共查询到20条相似文献,搜索用时 31 毫秒
1.
Nitrous oxide (N 2O) emission from farmland is a concern for both environmental quality and agricultural productivity. Field experiments were
conducted in 1996–1997 to assess soil N 2O emissions as affected by timing of N fertilizer application and straw/tillage practices for crop production under irrigation
in southern Alberta. The crops were soft wheat ( Triticum aestivumL.) in 1996 and canola ( Brassica napusL.) in 1997. Nitrous oxide flux from soil was measured using a vented chamber technique and calculated from the increase in
concentration with time. Nitrous oxide fluxes for all treatments varied greatly during the year, with the greatest fluxes
occurring in association with freeze-thaw events during March and April. Emissions were greater when N fertilizer (100 kg
N ha −1) was applied in the fall compared to spring application. Straw removal at harvest in the fall increased N 2O emissions when N fertilizer was applied in the fall, but decreased emissions when no fertilizer was applied. Fall plowing
also increased N 2O emissions compared to spring plowing or direct seeding. The study showed that N 2O emissions may be minimized by applying N fertilizer in spring, retaining straw, and incorporating it in spring. The estimates
of regional N 2O emissions based on a fixed proportion of applied N may be tenuous since N 2O emission varied widely depending on straw and fertilizer management practices.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Potato fields and cut (ungrazed) grassland in SE Scotland gave greater annual N 2O emissions per ha (1.0–3.2 kg N 2O–N ha -1) than spring barley or winter wheat fields (0.3–0.8 kg N 2O–N ha -1), but in terms of emission per unit of N applied the order was potatoes > barley > grass > wheat. On the arable land, especially the potato fields, a large part of the emissions occurred after harvest.When the grassland data were combined with those for 2 years' earlier work at the same site, the mean emission over 3 years, for fertilization with ammonium nitrate, was 2.24 kg N 2O–N ha -1 (0.62% of the N applied). Also, a very strong relationship between N 2O emission and soil nitrate content was found for the grassland, provided the water-filled pore space was > 70%. Significant relationships were also found between the emissions from potato fields and the soil mineral N content, with the added feature that the emission per unit of soil mineral N was an order of magnitude larger after harvest than before, possibly due to the effect of labile organic residues on denitrification.Generally the emissions measured were lower, as a function of the N applied, than those used as the basis for the current value adopted by IPCC, possibly because spring/early summer temperatures in SE Scotland are lower than those where the other data were obtained. The role of other factors contributing to emissions, e.g. winter freeze–thaw events and green manure inputs, are discussed, together with the possible implications of future increases in nitrogen fertilizer use in the tropics. 相似文献
3.
In 1991, on farm management practices contributed 57.6 Tg CO 2 equivalent in greenhouse gas emissions, that is, about 10% of the anthropogenic GHG emissions in Canada. Approximately 11%
of these emissions were in the form of CO 2, 36% in the form of CH 4 and 53% in the form of N 2O. The CO 2 emissions were from soils; CH 4 emissions were from enteric fermentation and manure, and N 2O emissions were primarily a function of cropping practices and manure management. With the emissions from all other agricultural
practices included, such as the emissions from fossil fuels used for transportation, manufacturing, food processing etc.,
the agricultural sector's contributions were about 15% of Canada's emissions. In this publication, several options are examined
as to their potential for reducing greenhouse gas emissions. These involve soil and crop management, soil nutrient management,
improved feeding strategies, and carbon storage in industrial by-products. The Canadian Economic Emissions Model for Agriculture
(CEEMA) was used to predict the greenhouse gas emissions for the year 2010, as well as the impact of mitigation options on
greenhouse gas emissions from the agricultural sector. This model incorporates the Canadian Regional Agricultural sub-Model
(CRAM), which predicts the activities related to agriculture in Canada up to 2010, as well as a Greenhouse Gas Emissions sub-Model
(GGEM), which estimates the greenhouse gas emissions associated with the various agricultural activities. The greenhouse gas
emissions from all agricultural sources were 90.5 Tg CO 2 equivalent in 1991. Estimates based on CEEMA for the year 2010 indicate emissions are expected to be 98.0 Tg CO 2 equivalent under a business as usual scenario, which assumes that the present trends in management practices will continue.
The agricultural sector will then need to reduce its emissions by about 12.9 Tg CO 2 equivalent below 2010 forecasted emissions, if it is to attain its part of the Canadian government commitment made in Kyoto.
Technologies focusing on increasing the soil carbon sink, reducing greenhouse gas emissions and improving the overall farming
efficiency, need to be refined and developed as best management practices. The soils carbon sink can be increased through
reduced tillage, reduced summer fallowing, increased use of grasslands and forage crops, etc. Key areas for the possible reduction
of greenhouse gas emissions are improved soil nutrient management, improved manure storage and handling, better livestock
grazing and feeding strategies, etc. The overall impact of these options is dependent on the adoption rate. Agriculture's
greenhouse gas reduction commitment could probably be met if soils are recognized as a carbon sink under the Kyoto Accord
and if a wide range of management practices are adopted on a large scale. None of these options can currently be recommended
as measures because their socio-economic aspects have not been fully evaluated and there are still too many uncertainties
in the emission estimates.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
This paper addresses three topics related to N 2O emissions from agricultural soils. First, an assessment of the current knowledge of N 2O emissions from agricultural soils and the role of agricultural systems in the global N 2O are discussed. Secondly, a critique on the methodology presented in the OECD/OCDE (1991) program on national inventories of N 2O is presented. Finally, technical options for controlling N 2O emissions from agricultural fields are discussed.The amount of N 2O derived from nitrogen applied to agricultural soils from atmospheric deposition, mineral N fertilizer, animal wastes or biologically fixed N, is not accurately known. It is estimated that the world-wide N 2O emitted directly from agricultural fields as a result of the deposition of all the above nitrogen sources is 2–3 Tg N annually. This amounts to 20–30% of the total N 2O emitted annually from the earth's surface. An unknown, but probably significant, amount of N 2O is generated indirectly in on and off farm activities associated with food production and consumption.Management options to limit direct N 2O emissions from N-fertilized soils should emphasize improving N-use efficiency. Such management options include managing irrigation frequency, timing and quantity; applying N only to meet crop demand through multiple applications during the growing season or by using controlled release fertilizers; applying sufficient N only to meet crop needs; or using nitrification inhibitors. Most of these options have not been field tested. Agricultural management practices may not appreciably affect indirect N 2O emissions. 相似文献
5.
Agricultural soils emit nitrous oxide (N 2O), a potent greenhouse gas. Predicting and mitigating N 2O emissions is not easy. To derive national coefficients for N 2O emissions from soil, we collated over 400 treatment evaluations (measurements) of N 2O fluxes from farming systems in various ecoregions across Canada. A simple linear coefficient for fertilizer-induced emission
of N 2O in non-manured soils (1.18% of N applied) was comparable to that used by the Intergovernmental Panel on Climate Change (IPCC)
(1.25% of N applied). Emissions were correlated to soil and crop management practices (manure addition, N fertilizer addition
and inclusion of legumes in the rotation) as well as to annual precipitation. The effect of tillage on emissions was inconsistent,
varying among experiments and even within experiments from year to year. In humid regions (e.g., Eastern Canada) no-tillage
tended to enhance N 2O emissions; in arid regions (e.g., Western Prairies) no-tillage sometimes reduced emissions. The variability of N 2O fluxes shows that we cannot yet always distinguish between potential mitigation practices with small (e.g., <10%) differences
in emission. Our analysis also emphasizes the need for developing consistent experimental approaches (e.g., ‘control’ treatments)
and methodologies (i.e. measurement period lengths) for estimating N 2O emissions. 相似文献
6.
Ammonia (NH 3) and nitrous oxide (N -2O) emissions were measured in the field for three months from three different herbage mulches and from bare soil, used as a control. The mulches were grass with a low N-content (1.15% N in DM), grass with a high N-content (2.12% N in DM) and alfalfa with a high N-content (4.33% N in DM). NH 3 volatilization was measured using a micrometeorological technique. N -2O emissions were measured using closed chambers. NH 3 and N -2O emissions were found to be much higher from the N-rich mulches than from the low-N grass and bare soil, which did not differ significantly. Volatilization losses of NH 3 and N -2O occurred mainly during the first month after applying the herbage and were highest from wet material shortly after a rain. The extent of NH 3-N losses was difficult to estimate, due to the low frequency of measurements and some problems with the denuder technique, used on the first occasions of measurements. Nevertheless, the results indicate that NH 3-N losses from herbage mulch rich in N can be substantial. Estimated losses of NH 3-N ranged from the equivalent of 17% of the applied N for alfalfa to 39% for high-N grass. These losses not only represent a reduction in the fertilizer value of the mulch, but also contribute appreciably to atmospheric pollution. The estimated loss of N -2O-N during the measurement period amounted to 1% of the applied N in the N-rich materials, which is equivalent to at least 13 kg N -2O-N ha -1 lost from alfalfa and 6 kg ha -1 lost from high-N grass. These emission values greatly exceed the 0.2 kg N -2O-N ha -1 released from bare soil, and thus contribute to greenhouse gas emissions. 相似文献
7.
Nitrous oxide (N 2O) flux simulations by four models were compared with year-round field measurements from five temperate agricultural sites in three countries. The field sites included an unfertilized, semi-arid rangeland with low N 2O fluxes in eastern Colorado, USA; two fertilizer treatments (urea and nitrate) on a fertilized grass ley cut for silage in Scotland; and two fertilized, cultivated crop fields in Germany where N 2O loss during the winter was quite high. The models used were daily trace gas versions of the CENTURY model, DNDC, ExpertN, and the NASA-Ames version of the CASA model. These models included similar components (soil physics, decomposition, plant growth, and nitrogen transformations), but in some cases used very different algorithms for these processes. All models generated similar results for the general cycling of nitrogen through the agro-ecosystems, but simulated nitrogen trace gas fluxes were quite different. In most cases the simulated N 2O fluxes were within a factor of about 2 of the observed annual fluxes, but even when models produced similar N 2O fluxes they often produced very different estimates of gaseous N loss as nitric oxide (NO), dinitrogen (N 2), and ammonia (NH 3). Accurate simulation of soil moisture appears to be a key requirement for reliable simulation of N 2O emissions. All models simulated the general pattern of low background fluxes with high fluxes following fertilization at the Scottish sites, but they could not (or were not designed to) accurately capture the observed effects of different fertilizer types on N 2O flux. None of the models were able to reliably generate large pulses of N 2O during brief winter thaws that were observed at the two German sites. All models except DNDC simulated very low N 2O fluxes for the dry site in Colorado. The US Trace Gas Network (TRAGNET) has provided a mechanism for this model and site intercomparison. Additional intercomparisons are needed with these and other models and additional data sets; these should include both tropical agro-ecosystems and new agricultural management techniques designed for sustainability. 相似文献
8.
In the following study N 2O emissions from 3 different grasslands and from 3 different arable lands, representing major agriculture areas with different
soil textures and normal agricultural practices in Belgium, have been monitored for 1 to 2 years. One undisturbed soil under
deciduous forest was also included in the study. Nitrous oxide emission was measured directly in the field from vented closed
chambers through photo-acoustic infrared detection. Annual N 2O emissions from the arable lands ranged from 0.3 to 1.5 kg N ha −1 y −1 and represent 0.3 to 1.0% of the fertilizer N applied. Annual N 2O emissions from the intensively managed grasslands and an arable land sown with grass were significantly larger than those
from the cropped arable lands. Emissions ranged from 14 to 32 kg N ha −1 y −1, representing fertilizer N losses between 3 and 11%. At the forest soil a net N 2O uptake of 1.3 kg N 2O-N ha −1 was recorded over a 2-year period. It seems that the N 2O-N loss per unit of fertilizer N applied is larger for intensively managed and heavily fertilized (up to 500 kg N ha −1) grasslands than for arable lands and is substantially larger than the 1.25% figure used for the global emission inventory.
Comparison of the annual emission fluxes from the different soils also indicated that land use rather than soil properties
influenced the N 2O emission. Our results also show once again the importance of year-round measurements for a correct estimate of N 2O losses from agricultural soils: 7 to 76% of the total annual N 2O was emitted during the winter period (October–February). Disregarding the emission during the off-season period can lead
to serious underestimation of the actual annual N 2O flux.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
The DNDC model was used to estimate direct N 2O emissions from agricultural soils in Canada from 1970 to 1999. Simulations were carried out for three soil textures in seven soil groups, with two to four crop rotations within each soil group. Over the 30-year period, the average annual N 2O emission from agricultural soils in Canada was found to be 39.9 Gg N 2O–N, with a range from 20.0 to 77.0 Gg N 2O–N, and a general trend towards increasing N 2O emissions over time. The larger emissions are attributed to an increase in N-fertilizer application and perhaps to a trend in higher daily minimum temperatures. Annual estimates of N 2O emissions were variable, depending on timing of rainfall events and timing and duration of spring thaw events. We estimate, using DNDC, that emissions of N 2O in eastern Canada (Atlantic Provinces, Quebec, Ontario) were approximately 36% of the total emissions in Canada, though the area cropped represents 19% of the total. Over the 30-year period, the eastern Gleysolic soils had the largest average annual emissions of 2.47 kg N 2O–N ha –1 y –1 and soils of the dryer western Brown Chernozem had the smallest average emission of 0.54 kg N 2O–N ha –1 y –1. On average, for the seven soil groups, N 2O emissions during spring thaw were approximately 30% of total annual emissions. The average N 2O emissions estimates from 1990 to 1999 compared well with estimates for 1996 using the IPCC methodology, but unlike the IPCC methodology our modeling approach provides annual variations in N 2O emissions based on climatic differences. 相似文献
10.
Understanding how agricultural management practices impact nitrous oxide (N 2O) emissions is prerequisite for developing mitigation protocols. We conducted a meta-analysis on 597 pairwise comparisons (129 papers) to assess how management affects N 2O emissions. Pairwise comparisons of practices aimed at improving fertilizer use efficiency (39%) and tillage (30%) dominated the dataset, while ecologically-based nutrient management (ENM) practices constituted 15% of the pairs. In general, across management practices, the quantity of N added was a more significant driver of N 2O fluxes than was the form of N (fertilizer, legume biomass or animal manures). Manure interacted with soil texture so that in coarse soils, N 2O emissions from manures tended to be higher compared to inorganic N fertilizers. The studies of ENM strategies frequently involved over-application of N inputs in the ENM treatments. Cover crops reduced N 2O emissions compared to bare fallows. However, during the cash crop growing season, when differences in N added and N source were confounded, the extra N inputs from cover crops were significantly correlated with the differences in N 2O emissions between treatments with and without cover crops. Overall, in 38% of the data pairs, N 2O emissions were reduced with limited impacts on yields; in half of these pairs, yields were maintained or increased while in the other half they were reduced by only ≤10%. Knowledge gaps on mitigation of agricultural N 2O emissions could be addressed by applying an ecosystem-based, cross-scale perspective in conjunction with the N saturation conceptual framework to guide research priorities and experimental designs. 相似文献
11.
In the North China Plain, a field experiment was conducted to measure nitrous oxide (N 2O) and methane (CH 4) fluxes from a typical winter wheat–summer maize rotation system under five integrated agricultural management practices: conventional regime [excessive nitrogen (N) fertilization, flood irrigation, and rotary tillage before wheat sowing; CON], recommended regime 1 (balanced N fertilization, decreased irrigation, and deep plowing before wheat sowing; REC-1), recommended regime 2 (balanced N fertilization, decreased irrigation, and no tillage; REC-2), recommended regime 3 (controlled release N fertilizer, decreased irrigation, and no tillage; REC-3), and no N fertilizer (CK). Field measurements indicated that pulse emissions after N fertilization and irrigation contributed 19–49 % of annual N 2O emissions. In contrast to CON (2.21 kg N 2O-N ha ?1 year ?1), the other treatments resulted in significant declines in cumulative N 2O emissions, which ranged from 0.96 to 1.76 kg N 2O-N ha ?1 year ?1, indicating that the recommended practices (e.g., balanced N fertilization, controlled release N fertilizer, and decreased irrigation) offered substantial benefits for both sustaining grain yield and reducing N 2O emissions. Emission factors of N fertilizer were 0.21, 0.22, 0.23, and 0.37 % under CON, REC-1, REC-3, and REC-2, respectively. Emissions of N 2O during the freeze–thaw cycle period and the winter freezing period accounted for 9.7 and 5.1 % of the annual N 2O budget, respectively. Thus, we recommend that the monitoring frequency should be increased during the freeze–thaw cycle period to obtain a proper estimate of total emissions. Annual CH 4 fluxes from the soil were low (?1.54 to ?1.12 kg CH 4-C ha ?1 year ?1), and N fertilizer application had no obvious effects on CH 4 uptake. Values of global warming potential were predominantly determined by N 2O emissions, which were 411 kg CO 2-eq ha ?1 year ?1 in the CK and 694–982 kg CO 2-eq ha ?1 year ?1 in the N fertilization regimes. When comprehensively considering grain yield, global warming potential intensity values in REC-1, REC-2, and REC-3 were significantly lower than in CON. Meanwhile, grain yield increased slightly under REC-1 and REC-3 compared to CON. Generally, REC-1 and REC-3 are recommended as promising management regimes to attain the dual objectives of sustaining grain yield and reducing greenhouse gas emissions in the North China Plain. 相似文献
12.
Accurate estimates of nitrous oxide (N2O) emissions from agricultural soils and management factors that influence emissions are necessary to capture the impact of mitigation measures and carry out life cycle analyses aimed at identifying best practices to reduce greenhouse gas emissions. We propose improvements to a country specific method for estimating N2O emissions from agricultural soils in Canada based on a compilation of soil N2O flux data from recent published literature. We provide a framework for the development of empirical models that could be applied in regions where similar data and information on N2O emissions are available. The method considers spatial elements such as soil texture, topography and climate based on a quantitative empirical relationship between synthetic N-induced soil N2O emission factor (EF) and growing season precipitation (P) {N2OEF?=?e(0.00558P?7.7)}. Emission factors vary from less than 0.0025 kg N2O-N kg N?1 in semi-arid regions of Canada to greater than 0.025 kg N2O-N kg N?1 in humid regions. This approach differentiates soil N2O EFs based on management factors. Specifically, empirical ratio factors are applied for sources of N of 1.0, 0.84, and 0.28 for synthetic N, animal manure N and crop residue N, respectively. Crop type ratio factors where soil N2O EFs from applied manure- and synthetic-N on perennial crops are approximately 19% of those on annual crops. This proposed approach improves the accuracy of the dominant factors that modulate N2O emissions from N application to soils. 相似文献
13.
Long-term studies of greenhouse gas fluxes from agricultural soils in different climate regions are needed to improve the existing calculation models used in greenhouse gas inventories. The aim of this study was to obtain more information on nitrous oxide (N 2O) emissions from agricultural mineral soils in the boreal region. N 2O emissions were studied during 2000–2002 on two soil types in Finland, a loamy sand and a clay with plots of grass, barley and fallow. N 2O fluxes were measured with static chambers throughout the year. Other parameters measured were water filled pore space (WFPS), soil mineral nitrogen concentration, soil porosity, soil temperature and depth of soil frost. The annual fluxes from the clay soil ranged from 3.7 to 7.8 kg N ha –1 and those from sandy loam from 1.5 to 7.5 kg N ha –1. On average 60% of the annual fluxes occurred outside the growing season, from October to April. Increasing the number of freeze-thaw events was found to increase the fluxes during winter and during the thawing period in spring. The results suggest that N 2O fluxes from these boreal mineral soils do not vary much as a function of applied fertiliser N and could probably be better estimated from soil physical properties, including soil porosity. 相似文献
14.
Mid-day field fluxes of nitrous oxide (N 2O), carbon dioxide (CO 2) and methane (CH 4) were measured during late winter/early spring in an arable field and an adjacent fallow in southern Germany. On the arable field, 2 dm high ridges, drawn as seed-beds for potato, were exposed to mild, partly diurnal freezing–thawing. Substantially elevated N 2O emission rates (6–750 µg N 2O-N m –2 h –1) were observed throughout the investigation period which coincided with freezing–thawing events in the surface soil (0–5 cm). Soil temperatures in the densely vegetated fallow were more isothermal due to an insulating snow/ice cover, resulting in much lower N 2O emission rates (0–57 µg N 2O-N m –2 h –1). CH 4 uptake rates were low in both habitats during soil frost (+2 to –7.5 µg CH 4-C m –2 h –1) but increased markedly in the fallow after spring thaw. Our data suggest that N 2O emission peaks may occur recurrently throughout the winter when soils are subjected to diurnal surface thawing. We concluded that microclimatic conditions strongly control N 2O winter loss, thus overriding ecosystem-level differences in off-season nutrient cycling. To further characterize winter-time nutrient cycling and habitat functioning in our sites, we determined NO 3
– and NH 4
+ contents, fumigation-extractable carbon (C mic) and nitrogen (N mic) and enumerated protozoa and nematoda throughout the investigation period. C mic and microbial C:N ratios in the fallow were higher in winter than during the rest of the year as indicated by a 2-year study, reflecting favorable conditions for microbial C assimilation at low temperatures in the absence of freeze–thaw perturbation. In the arable soil, C mic contents were significantly reduced during soil freezing but recovered quickly upon warming of the soil. Dynamics of C mic in the arable soil were paralleled by protozoan biomass and transient shifts in functional composition of the nematode community, indicating that microfaunal predation played an important role in nutrient cycling after freeze–thaw perturbation. Only minor microfaunal dynamics were observed in the climatically more stable fallow, essentially confirming the absence of perturbation at this site. Our findings provide strong evidence that overwinter N 2O formation is regulated by both the physical freeze–thaw susceptibility of the soil and the ecological functioning of the habitat. 相似文献
15.
The authors of this paper measured the methane and nitrous oxide fluxes emissions from rice field with different rice varieties
and the two fluxes from pot experiments with different soil water regime and fertilizer treatment. The experiment results
showed that: (1) The CH 4 emission rates were different among different varieties; (2) There was a trade-off between CH 4 and N 2O emissions from rice field with some agricultural practices; (3) We must consider the mitigation options comprehensively
to mitigate CH 4 and N 2O emissions from rice fields.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
The closed chamber method was used to measure the N 2O and CH 4 emissions from rice, maize, soybean and spring wheat fields in Northeast China. Rice field almost did not emit or deposit
N 2O in total during flooding period, whereas N 2O was substantially emitted during non-flooding period. The annual emission amount of N 2O was 1.70 kg N 2O ha -1, but that in flooding period was only 0.04 kg N 2O ha -1. Daily average and seasonal total CH 4 emission in rice field were 0.07 and 7.40 g CH 4m -2, respectively. A trade-off between N 2O and CH 4 emissions from rice field was found. The growth of Azolla in rice field greatly stimulated both N 2O and CH 4 emissions. Total N 2O emissions (270 days) from maize and soybean fields were 7.10 and 3.12 kg N 2O ha -1, respectively. The sink function of the uplands monitored as the atmospheric CH 4 was not significant.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Nations are now obligated to assess their greenhouse gas emissions under the protocols of Article 4 of the United Nations
Framework Convention on Climate Change. The IPCC has developed `spreadsheet-format' methodologies for countries to estimate
national greenhouse gas emissions by economic sector. Each activity has a magnitude and emission rate and their product is
summed over all included activities to generate a national total (IPCC, 1997). For N 2O emissions from cropland soils, field studies have shown that there are important factors that influence N 2O emissions at specific field sites that are not considered in the IPCC methodology. We used DNDC, a process-oriented agroecosystem
model, to develop an unofficial national inventory of direct N 2O emissions from cropland in China. We assembled county-scale data on soil properties, daily weather, crop areas, N-fertilizer
use, livestock populations (for manure inputs to cropland), and agricultural management for the 2500 counties in mainland
China. Total 1990 cropland area was 0.95 million km 2. Total N-fertilizer use in China in 1990 was 16.6 Tg N. The average fertilization rate was 175 kg N ha −1 cropland. One-year simulations with DNDC were run for each crop type in each county to generate estimates of direct N 2O emissions from soils. National totals were the sum of results for all crop simulations across all counties. Baseline simulations
estimated that total N 2O emission from arable land in China in 1990 was 0.31 Tg N 2O-N yr −1. We also ran simulations with zero N-fertilizer input; the difference between the zero-fertilizer and the baseline run is
an estimate of fertilizer-induced N 2O emissions. The fertilizer-induced emission was 0.13 Tg N 2O-N yr −1, about 0.8% of total N-fertilizer use (lower than the mean but within the IPCC range of 1.25±1.0%). We compared these results
to our estimates of county-scale IPCC methodology emissions. Total emissions were similar but geographical patterns were quite
different.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
The aim of this study was to analyze the influence of different crop sequences (soybean-corn and soybean?Csoybean) and tillage systems (no tillage and reduced tillage) on nitrous oxide (N 2O) soil emissions under field conditions. The experiment was carried out in Manfredi, Córdoba province, Argentina on an Entic Haplustoll and N 2O emissions were measured in the field during a year. N 2O fluxes were low during winter, but in late spring it peaked. For fallow, N-NO 3-content was the most important variable to explain N 2O emissions. For growing period water-filled pores was the main variable explaining N 2O emissions. Nitrogen fertilization of corn crop increased N 2O-N emissions, whereas no significant differences were found due to the tillage system. Measured annual N 2O-N emissions were generally lower than those calculated using the methodology proposed by the Intergovernmental Panel on Climate Change. 相似文献
19.
Biogenic emissions of methane (CH 4) and nitrous oxide (N 2O) from animal manure are stimulated by the degradation of volatile solids ( VS) which serves as an energy source and a sink for atmospheric oxygen. Algorithms are presented which link carbon and nitrogen turnover in a dynamic prediction of CH 4 and N 2O emissions during handling and use of liquid manure (slurry). A sub-model for CH 4 emissions during storage relates CH 4 emissions to VS, temperature and storage time, and estimates the reduction in VS. A second sub-model estimates N 2O emissions from field-applied slurry as a function of VS, slurry N and soil water potential, but emissions are estimated using emission factors. The model indicated that daily flushing of slurry from cattle houses would reduce total annual CH 4 + N 2O emissions by 35% (CO 2 eq.), and that cooling of pig slurry in-house would reduce total annual CH 4 + N 2O emissions by 21% (CO 2 eq.). Anaerobic digestion of slurry and organic waste produces CH 4 at the expense of VS. Accordingly, the model predicted a 90% reduction of CH 4 emissions from outside stores with digested slurry, and a >50% reduction of N 2O emissions after spring application of digested as opposed to untreated slurry. The sensitivity of the model towards storage temperature and soil water potential was examined. This study indicates that simple algorithms to account for ambient climatic conditions may significantly improve the prediction of CH 4 and N 2O emissions from animal manure. 相似文献
20.
Greenhouse gases (CO 2, CH 4 and N 2O) are emitted during livestock manure handling, including composting, storage and land application. However, published data
on emission rates of these gases during storage are sparse. In this study, the levels of GHG emissions and N levels during
compost storage were investigated. The compost materials were produced by composting livestock manure for 133 d with 0, 10,
20 and 30% phosphogypsum (PG) or 10, 20 and 30% sand amendment. These compost materials were then stored on a clay pad for
233 d. Results from this study indicated that TN content did not change but mineral N content increased significantly during
the 233 d storage for all treatments. The higher mineral N content in compost increases its agronomic value. There were only
trace amounts of CH 4 and N 2O emissions. The C loss during storage was mainly as CO 2 and accounted for about 2.9 to 10% of total C initially in the compost. This information is vital to livestock manure life
cycle analysis, and can be used to develop best manure management strategies that reduce GHG emissions from livestock production.
The LRC Contribution No. 387-06006. 相似文献
|