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 31 毫秒
1.
The influence of temperature (T) and water potential (ψ) on the denitrification potential, C and N mineralization and nitrification were studied in organic and mineral horizons of an acid spruce forest soil. The amount of N2O emitted from organic soil was 10 times larger than from the mineral one. The maximum of N2O emission was in both soils at the highest water potential 0 MPa and at 20°C. CO2 production in the organic soil was 2 times higher than in mineral soil. Net ammonification in organic soil was negative for most of the T‒ψ variations, while in mineral soil it was positive. Net nitrification in organic soil was negative only at the maximum water potential and temperature (0 MPa, 28°C). The highest rate was between 0 and −0.3 MPa and between 20 and 28°C. In mineral soil NO3− accumulated at all T‒ψ variations with a maximum at 20oC and −0.3 MPa. We concluded that in organic soil the immobilization of NH4+ is the dominant process in the N‒cycling. Nevertheless, decreasing of total N mineralized at 0 MPa and 20—28oC can be explained by denitrification.  相似文献   

2.

Purpose

Better understanding of N transformations and the regulation of N2O-related N transformation processes in pasture soil contributes significantly to N fertilizer management and development of targeted mitigation strategies.

Materials and methods

15N tracer technique combined with acetylene (C2H2) method was used to measure gross N transformation rates and to distinguish pathways of N2O production in two Australian pasture soils. The soils were collected from Glenormiston (GN) and Terang (TR), Victoria, Australia, and incubated at a soil moisture content of 60% water-filled pore space (WFPS) and at temperature of 20 °C.

Results and discussion

Two tested pasture soils were characterized by high mineralization and immobilization turnover. The average gross N nitrification rate (ntot) was 7.28 mg N kg?1 day?1 in TR soil () and 5.79 mg N kg?1 day?1 in GN soil. Heterotrophic nitrification rates (nh), which accounting for 50.8 and 41.9% of ntot, and 23.4 and 30.1% of N2O emissions in GN and TR soils, respectively, played a role similar with autotrophic nitrification in total nitrification and N2O emission. Denitrification rates in two pasture soils were as low as 0.003–0.004 mg N kg?1 day?1 under selected conditions but contributed more than 30% of N2O emissions.

Conclusions

Results demonstrated that two tested pasture soils were characterized by fast N transformation rates of mineralization, immobilization, and nitrification. Heterotrophic nitrification could be an important NO3?–N production transformation process in studied pasture soils. Except for autotrophic nitrification, roles of heterotrophic nitrification and denitrification in N2O emission in two pasture soils should be considered when developing mitigation strategies.
  相似文献   

3.
In recent years, identification of the microbial sources responsible for soil N2O production has substantially advanced with the development of isotope enrichment techniques, selective inhibitors, mathematical models and the discoveries of specific N-cycling functional genes. However, little information is available to effectively quantify the N2O produced from different microbial pathways (e.g. nitrification and denitrification). Here, a 15N-tracing incubation experiment was conducted under controlled laboratory conditions (50, 70 and 85% water-filled pore space (WFPS) at 25 and 35 °C). Nitrification was the main contributor to N2O production. At 50, 70 and 85% WFPS, nitrification contributed 87, 80 and 53% of total N2O production, respectively, at 25 °C, and 86, 74 and 33% at 35 °C. The proportion of nitrified N as N2O (P N2O) increased with temperature and moisture, except for 85% WFPS, when P N2O was lower at 35 °C than at 25 °C. Ammonia-oxidizing archaea (AOA) were the dominant ammonia oxidizers, but both AOA and ammonia-oxidizing bacteria (AOB) were related to N2O emitted from nitrification. AOA and AOB abundance was significantly influenced by soil moisture, more so than temperature, and decreased with increasing moisture content. These findings can be used to develop better models for simulating N2O from nitrification to inform soil management practises for improving N use efficiency.  相似文献   

4.
Acetylene blockage was evaluated as a method for measuring losses of N2O + N2 from two Denchworth series clay soils. The denitrification potential in anaerobic, dark incubations at 20°C with nitrate (equivalent to 100 kg N ha?1 0–20 cm depth), maximum water holding capacity, and acetylene (1%), was equivalent to 32 ± 11 and 39 ± 6 kg N ha?1 per day for the two 0–20 cm soils and was positively correlated with carbon content (r= 0.98). After 4 days N2O was reduced to N2 in the presence of C2H2. In April 1980 following irrigation (24 mm) and applications of ammonium nitrate (70 kg N ha?1) and acetylene, the mean nitrous oxide flux from soil under permanent grass was 0.05 ± 0.01 kg N2O-N ha?1 per day for 8 days. In June 1980, the losses of nitrogen from cultivated soils under winter wheat after irrigation (36 mm) and acetylene treatment were 0.006 ± 0.002 and 0.04–0.07 ± 0.01 kg N ha?1 per day respectively before and after fertilizer application (70 kg N ha?1). The nitrous oxide flux in the presence of acetylene decreased briefly, indicating that nitrification was rate determining in drying soil.  相似文献   

5.
A better understanding of the nitrogen (N) cycle in agricultural soils is crucial for developing sustainable and environmentally friendly N fertilizer management and to propose effective nitrous oxide (N2O) mitigation strategies. This laboratory study quantified gross nitrogen transformation rates in uncultivated and cultivated black soils in Northeast China. It also elucidated the contribution made by nitrification and denitrification to the emissions of N2O. In the laboratory, soil samples adjusted to 60 % water holding capacity (WHC) were spiked with 15NH4NO3 and NH4 15NO3 and incubated at 25 °C for 7 days. The size and 15N enrichment of the mineral N pools and the N2O emission rates were determined between 0 and 7 days. The results showed that the average N2O emission rate was 21.6 ng N2O-N kg?1 h?1 in cultivated soil, significantly higher than in the uncultivated soil (11.6 ng N2O-N kg?1 h?1). Denitrification was found to be responsible for 32.1 % of the N2O emission in uncultivated soil, and the ratio increased significantly to 43.2 % in cultivated soil, due to the decrease in soil pH. Most of the increase in net N2O-N emissions observed in the cultivated soil was resulting from the increased production of N2O through denitrification. Gross nitrification rate was significantly higher in the cultivated soil than in the uncultivated soil, and the ratio of gross nitrification rate/ammonium immobilization rate was 6.87 in cultivated soil, much larger than the uncultivated soil, indicating that nitrification was the dominant NH4 + consuming process in cultivated soil, and this will lead to the increased production of nitrate, whereas the increased contribution of denitrification to N2O emission promoted the larger emission of N2O. This double impact explains why the risk of N loss to the environment is increased by long-term cultivation and fertilization of native prairie sites, and controlling nitrification maybe effective to abate the negative environmental effects.  相似文献   

6.
Abstract

Two experiments were conducted to evaluate the inhibitory effects of 2-chloro-6 (trichloromethyl) pyridine (nitrapyrin) and dicyandiamide on nitrous oxide (N2O), a greenhouse gas, emission from soils amended with ammonium sulfate. In the two experiments, samples of an Andosol and a Gray Lowland soil were kept in glass vessels sealed with a butyl rubber cap and incubated at 25°C. In the first experiment, nitrapyrin (1 µg g?1 dry soil) and dicyandiamide (10 µg g?1 dry soil) were applied to samples of a water-saturated Andosol and a Gray Lowland soil to which ammonium sulfate had been applied at a rate of 0.1 mg N g?1 dry soil. Nitrapyrin decreased N2O emissions from the Andosol and the Gray Lowland soil by 71% and 24%, respectively. Dicyandiamide decreased N2O emissions from the Andosol and Gray Lowland soil by 31% and 18%, respectively. In the second experiment, nitrapyrin (1 µg g?1 dry soil) was applied to samples of an Andosol at 51% water-filled pore space to which ammonium sulfate had been applied at rates of 0.01, 0.1 and 0.5 mg N g?1 dry soil. Nitrapyrin decreased N2O emissions by 62%, 83% and 74%, respectively. Changes in the NH+ 4 and NO? 2 + NO? 3 concentrations in soil showed that nitrapyrin and dicyandiamide slowed down the nitrification process, but did not completely stop the process at any time. The results reveal the potential of nitrification inhibitors to decrease N2O emission from fertilized soil in a wide range of moisture conditions and nitrogen levels.  相似文献   

7.
Abstract

To understand the influence of basal application of N fertilizer on nitrification potential and N2O and NO emissions, four soil samples were collected from an upland Andisol field just before (sample 1) and 4 (sample 2), 36 (sample 3) and 72 (sample 4) days after the basal application of N fertilizer during the Chinese cabbage growing season from 12 September to 30 November 2005. The potentials of N2O production and nitrification of the soils were determined using a 15N tracer technique and the soils were incubated for 25 days at 25°C and 60% water-filled pore space (WFPS). The results revealed that as much as 84–97% N2O and almost all NO were produced by nitrification. The 15N2O emission peak occurred approximately 350 h after the beginning of incubation for samples 1 and 2, but just 48 h later in samples 3 and 4. Total 15N2O emission during the 25-day incubation of samples 3 and 4 ranged from 190 to 198 µg N kg?1 soil, which was significantly higher than the 99–108 µg N kg?1 soil recorded in samples 1 and 2. Basal application of N fertilizer did not immediately increase the nitrification potential and the ratio of N2O to N added, but did dramatically increase the nitrification potential and the ratio of N2O to N added as (15NH4)2SO4 36–72 days after the basal N fertilizer was added. In contrast, NO emission was negatively correlated with nitrification potential and total N2O emission. As a result, a trade-off relationship between total NO and N2O emissions was identified. The results indicated that there was a time-lagged induction of the change of N turnover in the soil, which was possibly caused by slow population growth of the nitrifiers and/or a slow shift in the microbial community in the soil.  相似文献   

8.
 The experiment, carried out on a forest and arable light-textured soil, was designed to study the temperature response of autotrophic and heterotrophic N2O production and investigate how the N2O flux relates to soil respiration and O2 consumption. Although N2O production seemed to be stimulated by a temperature increase in both soils, the relationship between production rate and temperature was different in the two soils. This seemed to depend on the different contribution of nitrification and denitrification to the overall N2O flux. In the forest soil, almost all N2O was derived from nitrification, and its production rate rose linearly from 2  °C to 40  °C. A stronger effect of temperature on N2O production was observed in the arable soil, apparently as a result of an incremental contribution of denitrification to the overall N2O flux with rising temperature. The soil respiration rate increased exponentially with temperature and was significantly correlated with N2O production. O2 consumption stimulated denitrification in both soils. In the arable soil, N2O and N2 production increased exponentially with decreasing O2 concentration, though N2O was the main gas produced at any temperature. In the forest soil, only the N2 flux was related exponentially to O2 consumption and it outweighed the rate of N2O production only at >34  °C. Thus, it appears that in the forest soil, where nitrification was the main source of N2O, temperature affected the N2O flux less dramatically than in the arable soil, where a temperature increase strongly stimulated N2O production by enhancing favourable conditions for denitrification. Received: 26 August 1998  相似文献   

9.
Experiments were conducted to study the effects of a range of CO2 concentrations (ambient to 100%) on nitrification, denitrification and associated nitrous oxide (N2O) production in a silt loam soil. It was found that increase in CO2 concentration from 0.3 to 100% CO2 increasingly retarded the rate of nitrification. No nitrification occurred at 100% CO2. Nitrous oxide production associated with nitrification increased as CO2 increased from 0.3 to 2.6% and tended to be greater as CO2 concentration increased to 73%. At 100% CO2, no N2O was produced during 7 days at 25°C.Carbon dioxide did not affect N2O production or reduction in a saturated NO3?amended soil or the rate of N2O reduction in anaerobic environments.  相似文献   

10.
Though engineered covers have been suggested for reducing landfill methane emissions via microbial methane oxidation, little is known about the covers' function at low temperature. This study aimed to determine the methane consumption rates of engineered soil columns at low temperature (4–12°C) and to identify soil characteristics that may enhance methane oxidation in the field. Engineered soils (30 cm thick) were mixtures of sewage sludge compost and de-inking waste, amended with sand (SDS soil) or bark chips (SDB soil). At 4–6°C, we achieved rates of 0.09 gCH4 kgTS?1d?1 (0.02 m3 m?2d?1) and 0.06 gCH4 kgTS?1d?1 (0.009 m3 m?2d?1) with SDS and SDB soils, respectively. With SDS, good movement and exchange of oxygen in porous soil moderated the slowdown of microbial activity so that the rate dropped only by half as temperature declined from 21–23°C to 4–6°C. In SDB, wet bark chips reduced the soil's air-filled porosity and intensified non-methanotrophic microbial activity, thus reducing the methane consumption rate at 4–6°C to one fourth of that at 21–23°C. In conclusion, soil characteristics such as air-filled porosity, water holding capacity, quantity and stabilization of organic amendments that affect the movement and exchange of oxygen are important variables in designing engineered covers for high methane oxidation at low temperature.  相似文献   

11.
The effects of temperature and water potential on nitrification were investigated in two Iowa soils treated with Stay‐N 2000. The soils were incubated at 10, 20, and 30 °C after soil water potentials of ?1, ?10, or ?60 kPa were applied to each soil. A first‐order equation was used to calculate the maximum nitrification rate (K max), duration of lag period (t′), period of maximum nitrification (Δt), and termination period of nitrification (t s). The highest K max were 18 and 24 mg kg?1 d?1 nitrate (NO3 ?)–nitrogen (N), respectively, at 30 °C and ?10 kPa in both the Nicollet (fine‐loamy, mixed, superactive, mesic Aquic Hapludoll) and Canisteo (fine‐loamy, mixed, superactive, calcareous, mesic Typic Endoaquoll) soils and reduced to 4 and 16 mg kg?1 d?1 NO3 ?‐N when Stay‐N 2000 was added. The extension of t′ due to the addition of Stay‐N 2000 was as high as 7 d in the Nicollet soil at 10 °C and ?1 kPa and as little as 2 d in the Canisteo soil at 20 °C and ?10 kPa.  相似文献   

12.
Soil moisture changes, arising from seasonal variation or from global climate changes, could influence soil nitrogen (N) transformation rates and N availability in unfertilized subtropical forests. A 15?N dilution study was carried out to investigate the effects of soil moisture change (30–90 % water-holding capacity (WHC)) on potential gross N transformation rates and N2O and NO emissions in two contrasting (broad-leaved vs. coniferous) subtropical forest soils. Gross N mineralization rates were more sensitive to soil moisture change than gross NH4 + immobilization rates for both forest soils. Gross nitrification rates gradually increased with increasing soil moisture in both forest soils. Thus, enhanced N availability at higher soil moisture values was attributed to increasing gross N mineralization and nitrification rates over the immobilization rate. The natural N enrichment in humid subtropical forest soils may partially be due to fast N mineralization and nitrification under relatively higher soil moisture. In broad-leaved forest soil, the high N2O and NO emissions occurred at 30 % WHC, while the reverse was true in coniferous forest soil. Therefore, we propose that there are different mechanisms regulating N2O and NO emissions between broad-leaved and coniferous forest soils. In coniferous forest soil, nitrification may be the primary process responsible for N2O and NO emissions, while in broad-leaved forest soil, N2O and NO emissions may originate from the denitrification process.  相似文献   

13.
The effects of seven different fertilization treatments on nitrification in the organic horizons of a Myrtillus-type (MT) and a Calluna-type pine forest in southern Finland were studied. No (NO?3 + NO?2)-N accumulated in unfertilized soils during 6 weeks at 14 or 20°C in the laboratory. Net nitrification was stimulated by urea in both soils (but more in the MT pine forest soil) and to a lesser degree by wood ash but not by ammonium nitrate or nitroform (ureaformaldehyde). Nitrification was not detected in nitroform fertilized soils although ammonium accumulation was high during incubation. In the MT pine forest soil, net nitrification appeared to be stimulated by apatite, biotite and micronutrients. Nitrapyrin inhibited nitrification indicating that it was carried out by autotrophic nitrifiers. In the urea-fertilized MT pine forest soil, nitrification took place at an incubation temperature of 0°C. Accumulation of (N0?3 + NO?2)-N was highest in soil sampled at < 10°C.  相似文献   

14.
On irrigated agricultural soils from semi-arid and arid regions, ammonia (NH3) volatilization and nitrous oxide (N2O) emission can be a considerable source of N losses. This study was designed to test the capture of 15N loss as NH3 and N2O from previous and recent manure application using a sandy, calcareous soil from Oman amended one or two times with 15N labeled manure to elucidate microbial turnover processes under laboratory conditions. The system allowed to detect 15N enrichments in evolved N2O-N and NH3-N of up to 17% and 9%, respectively, and total N, K2SO4 extractable N and microbial N pools from previous and recent 15N labeled manure applications of up to 7%, 8%, and 15%. One time manured soil had higher cumulative N2O-N emissions (141 µg kg?1) than repeatedly manured soil with 43 µg kg?1 of which only 22% derived from recent manure application indicating a priming effect.  相似文献   

15.
 Nitrification and denitrification are, like all biological processes, influenced by temperature. We investigated temperature effects on N trace gas turnover by nitrification and denitrification in two soils under two experimental conditions. In the first approach ("temperature shift experiment") soil samples were preincubated at 25  °C and then exposed to gradually increasing temperatures (starting at 4  °C and finishing at 40–45  °C). Under these conditions the immediate effect of temperature change was assessed. In the second approach ("discrete temperature experiment") the soil samples were preincubated at different temperatures (4–35  °C) for 5 days and then tested at the same temperatures. The different experimental conditions affected the results of the study. In the temperature shift experiment the NO release increased steadily with increasing temperature in both soils. In the discrete temperature experiment, however, the production rates of NO and N2O showed a minimum at intermediate temperatures (13–25  °C). In one of the soils (soil B9), the percent contribution of nitrification to NO production in the discrete temperature experiment reached a maximum (>95% contribution) at 25  °C. In the temperature shift experiment nitrification was always the dominant process for NO release and showed no systematic temperature dependency. In the second soil (soil B14), the percent contribution of nitrification to NO release decreased from 50 to 10% as the temperature was increased from 4  °C to 45  °C, but no differences were evident in the discrete temperature experiment. The N2O production rates were measured in the discrete temperature experiment only. The contribution of nitrification to N2O production in soil B9 was considerably higher at 25–35  °C (60–80% contribution) than at 4–13  °C (15–20% contribution). In soil B14 the contribution of nitrification to N2O production was lowest at 4  °C. The effects of temperature on N trace gas turnover differed between the two soils and incubation conditions. The experimental set-up allowed us to distinguish between immediate effects of short-term changes in temperature on the process rates, and longer-term effects by which preincubation at a particular temperature presumably resulted in the adaptation of the soil microorganisms to this temperature. Both types of effects were important in regulating the release of NO and N2O from soil. Received: 20 October 1998  相似文献   

16.
The effects of incubation at 20°, 30° and 40°C and urea concentrations of 0, 50, 100 and 200 μg N/g soil on urea hydrolysis and nitrification were investigated in three Nigerian soils. At constant temperature urea hydrolysis and rate of NO3? accumulation increased with increasing rate of urea addition. Urea was rapidly hydrolyzed within 1 week of incubation. Nitrification in Apomu soil increased with increasing incubation temperature. Nitrification was slow in acid Nkpologu soil (pH 4.7). Texture, cation exchange capacity and C:N ratios of the soils were not related to urea hydrolysis or nitrification. Nitrite accumulation in these soils was insignificant. Soil pH was decreased by nitrification of hydrolyzed urea-N.  相似文献   

17.
N2O emissions from soils treated with NH4+-N under aerobic conditions in the laboratory were 3- to 4-fold higher than those from controls (no extra N added) or when NO3?-N was added. Although the emission of N2O-N in these field and laboratory experiments represented only 0.1–0.8% of the applied fertilizer NH4+-N and are therefore not significant from an agronomic standpoint, these studies have conclusively demonstrated that the oxidation of applied ammoniacal fertilizers (nitrification) could contribute significantly to the stratospheric N2O pool.Like N-serve, acetylene was shown to be a potent inhibitor of nitrification as it stopped the oxidation of NH4+-N to (NO3+-N + NO2?)-N and hence reduced the evolution of N2O from nitrification within 60 min after its addition.Although high amounts of NO3?-N were present, the rate of denitrification was very low from soils with moisture up to 60% saturation. The further increase in the degree of saturation resulted in several-fold increase of denitrification which eventually became the predominant mechanism of gaseous N losses under anaerobic conditions.  相似文献   

18.
We assessed the effect of liming on (1) N2O production by denitrification under aerobic conditions using the 15N tracer method (experiment 1); and (2) the reduction of N2O to N2 under anaerobic conditions using the acetylene inhibition method (experiment 2). A Mollic Andosol with three lime treatments (unlimed soil, 4 and 20 mg CaCO3 kg?1) was incubated at 15 and 25 °C for 22 days at 50% and then 80% WFPS with or without 200 mg N kg?1 added as 15N enriched KNO3 in experiment 1. In experiment 2, the limed and unlimed soils were incubated under completely anaerobic conditions for 44 h (with or without 100 mg N kg?1 as KNO3). In experiment 1, limed treatments increased N2O fluxes at 50% WFPS but decreased these fluxes at 80% WFPS. At 25 °C, cumulative N2O and 15N2O emissions in the high lime treatment were the lowest (with at least 30% less 15N2O and total N2O than the unlimed soil). Under anaerobic conditions, the high lime treatment showed at least 50% less N2O than the unlimed treatment at both temperatures with or without KNO3 addition but showed enhanced N2 production. Our results suggest that the positive effect of liming on the mitigation of N2O evolution from soil was influenced by soil temperature and moisture conditions.  相似文献   

19.
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   

20.
Large temporal variability of N2O emissions complicates calculation of emission factors (EFs) needed for N2O inventories. To contribute towards improving these inventories, a process-based, 3-dimensional mathematical model, ecosys, was used to model N2O emissions from a canola crop. The objective of this study was to test the hypothesis in ecosys that large temporal variability of N2O is due to transition among alternative reduction reactions in nitrification/denitrification caused by small changes in soil water-filled pore space (WFPS) following a threshold response, which controls diffusivity (Dg) and solubility of O2. We simulated emissions at field scale, using a 20 × 20 matrix of 36 m × 36 m grid cells rendered in ArcGIS from a digital elevation model of the fertilized agricultural field. Modelled results were compared to measured N2O fluxes using the flux-gradient technique from a micrometeorological tower equipped with a tunable diode laser, to assess temporal N2O variability. Grid cell simulations were performed using original, earlier and later planting and fertilizer dates, to show the influence of changing precipitation and temperature on EFs. Fertilizer application (112 kg N ha?1), precipitation and temperature were the main factors responsible for N2O emissions. Ecosys represented the temporal variation of N2O emissions measured at the tower by modelling significant emissions at WFPS > 60% which reduced the oxygen diffusivity, causing a rising need for alternative electron acceptors, thus greater N2O production via nitrification/denitrification. Small changes in WFPS above a threshold value caused comparatively large changes in N2O flux not directly predictable from soil temperature and WFPS. In ecosys, little N2O production occurred at WFPS < 60% because the oxygen diffusivity was large enough to meet microbial demand. Coefficients of diurnal temporal variation in N2O fluxes were high, ranging from 25–51% (modelled) and 24–63% (measured), during emission periods (0–0.8 mg N2O–N m2 h?1). This variation was shown to rise strongly with temperature during nitrification of N fertilizer so that EFs were affected by timing of fertilizer application. EFs almost quadrupled when fertilizer applications were delayed (average: 1.67% (fertilizer-induced emissions), causing nitrification to occur in warmer soils (18 °C), compared to earlier applications (average: 0.45%) when nitrification occurred in cooler soils (12 °C). Large temporal variation caused biases in seasonal emissions if calculated from infrequent (daily and weekly) measurements. These results show the importance of the use of models that include climate impact on N2O, with appropriate time-steps that capture its temporal variation.  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