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1.
The emission of nitrous oxide (N2O) from soil under grass was measured, following applications of cow slurry and NH4NO3 fertilizer. The N2O-flux from untreated soil averaged 0.58 mg Nm?2 day?1 through April to August. Application of slurry at the end of April and at the middle of July caused increases in the daily N2O-flux of up to 40-fold, compared to untreated grass. Applications of NH4NO3 increased the N2O-flux up to 5 times during the same period. The N2O-flux often showed marked diurnal fluctuations. These fluctuations are not solely associated with change in temperature, but may also be related to grass root activity and to photosynthesis.  相似文献   

2.
Applying biochar to soil is an easy way to sequester carbon in soil, while it might reduce greenhouse gas (GHG) emissions and stimulate plant growth. The effect of charcoal application (0, 1.5, 3.0 and 4.5%) on GHG emission was studied in a wastewater sludge-amended arable soil (Typic Fragiudepts) cultivated with wheat (Triticum spp. L.) in a greenhouse. The application of charcoal at ≥1.5% reduced the CO2 emission rate significantly ≥37% compared to unamended soil (135.3 g CO2 ha−1 day−1) in the first two weeks, while the N2O emission rate decreased 44% when 4.5% charcoal was added (0.72 g N2O ha−1 day−1). The cumulative GHG emission over 45 days was 2% lower when 1.5% charcoal, 34% lower when 3.0% charcoal and 39% lower when 4.5% charcoal was applied to the sludge-amended soil cultivated with wheat. Wheat growth was inhibited in the charcoal-amended soil compared to the unamended soil, but not yields after 135 days. It was found that charcoal addition reduced the emissions of N2O and CO2, and the cumulative GHG emissions over 45 days, without altering wheat yield.  相似文献   

3.
Denitrification loss from a loam under a cut ryegrass sward receiving 0, 250 and 500 kg N ha?1 a?1 in four equal amounts was measured during 14 months using the acetylene-inhibition technique. The rate of denitrification responded rapidly to changes in soil water content as affected by rain. Mean rates of denitrification exceeded 0.2 kg N ha?1 day?1 only when the soil water content was >20% (w/w) and nitrate was >5μ N g?1 in the upper 20 cm of the profile and when soil temperature at 2 cm was >5–8°C. When the soil dried to a water content <20%, denitrification decreased to <0.05 kg N ha?1 day?1. Highest rates (up to 2.0 kg N ha?1 day?1) were observed following application of fertilizer to soil at a water content of about 30% (w/w) in early spring. Denitrification in the control plot during this period was generally about a hundredth of that in plots treated with ammonium nitrate. High rates of N2O loss (up to 0.30 kg N ha?1 day-1) were invariably associated with high rates of denitrification (> 0.2 kg N ha?1 day?1). However, within 2–3 weeks following application of fertilizer to the plot receiving 250 kg N ha?1 a?1 the soil acted as a sink for atmospheric N2O when its water content was >20% and its temperature >5–8°C. Annual N losses arising from denitrification were 1.6, 11.1 and 29.1 kg N ha?1 for the plots receiving 0, 250 and 500 kg N ha?1 a?1, respectively. More than 60% of the annual loss occurred during a period of 8 weeks when fertilizer was applied to soil with a water content >20%.  相似文献   

4.
The aim of our research was to obtain information on the isotopic fingerprint of nitrous oxide (N2O) associated with its production and consumption during denitrification. An arable soil was preincubated at high moisture content and subsequently amended with glucose (400 kg C ha?1) and KNO3 (80 kg N ha?1) and kept at 85% water‐filled pore space. Twelve replicate samples of the soil were incubated for 13 days under a helium‐oxygen atmosphere, simultaneously measuring gas fluxes (N2O, N2 and CO2) and isotope signatures (δ18O‐N2O, δ15Nbulk‐N2O, δ15Nα, δ15Nβ and 15N site preference) of emitted N2O. The maximum N2O flux (6.9 ± 1.8 kg N ha?1 day?1) occurred 3 days after amendment application, followed by the maximum N2 flux on day 4 (6.6 ± 3.0 kg N ha?1 day?1). The δ15Nbulk was initially ?34.4‰ and increased to +4.5‰ during the periods of maximum N2 flux, demonstrating fractionation during N2O reduction, and then decreased. The δ18O‐N2O also increased, peaking with the maximum N2 flux and remaining stable afterwards. The site preference (SP) decreased from the initial +7.5 to ?2.1‰ when the N2O flux peaked, and then simultaneously increased with the appearance of the N2 peak to +8.6‰ and remained stable thereafter, even when the O2 supply was removed. We suggest that this results from a non‐homogenous distribution of NO in the soil, possibly linked to the KNO3 amendments to the soil, causing the creation of several NO pools, which affected differently the isotopic signature of N2O and the N2O and N2 fluxes during the various stages of the process. The N2O isotopologue values reflected the temporal patterns observed in N2O and N2 fluxes. A concurrent increase in 15N site preference and δ18O of N2O was found to be indicative of N2O reduction to N2.  相似文献   

5.
The effects of the application of KNO3 and NH4Cl (100 kg N ha?1) on N2O release and CH4 uptake by a well-aerated topsoil (porosity: 55%, water-filled pore space: 67% of the total pore space) were studied in a laboratory incubation experiment over 50 days using a soil microcosm system with an automated registration of N2O and CH4 fluxes. The total N2O-N losses over 50 days were low for all treatments and amounted to 0.9 mg m?2 for the control, 1.2 mg m?2 for the soil columns fertilized with KNO3, and 7.3 mg m?2 for the soil columns fertilized with NH4Cl. The slightly elevated N2O release after the application Of NH4Cl was associated with the nitrification of NH4+ added. Only ?0.06% of the fertilized NH4?N was lost as N2O. This nitrogen fertilization reduced the CH4 uptake of the soil columns by 43% (NH4Cl) and 21% (KNO3), respectively.  相似文献   

6.
Nitrous oxide emission (N2O) from applied fertilizer across the different agricultural landscapes especially those of rainfed area is extremely variable (both spatially and temporally), thus posing the greatest challenge to researchers, modelers, and policy makers to accurately predict N2O emissions. Nitrous oxide emissions from a rainfed, maize-planted, black soil (Udic Mollisols) were monitored in the Harbin State Key Agroecological Experimental Station (Harbin, Heilongjiang Province, China). The four treatments were: a bare soil amended with no N (C0) or with 225?kg?N ha?1 (CN), and maize (Zea mays L.)-planted soils fertilized with no N (P0) or with 225?kg?N ha?1 (PN). Nitrous oxide emissions significantly (P?<?0.05) increased from 141?±?5?g N2O-N?ha?1 (C0) to 570?±?33?g N2O-N?ha?1 (CN) in unplanted soil, and from 209?±?29?g N2O-N?ha?1 (P0) to 884?±?45?g N2O-N?ha?1 (PN) in planted soil. Approximately 75?% of N2O emissions were from fertilizer N applied and the emission factor (EF) of applied fertilizer N as N2O in unplanted and planted soils was 0.19 and 0.30?%, respectively. The presence of maize crop significantly (P?<?0.05) increased the N2O emission by 55?% in the N-fertilized soil but not in the N-unfertilized soil. There was a significant (P?<?0.05) interaction effect of fertilization?×?maize on N2O emissions. Nitrous oxide fluxes were significantly affected by soil moisture and soil temperature (P?<?0.05), with the temperature sensitivity of 1.73–2.24, which together explained 62–76?% of seasonal variation in N2O fluxes. Our results demonstrated that N2O emissions from rainfed arable black soils in Northeast China primarily depended on the application of fertilizer N; however, the EF of fertilizer N as N2O was low, probably due to low precipitation and soil moisture.  相似文献   

7.
Nitrous oxide (N2O) emissions were measured by the closed chamber technique from five plots along a transect in a nitrogen‐fertilised grassland, together with soil water content, soil temperature and water table depth, to investigate the effect of water table depth on N2O emissions. N2O fluxes varied from <1 g N2O‐N ha?1 day?1 to peaks of around 500–1200 g N2O‐N ha?1 day?1 after N fertiliser applications. There was no significant difference in overall average water table depth between four of the five plots, but significant short‐term temporal variations in water table depth did occur. Rises in the water table were accompanied by exponential increases in N2O emissions, through the associated increases in the water‐filled pore space of the topsoil. Modelling predicted that if the water table could be managed such that it was kept to no less than 35 cm below the ground surface, fluxes during the growing season would be reduced by 50%, while lowering to 45 cm would reduce them by over 80%. The strong implication of these results is that draining grasslands, so that the water tables are only rarely nearer to the surface than 35 cm when N is available for denitrification, would substantially reduce N2O emissions.  相似文献   

8.
Concentrations of nitrous oxide (N2O) and oxygen were monitored over a 2-yr period in an imperfectly drained grassland soil receiving applications of N as cattle slurry or Ca(NO3)2. In both years N2O concentrations in the different treatments were in the order nitrate > slurry > control. Gaseous diffusion coefficients were determined in soil cores by a krypton-85 tracer method and used to calculate approximate N2O fluxes from the soil. Only 1–5 kg N ha?1 was lost as N2O after a single application of > 1200 kg N ha ?1 as slurry compared with 3–11 kg N ha ?1 lost after 100 kg was added as NO3?. Total gaseous losses (N2O+N2) could be expected to be higher in both cases.  相似文献   

9.
Application of crop residues and its biochar produced through slow pyrolysis can potentially increase carbon (C) sequestration in agricultural production systems. The impact of crop residue and its biochar addition on greenhouse gas emission rates and the associated changes of soil gross N transformation rates in agricultural soils are poorly understood. We evaluated the effect of wheat straw and its biochar applied to a Black Chernozemic soil planted to barley, two growing seasons or 15 months (at the full-bloom stage of barley in the second growing season) after their field application, on CO2 and N2O emission rates, soil inorganic N and soil gross N transformation rates in a laboratory incubation experiment. Gross N transformation rates were studied using the 15N isotope pool dilution method. The field experiment included four treatments: control, addition of wheat straw (30 t ha?1), addition of biochar pyrolyzed from wheat straw (20 t ha?1), and addition of wheat straw plus its biochar (30 t ha?1 wheat straw + 20 t ha?1 biochar). Fifteen months after their application, wheat straw and its biochar addition increased soil total organic C concentrations (p?=?0.039 and <0.001, respectively) but did not affect soil dissolved organic C, total N and NH4 +-N concentrations, and soil pH. Biochar addition increased soil NO3 ?-N concentrations (p?=?0.004). Soil CO2 and N2O emission rates were increased by 40 (p?p?=?0.03), respectively, after wheat straw addition, but were not affected by biochar application. Straw and its biochar addition did not affect gross and net N mineralization rates or net nitrification rates. However, biochar addition doubled gross nitrification rates relative to the control (p?2 and N2O emissions and enhance soil C sequestration. However, the implications of the increased soil gross nitrification rate and NO3 ?-N in the biochar addition treatment for long-term NO3 ?-N dynamics and N2O emissions need to be further studied.  相似文献   

10.
Nitrogen-fixing heterotrophic bacteria, mainly Clostridium butyricum and, less frequently, Enterobacter agglomerons and Klebsiella pneumoniae, are found throughout the aerial and soil layers of an oak forest. However they are only active in nitrogen fixation in the soil. Soil slurry experiments show that the main factors limiting N2 fixation in the forest are low temperature, low pH and shortage of C sources. Raising the pH of the soil with lime to pH 6, which is the optimum for N2 fixation by C. butyricum in soil slurries, more than doubles the rate of N2 fixation (as measured by in situ15N2 methods) from 7.84 to 16.1 kg N ha?1yr?1. The N fixed by C. butyricum can rapidly be taken up by oak seedlings and translocated to the actively-growing leaves.  相似文献   

11.
The objective of this work was to evaluate the effect of the chemical nature and application frequency of N fertilizers at different moisture contents on soil N2O emissions and N2O/(N2O+N2) ratio. The research was based on five fertilization treatments: unfertilized control, a single application of 80 kg ha−1 N-urea, five split applications of 16 kg ha−1 N-urea, a single application of 80 kg ha−1 N–KNO3, five split applications of 16 kg ha−1 N–KNO3. Cumulative N2O emissions for 22 days were unaffected by fertilization treatments at 32% water-filled pore space (WFPS). At 100% and 120% WFPS, cumulative N2O emissions were highest from soil fertilized with KNO3. The split application of N fertilizers decreased N2O emissions compared to a single initial application only when KNO3 was applied to a saturated soil, at 100% WFPS. Emissions of N2O were very low after the application of urea, similar to those found at unfertilized soil. Average N2O/(N2O+N2) ratio values were significantly affected by moisture levels (p = 0.015), being the lowest at 120% WFPS. The N2O/(N2O+N2) ratio averaged 0.2 in unfertilized soil and 0.5 in fertilized soil, although these differences were not statistically significant.  相似文献   

12.
In Sweden, 90% of ammonia (NH3) emissions to the atmosphere originate from agriculture, predominantly from animal manure handling. It is well known that incorporation of manure into soil can reduce NH3 emissions after spreading. However, there is a risk of increased nitrous oxide (N2O) and methane (CH4) emissions caused by bacterial activity and limited oxygen availability under these conditions. A full‐scale injector was developed and evaluated in a field experiment on grassland. Cattle slurry was either injected in closed slots 5 cm below ground or band spread on the soil surface above the crop canopy at a rate of 25 t ha?1. In a control treatment, no slurry was applied. During a 5‐day period after application, NH3 emissions were measured using an equilibrium concentration method. Gas samples for estimating CH4 and N2O emissions were also collected during 7 weeks following slurry application. Injection in closed slots resulted in no detectable NH3 emissions. After band spreading, however, NH3 emissions corresponded to nearly 40% of the total ammoniacal nitrogen in the applied slurry. The injection of slurry gave rise to a broad peak of N2O emissions during the first 3 weeks after application. In total, for the measuring period, N2O emissions corresponded to 0.75 kg N ha?1. Band spreading resulted in only a very small N2O release of about 0.2 kg N ha?1 during the same period. Except for the first sampling occasion, the soil was predominantly a sink for CH4 in all the treatments. The use of the injector without slurry application reduced grass yield during unfavourable growing conditions. In conclusion, shallow injection in closed slots seems to be a promising technique to reduce negative environmental impacts from NH3 emissions with a limited release of N2O and CH4.  相似文献   

13.
A field experiment was conducted to evaluate the combined or individual effects of biochar and nitrapyrin (a nitrification inhibitor) on N2O and NO emissions from a sandy loam soil cropped to maize. The study included nine treatments: addition of urea alone or combined with nitrapyrin to soils that had been amended with biochar at 0, 3, 6, and 12 t ha?1 in the preceding year, and a control without the addition of N fertilizer. Peaks in N2O and NO flux occurred simultaneously following fertilizer application and intense rainfall events, and the peak of NO flux was much higher than that of N2O following application of basal fertilizer. Mean emission ratios of NO/N2O ranged from 1.11 to 1.72, suggesting that N2O was primarily derived from nitrification. Cumulative N2O and NO emissions were 1.00 kg N2O-N ha?1 and 1.39 kg NO-N ha?1 in the N treatment, respectively, decreasing to 0.81–0.85 kg N2O-N ha?1 and 1.31–1.35 kg NO-N ha?1 in the biochar amended soils, respectively, while there was no significant difference among the treatments. NO emissions were significantly lower in the nitrapyrin treatments than in the N fertilization-alone treatments (P?<?0.05), but there was no effect on N2O emissions. Neither biochar nor nitrapyrin amendment affected maize yield or N uptake. Overall, our results showed that biochar amendment in the preceding year had little effect on N2O and NO emissions in the following year, while the nitrapyrin decreased NO, but not N2O emissions, probably due to suppression of denitrification caused by the low soil moisture content.  相似文献   

14.
Field management is expected to influence nitrous oxide (N2O) production from arable cropping systems through effects on soil physics and biology. Measurements of N2O flux were carried out on a weekly basis from April 2008 to August 2009 for a spring sown barley crop at Oak Park Research Centre, Carlow, Ireland. The soil was a free draining sandy loam typical of the majority of cereal growing land in Ireland. The aims of this study were to investigate the suitability of combining reduced tillage and a mustard cover crop (RT?CCC) to mitigate nitrous oxide emissions from arable soils and to validate the DeNitrification?CDeComposition (DNDC) model version (v. 9.2) for estimating N2O emissions. In addition, the model was used to simulate N2O emissions for two sets of future climate scenarios (period 2021?C2060). Field results showed that although the daily emissions were significantly higher for RT?CCC on two occasions (p?<?0.05), no significant effect (p?>?0.05) on the cumulative N2O flux, compared with the CT treatment, was found. DNDC was validated using N2O data collected from this study in combination with previously collected data and shown to be suitable for estimating N2O emissions (r 2?=?0.70), water-filled pore space (WFPS) (r 2?=?0.58) and soil temperature (r 2?=?0.87) from this field. The relative deviations of the simulated to the measured N2O values with the 140?kg N ha?1 fertiliser application rate were ?36?% for RT?CCC and ?19?% for CT. Root mean square error values were 0.014 and 0.007?kg N2O?CN ha?1 day?1, respectively, indicating a reasonable fit. Future cumulative N2O fluxes and total denitrification were predicted to increase under the RT?CCC management for all future climate projections, whilst predictions were inconsistent under the CT. Our study suggests that the use of RT?CCC as an alternative farm management system for spring barley, if the sole objective is to reduce N2O emissions, may not be successful.  相似文献   

15.
The DNDC (DeNitrification-DeComposition)-Rice model, one of the most advanced process-based models for the estimation of greenhouse gas emissions from paddy fields, has been discussed mostly in terms of the reproducibility of observed methane (CH4) emissions from Japanese rice paddies, but the model has not yet been validated for tropical rice paddies under alternate wetting and drying (AWD) irrigation management, a water-saving technique. We validated the model by using CH4 and nitrous oxide (N2O) flux data from rice in pots cultivated under AWD irrigation management in a screen-house at the International Rice Research Institute (Los Baños, the Philippines). After minor modification and adjustment of the model to the experimental irrigation conditions, we calculated grain yield and straw production. The observed mean daily CH4 fluxes from the continuous flooding (CF) and AWD pots were 4.49 and 1.22?kg?C?ha?1?day?1, respectively, and the observed mean daily N2O fluxes from the pots were 0.105 and 34.1?g?N?ha?1?day?1, respectively. The root-mean-square errors, indicators of simulation error, of daily CH4 fluxes from CF and AWD pots were calculated as 1.76 and 1.86?kg?C?ha?1?day?1, respectively, and those of daily N2O fluxes were 2.23 and 124?g?N?ha?1?day?1, respectively. The simulated gross CH4 emissions for CF and AWD from the puddling stage (2 days before transplanting) to harvest (97 days after transplanting) were 417 and 126?kg?C?ha?1, respectively; these values were 9.8% lower and 0.76% higher, respectively, than the observed values. The simulated gross N2O emissions during the same period were 0.0279 and 1.45?kg?N?ha?1 for CF and AWD, respectively; these values were respectively 87% and 29% lower than the observed values. The observed total global warming potential (GWP) of AWD resulting from the CH4 and N2O emissions was approximately one-third of that in the CF treatment. The simulated GWPs of both CF and AWD were close to the observed values despite the discrepancy in N2O emissions, because N2O emissions contributed much less than CH4 emissions to the total GWP. These results suggest that the DNDC-Rice model can be used to estimate CH4 emission and total GWP from tropical paddy fields under both CF and AWD conditions.  相似文献   

16.
The N2-ase activities of field-grown Brazilian grasses were measured with C2H2 reduction by soil cores containing the plants. C2H2 and C2H4 were observed to diffuse at similar rates through soil and equilibrated across the Brazilian soil in 3 h, but could take up to 30 h or more with some British soils. The diurnal fluctuation in the rates of N2-ase activity by Brachiaria mutica and Sorghum vulgare were similar and the variation in rate was correlated with soil temperature. Estimates of N2-fixation by measurement of C2H2 reduction by soil cores ranged from 14.7 to 51.4 g N ha?1 day?1 and were much lower than with “pre-incubated” excised roots from the cores or taken directly from the field. The merits of the soil core and the “pre-incubated” excised root assays are discussed. ft1|Present address: U.S. Department of Agriculture, Science and Education Administration, Agricultural Research, Northeastern Region, Room 309, Building 001, Beltsville, MD 20705, U.S.A.  相似文献   

17.
Two concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) 1.7 kg ha?1 and 3.4 kg ha?1 were applied to oats (Avena sativa L. ‘Orbit’) grown in terrestrial microcosms in a sandy soil. Carbon dioxide evolution and non-symbiotic N2 fixation (C2H2 reduction) were measured weekly. On day 70 of the study, 2,4-D was applied a second time at the same application rates and soil CO2 evolution and N2 fixation were measured more frequently. Soil CO2 evolution over 24 h period was significantly decreased by 40 to 50% at both application rates of 2,4-D. This response lasted less than 7 days. Nitrogen fixation was unaffected by 2,4-D except for an unexplained decrease observed in the 1.7 kg ha?1 treatment 35 days after 2,4-D application. This effect was not observed on the following sampling date. The second application of 2,4-D failed to produce any significant change in soil CO2 evolution or N2 fixation. From these studies we conclude soil microbial populations either degraded or became acclimated to 2,4-D as a result of the initial application and that 2,4-D has no significant adverse effect on N2 fixation or soil CO2 evolution.  相似文献   

18.
Denitrification losses from a horticultural soil as affected by mineral N-fertilization To investigate denitrification in the Ap-horizon from a horticultural cambisol as affected by mineral N-fertilization, measurements of N2O-release from the soil surface and N2O-production in the upper 10 cm soil layer were carried out. The acetylene inhibition technique was used. The loamy sand was amended with 86 and 186 kg N·ha?1 (ammonium nitratecalcium carbonate mixture). The field was cropped with celeriac (Apium graveolens L. var. rapaceum). Denitrification rates as well as soil temperature, moisture, nitrate and watersoluble carbon were measured from mid July until the end of October. In both N treatments denitrification rates were low, but higher rates could be measured in the higher N-treatment. They reached amounts of 0.6 to 134.3 g N2O-N·ha?1day?1. Estimated N-loss by denitrification totalled about 3.5 in the low and 4.9 kg N·ha?1 in the high N-treatment for the whole sampling period (107 days). Spatial variability of denitrification rates was high (39–283%). The relationship between soil temperature, moisture, nitrate content as well as watersoluble carbon and denitrification rate was shown by regression analysis.  相似文献   

19.
The effect of organic amendments and irrigation management in the field were studied with respect to Eh, NO3?, and soluble organic C concentrations in the soil solution, and gaseous concentrations of N2O, CO2, and the ratio N2 to O2. Duplicate plots were treated with fresh bovine manure as follows: control 45t·ha?1, 180 t·ha?1 with a standard irrigation cycle (SI), and 180 t·ha?1 with a double irrigation (DI). Samples to 230cm were obtained at several depths in each profile during the 84-day study. The general order for treatment effects upon CO2 concentrations and soluble C was the same: SI > DI > 45 t·ha?1 > control. The order for N2/O2 was 180 t·ha?1 (SI and DI) > 45 t·ha?1 and control. The order for both N2O and NO?1 was the same: 45 t.ha?1 and DI > SI and control. The most important factor affecting N2O concentrations was the NO3? concentration; soil solution concentrations greater than 16 μN·ml?1 had much higher frequencies of high N2O concentrations. The sequential reduction of NO?13→ N2O → N2 was noted in all treatments by the following observations: (i) the concentrations of both NO?3 and N2O were highest at the beginning of the experiment; (ii) the concentrations of CO2 and N2/O2 were higher near the end: (iii) sub-ambient concentrations of N2O were more frequent near the end of the study. Use of N2O as an indicator of denitrification is cautioned since one of the highest manured treatments (SI) had N2O concentrations no different than the control, but had much higher CO2 and N2/O2 concentrations and more reduced (Eh) conditions. We conclude that use of a single irrigation method is far superior to the double irrigation method with respect to reducing losses of NO3? and N2O and for conserving organic N arid water.  相似文献   

20.
 N2O emissions were periodically measured using the static chamber method over a 1-year period in a cultivated field subjected to different agricultural practices including the type of N fertilizer (NH4NO3, (NH4)2SO4, CO(NH2)2 or KNO3 and the type of crop (rapeseed and winter wheat). N2O emissions exhibited the same seasonal pattern whatever the treatment, with emissions between 1.5 and 15 g N ha–1 day–1 during the autumn, 16–56 g N ha–1 day–1 in winter after a lengthy period of freezing, 0.5–70 g N ha–1 day–1 during the spring and lower emissions during the summer. The type of crop had little impact on the level of N2O emission. These emissions were a little higher under wheat during the autumn in relation to an higher soil NO3 – content, but the level of emissions was similar over a 7-month period (2163 and 2093 g N ha–1 for rape and wheat, respectively). The form of N fertilizer affected N2O emissions during the month following fertilizer application, with higher emissions in the case of NH4NO3 and (NH4)2SO4, and a different temporal pattern of emissions after CO(NH2)2 application. The proportion of applied N lost as N2O varied from 0.42% to 0.55% with the form of N applied, suggesting that controlling this agricultural factor would not be an efficient way of limiting N2O emissions under certain climatic and pedological situations. Received: 1 December 1997  相似文献   

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