in the DSR compared to TPR.     

Rice-related greenhouse gases in Japan, variations in scale and time and significance for the Kyoto Protocol

The contribution of rice production to the three major greenhouse gases CO₂, CH₄ and N₂O in 1990, the base year of the Kyoto protocol is investigated for Japan. For the CO₂ assessment, we use a top-down life cycle approach, CH₄ is assessed using the Japanese GHG emission inventory and N₂O is assessed according to the ratio of rice area divided by the total area of agricultural soils. In total, 1.6% of greenhouse gas (GHG) emissions in 1990 originated from rice production. Next, we assess regional variations in nine rice-producing regions, based on the CO₂ data of 1990. General trends in rice production from 1960 to 2000 and data from the Japanese GHG emission inventory since 1990 are used to assess variations in time. The rice-related GHG emissions decreased to 1.05% of the total GHG emissions in 2001 and will be less than half the 1990 level in 2012, mainly due to the decrease in rice production. Contrary to the trend in GHG emissions of rice, overall GHG emissions increased as rice production fulfils important roles, in mitigating global warming and in adapting to changing climates. The protection of rice production is required to counter the increase of GHG emissions in transportation, waste and domestic sectors and to minimize problems related to landscape, water and natural hazard management.     

Feasibility for use of digested slurry by the pouring method in paddy fields of Southern Vietnam

In this study, we evaluated the feasibility for the use of digested slurry from livestock manure (hereafter, slurry) in paddy fields through field experiments conducted in Southern Vietnam. The pouring method for slurry was used, and a vacuum truck was used for transportation and pouring of the slurry. A prototype slurry tanker was manufactured for transportation and application of slurry, because vacuum trucks are rarely available in rural areas of Vietnam. For evaluation of feasibility, costs and labor for application of slurry and rice production were examined and compared with conventional cultivation methods using chemical fertilizers. As the results, rice production with the use of slurry was 485 g m^?2, which is within the range of on-site conventional cultivation, so slurry may be a good substitute for chemical fertilizers in rice production. Costs for slurry fertilization with a prototype slurry tanker and a vacuum truck were estimated at 0.13 USD m^?2 and 0.10 USD m^?2, respectively. These costs were higher than for conventional cultivation of 0.06 USD m^?2 under the present conditions with T-N concentrations of approximately 400 mg L^?1 in the slurry. However, we clarified that the cost for slurry fertilization can be lower than conventional cultivation when the concentrations of nitrogen in slurry increase from 400 to 2000 mg L^?1. These results show that an increase in nitrogen concentrations in slurry make slurry fertilization feasible if the amounts of water for washing livestock sheds that enter into the biogas digesters are reduced.     

Nitrogen Fertilizer Management Practices to Reduce N<Subscript>2</Subscript>O Emissions from Irrigated Processing Potato in Manitoba

Nitrogen fertilizer practices affect nitrous oxide (N₂O) emissions from agricultural soils. The “4R” nutrient stewardship framework of using N fertilizer at the right rate, right source, right placement and right time can reduce N₂O emissions while maintaining or improving yield of field crops, but understanding of how the various factors affect N₂O emissions from irrigated processing potato is lacking. We examined the effects of selected 4R practices on emissions, using results from two irrigated processing potato studies each conducted in 2011 and 2012 in Manitoba, Canada. Experiment 1 examined combinations of source (urea, ESN), placement (pre-plant incorporation [PPI], banding), and rate (100 and 200 kg N ha^-1) on a clay loam soil. Experiment 2 examined timing and source treatment combinations (urea PPI, ESN PPI, urea split, urea split/fertigation) on a loamy fine sandy soil. For Experiment 1, use of ESN at 200 kg ha^-1 did not reduce area-, yield- and applied fertilizer N- based N₂O emissions compared to urea at 200 kg ha^-1, irrespective of placement. Emissions from pre-plant banding ESN at 200 kg ha^?1, however, were 32% lower than from PPI ESN. For Experiment 2, compared to single pre-plant urea application, fertigation simulated by in-season application of urea ammonium nitrate (UAN) gave lower area-, yield- and applied fertilizer N- based emissions. Split urea ( \( \raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right. \) pre-plant, \( \raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right. \) hilling) also reduced area- and yield- based N₂O emissions compared to single pre-plant urea application. Emissions were generally lower at the site with loamy fine sandy soil than the site with clay loam soil. These results demonstrate that combinations of “4R” practices rather than source alone are best to achieve reductions in N₂O emissions from irrigated potato production.     

Tracing the fate of nitrogen with <Superscript>15</Superscript>N isotope considering suitable fertilizer rate related to yield and environment impacts in paddy field

While the application rate of nitrogen fertilizer is believed to dramatically influence rice fields and improve the soil conditions in paddy fields, fertilization with low use efficiency and nitrogen loss may cause environmental pollution. In this paper, ¹⁵N-labeled urea was used to trace the fate of nitrogen at four rates (0, 75, 225 and 375 kg N/ha) of urea fertilizer over three split applications in Hangzhou, Zhejiang, in 2014. Plant biomass, the soil nitrogen content of different layers, NH₃ volatilization and N₂O emissions were determined using the ¹⁵N abundance to calculate the portion from nitrogen fertilizer. The results indicated that rice yields increased with the application rate of nitrogen fertilizer. NH₃ volatilization is the main nitrogen loss pathway, and N₂O emissions were significantly associated with nitrogen application rates in the paddy. The percent of nitrogen loss by NH₃ volatilization and N₂O emissions increased with the nitrogen application rate. This study showed that the suitable N fertilizer in a loam clay paddy, considering the yield requirements and environmental issues, is approximately 225 kg N/ha in Hangzhou, with a distribution of 50.06% of the residual in the rice and soil and 48.77% loss as NH₃ volatilization and N₂O emissions. The nitrate from fertilization mainly remained in the 0–20 cm level of the topsoil.     

Carbon and Nitrogen Footprints of Major Cereal Crop Production in China: A Study Based on Farm Management Surveys

Greenhouse gas (GHG) emissions and reactive nitrogen (Nr) releases are central environmental problems, which are closely linked to climate change, environmental ecology and crop production. Sustainable development of agriculture plays an important role in GHG emissions and Nr loss. The life cycle assessment (LCA) method was used to calculate the product and farm carbon footprints (CFs) and nitrogen footprints (NFs) in rice, wheat and maize production in China based on farm survey data. The results pinpointed that the CFs of rice, wheat and maize were 0.87, 0.30 and 0.24 kg/kg. Meanwhile, the computed NFs were 17.11, 14.26 and 6.83 g/kg, respectively. Synthetic nitrogen fertilizer applications and methane (CH₄) emissions were dominant CF sources, while ammonia (NH₃) volatilization was the main NF contributor. Moreover, significant decreases in CF and NF by 20%–54% and 33%–61%, respectively, were found in large-size farms (> 20 hm²) when compared to small-size farms (< 0.7 hm²). Furthermore, the significantly positive relationships between CF and NF indicated the potential for simultaneous mitigation in the regions with high agricultural inputs, like amounts of fertilizer. Based on our results, some effective solutions would be favorable toward mitigating climate change and eutrophication of the major cereal crop production in China, especially optimizing fertilizer use and farm machinery operation efficiencies, as well as developing large-size farms with intensive farming.     

Rice husk biochar application to paddy soil and its effects on soil physical properties,plant growth,and methane emission

The objective of this study was to investigate the effects of the application of rice husk biochar on selected soil physical properties, rice growth, including root extension, and methane (CH₄) emissions from paddy field soil. Three replication experiments were conducted using outdoor pot experiments utilizing commercial rice husk biochar mixed with paddy soil at a rate of 0 (control), 2, and 4 % (weight biochar/weight soil) in which the rice was cultivated for 100 days under a continuously flooded condition. The physical properties of soils were analyzed before and after the growing periods. Some parameters of rice growth and CH₄ emissions of paddy soils were monitored weekly during the experiment. Root extension was also analyzed after harvesting. The experiments showed that the application of rice husk biochar improved the physical properties of paddy soils. It led to a decrease in bulk density and an increase in saturated hydraulic conductivity, including the total pore volume as well as the available soil water content. The shoot height of rice plants was significantly higher in soil amended with 4 % biochar than that in the control soil. However, other plant growth parameters and root extension were only slightly affected by the application. It was also found that amending soil with biochar led to a reduction of the total CH₄ emissions by 45.2 and 54.9 % for an application rate of 2 and 4 %, respectively, compared with the control. Our results showed that the higher the application rate, the stronger the effect of biochar was observed. More research is still necessary for a better understanding of the underlying mechanisms.     

Effect of slurry application techniques on nitrous oxide emission from temperate grassland under varying soil and climatic conditions

The effect of slurry application techniques and slurry N stabilizing strategies on nitrous oxide emission from grasslands is poorly understood and, therefore, can result in large uncertainties in national/regional inventories. Field experiments were, thus, conducted to estimate the effect of different fertilization techniques on nitrous oxide (N₂O) emissions. Fertilizer was applied (135–270 kg N ha⁻¹ year⁻¹) as calcium ammonium nitrate (CAN), untreated or treated cattle slurry. The slurry was either treated with sulfuric acid (target pH = 6.0), applied using trailing shoes or treated with 3,4-dimethyl pyrazole phosphate and applied via slot injection. N₂O fluxes were sampled using the closed chamber technique. Cumulative N₂O emissions ranged 0.1–2.9 kg N ha⁻¹ year⁻¹ across the treatment, sites and years. The N application techniques showed inconsistent effects on soil mineral N content, cumulative N₂O emission and N yield. The fertilizer replacement value of slurry was low due to low N use efficiencies at the sites. However, a close positive relationship (r = 0.5; p = .013) between slurry value and biomass yield was observed, highlighting the benefit of high slurry value on crop productivity. N₂O-N emission factors were low for all treatments, including CAN, but were 2–6 times higher in 2019 than in 2020 due to lower precipitation in 2020. Variations in N₂O emission were largely explained by soil and climatic factors. Even with the low N₂O emissions, this study highlights the benefit (significant mitigation of N₂O emissions) of replacing the increasingly expensive chemical fertilizer N with input from slurry under favourable conditions for denitrification.     

Analyzing soil-available phosphorus by the Mehlich-3 extraction method to recommend a phosphorus fertilizer application rate for maize production in northern Mozambique

ABSTRACT

The available phosphorus (P) in soil is a major limiting factor for maize productivity in the Nacala corridor, Mozambique. In this study, soils were collected from three representative sites, Ribaue, Nampula, and Nacala, in the area, and each was used for maize pot experiment with five P fertilizer levels. The soil-available P content was determined by the Mehlich-3 method at 30 days after P fertilization. The shoot biomass and P concentration at the tasseling stage increased as the P fertilizer level increased and were significantly expressed as a function of soil-available P. Based on the function, the available P that attains 90% of the maximum shoot biomass was estimated as 79 mg P₂O₅ kg^?1. Consequently, the results in this study suggest a recommendation of 32–74 kg P₂O₅ ha^?1 fertilizer for maize production in the Nacala corridor although a field evaluation and economical evaluation are necessary.     

Evaluation of technologies for sequestering carbon in agricultural land by using organic filter underdrains

Technology for storing carbon in the subsoil of agricultural land using organic filter materials in underdrains was evaluated as an activity for sequestering CO₂ to mitigate global warming. First, the quantity of carbon remaining in wood chips and rice husks in underdrains was determined over 11 years after construction. Moreover, the quantity of CO₂ emissions from the construction of two underdrain types was calculated. Then, a survey was conducted to investigate the effect on greenhouse gas emissions of the filter material. The results indicate that greenhouse gas emissions would not increase. The quantity of storage carbon in the wood chip filter material of underdrains during their 15-year service life was estimated to be 6.76 tCO₂eq ha⁻¹. Rice husks, in contrast, were found ineffective in storing carbon. Therefore, the selection of the filter material for underdrains is important. The value of storage carbon in the wood chip filter material is similar to the amount of carbon sequestered by no-till farming, which is now being implemented as a global warming countermeasure based on soil management in agricultural land.

     

In vitro rumen methane output of grasses and grass silages differing in fermentation characteristics using the gas‐production technique (GPT)

The chemical composition of silage consumed by cattle can influence the subsequent rumen microbial fermentation patterns and methane (CH₄) emissions. The objectives of this study were to (i) evaluate the effect of ensilage on the in vitro rumen methane output of perennial ryegrass and (ii) relate the silage fermentation characteristics of grass silages with in vitro rumen methanogenesis. Three pre‐harvest herbage‐conditioning treatments and seven silage‐additive treatments were used in a laboratory‐scale silo experiment to produce a diversity of silage fermentation characteristics. Ensilage reduced (P < 0·01) the in vitro rumen CH₄ output (mL CH₄ g^?1 dry matter (DM) disappeared). This reflected differences in the direction of rumen fermentation (lower acetic (P < 0·05) and higher propionic (P < 0·001) acid proportions in volatile fatty acids) rather than major changes in the extent of in vitro rumen fermentation (i.e. mmol VFA g^?1 DM). The magnitude of the decrease in CH₄ output (mL g^?1 DM incubated) owing to ensilage increased as the extent of silage fermentation, and in particular the lactic acid concentration, increased. In contrast, among silages with relatively similar extents of silage fermentation (i.e. total fermentation products), an increase in the proportion of lactic acid in silage fermentation products led to a more extensive in vitro rumen fermentation and thus to a greater CH₄ output (mL g^?1 DM).     

Effect of fertilization on crop responses and solute transport for rice crop in a sub-humid and sub-tropical region

In order to increase the efficacy of water and control the losses of fertilizer, it is necessary to assess the influence of level of fertilization on crop responses, movement and balance of water and solutes from fertilizers in the root zone. With this goal, the reported study was undertaken to determine the effect of fertilization on crop responses and fertilizer solute transport in rice crop field in a sub-humid and sub-tropical region. Field experiment was conducted on rice crop (cultivar IR 36) during the years 2003, 2004, and 2005. The experiment included four fertilizer treatments comprising different levels of fertilizer application. The fertilizer treatments during the experiment were: F₁ = control with N:P₂O₅:K₂O as 0:0:0 kg ha^?1; F₂ = fertilizer application of N:P₂O₅:K₂O as 80:40:40 kg ha^?1; F₃ = fertilizer application of N:P₂O₅:K₂O as 120:60:60 kg ha^?1 and F₄ = fertilizer application of N:P₂O₅:K₂O as 160:80:80 kg ha^?1. The results of the investigation revealed that the magnitudes of crop parameters such as grain yield, straw yield, and maximum leaf area index increased with increase in fertilizer application rate. The levels of fertilization had very little effect on water loss via deep percolation and water use by the crop. The levels of fertilization had considerable effect on N leaching loss and uptake of N whereas it had no significant impact on leaching loss of water-soluble phosphorus. This indicated that PO₄-P leaching loss was very low in the soil solution as compared to nitrogen due to fixation of phosphorus in soils. The results also revealed that increase in level of fertilization increased water use efficiency considerably by increased crop yield. From the observed data of nutrient use efficiency, crop yield and environmental pollution, the fertilization rate of N:P₂O₅:K₂O as 80:40:40 kg ha^?1 (F₂) was the most suitable fertilizer treatment for rice crop among studied treatments.     

沼液与氮肥配施对小麦产量及品质的影响

为给小麦高产优质生产中沼液利用提供依据,在大田条件下,研究了沼液与氮肥配施对小麦籽粒产量及品质的影响.结果表明,在全生育期总施氮量240 kg·hm-2条件下,在基施化肥氮基础上追施沼液,尤其基施75％化肥氮和追施25％沼液氮配合处理(3/4U+1/4B)显著提高了淀粉糊化特性参数(峰值黏度、最终黏度、稀懈值和反弹值)、粉质参数(形成时间、稳定时间、粉质指数)和拉伸参数(拉伸面积、拉伸阻力和拉伸比).籽粒蛋白组分(总蛋白、球蛋白、醇溶蛋白和谷蛋白)含量以基施50％化肥氮和追施50％沼液氮配合处理(1/2U+1/2B)最高,3/4U+1/4B处理次之.籽粒蛋白组分、粉质与拉伸参数均以单施沼液处理(1/2B+1/2B)最低,单施化肥氮的处理(1/2U+1/2U)次之,而淀粉糊化特性参数以1/2U+1/2U处理最差,施用沼液的处理较1/2U+1/2U处理提高2.0％～6.5％.与1/2U十1/2U处理相比,基施沼液与追施化肥氮配合处理产量提高,而基施化肥氮与追施沼液氮处理的产量降低.可见在基施沼液的基础上追施化肥氮可提高小麦产量,其中1/2B+1/2U处理能够高产和优质兼顾,单施沼液效果低下.     

Simulating the effects of chemical and non-chemical fertilization practices on carbon sequestration and nitrogen loss in subtropical paddy soils using the DNDC model

Understanding the long-term and quantitative effects of different fertilization practices on carbon sequestration and nitrogen loss is important when establishing the best fertilization regime. In this study, the DeNitrification–DeComposition (DNDC) model was validated first for the change of soil organic carbon (SOC) at the site mode and at the regional mode, and then it was used to simulate the effects of three fertilization practices including rice straw (RS) returning, chemical fertilizer application (CF), and green manure planting (GM) on C and N dynamics in paddy soils from a subtropical area of China. The prevailing fertilization practices in the study area were set as the baseline scenario, and alternative scenarios were assigned by varying only one of the three fertilization practices. All three fertilization practices increased SOC content but had different effects on rice yield, N₂O emission, and nitrate leaching loss. Compared with a baseline RS rate of 15 %, the SOC contents less than RS rates of 30, 50, and 80 % were increased on average by 12.84, 29.48, and 53.50 %, respectively. SOC content also increased as the CF rate rose from 70 to 130 % of the baseline scenario and then leveled off from 130 to 160 %. SOC contents under GM were higher than that without GM by 35.74 %. Both the N₂O emissions and the nitrate leaching were increased with the increasing CF rate, while they decreased under GM treatment. However, RS increased the N₂O emissions but decreased the nitrate leaching. The polygon-based modeling method with the DNDC could accurately evaluate the general trend of SOC dynamics and nitrogen loss from paddy soils.     

In vitro total and methane gas production as influenced by rate of nitrogen application, season of harvest and perennial ryegrass cultivar

The effects of rate of inorganic nitrogen (N) fertilization (0, 80 or 160 kg N ha^?1 per regrowth), season of harvest (regrowths 1, 2 and 3) and perennial ryegrass (Lolium perenne L.) cultivar [classified as having either a normal or elevated water soluble carbohydrate (WSC) concentration genotype] on in vitro gas production and digestibility were assessed. Increased N fertilizer application significantly decreased total gas production (TGP), methane (CH₄) production and organic matter digestibility (OMD). The results suggest that the decreases in TGP and CH₄ production were associated with a restriction in organic matter (OM) fermentation and an altered crude protein (CP) to structural carbohydrate ratio rather than a modification in the stoichiometry of fermentation. Season of harvest only significantly (P < 0·05) altered in vitro OMD and CH₄ production at 8 h, despite altering the chemical composition of the herbage. Cultivar effects on all measured in vitro parameters were not significant presumably because the elevated WSC concentration trait was not expressed strongly in the study.     

水稻低碳生产研究进展

 稻田是甲烷(methane,CH4)和氧化亚氮(nitrous oxide,N2O)的重要发生源。稻田中CH4和N2O的产生、消耗以及传输过程受稻田土壤类型、水分条件、肥料种类、施肥量及方法、耕作模式和制度、水稻品种等多种因素影响。CH4和N2O具有不同的排放特性,很多研究结果表明,水稻生长期间的中期排水烤田、后期干湿交替能显著降低CH4排放量,但同时也可能促进N2O的排放,因此,如何同时减少CH4和N2O的排放量是实现稻田低碳生产的关键要素;另一方面,稻田土壤的碳固定也是使稻田系统从源转变成汇的关键技术。从水稻生产过程中CH4排放、N2O排放、稻田土壤有机碳动态、减排措施四个方面综述了近年来水稻低碳生产相关研究状况,重点总结了国内外有关影响稻田CH4和N2O排放的关键影响因素、增加稻田土壤有机质含量的主要措施以及各种减排措施的全球增温潜势评价研究,并对水稻低碳生产研究作了展望。     

Lasting effects of controlled irrigation during rice-growing season on nitrous oxide emissions from winter wheat croplands in Southeast China

Nitrous oxide (N₂O) emission from croplands in China is a serious environmental concern. Water management is an important factor in regulating N₂O emissions from croplands. In China, controlled irrigation (CI) is one mode of the water-saving irrigation for rice and is widely used. This study aims to assess the lasting effects of CI on N₂O emissions from winter wheat croplands in Southeast China, with traditional irrigation (TI) as the control. CI performed during the rice-growing season had obvious lasting effects on N₂O emissions of the subsequent winter wheat-growing season. Compared with TI, CI significantly increased the cumulative N₂O emission by 129.1 % during the rice-growing season (p < 0.05), but significantly decreased it by 47.7 % during the wheat season (p < 0.05). Continuous flooding of the TI during most of the rice-growing season resulted in an increase in N₂O emissions during the winter wheat-growing season. Over the whole annual cycle, the cumulative N₂O emission from the plots under CI during the rice-growing season was 5.3 kg N₂O–N ha^?1, which was 103.2 % of that under TI (p > 0.05). The results suggest that CI does not significantly increase the cumulative N₂O emission from the rice–winter wheat rotation systems while insuring rice and wheat yields. This study focuses on the lasting effects of water-saving irrigation mode during rice-growing season on N₂O emissions during the following wheat-growing season. Thus, it is a development and complement of the previous researches on the effects of water-saving irrigation on N₂O emissions from rice–winter wheat rotation croplands.