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1.
Slurries are a significant source of CH4, NH3 and N2O emissions to the atmosphere. The research project aimed at quantifying CH4, NH3 and N2O emissions from liquid manure stores and after manure application under field conditions. The influence of the manure treatment options “no treatment”, “slurry separation”, “anaerobic digestion”, “slurry aeration” and “straw cover” on the emission level was investigated. Approximately 10 m3 of differently treated slurry were stored in pilot scale slurry tanks. Emissions were followed for c. 80 days. After the storage period, slurries were applied to permanent grassland. Greenhouse gas emissions from slurry were mainly caused by methane emissions during storage and by nitrous oxide emissions after field application of manures. Mitigation of GHG emissions can be achieved by a reduction in slurry dry matter and easily degradable organic matter content. Ammonia emissions mainly occurred after field application. Untreated slurry emitted 226.8 g NH3 m−3 and 92.4 kg CO2 eq. m−3 (storage and field application). Slurry separation (liquid fraction and composting of the solid fraction) resulted in NH3 losses of 402.9 g m−3 and GHG losses of 58.5 kg CO2 eq. m−3. Anaerobic digestion was a very effective means to reduce GHG emissions. 37.9 kg CO2 eq. m−3 were lost. NH3 emissions were similar to those from untreated slurry. Covering the slurry store with a layer of chopped straw instead of a wooden cover increased NH3 emissions to 320.4 g m−3 and GHG emissions to 119.7 kg CO2 eq. m−3. Slurry aeration nearly doubled NH3 emissions compared to untreated slurry. GHG emissions were reduced to 53.3 kg CO2 eq. m−3.  相似文献   

2.
Stored solid manure heaps can be a significant source of nitrous oxide (N2O) and methane (CH4) emissions. The manure characteristics influence emissions and solid manure heaps can be managed to promote aerobic decomposition during storage. Increasing the carbon (C) content of the manure heap with high-C additives, such as straw, may provide the opportunity for N2O and CH4 emission reduction. Greenhouse gas (GHG) emissions from conventionally produced farmyard manure (FYM) have been quantified, but there is little data on emissions from organically produced FYM. N2O and CH4 emissions were measured using a small-scale storage method from FYM collected from organic and conventional dairy units under a range of storage conditions with and without extra straw addition.The organic and the conventional FYM were similar in composition except for the higher C and dry matter content in the organic FYM and in the FYM with added straw. This resulted in mean total emissions of N2O and CH4 being lower from the organic (27 g N t−1) than the conventional FYM (52 g N t−1) and from the treatments with straw added (32 g N t−1) than those without (47 g N t−1). The initial C:N ratio and dry matter content of the stored FYM were the most important factors affecting N2O and CH4 emissions although the FYM temperature also affected CH4 emissions. Adding high-C additives, such as straw could be a promising strategy for reducing GHG emissions because it influences the dry matter content, C:N ratio and aeration of the manure. The small-scale FYM storage method were shown to be a reliable and an easy method to quantify emissions under a range of environmental conditions and manure manipulations and so develop effective manure management practices to reduce GHG emissions.  相似文献   

3.
Biogas treatment of animal manures is an upcoming technology because it is a way of producing renewable energy (biogas). However, little is known about effects of this management strategy on greenhouse gas (GHG) emissions during fermentation, storage, and field application of the substrates compared to untreated slurries. In this study, we compared cattle slurry and cattle slurry with potato starch as additive during the process of fermentation, during storage and after field application. The addition of potato starch strongly enhanced CH4 production from 4230 l CH4 m−3 to 8625 l CH4 m−3 in the fermenter at a hydraulic retention time (HRT) of 29 days. Extending the HRT to 56 days had only a small effect on the CH4 production. Methane emissions from stored slurry depended on storage temperature and were highest from unfermented slurry followed by the slurry/starch mixture. Gas emissions from untreated and fermented slurry during storage were further analyzed in a pilot-scale experiment with different levels of covering such as straw cover, a wooden lid and no cover. Emissions of greenhouse gases (CH4, N2O, NH3) were in the range of 14.3–17.1 kg CO2 eq. m−3 during winter (100 day storage period) and 40.5–90.5 kg CO2 eq. m−3 during summer (140 day storage period). A straw cover reduced NH3 losses, but not overall GHG emissions, whereas a solid cover reduced CH4 and NH3 emissions. After field application, there were no significant differences between slurry types in GHG emissions (4.15–8.12 kg CO2 eq. m−3 a−1). GHG emissions from slurry stores were more important than emissions after field application. Co-digestion of slurry with additives such as starch has a large potential to substitute fossil energy by biogas. On a biogas plant, slurry stores should be covered gas-tight in order to eliminate GHG emissions and collect CH4 for electricity production.  相似文献   

4.
The greenhouse gas emissions from agricultural systems contribute significantly to the national budgets for most countries in Europe. Measurement techniques that can identify and quantify emissions are essential in order to improve the selection process of emission reduction options and to enable quantification of the effect of such options. Fast box emission measurements and mobile plume measurements were used to evaluate greenhouse gas emissions from farm sites. The box measurement technique was used to evaluate emissions from farmyard manure and several other potential source areas within the farm. Significant (up to 250 g CH4 m−2 day−1and 0.4 g N2O m−2 day−1) emissions from ditches close to stables on the farm site were found.Plume emission measurements from individual manure storages were performed at three sites. For a manure storage with 1200 m3 dairy slurry in Wageningen emission factors of 11 ± 5 g CH4 m−3 manure day−1 and 14 ± 8 mg N2O m−3 manure day−1 were obtained in February 2002.Mobile plume measurements were carried out during 4 days at distances between 30 and 300 m downwind of 20 different farms. Total farm emissions levels ranged from 14 to 95 kg CH4 day−1 for these sites. Expressed as emission per animal the levels were 0.7 ± 0.4 kg CH4 animal−1 day−1 for conventional farms. For three farms that used straw bedding for the animals1.4 ± 0.2 kg CH4 animal−1 day−1 was obtained. These factors include both respired methane and emission from manure in the stable and the outside storages.For a subset of these farms the CH4 emission was compared with monthly averaged model emission calculations using FarmGHG. This model calculates imports, exports and flows of all products through the internal chains on the farm using daily time steps. The fit of modelled versus measured data has a slope of 0.97 but r2 = 0.27. Measurements and model emission estimates agree well on average, for large farms within 30%. For small farms the differences can be up to a factor of 3. CH4 emissions during winter seem to be underestimated.  相似文献   

5.
Using the organic fraction of municipal solid waste (OFMSW) for biogas production might contribute to greenhouse gas mitigation, but emissions linked with biogas production can reduce these beneficial effects. Therefore the emissions of NH3, CH4 and N2O and costs caused by treating OFMSW by co-fermentation with slurry were calculated in detail from literature data, and strategies for reducing emissions were evaluated. Emission factors were calculated for single gases during storage and after application. The sensitivity of the calculations concerning the organic dry matter content of OFMSW, retention time and CH4-yield was analyzed. The anaerobic co-fermentation of OFMSW increased biogas yields and contributed to the reduction of CO2 emissions with 32 to 152 kg CO2 t−1 organic waste depending on application and storage techniques used for the fermentation residues. Considering a payment of 0.1 €/kWh for the electricity produced, the costs for utilization of OFMSW in slurry based biogas plants were calculated to range between 34 and 38  t−1. Measures for mitigating greenhouse gas emissions by covering the fermentation residue stores proved to be more cost effective with 3–31  t−1 CO2 compared to immediate harrowing or injecting the residues during field application.  相似文献   

6.
Agriculture is an important contributor to global emissions of greenhouse gases (GHG), in particular for methane (CH4) and nitrous oxide (N2O). Emissions from farms with a stock of ruminant animals are particularly high due to CH4 emissions from enteric fermentation and manure handling, and due to the intensive nitrogen (N) cycle on such farms leading to direct and indirect N2O emissions. The whole-farm model, FarmGHG, was designed to quantify the flows of carbon (C) and nitrogen (N) on dairy farms. The aim of the model was to allow quantification of effects of management practices and mitigation options on GHG emissions. The model provides assessments of emissions from both the production unit and the pre-chains. However, the model does not quantify changes in soil C storage.Model dairy farms were defined within five European agro-ecological zones for both organic and conventional systems. The model farms were all defined to have the same utilised agricultural area (50 ha). Cows on conventional and organic model farms were defined to achieve the same milk yield, so the basic difference between conventional and organic farms was expressed in the livestock density. The organic farms were defined to be 100% self-sufficient with respect to feed. The conventional farms, on the other hand, import concentrates as supplementary feed and their livestock density was defined to be 75% higher than the organic farm density. Regional differences between farms were expressed in the milk yield, the crop rotations, and the cow housing system and manure management method most common to each region.The model results showed that the emissions at farm level could be related to either the farm N surplus or the farm N efficiency. The farm N surplus appeared to be a good proxy for GHG emissions per unit of land area. The GHG emissions increased from 3.0 Mg CO2-eq ha−1 year−1 at a N surplus of 56 kg N ha−1 year−1 to 15.9 Mg CO2-eq ha−1 year−1 at a N surplus of 319 kg N ha−1 year−1. The farm N surplus can relatively easily be determined on practical farms from the farm records of imports and exports and the composition of the crop rotation. The GHG emissions per product unit (milk or metabolic energy) were quite closely related to the farm N efficiency, and a doubling of the N efficiency from 12.5 to 25% reduced the emissions per product unit by ca. 50%. The farm N efficiency may therefore be used as a proxy for comparing the efficiencies of farms with respect to supplying products with a low GHG emission.  相似文献   

7.
Dung heaps provide a large, spatial and temporal variable, source of the greenhouse gas N2O. In this paper emission rates measured by static and flow through chamber methods, which enclose only a small area of the heap, were compared with Gaussian plume and tracer ratio methods, which measure the emissions from the entire dung heap. The dung heap was a 300 m3 heap, composed of material from nearby cattle sheds. From the flow through and static chambers it was estimated that the dung heap emitted 315 and 51 g N2ON m−3 day−1, respectively. The spatial variability between the chambers and chamber methods was large. Standard deviations of the mean fluxes were >75% of the average flux. The smaller emissions were measured on the slopes of the heap and the larger emissions on the ridge. The plume of N2O was measured downwind of the dung heap by (1) tunable diode laser spectroscopy and calculation of the N2O source strength of the heap using Gaussian plume theory and (2) tracer ratio method releasing SF6 from the heap summit and capture in Tedlar bags downwind with subsequent analysis by gas chromatography. The Gaussian plume theory calculated an average N2O source strength of 5.3 g N2ON m−3 day−1 (1.4–6.7 g N2ON m−3 day−1). The tracer ratio method calculated a slightly larger average emission rate of 14.4 g N2ON m−3 day−1 (7.4–38.6 g N2ON m−3 day−1). Both methods were successfully validated by point release of SF6 and N2O, which suggests that the micrometeorological methods provided a good estimate of the source strength of the heap, whereas the few chamber measurements overestimated its source strength.  相似文献   

8.
RothC and Century are two of the most widely used soil organic matter (SOM) models. However there are few examples of specific parameterisation of these models for environmental conditions in East Africa. The aim of this study was therefore, to evaluate the ability of RothC and the Century to estimate changes in soil organic carbon (SOC) resulting from varying land use/management practices for the climate and soil conditions found in Kenya. The study used climate, soils and crop data from a long term experiment (1976–2001) carried out at The Kabete site at The Kenya National Agricultural Research Laboratories (NARL, located in a semi-humid region) and data from a 13 year experiment carried out in Machang’a (Embu District, located in a semi-arid region). The NARL experiment included various fertiliser (0, 60 and 120 kg of N and P2O5 ha−1), farmyard manure (FYM—5 and 10 t ha−1) and plant residue treatments, in a variety of combinations. The Machang’a experiment involved a fertiliser (51 kg N ha−1) and a FYM (0, 5 and 10 t ha−1) treatment with both monocropping and intercropping. At Kabete both models showed a fair to good fit to measured data, although Century simulations for treatments with high levels of FYM were better than those without. At the Machang’a site with monocrops, both models showed a fair to good fit to measured data for all treatments. However, the fit of both models (especially RothC) to measured data for intercropping treatments at Machang’a was much poorer. Further model development for intercrop systems is recommended. Both models can be useful tools in soil C predictions, provided time series of measured soil C and crop production data are available for validating model performance against local or regional agricultural crops.  相似文献   

9.
This paper combines life-cycle analyses and economic analyses for Miscanthus and willow heat and electricity fuel-chains in Ireland. Displaced agricultural land-uses and conventional fuels were considered in fuel-chain permutations. Avoided greenhouse gas (GHG) emissions ranged from 7.7 to 35.2 t CO2 eq. ha−1 a−1. Most fuel-chain permutations exhibited positive discounted financial returns, despite losses for particular entities at a farm-gate processed-biomass price of €100 t−1 dry-matter. Attributing a value of €10 t−1 CO2 eq. to avoided GHG emissions, but subtracting financial returns associated with displaced fuel supplies, resulted in discounted annual national economic benefits (DANEBs) ranging from −457 to 1887€ ha−1 a−1. Extrapolating a plausible combination of fuel-chains up to a national indicative scenario resulted in GHG emission avoidance of 3.56 Mt CO2 eq. a−1 (5.2% of national emissions), a DANEB of 167 M€, and required 4.6% of national agricultural land area. As cost-effective national GHG avoidance options, Miscanthus and willow fuel-chains are robust to variation in yields and CO2 price, and appear to represent an efficient land-use option (e.g. compared with liquid biofuel production). Policies promoting utilisation of these energy-crops could avoid unnecessary, and environmentally questionable, future purchase of carbon credits, as currently required for national Kyoto compliance.  相似文献   

10.
Estimates of regional greenhouse gas emissions from agricultural systems are needed to evaluate possible mitigation strategies with respect to environmental effectiveness and economic feasibility. Therefore, in this study, we used the GIS-coupled economic-ecosystem model EFEM–DNDC to assess disaggregated regional greenhouse gas (GHG) emissions from typical livestock and crop production systems in the federal state of Baden-Württemberg, Southwest Germany. EFEM is an economic farm production model based on linear programming of typical agricultural production systems and simulates all relevant farm management processes and GHG emissions. DNDC is a process-oriented ecosystem model that describes the complete biogeochemical C and N cycle of agricultural soils, including all trace gases.Direct soil emissions were mainly related to N2O, whereas CH4 uptake had marginal influence (net soil C uptake or release was not considered). The simulated N2O emissions appeared to be highly correlated to N fertilizer application (R2 = 0.79). The emission factor for Baden-Württemberg was 0.97% of the applied N after excluding background emissions.Analysis of the production systems showed that total GHG emissions from crop based production systems were considerably lower (2.6–3.4 Mg CO2 eq ha−1) than from livestock based systems (5.2–5.3 Mg CO2 eq ha−1). Average production system GHG emissions for Baden-Württemberg were 4.5 Mg CO2 eq ha−1. Of the total 38% were derived from N2O (direct and indirect soil emissions, and manure storage), 40% were from CH4 (enteric fermentation and manure storage), and 22% were from CO2 (mainly fertilizer production, gasoline, heating, and additional feed). The stocking rate was highly correlated (R2 = 0.85) to the total production system GHG emissions and appears to be a useful indicator of regional emission levels.  相似文献   

11.
Dietary adjustments have been suggested as a means to reduce N losses from dairy systems. Differences in fertilizing value of dairy slurry as a result of dietary adjustments were evaluated in a 1-year grassland experiment and by long-term modelling. Slurry composition of non-lactating dairy cows was manipulated by feeding diets with extreme high and low levels of dietary protein and energy. C:Ntotal ratio of the produced slurries ranged from 5.1 to 11.4. To evaluate their short-term fertilizer N value, the experimental slurries (n = 8) and slurries from commercial farms with variable composition (n = 4), were slit-injected in two grassland fields on the same sandy soil series in the north of The Netherlands (53°10′N, 6°04′E), with differences in sward age and ground water level. The recently established grassland field (NEW) was characterized by lower soil OM, N and moisture contents, less herbs and more modern grass varieties compared to the older grassland field (OLD). Slurry was applied in spring (100 kg N ha−1) and after the first cut (80 kg N ha−1) while in total four cuts were harvested. Artificial fertilizer N treatments were included in the experiment to calculate the mineral fertilizer equivalent (MFE) of slurry N. The OLD field showed a higher total N uptake whereas DM yields were similar for the two fields. Average MFE of the slurries on the OLD field (47%) was lower than on the NEW field (56%), probably as a result of denitrification of slurry N during wet conditions in spring. Slurries from high crude protein diets showed a significantly higher MFE (P < 0.05) compared to low crude protein diets. No significant differences in MFE were observed between slurries from high and low energy diets. On both fields, MFE appeared to be positively related to the ammonium content (P < 0.001) and negatively to the C:Ntotal ratio of the slurry DM (P = 0.001). Simulation of the effect of long-term annual application of 180 kg N ha−1 with highest and lowest C:Ntotal ratio suggested that both slurries would lead to an increase in annual soil N mineralization. Both soil N mineralization and SOC appeared to be substantially higher in equilibrium state for the slurry with the highest C:Ntotal ratio. It is concluded that in a situation with slit-injection, the reduced first-year N availability of slurry with a high C:Ntotal ratio as observed in the grassland experiment will only be compensated for by soil N mineralization on the very long term.  相似文献   

12.
The projected increase of atmospheric CO2 concentration [CO2] is expected to increase yield of agricultural C3 crops, but little is known about effects of [CO2] on lodging that can reduce yield. This study examined the interaction between [CO2] and nitrogen (N) fertilization on the lodging of rice (Oryza sativa L.) using free-air CO2 enrichment (FACE) systems installed in paddy fields at Shizukuishi, Iwate, Japan (39°38′N, 140°57′E). Rice plants were grown under two levels of [CO2] (ambient = 365 μmol mol−1; elevated [CO2] = 548 μmol mol−1) and three N fertilization regimes: a single initial basal application of controlled-release urea (8 g N m−2, CRN), split fertilization with a standard amount of ammonium sulfate (9 g N m−2, MN), and ample N (15 g N m−2, HN). Lodging score (six ranks at 18° intervals, with larger scores indicating greater bending), yield, and yield components were measured at maturity. The lodging score was significantly higher under HN than under CRN and MN, but lodging was alleviated by elevated [CO2] under HN. This alleviation was associated with the shortened and thickened lower internodes, but was not associated with a change in the plant's mass moment around the culm base. A positively significant correlation between lodging score and ripening percentage indicated that ripening percentage decreased by 4.5% per one-unit increase in lodging score. These findings will be useful to develop functional algorithm that can be incorporated into mechanistic crop models to predict rice production more accurately in a changing climate and with different cultural practices.  相似文献   

13.
Tree/crop systems under agroforestry practice are capable of sequestering carbon (C) in the standing biomass and soil. Although studies have been conducted to understand soil organic C increases in some agroforestry technologies, little is known about C sequestered in simultaneous tree/crop intercropping systems. The main objective of this study was to determine the effect of agroforestry practice on C sequestration and CO2-C efflux in a gliricidia-maize intercropping system. The experiment was conducted at an experimental site located at the Makoka Agricultural Research Station, in Malawi. The studies involved two field plots, 7-year (MZ21) and 10-year (MZ12), two production systems (sole-maize and gliricidia-maize simultaneous intercropping systems). A 7-year-old grass fallow (Grass-F) was also included. Gliricidia prunings were incorporated at each time of tree pruning in the gliricidia-maize. The amount of organic C recycled varied from 0.8 to 4.8 Mg C ha−1 in gliricidia-maize and from 0.4 to 1.0 Mg C ha−1 in sole-maize. In sole-maize, net decreases of soil carbon of 6 Mg C ha−1 at MZ12 and 7 Mg C ha−1 at MZ21 in the topsoil (0–20 cm) relative to the initial soil C were observed. After 10 years of continuous application of tree prunings C was sequestered in the topsoil (0–20 cm) in gliricidia-maize was 1.6 times more than in sole-maize. A total of 123–149 Mg C ha−1 were sequestered in the soil (0–200 cm depth), through root turnover and pruning application in the gliricidia-maize system. Carbon dioxide evolution varied from 10 to 28 kg ha−1 day−1 in sole-maize and 23 to 83 kg ha−1 day−1 in gliricidia-maize. We concluded that gliricidia-maize intercropping system could sequester more C in the soil than sole-maize.  相似文献   

14.
Reducing phosphorus (P) in dairy diets may result in different types of manure with different chemical composition. Application of these manures to soils may affect the soil P solubility and lead to different environmental consequences. A laboratory incubation study determined the impact of 40 dairy manures on P dynamics in two soil types, Mattapex silt loam (Aquic Hapludult) and Kalmia sandy loam (Typic Hapludult). The manures were fecal samples of lactating cows, collected from commercial dairy farms located in Northeastern and Mid-Atlantic United States, with a wide range of dietary P concentrations (from 2.9 to 5.8 g P kg−1 feed dry matter, DM). Dried and ground fecal samples were mixed with surface horizon (0–15 cm) of soils at 150 kg P ha−1 and the mixtures were incubated at 25 °C for 21 days. At the end of incubation, water soluble P (WS-P) and Mehlich-3 P (M3-P) in the soil–manure mixtures were substantially higher than the control (soil alone) but were lower than the soils receiving fertilizer KH2PO4 at 150 kg P ha−1. Similarly, the relative extractability of P in soils amended with low- and high-P manures was always lower (<93%) than KH2PO4 suggesting that fertilizer P is more effective at increasing soil solution P in the short-term. Concentrations of WS-P or M3-P in soil–manure mixtures did not differ regardless of the source of manure (i.e. different farms and different diets). This suggests that when the same amount of P is added to soils through manure applications, the solubility or bioavailability of P in soils will be the same. However, P concentrations in feces correlate significantly with that in diets (r = 0.82**); and when the manures were grouped into high-P diets (averaging 5.1 g P kg−1) versus low-P diets (3.6 g P kg−1), manure P was 40% greater in the high-P group (10.6 g kg−1 DM) than the low-P group (7.6 g kg−1 DM). Thus, lowering excess P in diets would reduce P excretion in manures, P accumulation in soils, improve P balance on farms, require less area for land disposal, and decrease potential for P loss to waters.  相似文献   

15.
To reduce the environmental burden of agriculture, suitable methods to comprehend and assess the impact on natural resources are needed. One of the methods considered is the life cycle assessment (LCA) method, which was used to assess the environmental impacts of 18 grassland farms in three different farming intensities — intensive, extensified, and organic — in the Allgäu region in southern Germany. Extensified and organic compared with intensive farms could reduce negative effects in the abiotic impact categories of energy use, global warming potential (GWP) and ground water mainly by renouncing mineral nitrogen fertilizer. Energy consumption of intensive farms was 19.1 GJ ha−1 and 2.7 GJ t−1 milk, of extensified and organic farms 8.7 and 5.9 GJ ha−1 along with 1.3 and 1.2 GJ t−1 milk, respectively. Global warming potential was 9.4, 7.0 and 6.3 CO2-equivalents ha−1 and 1.3, 1.0 and 1.3 CO2-equivalents t−1 milk for the intensive, extensified and organic farms, respectively. Acidification calculated in SO2-equivalents was high, but the extensified (119 kg SO2 ha−1) and the organic farms (107 kg SO2 ha−1) emit a lower amount compared with the intensive farms (136 kg SO2 ha−1). Eutrophication potential computed in PO4-equivalents was higher for intensive (54.2 kg PO4 ha−1) compared with extensified (31.2 kg PO4 ha−1) and organic farms (13.5 kg PO4 ha−1). Farmgate balances for N (80.1, 31.4 and 31.1 kg ha−1) and P (5.3, 4.5 and −2.3 kg ha−1) for intensive, extensified and organic farms, respectively, indicate the different impacts on ground and surface water quality. Analysing the impact categories biodiversity, landscape image and animal husbandry, organic farms had clear advantages in the indicators number of grassland species, grazing cattle, layout of farmstead and herd management, but indices in these categories showed a wide range and are partly independent of the farming system.  相似文献   

16.
Nitrous oxide (N2O) emissions from agriculture are currently estimated from N inputs using emission factors, and little is known about the importance of regional or management-related differences. This paper summarizes the results of a study in which N2O emission rates were recorded on 15–26 occasions during a 12-month period in organic and conventional dairy crop rotations in five European countries (Austria, Denmark, Finland, Italy, UK). A common methodology based on static chambers was used for N2O flux measurements, and N2O data were compiled together with information about N inputs (from fertilizers, N2 fixation, atmospheric deposition and excretal returns), crop rotations and soil properties. Organic rotations received only manure as N fertilizer, while manure accounted for 0–100% of fertilizer N in conventional rotations. A linear regression model was used to examine effects of location, system and crop category on N2O emissions, while a second model examined effects of soil properties. Nitrous oxide emissions were higher from conventional than from organic crop rotations except in Austria and, according to the statistical analysis, the differences between locations and crop categories were significant. Ammonium was significantly related to N2O emissions, although this effect was dominated by observations from a grazing system. Despite the limited number of samplings, annual emissions were estimated by interpolation. Across the two systems and five locations there was a significant relationship between total N inputs and N2O emissions at the crop rotation level which indicated that annually 1.6 ± 0.2% (mean ± standard error) of total N inputs were lost as N2O, while there was a background emission of 1.4 ± 0.3 kg N2O-N ha−1 year−1. Although this measurement program emphasized system effects at the expense of high temporal resolution, the results indicate that N input is a significant determinant for N2O emissions from agricultural soils.  相似文献   

17.
Long-term manure-borne copper and zinc inputs (18–324 mg Cu m−2 yr−1 and 100–800 mg Zn m−2 yr−1) to grassland soils resulted in their catchment in water concentrations that often exceeded the surface water quality criteria (2 μg Cu l−1 and 5 μg Zn l−1). This paper compares retention and release of Cu and Zn by two types of soil, a mineral soil (MS) and a dark colored soil rich in organic matter (OS). On the basis of dry soil mass, the OS has a higher retention/affinity for Cu and Zn than the MS, but much less Zn accumulated in the MS when compared on an areal basis. This is largely because of the much smaller bulk OS density and larger dissolved metal concentrations in the OS drainage than that for the MS. However, because of the greater water retention capacity of the OS, elevated metal concentrations in the soil solution do not necessarily cause greater loss to water. It is concluded that artificially drained OS can contribute significantly to the observed elevated Cu and Zn concentrations of the river, especially during relatively dry weather conditions when the contribution of water seeping from OS to the total river water discharge becomes increasingly important.  相似文献   

18.
There is an increasing world wide demand for energy crops and animal manures for biogas production. To meet these demands, this research project aimed at optimising anaerobic digestion of maize and dairy cattle manures. Methane production was measured for 60 days in 1 l eudiometer batch digesters at 38 °C. Manure received from dairy cows with medium milk yield that were fed a well balanced diet produced the highest specific methane yield of 166.3 Nl CH4 kg VS−1. Thirteen early to late ripening maize varieties were grown on several locations in Austria. Late ripening varieties produced more biomass than medium or early ripening varieties. On fertile locations in Austria more than 30 Mg VS ha−1 can be produced. The methane yield declined as the crop approaches full ripeness. With late ripening maize varieties, yields ranged between 312 and 365 Nl CH4 kg VS−1 (milk ripeness) and 268–286 Nl CH4 kg VS−1 (full ripeness). Silaging increased the methane yield by about 25% compared to green, non-conserved maize. Maize (Zea mays L.) is optimally harvested, when the product from specific methane yield and VS yield per hectare reaches a maximum. With early to medium ripening varieties (FAO 240–390), the optimum harvesting time is at the “end of wax ripeness”. Late ripening varieties (FAO ca. 600) may be harvested later, towards “full ripeness”. Maximum methane yield per hectare from late ripening maize varieties ranged between 7100 and 9000 Nm3 CH4 ha−1. Early and medium ripening varieties yielded 5300–8500 Nm3 CH4 ha−1 when grown in favourable regions. The highest methane yield per hectare was achieved from digestion of whole maize crops. Digestion of corns only or of corn cob mix resulted in a reduction in methane yield per hectare of 70 and 43%, respectively. From the digestion experiments a multiple linear regression equation, the Methane Energy Value Model, was derived that estimates methane production from the composition of maize. It is a helpful tool to optimise biogas production from energy crops. The Methane Energy Value Model requires further validation and refinement.  相似文献   

19.
The study is devoted to the issue of direct transformation of triacylglycerols (TAG) to diesel fuels applying a commercially available NiMo and NiW hydrorefining catalysts. It was proved that during hydrodesulphurisation also hydrodeoxygenation occurs and TAG can be converted to the fuel biocomponent by adding 6.5 % vol. of TAG to atmospheric gas oil. In this way, after hydroprocessing at mild conditions (temperature 320–360 °C, pressure 3.5–5.5 MPa, LHSV: 1.0 h?1 and ratio H2:HC = 500–1000 Nm3/m3, catalyst presence), gas oil containing 5–5.5% of biocomponent was prepared, characterized with standard performance and emission parameters. Performance and emission tests documented that even 5% vol. portion of bio-components reduces the controlled and uncontrolled emissions.  相似文献   

20.
Nitrous oxide (N2O) and ammonia (NH3) emissions from surface applied high (HN) and low (LN) nitrogen pig manures were measured under field conditions. Manures were band-spread to a winter wheat crop at three growth stages—mid-tillering, stem elongation and flag leaf emergence. The N2O flux rates were measured using the static chamber technique while NH3 volatilisation was assessed using a micrometeorological mass balance technique with passive flux samplers. The N2O emissions were episodic in nature with flux rates observed ranging from 2.8 to 31.5 g N2O–N ha?1 day?1 (P < 0.001). Higher N2O emissions generally occurred after rainfall events. Highest N2O losses were observed from the HN treatment with LN manure use decreasing emissions by 18% (P < 0.03). The NH3 volatilisation rates were highest within 1 h of manure application with 95% of emissions occurring within 24 h (P < 0.001). Cumulative N loss was highest at mid-tillering as low crop canopy cover and increased wind-speeds enhanced NH3 loss (P < 0.001). Highest emissions were measured from the HN manure (P < 0.03). Total ammoniacal N loss ranged from 6 to 11%. Crop N uptake and grain yield were unaffected by application timing or manure type. Therefore, the use of LN manures decreased gaseous emissions of N2O and NH3 without any adverse effects on crop performance.  相似文献   

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