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1.
李振高  俞慎  吴胜春  王俊华  潘映华 《土壤》2003,35(6):490-494
本文采用自行设计根箱,研究了不同形态N肥(硫铵、尿素)施用条件下,植稻模拟生态系统中水稻苗期根圈微生物生物量C、N和亚硝酸细菌及反硝化细菌的动态变化。结果表明:不同N肥处理的水稻根圈土壤中微生物生物量C和N均高于非根圈土壤,而尿素处理又高于硫铵。两组N肥处理的水稻根圈土壤中亚硝酸细菌和反硝化细菌数量也比非根圈土壤高。硫铵处理的根圈亚硝酸细菌数量在施肥后第7天达到高峰;反硝化细菌数量有随时间呈递增现象。而尿素处理的根圈亚硝酸细菌和反硝化细菌均在第11天出现数量高峰。说明水稻根圈有明显的根圈效应,亚硝酸细菌和反硝化细菌的存在,是引起土壤硝化、反硝化气态N损失的潜在动力;对N的生物有效性而言,施用尿素比硫铵具有明显滞后期,有利于土壤N素对植物生长的持续供应,减少N素损失和环境污染。  相似文献   

2.
加气灌溉水氮互作对温室芹菜地N2O排放的影响   总被引：2，自引：2，他引：0  
为揭示加气条件下不同灌溉和施氮量对设施菜地N2O排放的影响,提出有效的N2O减排措施,该研究以温室芹菜为例,设置充分灌溉(1.0 Ep,I1;Ep为2次灌水间隔内φ20 cm标准蒸发皿的累计蒸发量)和亏缺灌溉(0.75 Ep,I2)2个灌溉水平和0 (N0)、150 (N150)、200 (N200)、250 kg/hm2 (N250)4个施氮水平,采用静态箱-气相色谱法对各处理土壤N2O的排放进行监测,并分析不同灌溉和氮肥水平下土壤温度、湿度、矿质氮(NH4+-N和NO3--N)、硝化细菌和反硝化细菌的变化,以及对土壤N2O排放的影响.结果表明:充分灌水温室芹菜地N2O排放显著(P＜0.05)高于亏缺灌溉;施氮显著(P＜0.05)增加了土壤N2O排放,N150、N200和N250处理的N2O累积排放量分别是N0处理的2.30、4.14和7.15倍.设施芹菜地N2O排放与土壤温度、湿度和硝态氮含量呈指数相关关系(P＜0.01),与硝化细菌和反硝化细菌数量呈线性相关关系(P＜0.01),而与土壤铵态氮没有显著相关关系.灌水和施氮提高芹菜产量的同时,显著增强了土壤N2O排放.综合考虑产量和温室效应,施氮量150 kg/hm2、亏缺灌溉为较佳的管理模式.该研究为设施菜地N2O减排及确定合理的水氮投入量提供参考.  相似文献   

3.
长期定位施氮对连作番茄土壤可培养微生物数量的影响   总被引：3，自引：0，他引：3  
以蔬菜长期定位施肥试验为基础,采用选择性培养基培养微生物,研究长期施氮对连作番茄土壤微生物的组成及数量的影响,并测定了土壤养分,探讨了土壤微生物与土壤养分的相关性。结果表明:处理AN0土壤好气性固氮菌数量最多,显著高于其他处理,处理AN1和BN2显著低于其他处理,施用有机肥可提高土壤中好气性固氮菌的数量。处理AN1氨化细菌数量,显著高于其他处理,BN2和AN2氨化细菌数量较少,有机肥和低浓度氮肥配施可提高土壤中氨化细菌数量,施用高浓度氮肥降低氨化细菌数量。施用有机肥可提高土壤中亚硝化细菌、反硝化细菌和纤维素分解菌的数量。反硝化细菌数量与全磷和速效磷含量显著相关,亚硝化细菌数量与碱解氮、速效钾和速效磷含量显著相关。纤维素分解菌与全氮、碱解氮、速效磷、有机质和速效钾含量显著相关。  相似文献   

4.
有机肥与无机肥配施对菜地土壤N2O排放及其来源的影响   总被引：1，自引：1，他引：0  
该研究采用同位素自然丰度法,通过室内培养试验研究北京地区菜地有机肥和无机肥配施对土壤释放N2O及同位素位嗜值SP（site preference）的影响,以期获得不同肥料及其配比下土壤N2O的来源及变化规律。结果表明：施用无机肥释放的N2O显著高于有机肥,其累积排放量是有机肥的6.63倍,且无机肥施用比例越高,排放量越大;各肥料组合在施用后7天内均以反硝化作用生成N2O为主,贡献最高达到78.89%,SP为6.97‰,之后硝化作用逐渐增强并成为主要途径,最高占比达76.48%,SP为25.24‰;培养期内施用无机肥可以促进反硝化作用,平均占比52.98%,SP为15.52‰,而有机肥会使硝化作用增强,平均占比71.35%,SP为23.55‰。因此,在北京潮褐土地区菜地土壤施用有机肥对N2O有良好的减排效果,可为蔬菜生产中肥料的合理应用提供科学依据。  相似文献   

5.
有机无机肥料配合施用对设施菜田土壤N2O排放的影响   总被引：11，自引：3，他引：8  
采用静态箱气相色谱法研究了有机无机肥料配合施用对设施菜田土壤N2O排放的影响。结果表明: 1）设施芹菜和番茄施基肥后57 d（灌溉后13 d）出现土壤N2O排放通量峰值,追肥后（施肥与灌溉同步）1 d出现土壤N2O排放通量峰值; 芹菜季和番茄季施用基肥后20 d内N2O排放量分别占当季总排放量的40%65%左右,是土壤N2O主要排放期。2）施用基肥后至定植灌水前各处理土壤N2O排放量逐渐降低,灌水后N2O排放通量迅速上升。各处理土壤N2O排放通量与土壤含水量之间呈显著相关,相关系数在0.43~0.72之间。3）土壤N2O排放主要发生在番茄季,番茄生育期各处理土壤N2O总排放量是芹菜生育期的3.1倍; 各处理土壤N2O排放通量与5 cm土层温度之间总体上呈显著相关,相关系数在0.40~0.58之间。4）设施菜田大幅减施化肥的有机无机肥配合施用模式可显著降低土壤N2O排放量和肥料损失率,芹菜季和番茄季土壤N2O排放量较习惯施肥处理分别降低66.3%和85.1%,肥料损失率分别降低45.2%和74.9%。5）等氮量投入时,施用秸秆较施用猪粪可有效降低土壤N2O排放,芹菜季和番茄季分别降低43.4%和74.2%。  相似文献   

6.
有机肥提升高产稻田生产力及土壤生物活性作用研究   总被引：1，自引：0，他引：1  
两年四季双季连作稻田间试验结果表明,有机肥与化肥配合施用对提升高产稻田生产力有明显作用,增产效果以鸡粪猪粪牛粪。不同施肥处理土壤农化性状测试结果表明,配施有机肥处理土壤有机质含量比全化肥区提高,土壤有效磷及有效钾含量的增加作用明显,以鸡粪猪粪牛粪。配施猪粪及牛粪增加土壤全氮、碱解氮含量,而配施鸡粪没有表现增加作用。早稻施用有机肥后7 d、28 d、51 d后采样测定土壤中微生物区系及氮代谢有关的细菌量及土壤酶活性,结果表明,配施有机肥料明显提高土壤中细菌、真菌和放线菌数量,减少土壤中氨化细菌量,对硝化细菌和反硝化细菌量影响较小;配施有机肥处理土壤中脲酶活性明显大于全化肥处理,有机肥对土壤硝酸还原酶、亚硝酸还原酶的活性前期(7 d)表现有所增加,而在后期影响较小。配施有机肥不仅为当季作物提供有效养分,还明显提高土壤肥力和生物活性,改善土壤氮的代谢特性,是提升高产稻田的生产力的主要原因。  相似文献   

7.
在实验室培养条件下,研究了3种控释肥对土壤氮素硝化反硝化损失和N2O排放的影响。结果表明,控释肥具有明显控制氮素释放的作用。在培养的前23d,控释肥处理的土壤NH4＋-N含量低于尿素处理,而后则高于尿素处理。各肥料处理土壤NO3--N含量均随培养时间逐渐增加,但不同肥料处理间差异不显著。28d培养期间,施入控释肥的土壤反硝化氮损失量为30.33～30.91mg N·kg-1土,比施加尿素处理土壤低13.83～14.41mgN·kg-1土,差异达到显著水平（P〈0.05）,控释肥降低氮肥的反硝化损失达3.45～3.60个百分点。控释肥处理土壤N2O累积释放量约为15.71～20.45mgN·kg-1土,比尿素处理高0.86～5.60mgN·kg-1土,但差异未达到显著水平。  相似文献   

8.
N2O是重要的温室气体之一,由此引起的全球变暖和臭氧层破坏是当今重要的环境问题。采用遮光密闭箱和气相色谱法研究了氮肥施用对小麦地N2O释放和反硝化作用的影响。结果表明,小麦生长季节里,高氮、中氮以及不施氮处理N2O平均排放通量分别为2.71、2.42、1.97 gN.hm-.2d-1;尿素、硫酸铵、硝酸钾3种氮肥品种处理下,平均N2O排放通量分别为2.42、2.14、3.13 gN.hm-2.d-1。小麦生长季节里,高氮、中氮以及不施氮处理平均反硝化速率分别为4.91、4.50、1.67 gN.hm-.2d-1;尿素、硫酸铵、硝酸钾3种氮肥品种处理下,平均反硝化速率分别为4.50、3.68、5.29 gN.hm-.2d-1。氮肥施用明显促进了土壤-植物系统中N2O排放通量和反硝化作用,氮肥施用量水平和N2O排放通量、反硝化作用呈正相关。硝酸钾对N2O排放通量和反硝化作用贡献最大,硫酸铵最小。研究还表明,小麦地N2O释放和反硝化作用与季节有一定相关性,温度较高季节排放量及反硝化作用明显,反之则较弱。  相似文献   

9.
南京郊区番茄地中氮肥的气态氮损失   总被引：13，自引：0，他引：13       下载免费PDF全文
采用田间试验研究了番茄地施用化学氮肥后的氨挥发、反硝化损失和N2O排放及其影响因素。氨挥发采用通气密闭室法测定，反硝化损失（N2＋N2O）采用乙炔抑制-土柱培养法测定，不加乙炔测定N2O排放。结果表明，番茄生长期间全部处理均未检测到氨挥发，其原因是土表氨分压低于检测灵敏度，较低的氨分压是由于表层土壤的铵态氮浓度和pH都不高所致。在番茄生长期间，对照区即来自有机肥和土壤本身的反硝化损失和N2O℃排放量相当高，反硝化损失总量高达N29．6kghm^-2，N2O排放量为N7．76kghm^-2。施用化学氮肥显著增加了反硝化损失和N2O排放，3个施用化学氮肥处理的反硝化损失变化在N40．8～46．1kghm^-2之间，占施入化肥氮量的5．50％～6．01％；N2O排放量为N13．6～17．6kghm^-2，占施入化肥氮量的2．62％～4．92％；与尿素相比，包衣尿素未能显著减低反硝化损失和N2O排放。施用尿素的处理在每次追肥后，耕层土壤均会出现NO3^--N高峰，继之的反硝化和N2O排放高峰。反硝化速率与土壤含水量呈极显著正相关。总的看来，番茄生长期间没有氨挥发，而硝化反硝化是氮素损失的重要途径之一。  相似文献   

10.
不同水肥处理对设施菜地N2O排放的影响   总被引：2，自引：1，他引：1  
设施菜地是N2O排放的重要来源。本文通过田间试验对北京地区不同水肥处理的设施有机大白菜进行了全生长季N2O排放监测,以期为设施菜地N2O减排提供数据支撑。试验为灌溉和施氮量的双因素设计,分别为高灌溉量下的常规施氮（高氮 HN1）、 优化施氮（低氮 HN2）和不施氮（HCK）以及低灌溉量下的常规施氮（LN1）、 优化施氮（LN2）和不施氮（LCK）处理。结果显示,不同灌溉量对大白菜产量影响不显著,但常规施氮处理均显著高于优化和不施氮处理。试验初期,土壤N2O排放通量较高,随后逐渐降低; 到第30 d,各施氮处理已累积释放了生育期N2O排放总量的80%以上; 灌水对N2O排放的影响显著,试验期间灌溉三次后均出现排放高峰,且高灌溉量下各处理N2O的排放通量均高于低灌溉处理。常规施氮N2O排放通量高于优化施氮处理,并均显著高于不施氮处理。各施氮处理的N2O排放系数介于0.29%~0.39%之间。  相似文献   

11.
The contribution of nitrifiers (ammonia-oxidizing bacteria (AOB)) and denitrifiers to nitrous oxide (N2O) emission from arctic soils remains inconclusive. Based on preliminary experiments, we hypothesized that AOB are the primary producers of N2O in a high arctic lowland ecosystem on Devon Island, Nunavut, Canada. In part 1 of the study, flux chambers were installed in a catena to determine in situ fluxes of gases (N2O and carbon dioxide (CO2)) from 16 June to 13 July 2004. Although fluxes were low, N2O production occurred in the wettest area of the landscape when ammonium levels were high. As ammonium, but not nitrate, levels declined in the wet sedge meadow, N2O emissions correspondingly decreased. In part 2, the contribution of nitrification and denitrification to N2O production was assessed by Acetylene Inhibition Assay and 15N isotopically enriched incubations. Ammonium fertilization stimulated N2O emissions to a greater extent than nitrate, and acetylene had a greater impact on N2O emissions in ammonium-fertilized soils than in nitrate-amended soils. Stable isotope analysis indicated that at 50-55% water filled pore space, nitrification was the dominant (>80%) N2O emitting process. In part 3, molecular analyses of the two N2O producing groups indicated the both nitrifiers and denitrifiers did not differ between landforms. Our results suggest nitrifier denitrification is the dominant process occurring in these arctic soils and that the role of denitrifiers in N2O release from arctic soils needs to be re-evaluated.  相似文献   

12.
Summary The effect of soil water content [60%–100% water-holding capacity (WHC)] on N2O production during autotrophic nitrification and denitrification in a loam soil was studied in a laboratory experiment by selectively inhibiting nitrification with a low C2H2 concentration (2.1 Pa). Nitrifiers usually produced more N2O than denitrifiers. During an initial experimental period of 0–6 days the nitrifiers produced more N2O than the denitrifiers by a factor ranging from 1.4 to 16.5, depending on the water content and length of incubation. The highest N2O production rate by nitrifiers was observed at 90% WHC, when the soil had become partly anaerobic, as indicated by the high denitrification rate. At 100% WHC there were large gaseous losses from denitrification, while nitrification losses were smaller except for the first period of measurement, when there was still some O2 remaining in the soil. The use of 10 kPa C2H2 to inhibit reduction of N2O to N2 stimulated the denitrification process during prolonged incubation over several days; thus the method is unsuitable for long-term studies.  相似文献   

13.
Soils are the major source of the greenhouse gas nitrous oxide (N2O) to our atmosphere. A thorough understanding of terrestrial N2O production is therefore essential. N2O can be produced by nitrifiers, denitrifiers, and by nitrifiers paradoxically denitrifying. The latter pathway, though well-known in pure culture, has only recently been demonstrated in soils. Moreover, nitrifier denitrification appeared to be much less important than classical nitrate-driven denitrification. Here we studied a poor sandy soil, and show that when moisture conditions are sub-optimal for denitrification, nitrifier denitrification can be a major contributor to N2O emission from this soil. We conclude that the relative importance of classical and nitrifier denitrification in N2O emitted from soil is a function of the soil moisture content, and likely of other environmental conditions as well. Accordingly, we suggest that nitrifier denitrification should be routinely considered as a major source of N2O from soil.  相似文献   

14.
Drained organic forest soils represent a hotspot for nitrous oxide (N2O) emissions, which are directly related to soil fertility, with generally higher emissions from N-rich soils. Highest N2O emissions have been observed in organic forest soils with low pH. The mechanisms for these high emissions are not fully understood. Therefore, the present study was conducted to gain a deeper insight into the underlying mechanisms that drive high N2O emissions from acid soils. Specifically, we investigated the microbial community structure, by phospholipid fatty acid analysis, along a natural pH gradient in an organic forest soil combined with measurements of physico-chemical soil properties. These were then statistically related to site-specific estimates of annual N2O emissions along the same natural pH gradient. Our results indicate that acidic locations with high N2O emissions had a microbial community with an increased fungal dominance. This finding points to the importance of fungi for N2O emissions from acid soils. This may either be directly via fungal N2O production or indirectly via the effect of fungi on the N2O production by other microorganisms (nitrifiers and denitrifiers). The latter may be due to fungal mediated N mineralization, providing substrate for N2O production, or by creating favourable conditions for the bacterial denitrifier community. Therefore, we conclude that enhanced N2O emission from acid forest soil is related, in addition to the known inhibitory effect of low pH on bacterial N2O reduction, to a soil microbial community with increased fungal dominance. Further studies are needed to reveal the exact mechanisms.  相似文献   

15.
Abstract

Methane (CH4) and nitrous oxide (N2O) emissions from an irrigated rice field under continuous flooding and intermittent irrigation water management practices in northern China were measured in situ by the static chamber technique during May to October in 2000. The intermittent irrigation reduced total growing‐season CH4 emission by 24.22% but increased N2O emission by 23.72%, when compared with the continuous flooding. Soil Eh and four related bacterial groups were also measured to clarify their effects on gaseous emissions. Three ranges of soil redox potential were related to gas emissions: below ?100 mV with vigorous CH4 emission, above +100 mV with significant N2O emission, and +100 to ?100 mV with little CH4 and N2O emissions. Intermittently draining the field increased soil oxidation, with a decrease in CH4 emission and an increase in N2O emission. In general the mid‐season drainage slightly increased the populations of methanotrophs, nitrifiers, and denitrifiers but decreased that of methanogens.  相似文献   

16.
Animal manures from intensive livestock operations can be pelleted to improve handlings and recyclings of embodied nutrients. The aim of this study was to evaluate the influence of pelleted poultry manure on N2O and NO fluxes from an Andisol field. In autumn 2006 and summer 2007, poultry manure (PM), pelleted poultry manure (PP), and chemical fertilizer (CF) were applied at a rate of 120 kg N ha−1 in each cultivation period to Komatsuna (Brassica rapa var. peruviridis). Nitrous oxide and NO fluxes were measured using an automated monitoring system. A soil incubation experiment was also conducted to determine the influence of intact and ground pelleted manure on N2O, NO, and CO2 production with a water-filled pore space (WFPS) of 30 or 50%. In the field measurements, N2O emission rates from the organic fertilizer treatments were larger than that from the CF treatment, possibly because organic C stimulated denitrification. The highest N2O flux was observed from the PP treatment after a rainfall following fertilization, and the cumulative emission rate (2.72 ± 0.22 kg N ha−1 y−1) was 3.9 and 7.1 times that from the PM and CF treatments, respectively. In contrast, NO emission rates were highest from the CF treatment. The NO/N2O flux ratio indicated that nitrification was the dominant process for NO and N2O production from the CF treatment. Cumulative N2O emission rates from all treatments were generally higher during the wetter cultivation period (autumn 2006) than during the drier cultivation period (summer 2007). In contrast, NO emission rates were higher in the drier than in the wetter cultivation period. The incubation experiment results showed a synergistic effect of soil moisture and the pelleted manure form on N2O emission rates. The intact pelleted manure with the 50% WFPS treatment produced the highest N2O and CO2 fluxes and resulted in the lowest soil NO3− content after the incubation. These results indicate that anaerobic conditions inside the pellets, caused by rainfall and heterotrophic microbial activities, led to denitrification, resulting in high N2O fluxes. Controlling the timing of N application by avoiding wet conditions might be one mitigation option to reduce N2O emission rates from the PP treatment in this study field.  相似文献   

17.
Agricultural management significantly affects methane (CH4) and nitrous oxide (N2O) emissions from paddy fields. However, little is known about the underlying microbiological mechanism. Field experiment was conducted to investigate the effect of the water regime and straw incorporation on CH4 and N2O emissions and soil properties. Quantitative PCR was applied to measure the abundance of soil methanogens, methane-oxidising bacteria, nitrifiers, and denitrifiers according to DNA and mRNA expression levels of microbial genes, including mcrA, pmoA, amoA, and nirK/nirS/nosZ. Field trials showed that the CH4 and N2O flux rates were negatively correlated with each other, and N2O emissions were far lower than CH4 emissions. Drainage and straw incorporation affected functional gene abundance through altered soil environment. The present (DNA-level) gene abundances of amoA, nosZ, and mcrA were higher with straw incorporation than those without straw incorporation, and they were positively correlated with high concentrations of soil exchangeable NH4+ and dissolved organic carbon. The active (mRNA-level) gene abundance of mcrA was lower in the drainage treatment than in continuous flooding, which was negatively correlated with soil redox potential (Eh). The CH4 flux rate was significantly and positively correlated with active mcrA abundance but negatively correlated with Eh. The N2O flux rate was significantly and positively correlated with present and active nirS abundance and positively correlated with soil Eh. Thus, we demonstrated that active gene abundance, such as of mcrA for CH4 and nirS for N2O, reflects the contradictory relationship between CH4 and N2O emissions regulated by soil Eh in acidic paddy soils.  相似文献   

18.
Little information is available on the effects of urease inhibitor, N-(n-butyl)thiophosphoric triamide (NBPT), and nitrification inhibitor, dicyandiamide (DCD), on nitrous oxide (N2O) emissions from fluvo-aquic soil in the North China Plain. A field experiment was conducted at the Fengqiu State Key Agro-Ecological Experimental Station, Henan Province, China, to study the influence of urea added with NBPT, DCD, and combination of both NBPT and DCD on N2O emissions during the maize growing season in 2009. Two peaks of N2O fluxes occurred during the maize growing season: the small one following irrigation and the big one after nitrogen (N) fertilizer application. There was a significant positive relationship between ln [N2O flux] and soil moisture during the maize growing season excluding the 11-day datasets after N fertilizer application, indicating that N2O flux was affected by soil moisture. Mean N2O flux was the highest in the control with urea alone, while the application of urea together with NBPT, DCD, and NBPT + DCD significantly lowered the mean N2O flux. Total N2O emission in the NBPT + DCD, DCD, NBPT, and urea alone treatments during the experimental period was 0.41, 0.47, 0.48, and 0.77 kg N2O–N ha−1, respectively. Application of urea with NBPT, DCD, and NBPT + DCD reduced N2O emission by 37.7%, 39.0%, and 46.8%, respectively, over urea alone. Based on our findings, the combination of DCD and NBPT together with urea may reduce N2O emission and improve the maize yield from fluvo-aquic soil in the North China Plain.  相似文献   

19.
Abstract

Microbial nitrification and denitrification are responsible for the majority of soil nitrous (N2O) emissions. In this study, N2O emissions were measured and the abundance of ammonium oxidizers and denitrifiers were quantified in purple soil in a long-term fertilization experiment to explore their relationships. The average N2O fluxes and abundance of the amoAgene in ammonia-oxidizing bacteria during the observed dry season were highest when treated with mixed nitrogen, phosphorus and potassium fertilizer (NPK) and a single N treatment (N) using NH4HCO3as the sole N source; lower values were obtained using organic manure with pig slurry and added NPK at a ratio of 40%:60% (OMNPK),organic manure with pig slurry (OM) and returning crop straw residue plus synthetic NH4HCO3fertilizer at a ratio of 15%:85% (SRNPK). The lowest N2O fluxes were observed in the treatment that used crop straw residue(SR) and in the control with no fertilizer (CK). Soil NH4+provides the substrate for nitrification generating N2O as a byproduct. The N2O flux was significantly correlated with the abundance of the amoA gene in ammonia-oxidizing bacteria (r = 0.984, p < 0.001), which was the main driver of nitrification. During the wet season, soil nitrate (NO3?) and soil organic matter (SOC) were found positively correlated with N2O emissions (r = 0.774, p = 0.041 and r = 0.827, p = 0.015, respectively). The nirS gene showed a similar trend with N2O fluxes. These results show the relationship between the abundance of soil microbes and N2O emissions and suggest that N2O emissions during the dry season were due to nitrification, whereas in wet season, denitrification might dominate N2O emission.  相似文献   

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