UV-B增强下施硅对稻田CH4和N2O排放及其增温潜势的影响

大气平流层臭氧损耗导致的地表紫外辐射增强作为全球变化重要问题之一,受到广泛关注。硅是水稻生长有益元素,但施硅是否影响稻田CH_4和 N_2O排放,迄今相关报道尚不多见。通过大田试验,研究UV-B增强下施硅对水稻生长、稻田甲烷(CH_4)和氧化亚氮( N_2O)排放及其增温潜势的影响。UV-B辐照设2水平,即对照(A,自然光)和增强20%(E);施硅量设2水平,即对照(Si0,0 kg SiO_2/hm2)和施硅(Si1,200 kg SiO_2/hm2)。结果表明,UV-B增强降低了成熟期水稻地上部和地下部生物量,而施硅能缓解UV-B增强对水稻生长的抑制作用,使水稻地上部和地下部生物量增加。UV-B增强可显著提高稻田CH_4和 N_2O排放通量和累积排放量,增加稻田CH_4和 N_2O排放的综合增温潜势。施硅能明显降低稻田CH_4排放,促进 N_2O排放,降低稻田CH_4和 N_2O排放的综合增温潜势。研究表明,施硅显著降低稻田CH_4和 N_2O的全球增温潜势,缓解UV-B增强对稻田CH_4和 N_2O的全球增温潜势的促进作用。     

夜间增温品种混栽对稻田土壤CH4和N2O排放的影响

夜间增温幅度大于白天是气候变暖主要特征之一。夜间增温对水稻生产及CH₄和N₂O排放的影响备受关注。品种混栽可提高水稻产量,增强水稻植株抗性。增温或混栽单因子对稻田CH₄和N₂O排放影响已有报道,但二者耦合如何影响水稻生产及稻田CH₄和N₂O排放,尚不清楚。采用2因素随机区组设计,通过田间试验研究了夜间增温下品种混栽对水稻产量、CH₄和N₂O综合增温潜势和排放强度的影响。夜间增温设2水平,即对照（CK,control）和增温（NW,nighttime warming）;品种混栽设2水平,即混作（I,intercropping）,单作（M,monocropping）,混栽处理将主栽品种（超级稻南粳9108）与次栽品种（杂交稻深两优884）以3：1的比例种植。水稻生长期用铝箔反射膜覆盖水稻冠层进行被动式夜间增温试验（19：00-6：00）。结果表明,夜间增温或品种混栽均显著降低水稻植株分蘖数和生物量。品种混栽显著提高水稻产量,而夜间增温则显著降低产量。品种混栽可缓解夜间增温对水稻产量的抑制作用。夜间增温下品种混栽处理稻田CH₄累计排放量在分蘖期、拔节-孕穗期、抽穗-扬花期和灌浆-成熟期比单作对照分别高55.32%、45.89%、43.49和125.82%。夜间增温下品种混栽处理稻田N₂O累计排放量在分蘖期、拔节-孕穗期和抽穗-扬花期分别比单作对照高64.44%、46.26%和42.07%。研究认为,夜间增温下品种混栽显著提高稻田CH₄和N₂O排放通量和累积排放量,显著增加综合增温潜势（GWP）和排放强度（GHGI）。     

复合稻田生态系统温室气体交换及其综合增温潜势

研究稻田CO2、CH4、N2O等温室气体的综合增温潜势,有助于科学评价复合稻田生态系统在减少温室气体排放和减缓全球变暖方面的作用,为稻鸭、稻鱼复合种养模式的发展提供依据。2006年采用静态箱法研究了养鸭稻田（RD）、养鱼稻田（RF）和常规淹水稻田（CK）的CH4、N2O的排放量。水稻整个生育期间,RD、CK和RF的CH4排放量分别是19.11、26.71g/m^2和25.01g/m^2;N2O排放量分别是0.237、0.229、0.237g/m^2。采用干物质积累法测得,水稻整个生长期内RD处理地上稻株对CO2的净固定量为2766.4g/m2,RF为2759.59g/m^2,CK为2533.9g/m^2。采用土壤有机碳库的变化估算土壤CO2净交换通量,水稻整个生育期间,三类稻田土壤亚系统均表现为对CO2的净固定,相当于固定CO2量分别为RD675.55g/m^2、CK575.43g/m^2、RF562.62g/m^2。三类稻田温室气体的交换均表现为CO2的净吸收、CH4、N2O的净排放,综合增温潜势以RD为最低。稻田养鸭能显著减少甲烷排放,降低增温潜势,其减缓综合温室效应的潜力是常规淹水稻田的1.6倍左右。     

黄河上游灌区稻田N2O排放特征

黄河上游灌区稻田高产区过量施肥现象十分突出,氮肥过量施用引起土壤氮素盈余,导致N₂O排放量增大,由此引起的温室效应引起广泛关注。采用静态箱-气相色谱法研究黄河上游灌区稻田不同施肥处理下N₂O排放特征。试验设置5个施肥处理,包括常规氮肥300 kg/hm²下单施尿素和有机肥配施2个处理,分别用N300和N300-OM代表;优化氮肥240 kg/hm²下单施尿素和有机肥配施2个处理,分别用N240和N240-OM代表;对照不施氮肥用N0代表。试验结果得出,灌区水稻生长季稻田土壤N₂O排放主要集中在水稻分蘖前及水稻生长的中后期,稻田氮肥施用、灌水及土壤温度的变化对N₂O排放通量影响较大,不同处理水稻各生育阶段N₂O累积排放量与稻田土壤耕层NO^-₃-N含量动态变化显著相关。稻田N₂O排放不是黄河上游灌区稻田氮素损失的主要途径,但灌区稻田N₂O排放的增温潜势较大;稻田氮肥过量施用会显著增加N₂O排放量,在相同氮素水平下,有机肥配施会显著增加稻田土壤N₂O的排放量(P＜0.01)。优化施氮能有效减少灌区稻田水稻生长季N₂O排放量。稻田不同处理的水稻整个生长季土壤N₂O排放总量为2.69-3.87 kg/hm²,肥料氮通过N₂O排放损失的百分率仅为0.43%-0.64%。在灌区习惯灌水和高氮肥300 kg/hm²时,N300-OM处理的稻田N₂O排放量达3.87 kg/hm²,在100 a时间尺度上的全球增温潜势(GWPs)为20.76×10⁷ kg CO₂/hm²;优化施氮240 kg/hm²水平下,N240和N240-OM处理的N₂O累计排放量较N300-OM处理,分别降低了1.18 kg/hm²和0.57 kg/hm²,在100 a尺度上每年由稻田N₂O排放引起的GWPs分别降低了6.33×10⁷ kg CO₂/hm²和3.06×10⁷ kg CO₂/hm²。     

不同冬季覆盖作物对稻田CH4 和 CO2 排放的影响

冬季稻田排放的甲烷( CH4)和二氧化碳(CO2)是影响稻田温室气体排放的重要因素。为探求种植适宜的冬季覆盖作物并减少稻田冬季CH4 和CO2 排放, 试验采用静态暗箱法对播种油菜的稻田(YC)、播种小麦的稻田(XM)及冬闲 田(CK)三个处理下稻田的CH4 和CO2 排放进行了观测, 分析了不同冬季覆盖作物对稻田CH4 和CO2 的排放影响。结果表明, 不同处理CH4 排放通量为YC＞XM＞CK, CO2 排放通量为XM＞YC＞CK。不同冬季作物覆盖下, 各处理CH4 和 CO2 的累计排放量表现同其平均排放通量相同。YC 处理的CH4 累计排放量与冬闲田(CK)处理的相比较达到显著水平(p<0.05), XM 处理CO2 的累计排放量与YC 和CK 相比都有显著性差异(p<0.05)。根据稻田CH4 和 CO2 季节排放量以及在 100 年尺度上的 CO2 当量计算, 不同处理温室气体全球增温潜势(GWP)大小顺序为XM＞YC＞CK, 在YC、XM 和CK 中, 小麦(Triticum aestivum L.)处理的增温潜势最大, 且最大值达到6442.58 (kg·hm–2)。小麦处理的CO2 和CH4 的总温室效应最大, 机耕直播油菜(Brassica napus L.)次之, 冬闲田最小。研究水稻(Oryza sativa L.)收获后稻田种植不同冬季作物, 观察在其生长季节内CH4 和 CO2 和的排放特征, 为合理利用冬闲稻田控制温室效应提供理论依据。     

DCD不同施用时间对水稻生长期CH4和N2O排放的影响

硝化抑制剂传统的施用方法是在作物移栽或播种前与基肥配合施用.通过温室盆栽试验研究相同施肥条件下,硝化抑制剂双氢胺(dicyandiamide, DCD)不同施用时间(与基肥混施、分孽肥后施入、穗肥后施入)对水稻生长期CH4和N2O排放的影响.结果表明,施入DCD能同时降低CH4和N2O排放量.就整个水稻生长期而言,与基肥混施DCD分别降低21.41%的CH4排放量和8.00%的N2O排放量;调节DCD施用时间至分孽肥后显著降低30.30%的N2O排放量,同时降低5.24%的CH4排放量.就施入DCD到水稻收获的特定生长阶段而言,缓施DCD分别降低32.65%的N2O排放量和11.18%的CH4排放量;晚施DCD对CH4和N2O排放的影响不大.CK、早施DCD、缓施DCD及晚施DCD处理CH4平均排放通量分别为0.95、0.75、0.87 mg/(m2 · h)及0.94 mg/(m2 · h),N2O平均排放通量为155.67、143.24、108.50 μg/(m2 · h)及153.24 μg/(m2 · h),缓施DCD显著降低CH4和N2O排放量(p＜0.01).土壤温度是影响N2O排放的主要因素,而CH4排放通量与土壤Eh呈显著负相关(p＜0.01).     

华东稻麦轮作生态系统的N2O排放研究

根据对华东稻麦轮作周期的N2 O排放及其影响因子的连续观测结果 ,分析了N2 O排放时间变化以及施肥、灌溉、温度、土壤湿度和土壤速效N素含量对N2 O排放的影响 ,同时还比较分析了稻田N2 O和CH4排放 .研究结果表明 ,稻麦轮作周期内 ,水稻生长季的N2 O排放量仅占 30 % ,稻田持续淹水可比常规灌溉增加CH4排放量 2 6% ,减少N2 O排放量 1 1～ 2 6% .     

UV-B辐射增强对抗除草剂转基因水稻 CH4排放的影响

在大田条件下,研究了UV-B(ultraviolet-B)辐射增强对抗除草剂转基因水稻及亲本常规水稻甲烷(CH4)排放的影响。UV-B辐射设2水平,即对照(CK,自然光),增强(Elevated,14.4 kJ·m-·2d-1),相当于南京地区大气臭氧耗损25%的辐射剂量。结果表明,UV-B辐射增强并没有改变稻田CH4排放通量的季节性变化规律。与对照相比,UV-B辐射增强显著提高CH4排放通量和累积排放量。水稻分蘖期CH4累积排放量最高,占全生育累积排放量的51.55%—61.01%;其次是拔节至孕穗期,占20.00%—26.64%。抗除草剂转基因水稻的CH4排放通量和累积排放量显著低于亲本常规水稻。研究说明,UV-B辐射增强下种植抗除草剂转基因水稻对于减缓稻田甲烷排放有积极意义。     

UV-B增强下施硅对水稻生长及CH4排放的影响

通过盆栽试验,研究了UV-B增强下不同施硅量和硅肥种类对水稻生长及甲烷(CH₄)排放的影响.UV-B辐射设2个水平,即对照(自然光,A)和增强20%(E);硅肥设4个水平,即Si₀(不施硅,0 kg SiO₂·hm^-2)、Si₁(硅酸钠,100 kg SiO₂·hm^-2)、Si₂(硅酸钠,200 kg SiO₂·hm^-2)和Si₃(钢渣硅肥,200 kg SiO₂·hm^-2).结果表明: 施硅能缓解UV-B增强对水稻生长的抑制作用,使分蘖数、叶绿素含量、地上部和地下部生物量增加.施硅对水稻生长的促进作用随施硅量(硅酸钠)的增加而增加,钢渣硅肥的促进作用大于硅酸钠.UV-B增强可提高稻田CH₄的排放通量和累积排放量,施硅显著降低CH₄的排放通量和累积排放量,且CH₄排放随施硅量的增加而减少.在施硅量相同的情况下,钢渣硅肥的减排效果优于硅酸钠.表明在水稻生产中,施用钢渣硅肥不仅能实现废弃物利用,而且可有效降低UV-B增强下CH₄的排放量.     

施硅对夜间增温下南方水稻生长、产量和品质的影响

气温增幅夜间大于白天是全球气候变暖的显著特征之一。夜间增温引起南方单季稻减产,而施硅可提高水稻产量。本研究通过田间模拟试验,分析了施硅对夜间增温下水稻主要生育期植株分蘖数、生物量等生长指标以及产量和品质的影响。增温设2水平：常温对照(CK)和夜间增温(NW),采用被动式夜间增温方法,即夜间(19:00—6:00)用铝箔膜覆盖植株冠层以模拟夜间增温;硅肥(钢渣)用量设2水平：不施硅(Si₀)和施硅(Si₁,200 kg SiO₂·hm^-2)。结果表明：与常温对照比,夜间增温使水稻生长期冠层和5 cm土层夜间平均温度分别升高0.51～0.58℃和0.28～0.41℃。夜间增温使分蘖数和叶绿素含量分别较CK降低2.5%～15.9%和0.2%～7.7%;而施硅使分蘖数和叶绿素含量较不施硅分别提高1.7%～16.2%和1.6%～16.6%。与CK相比,夜间增温下施硅显著提高了灌浆-成熟期地上部干重、全株干重和产量,增幅分别为64.1%、55.3%和7.1%;显著增加了精米率、整精米率和淀粉含量,增幅分别为2....     

夜间增温对稻田甲烷排放的影响及其高光谱估算

昼夜不对称增温是全球气候变化的主要特征之一,有关夜间增温对稻田甲烷(CH_4)排放影响的报道尚不多见。通过田间模拟试验,研究了被动式夜间增温下水稻田CH_4排放及高光谱的特征,并用高光谱数据对稻田甲烷排放进行定量模拟。田间试验设夜间增温(NW)和对照处理(CK),夜间增温即在整个水稻生育期的夜间(19:00—6:00)用铝箔反射膜覆盖水稻冠层。结果表明,夜间增温显著促进水稻拔节期和抽穗期-灌浆期CH_4排放。水稻冠层近红外光谱反射率表现为,在分蘖期和拔节期时,NWCK;而在抽穗-灌浆期和成熟期时,CKNW。水稻冠层光谱反射率、一阶导数光谱及光谱特征值均与CH_4排放通量显著相关,相关系数最大可达0.8(P0.01),其中以"蓝边面积"(SD_b)构成的二次多项式模型模拟精度和检验精度综合最佳,决定系数R~2分别为0.70和0.72。研究结果对稻田CH_4排放通量遥感监测的可行性提供了理论依据和技术支持。     

Nitrous oxide emission from paddy fields in China

The main research results of nitrous oxide (N₂O) emission from paddy fields in China were summarized. Paddy fields are an important source of N₂O emission. Denitrification process exists not only in the upper flooded cultivated layer in paddy fields but also in the underground saturated soil layer. The cropping system with rice–wheat rotation and the water regime with mid-season aeration (MSA) in paddy fields of China are not only the controlling factors of N₂O emission but also the main factors influencing methane (CH₄) emission. There is a trade-off relationship between N₂O and CH₄ emissions from paddy fields. Straw amendment reduced N₂O emission but promoted CH₄ emission. Therefore, effects of both CH₄ and N₂O emissions from rice fields on the global warming potential (GWP) should be taken into consideration when any mitigation options are to be established.     

Methane and nitrous oxide emissions from rice paddy fields as affected by nitrogen fertilisers and water management

Methane and N₂O emissions affected by nitrogen fertilisers were measured simultaneously in rice paddy fields under intermittent irrigation in 1994. Ammonium sulphate and urea were applied at rates of 0 (control), 100 and 300 kg N ha^-1. The results showed that CH₄ emission, on the average, decreased by 42 and 60% in the ammonium sulphate treatments and 7 and 14% in the urea treatments at rates of 100 and 300 kg N ha^-1, respectively, compared to the control. N₂O emission increased significantly with the increase in the nitrogen application rate. N₂O emission was higher from ammonium sulphate treatments than from the urea treatments at the same application rate. A trade-off effect between CH₄ and N₂O emission was clearly observed. The N₂O flux was very small when the rice paddy plots were flooded, but peaked at the beginning of the disappearance of floodwater. In contrast, the CH₄ flux peaked during flooding and was significantly depressed by mid-season aeration (MSA). The results suggest that it is important to evaluate the integrative effects of water management and fertiliser application for mitigating greenhouse gas emissions in order to attenuate the greenhouse effect contributed by rice paddy fields.     

Emissions of CH4 and N2O under Different Tillage Systems from Double-Cropped Paddy Fields in Southern China

Understanding greenhouse gases (GHG) emissions is becoming increasingly important with the climate change. Most previous studies have focused on the assessment of soil organic carbon (SOC) sequestration potential and GHG emissions from agriculture. However, specific experiments assessing tillage impacts on GHG emission from double-cropped paddy fields in Southern China are relatively scarce. Therefore, the objective of this study was to assess the effects of tillage systems on methane (CH₄) and nitrous oxide (N₂O) emission in a double rice (Oryza sativa L.) cropping system. The experiment was established in 2005 in Hunan Province, China. Three tillage treatments were laid out in a randomized complete block design: conventional tillage (CT), rotary tillage (RT) and no-till (NT). Fluxes of CH₄ from different tillage treatments followed a similar trend during the two years, with a single peak emission for the early rice season and a double peak emission for the late rice season. Compared with other treatments, NT significantly reduced CH₄ emission among the rice growing seasons (P<0.05). However, much higher variations in N₂O emission were observed across the rice growing seasons due to the vulnerability of N₂O to external influences. The amount of CH₄ emission in paddy fields was much higher relative to N₂O emission. Conversion of CT to NT significantly reduced the cumulative CH₄ emission for both rice seasons compared with other treatments (P<0.05). The mean value of global warming potentials (GWPs) of CH₄ and N₂O emissions over 100 years was in the order of NT<RT<CT, which indicated NT was significantly lower than both CT and RT (P<0.05). This suggests that adoption of NT would be beneficial for GHG mitigation and could be a good option for carbon-smart agriculture in double rice cropped regions.     

Annual emissions of dissolved CO2, CH4, and N2O in the subsurface drainage from three cropping systems

Indirect emission of nitrous oxide (N₂O), associated with nitrogen (N) leaching and runoff from agricultural lands is a major source of atmospheric N₂O. Recent studies have shown that carbon dioxide (CO₂) and methane (CH₄) are also emitted via these pathways. We measured the concentrations of three dissolved greenhouse gases (GHGs) in the subsurface drainage from field lysimeter that had a shallow groundwater table. Aboveground fluxes of CH₄ and N₂O were monitored using an automated closed‐chamber system. The annual total emissions of dissolved and aboveground GHGs were compared among three cropping systems; paddy rice, soybean and wheat, and upland rice. The annual drainage in the paddy rice, the soybean and wheat, and the upland rice plots was 1435, 782, and 1010 mm yr^?1, respectively. Dissolved CO₂ emissions were highest in the paddy rice plots, and were equivalent to 1.05–1.16% of the carbon storage in the topsoil. Dissolved CH₄ emissions were also higher in the paddy rice plots, but were only 0.03–0.05% of the aboveground emissions. Dissolved N₂O emissions were highest in the upland rice plots, where leached N was greatest due to small crop biomass. In the soybean and wheat plots, large crop biomass, due to double cropping, decreased the drainage volume, and thus decreased dissolved GHG emissions. Dissolved N₂O emissions from both the soybean and wheat plots and the upland rice plots were equivalent to 50.3–67.3% of the aboveground emissions. The results indicate that crop type and rotation are important factors in determining dissolved GHG emissions in the drainage from a crop field.     

Effects of Winter Cover Crops Straws Incorporation on CH4 and N2O Emission from Double-Cropping Paddy Fields in Southern China

Residue management in cropping systems is believed to improve soil quality. However, the effects of residue management on methane (CH₄) and nitrous oxide (N₂O) emissions from paddy field in Southern China have not been well researched. The emissions of CH₄ and N₂O were investigated in double cropping rice (Oryza sativa L.) systems with straw returning of different winter cover crops by using the static chamber-gas chromatography technique. A randomized block experiment with three replications was established in 2004 in Hunan Province, China, including rice–rice–ryegrass (Lolium multiflorum L.) (Ry-R-R), rice–rice–Chinese milk vetch (Astragalus sinicus L.) (Mv-R-R) and rice–rice with winter fallow (Fa-R-R). The results showed that straw returning of winter crops significantly increased the CH₄ emission during both rice growing seasons when compared with Fa-R-R. Ry-R-R plots had the largest CH₄ emissions during the early rice growing season with 14.235 and 15.906 g m⁻² in 2012 and 2013, respectively, when Ry-R-R plots had the largest CH₄ emission during the later rice growing season with 35.673 and 38.606 g m⁻² in 2012 and 2013, respectively. The Ry-R-R and Mv-R-R also had larger N₂O emissions than Fa-R-R in both rice seasons. When compared to Fa-R-R, total N₂O emissions in the early rice growing season were increased by 0.05 g m⁻² in Ry-R-R and 0.063 g m⁻² in Mv-R-R in 2012, and by 0.058 g m⁻² in Ry-R-R and 0.068 g m⁻² in Mv-R-R in 2013, respectively. Similar result were obtained in the late rice growing season, and the total N₂O emissions were increased by 0.104 g m⁻² in Ry-R-R and 0.073 g m⁻² in Mv-R-R in 2012, and by 0.108 g m⁻² in Ry-R-R and 0.076 g m⁻² in Mv-R-R in 2013, respectively. The global warming potentials (GWPs) from paddy fields were ranked as Ry-R-R>Mv-R-R>Fa-R-R. As a result, straw returning of winter cover crops has significant effects on increase of CH₄ and N₂O emission from paddy field in double cropping rice system.     

Steel slag amendment reduces methane emission and increases rice productivity in subtropical paddy fields in China

Paddy field, being a man-made wetland, is recognized as one of the major sources of global methane (CH₄) emission. Since China has the second-largest area of rice cultivation in the world, it is important to develop valid and reliable strategies to reduce CH₄ emission and sustain rice productivity in Chinese paddy fields. In this study, we applied steel slag fertilizer, a by-product of steel industry with a high concentration of active iron (Fe), at rates of 0, 2, 4, and 8 Mg ha^?1 in subtropical rice (Oryza sativa L.) paddy fields in China to assess the effect of steel slag amendment on CH₄ emissions as well as rice growth and yield characteristics. Results showed that the Fe concentrations in paddy soils significantly increased with the application levels of steel slag fertilizer. Steel slag amendment in paddy fields largely reduced the CH₄ production rate, resulting in a decrease in the overall CH₄ emission rate. In response to the applications of steel slag at a rate of 2, 4 and 8 Mg ha^?1, total CH₄ emission during rice cultivation decreased by 26.6, 43.3 and 49.3 %, respectively. Furthermore, steel slag amendment had a significant, positive effect on the rice grain yield and the percentage of ripened grain, most probably due to the increased availability of inorganic nutrients such as silicate and manganese. Our results suggest that steel slag can be an effective soil amendment for reducing CH₄ emissions as well as increasing rice productivity in subtropical paddy fields in China.     

Stimulation of N2O emission by manure application to agricultural soils may largely offset carbon benefits: a global meta‐analysis

Animal manure application as organic fertilizer does not only sustain agricultural productivity and increase soil organic carbon (SOC) stocks, but also affects soil nitrogen cycling and nitrous oxide (N₂O) emissions. However, given that the sign and magnitude of manure effects on soil N₂O emissions is uncertain, the net climatic impact of manure application in arable land is unknown. Here, we performed a global meta‐analysis using field experimental data published in peer‐reviewed journals prior to December 2015. In this meta‐analysis, we quantified the responses of N₂O emissions to manure application relative to synthetic N fertilizer application from individual studies and analyzed manure characteristics, experimental duration, climate, and soil properties as explanatory factors. Manure application significantly increased N₂O emissions by an average 32.7% (95% confidence interval: 5.1–58.2%) compared to application of synthetic N fertilizer alone. The significant stimulation of N₂O emissions occurred following cattle and poultry manure applications, subsurface manure application, and raw manure application. Furthermore, the significant stimulatory effects on N₂O emissions were also observed for warm temperate climate, acid soils (pH < 6.5), and soil texture classes of sandy loam and clay loam. Average direct N₂O emission factors (EFs) of 1.87% and 0.24% were estimated for upland soils and rice paddy soils receiving manure application, respectively. Although manure application increased SOC stocks, our study suggested that the benefit of increasing SOC stocks as GHG sinks could be largely offset by stimulation of soil N₂O emissions and aggravated by CH₄ emissions if, particularly for rice paddy soils, the stimulation of CH₄ emissions by manure application was taken into account.