首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 16 毫秒
1.
A 56-day aerobic incubation experiment was performed with 15-nitrogen (N) tracer techniques after application of wheat straw to investigate nitrate-N (NO3-N) immobilization in a typical intensively managed calcareous Fluvaquent soil. The dynamics of concentration and isotopic abundance of soil N pools and nitrous oxide (N2O) emission were determined. As the amount of straw increased, the concentration and isotopic abundance of total soil organic N and newly formed labeled particulate organic matter (POM-N) increased while NO3-N decreased. When 15NO3-N was applied combined with a large amount of straw at 5000 mg carbon (C) kg?1 only 1.1 ± 0.4 mg kg?1 NO3-N remained on day 56. The soil microbial biomass N (SMBN) concentration and newly formed labeled SMBN increased significantly (P < 0.05) with increasing amount of straw. Total N2O-N emissions were at levels of only micrograms kg?1 soil. The results indicate that application of straw can promote the immobilization of excessive nitrate with little emission of N2O.  相似文献   

2.
Abstract

Both nitrogen (N) deposition and biochar can affect the emissions of nitrous oxide (N2O), carbon dioxide (CO2) and ammonia (NH3) from different soils. Here, we have established a simulated wet N deposition experiment to investigate the effects of N deposition and biochar addition on N2O and CO2 emissions and NH3 volatilization from agricultural and forest soils. Repacked soil columns were subjected to six N deposition events over a 1-year period. N was applied at rates of 0 (N0), 60 (N60), and 120 (N120) kg Nh a?1 yr?1 without or with biochar (0 and 30 t ha?1 yr?1). For agricultural soil, adding N increased cumulative N2O emissions by 29.8% and 99.1% (p < 0.05) from the N60 and N120 treatments, respectively as compared to without N treatments, and N120 emitted 53.4% more (p < 0.05) N2O than the N60 treatment; NH3 volatilization increased by 33.6% and 91.9% (p < 0.05) from the N60 and N120 treatments, respectively, as compared to without N treatments, and N120 emitted 43.6% more (p < 0.05) NH3 than N60; cumulative CO2 emissions were not influenced by N addition. For forest soil, adding N significantly increased cumulative N2O emissions by 141.2% (p < 0.05) and 323.0% (p < 0.05) from N60 and N120 treatments, respectively, as compared to without N treatments, and N120 emitted 75.4% more (p < 0.05) N2O than N60; NH3 volatilization increased by 39.0% (p < 0.05) and 56.1% (p < 0.05) from the N60 and N120 treatments, respectively, as compared to without N treatments, and there was no obvious difference between N120 and N60 treatments; cumulative CO2 emissions were not influenced by N addition. Biochar amendment significantly (p < 0.05) decreased cumulative N2O emissions by 20.2% and 25.5% from agricultural and forest soils, respectively, and increased CO2 emissions slightly by 7.2% and NH3 volatilization obviously by 21.0% in the agricultural soil, while significantly decreasing CO2 emissions by 31.5% and NH3 volatilization by 22.5% in the forest soil. These results suggest that N deposition would strengthen N2O and NH3 emissions and have no effect on CO2 emissions in both soils, and treatments receiving the higher N rate at N120 emitted obviously more N2O and NH3 than the lower rate at N60. Under the simulated N deposition circumstances, biochar incorporation suppressed N2O emissions in both soils, and produced contrasting effects on CO2 and NH3 emissions, being enhanced in the agricultural soil while suppressed in the forest soil.  相似文献   

3.
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   

4.
Abstract

The aim of this study was to assess the mitigating effects of lime nitrogen (calcium cyanamide) and dicyandiamide (DCD) application on nitrous oxide (N2O) emissions from fields of green tea [Camellia sinensis (L.) Kuntze]. The study was conducted in experimental tea fields in which the fertilizer application rate was 544 kg nitrogen (N) ha?1 yr?1 for 2 years. The mean cumulative N2O flux from the soil between the canopies of tea plants for 2 years was 7.1 ± 0.9 kg N ha?1 yr?1 in control plots. The cumulative N2O flux in the plots supplemented with lime nitrogen was 3.5 ± 0.1 kgN ha?1, approximately 51% lower than that in control plots. This reduction was due to the inhibition of nitrification by DCD, which was produced from the lime nitrogen. In addition, the increase in soil pH by lime in the lime nitrogen may also be another reason for the decreased N2O emissions from soil in LN plots. Meanwhile, the cumulative N2O flux in DCD plots was not significantly different from that in control plots. The seasonal variability in N2O emissions in DCD plots differed from that in control plots and application of DCD sometimes increased N2O emissions from tea field soil. The nitrification inhibition effect of lime nitrogen and DCD helped to delay nitrification of ammonium-nitrogen (NH4+-N), leading to high NH4+-N concentrations and a high ratio of NH4+-N /nitrate-nitrogen (NO3–-N) in the soil. The inhibitors delayed the formation of NO3–-N in soil. N uptake by tea plants was almost the same among all three treatments.  相似文献   

5.
Amending vegetable soils with organic materials is increasingly recommended as an agroecosystems management option to improve soil quality. However, the amounts of NO, N2O, and N2 emissions from vegetable soils treated with organic materials and frequent irrigation are not known. In laboratory-based experiments, soil from a NO 3 ? -rich (340 mg N?kg?1) vegetable field was incubated at 30°C for 30 days, with and without 10 % C2H2, at 50, 70, or 90 % water-holding capacity (WHC) and was amended at 1.19 g?C kg?1 (equivalent to 2.5 t?C ha?1) as Chinese milk vetch (CMV), ryegrass (RG), or wheat straw (WS); a soil not amended with organic material was used as a control (CK). At 50 % WHC, cumulative N2 production (398–524 μg N?kg?1) was significantly higher than N2O (84.6–190 μg N?kg?1) and NO (196–224 μg N?kg?1) production, suggesting the occurrence of denitrification under unsaturated conditions. Organic materials and soil water content significantly influenced NO emissions, but the effect was relatively weak since the cumulative NO production ranged from 124 to 261 μg N?kg?1. At 50–90 % WHC, the added organic materials did not affect the accumulated NO 3 ? in vegetable soil but enhanced N2O emissions, and the effect was greater by increasing soil water content. At 90 % WHC, N2O production reached 13,645–45,224 μg N?kg?1 from soil and could be ranked as RG?>?CMV?>?WS?>?CK. These results suggest the importance of preventing excess water in soil while simultaneously taking into account the quality of organic materials applied to vegetable soils.  相似文献   

6.
Abstract

Forest fires can change the greenhouse gase (GHG) flux of borea forest soils. We measured carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes with different burn histories in black spruce (Picea mariana) stands in interior Alaska. The control forest (CF) burned in 1920; partially burned (PB) in 1999; and severely burned (SB1 and SB2) in 2004. The thickness of the organic layer was 22 ± 6 cm at CF, 28 ± 10 cm at PB, 12 ± 6 cm at SB1 and 4 ± 2 cm at SB2. The mean soil temperature during CO2 flux measurement was 8.9 ± 3.1, 6.4 ± 2.1, 5.9 ± 3.4 and 5.0 ± 2.4°C at SB2, SB1, PB and CF, respectively, and differed significantly among the sites (P < 0.01). The mean CO2 flux was highest at PB (128 ± 85 mg CO2-C m?2 h?1) and lowest at SB1 (47 ± 19 mg CO2-C m?2 h?1) (P < 0.01), and within each site it was positively correlated with soil temperature (P < 0.01). The CO2 flux at SB2 was lower than that at CF when the soil temperature was high. We attributed the low CO2 flux at SB1 and SB2 to low root respiration and organic matter decomposition rates due to the 2004 fire. The CH4 uptake rate was highest at SB1 [–91 ± 21 μg CH4-C m?2 h?1] (P < 0.01) and positively correlated with soil temperature (P < 0.01) but not soil moisture. The CH4 uptake rate increased with increasing soil temperature because methanotroph activity increased. The N2O flux was highest [3.6 ± 4.7 μg N2O-N m?2 h?1] at PB (P < 0.01). Our findings suggest that the soil temperature and moisture are important factors of GHG dynamics in forest soils with different fire history.  相似文献   

7.
Soil cultivation changes and usage of agricultural wastes can have profound impacts on greenhouse gas (GHG) emission from soil. In this study, the effects of soil cultivation and organic amendment on GHG emission were investigated using aerobic incubation. Surface soil (0–20 cm) from (1) rice–legume consecutive rotation (Rice) and (2) recently (<3 years) converted from rice field to plastic-covered intensive vegetable and flower production (VegC) were collected in Kunming, P.R. China. Rose (Rosa rugosa Thunb.) residues and cattle manure were applied at 5% by weight. Results indicated that N2O and CO2 fluxes were significantly influenced by soil cultivation, organic amendment, incubation time and their interaction (p <0.05). Applying cattle manure increased, while rose residue decreased, cumulative N2O emissions from soil (84 days). Rose residue application significantly increased cumulative CO2 emissions with peak values of 6371 (Rice) and 7481 mg kg?1 (VegC), followed by cattle manure addition figure of 2265 (VegC) and 3581 mg kg?1 (Rice). Both were significantly higher (p <0.05) than the un-amended Control at 709 (VegC) and 904 mg kg?1 (Rice). Our study demonstrates that a low C/N ratio in cattle manure is better than a high C/N ratio in rose residue in regard to reducing the global warming potential of agricultural soil.  相似文献   

8.
To investigate the influence of plant residues decomposition on N2O emission, laboratory incubations were carried out for a period of 21 days using urea and five plant residues with a wide range of C:N ratios from 8 to 118. Incorporation of plant residues enhanced N2O and CO2 emissions. The two gas fluxes were significantly correlated (R2=0.775, p<0.001). Cumulative emissions of N2O and CO2 were negatively correlated with the C:N ratio in plant residues (R2=0.783 and 0.986 for N2O, and 0.854 for CO2, respectively). A negative relationship between the N2O-N/NO3−-N ratio and the C:N ratio was observed (R2=0.867) when residue plus urea was added. We calculated the changes in dissolved organic C (DOC) and the relevant changes in N2O emission. The incorporation of residues increased DOC when compared with the control, while the incorporation of residue plus urea decreased DOC. Cumulative emissions of N2O and CO2 were positively correlated with DOC concentration measured at the end of the incubation. In addition, the N2O emission fraction, defined as N2O-N emissions per unit N input, was not found to be a constant for either residue-N or urea-N amendment but dependent on C:N ratio when plant residue was incorporated.  相似文献   

9.
为揭示亚热带森林土壤N2O排放对林分类型和氮添加的响应特征,选取位于福建省三明市的中亚热带米槠次生林、杉木人工林和马尾松人工林土壤为研究对象,分别设置无氮添加(N0 mg/kg)、低氮添加(N10 mg/kg)、中氮添加(N25 mg/kg)和高氮添加(N50 mg/kg)4个氮添加水平,进行微宇宙培养试验,测定土壤N2O排放。结果表明：与无氮添加处理相比,氮添加整体上降低3种林分土壤pH,增加土壤NH4+-N和NO3--N含量。无氮添加处理中杉木人工林和马尾松人工林土壤N2O累积排放量分别为9.67和9.62 mg/kg,显著高于米槠次生林土壤N2O累积排放量6.81 mg/kg。低氮添加处理中杉木人工林和马尾松人工林土壤N2O累积排放量显著高于米槠次生林。但在中氮和高氮添加处理中,3种林分土壤N2O累积排放量均无显著性差异。不同氮添加处理均促进3种林分土壤N  相似文献   

10.
ABSTRACT

Legumes, including hairy vetch (Vicia villosa Roth), are widely used as green manures. They fix nitrogen (N) and provide the N to other crops when they decompose, and thus are considered alternatives for chemical N fertilizers. However, N-rich plant residues, including hairy vetch, are also sources of soil nitrous oxide (N2O) emissions, a greenhouse gas. On one hand, rice (Oryza sativa L. ssp. japonica) husk biochar is widely used as a soil conditioner in Japan and has been reported as a tool to mitigate soil N2O emissions. We conducted a soil core incubation experiment (1.5 months) to compare the N2O emissions during the decomposition of surface-applied hairy vetch (0.8 kg dried hairy vetch m?2 soil) under semi-saturated soil moisture conditions (~100% water-filled pore space (WFPS)), using two soil types, namely Andosol and Fluvisol. Throughout the incubation period, the use of biochar suppressed soil NH4+-N concentrations in Andosol, whereas the effect of biochar on NH4+-N was not clear in Fluvisol. Biochar increased the nitrate (NO3?-N) levels both in Andosol and Fluvisol, suggesting a negative influence on denitrification and/or a positive influence on nitrification. Biochar application did not influence the cumulative N2O emissions. Our study suggests that rice husk biochar is not a good option to mitigate N2O emissions during the decomposition of surface-applied hairy vetch, although this study was performed under laboratory conditions without plants. However, the trends of the inorganic-N concentration changes followed by the addition of hairy vetch and biochar were markedly different between the two soil types. Thus, factors behind the differences need to be further studied.  相似文献   

11.
Application of crop residues and its biochar produced through slow pyrolysis can potentially increase carbon (C) sequestration in agricultural production systems. The impact of crop residue and its biochar addition on greenhouse gas emission rates and the associated changes of soil gross N transformation rates in agricultural soils are poorly understood. We evaluated the effect of wheat straw and its biochar applied to a Black Chernozemic soil planted to barley, two growing seasons or 15 months (at the full-bloom stage of barley in the second growing season) after their field application, on CO2 and N2O emission rates, soil inorganic N and soil gross N transformation rates in a laboratory incubation experiment. Gross N transformation rates were studied using the 15N isotope pool dilution method. The field experiment included four treatments: control, addition of wheat straw (30 t ha?1), addition of biochar pyrolyzed from wheat straw (20 t ha?1), and addition of wheat straw plus its biochar (30 t ha?1 wheat straw + 20 t ha?1 biochar). Fifteen months after their application, wheat straw and its biochar addition increased soil total organic C concentrations (p?=?0.039 and <0.001, respectively) but did not affect soil dissolved organic C, total N and NH4 +-N concentrations, and soil pH. Biochar addition increased soil NO3 ?-N concentrations (p?=?0.004). Soil CO2 and N2O emission rates were increased by 40 (p?p?=?0.03), respectively, after wheat straw addition, but were not affected by biochar application. Straw and its biochar addition did not affect gross and net N mineralization rates or net nitrification rates. However, biochar addition doubled gross nitrification rates relative to the control (p?2 and N2O emissions and enhance soil C sequestration. However, the implications of the increased soil gross nitrification rate and NO3 ?-N in the biochar addition treatment for long-term NO3 ?-N dynamics and N2O emissions need to be further studied.  相似文献   

12.
Emissions of nitrous oxide (N2O), a potent greenhouse gas, from agricultural soil have been recognized to be affected by nitrogen (N) application and temperature. Most of the previous studies were carried out to determine effects of temperature on N2O emissions at a fixed N application rate or those of N application rates at a specific temperature. Knowledge about the effects of different ammonium (NH4+) application rates and temperatures on N2O emissions from tropical agricultural soil and their interactions is limited. Five grams of air-dried sandy loam soil, collected in Central Vietnam, were adjusted to 0, 400, 800 and 1200 mg NH4-N kg–1 soil (abbreviated as 0 N, 400 N, 800 N and 1200 N, respectively) at 60% water holding capacity were aerobically incubated at 20°C, 25°C, 30°C or 35°C for 28 days. Mineral N contents and N2O emission rates were determined on days 1, 3, 5, 7, 14, 21 and 28. Cumulative N2O emissions for 28 days increased with increasing NH4+ application rates from 0 to 800 mg N kg–1 and then declined to 1200 mg N kg–1. Cumulative N2O emissions increased in the order of 35°C, 20°C, 30°C and 25°C. This lowest emission at 35°C occurred because N2O production was derived only from autotrophic nitrification while other N2O production processes, e.g., nitrifier denitrification and coupled nitrification-denitrification occurred at lower temperatures. More specifically, cumulative N2O emissions peaked at 800 N and 25°C, and the lowest emissions occurred at 1200 N and 35°C. In conclusion, N2O emissions were not exponentially correlated with NH4+ application rates or temperatures. Higher NH4+ application rates at higher temperatures suppressed N2O emissions.  相似文献   

13.
Molecular nitrogen (N2) and nitrous oxide (N2O) generated by denitrification increase N losses in the soil–plant system. This study aimed to quantify N2 and N2O from potassium nitrate (K15NO3) applied to soils with different textures and moisture contents in the absence and presence of a source of carbon (C) using the 15N tracer method. In the three soils used (sandy texture (ST), sandy clay loam texture (SCLT), and clayey texture (CT)), three moisture contents were evaluated (40%, 60%, and 80% of the water holding capacity (WHC)) with (D+) and without (D?) dextrose added. The treatments received 100 mg N kg?1 (KNO3 with 23.24 atom% 15N). N2 emissions occurred in all of the treatments, but N2O emissions only occurred in the D+ treatment, showing increases with increasing moisture content. SCLT with 80% WHC in the D+ treatment exhibited the highest accumulated N emission (48.26 mg kg?1). The 15N balance suggested trapping of the gases in the soil.  相似文献   

14.
Abstract

Nitrous oxide (N2O) contributes to global climate change, and its emission from soil–crop systems depend on soil, environmental, and anthropogenic factors. Thus, we evaluated the variability of N2O emissions measured by microchambers (cross section: 184 cm2) from a groundnut–fallow–maize–fallow cropping system of the humid tropics. The crops received inorganic nitrogen (N) plus crop residues (NC), inorganic N alone as ammonium sulfate (RN), and half of the inorganic N along with crop residues and chicken manure (N1/2CM), amounting for the crop rotation to 322, 180, and 400 kg N ha?1 yr?1, respectively. The N2O fluxes during the groundnut–maize crop rotation were log‐normally distributed, and the frequency distributions were positively skewed. Daytime changes in N2O fluxes were inconsistent, and the 50% of total N2O emission during the 12 h measurement periods was attained earlier under maize (～11∶00 h) than groundnut covers (～13∶00 h). Spatial variability in each treatment with eight gas chambers was large but smaller during the cropping periods than the fallow, indicating masking efficiency of crop covers for the soil heterogeneity that was accelerated presumably by antecedent climatic variables. The temporal variability of N2O emissions was also large (coefficients of variation, CV, ranged from 60 to 81%), involving both input differences between treatments and measurement periods. As such, the relative deviation from the annual mean of total N2O emission was high during the period after a large N application with a maximum of +480%, due to addition of chicken manure. The seasonal contribution of summer and monsoon to N2O emissions was insignificant. However, intensive rainfall negatively (?0.65**) and the amount of added N from either source positively (0.83***) correlated with the integrated N2O emissions, and those were exponential. Results suggest that around noon (12∶00 h) gas collection could represent well the daily N2O fluxes, increasing the number or size of the gas chambers could minimize the large variability, and mainly the rainfall and N inputs regulated its emissions in the humid tropics of Malaysia.  相似文献   

15.
This study investigated the maturity and gaseous emissions from vermicomposing with agricultural waste. A vermicomposting treatment (inoculated Eisenia fetida) was conducted over a 50-day period, taking tomato stems as the processing object and using cow dung as the nutrient substrate. A thermophilic composting treatment without earthworm inoculation was operated as a control treatment. During the experiment, maturity indexes such as temperature, pH, C/N ratio, and germination index (GI) were determined and continuous measurements of earthworm biomass and CH4, N2O, and NH3 emissions were carried out. The results showed that the temperature during vermicomposting was suitable for earthworm survival, and the earthworm biomass increased from 10.0 to 63.1 kg m?3. Vermicomposting took less time on average to reach the compost maturity standard (GI 80%), and reached a higher GI (132%) in the compost product compared with the thermophilic composting treatment. Moreover, the decrease of the C/N ratio in vermicompost indicated stabilization of the waste. The activities of earthworms played a positive role in reducing gaseous emissions in vermicompost, resulting in less emissions of NH3 (12.3% NH3-N of initial nitrogen) and total greenhouse gases (8.1 kg CO2-eq/t DM) than those from thermophilic compost (24.9% NH3-N of initial nitrogen, 22.8 kg CO2-eq/t DM). Therefore, it can be concluded that vermicomposting can shorten the period required to reach compost maturity, can obtain better maturity compost, and at the same time reduce gaseous emissions. As an added advantage, the earthworms after processing could have commercial uses.  相似文献   

16.
A field study was conducted in the sub-humid tropical region of India to examine the effect of different nitrogen (N) management strategies on nitrate leaching, nitrous oxide (N2O) emission and N use efficiency in aerobic rice. Treatments were: control (no N), 120 kg N ha?1 applied as prilled urea (PU) in conventional method, 120 kg N ha?1 applied as neem coated urea (NCU) in conventional method, N applied as PU on the basis of leaf colour chart (LCC) reading, N applied as NCU on the basis of LCC reading, and 120 kg N ha?1 applied as PU and farm yard manure (FYM) in 1:1 ratio. Results showed that 3.4–16.1 kg NO3-N ha?1 was leached below 45 cm depth and 0.61–1.12 kg N2O-N ha?1 was emitted from aerobic rice during the growing season. NCU when applied conventionally reduced nitrate-nitrogen (NO3-N) leaching and N2O emission by 18.6% and 21.4%, respectively However when applied on the basis of LCC reading NCU reduced NO3-N leaching by 39.8% as compared to PU applied in conventional method. NCU when applied on the basis of LCC reading synchronized N supply with demand and reduced N loss, which resulted in higher yield and N use efficiency.  相似文献   

17.
In the context of sustainable soil-quality management and mitigating global warming, the impacts of incorporating raw or field-burned adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) and wheat (Triticum aestivum L.) straw residues on carbon dioxide (CO2) and nitrous oxide (N2O) emission rates from soil were assessed in an Andosol field in northern Japan. Losses of carbon (C) and nitrogen (N) in residue biomass during field burning were much greater from adzuki bean residue (98.6% of C and 98.1% of N) than from wheat straw (85.3% and 75.3%, respectively). Although we noted considerable inputs of carbon (499 ± 119 kg C ha–1) and nitrogen (5.97 ± 0.76 kg N ha–1) from burned wheat straw into the soil, neither CO2 nor N2O emission rates from soil (over 210 d) increased significantly after the incorporation of field-burned wheat straw. Thus, the field-burned wheat straw contained organic carbon fractions that were more resistant to decomposition in soil in comparison with the unburned wheat straw. Our results and previously reported rates of CO2, methane (CH4) and N2O emission during wheat straw burning showed that CO2-equivalent greenhouse gas emissions under raw residue incorporation were similar to or slightly higher than those under burned residue incorporation when emission rates were assessed during residue burning and after subsequent soil incorporation.  相似文献   

18.
ABSTRACT

Antecedent soil moisture before freezing can affect greenhouse gases (GHG) fluxes from soils during thaw, but their critical threshold values for GHG fluxes and the underlying mechanisms are still not clear. By using packed soil-core incubation experiments, we have studied nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) fluxes from a mature broadleaf and Korean pine-mixed forest soil and an adjacent white birch forest soil with nine levels of soil moisture ranging from 10 to 90% water-filled pore space (WFPS) during a 2-month freezing at ?8°C and the following 10-day thaw at 10°C. The threshold values of soil moisture ranged from 50 to 70% WFPS for CH4 uptake and from 70 to 90% WFPS for N2O and CO2 emissions from the two soils during the freeze-thaw period. Under the optimum soil moisture condition, fulvic-like compounds with high bioavailability contributed more than 60% of dissolved organic matter (DOM) in the soil. Cumulative N2O emissions from forest soils during the freeze-thaw period were greatest when the concentration ratio of nitrate-N to dissolved organic carbon (DOC) was 0.04 g N g?1 C. Cumulative soil CO2 emissions and CH4 uptake during the freeze-thaw period were both regulated by the interaction between soil DOC and net N mineralization. The activities of β-1,4-glucosidase and β-1,4-N-acetyl-glucosaminidase, microbial biomass C and N, and the microbial biomass C-to-N ratios, were all significantly correlated to the soil N2O, CO2, and CH4 fluxes. Overall, upon a freeze-thaw period with different soil moistures, GHG fluxes from forest soils were jointly regulated by inorganic N and DOC concentrations, and related to the labile components of DOM released into the soil, which could be strictly controlled by the related microbial properties.  相似文献   

19.
施肥方式对冬小麦季紫色土N2O排放特征的影响   总被引：6，自引：2，他引：6  
利用紫色土养分循环长期定位施肥试验平台,通过静态箱-气相色谱法,于2012年11月至2013年5月,研究了单施氮肥(N)、猪厩肥(OM)、常规氮磷钾肥(NPK)、猪厩肥配施氮磷钾肥(OMNPK)、秸秆还田配施氮磷钾肥(CRNPK)及对照不施肥(NF)6种施肥方式下,紫色土冬小麦季土壤N2O的排放特征。结果表明,在相同施氮水平[130 kg(N)·hm-2]下,施肥方式对N2O排放量有显著影响(P0.05)。N、OM、NPK、OMNPK和CRNPK处理下,土壤N2O排放量[kg(N)·hm-2]分别为0.38、0.36、0.29、0.33和0.19,N2O排放系数分别为0.25%、0.23%、0.18%、0.21%和0.10%。NF的土壤N2O排放量为0.06 kg(N)·hm-2。土壤无机氮含量(NO3--N和NH4+-N)是N2O排放的主要影响因子,降雨能有效激发N2O排放。基于小麦产量评价不同施肥方式下的N2O排放,结果表明,N、OM、NPK、OMNPK和CRNPK单位小麦产量N2O的GWP值[yield-scaled GWP,kg(CO2 eq)·t-1]分别为132.57、45.70、49.07、48.92和26.41。CRNPK的小麦产量与6种施肥方式中获得最大产量的OM间没有显著差异,但显著高于其他处理。而且,CRNPK的yield-scaled GWP比紫色土地区冬小麦种植中常规施肥方式(NPK)显著减少46%,并显著低于其他4种施肥方式。可见,秸秆还田配施氮磷钾肥在保证小麦产量的同时,能有效减少因施肥引发的N2O排放,可作为紫色土地区推荐的最佳施肥措施。  相似文献   

20.
Abstract

Denitrification products nitrous oxide ((N2O) and nitrogen (N2)) were measured in three flooded soils (paddy soil from Vietnam, PV; mangrove soil from Vietnam, MV; paddy soil from Japan, PJ) with different nitrate (NO3–) concentrations. Closed incubation experiments were conducted in 100-mL bottles for 7 d at 25°C. Each bottle contained 2 g of air-dried soil and 25 mL solution with NO3– (concentration 0, 5 or 10 mg N L?1) with or without acetylene (C2H2). The N2O + N2 emissions were estimated by the C2H2 inhibition method. Results showed that N2O + N2 emissions for 7 d were positively correlated with those of NO3– removal from solution with C2H2 (R2 = 0.9872), indicating that most removed NO3– was transformed to N2O and N2 by denitrification. In PJ soil, N2O and N2 emissions were increased significantly (P < 0.05) by the addition of greater NO3– concentrations. However, N2O and N2 emissions from PV and MV soils were increased by the addition of 0 to 5 mg N L?1, but not by 5 to 10 mg N L?1. At 10 mg N L?1, N2 emissions for 7 d were greater in PJ soil (pH 7.0) than in PV (pH 5.8) or MV (pH 4.3) soils, while N2O emissions were higher in PV and MV soils than in PJ soil. In MV soil, N2O was the main product throughout the experiment. In conclusion, NO3– concentration and soil pH affected N2O and N2 emissions from three flooded soils.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号