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1.
T. Mahmood R. Ali M. I. Sajjad M. B. Chaudhri G. R. Tahir F. Azam 《Biology and Fertility of Soils》2000,31(3-4):270-278
In a 2-year field study, denitrification loss was measured from an irrigated sandy-clay loam under cotton receiving urea-N
at 158–173 kg ha–1. An acetylene inhibition-soil core method was employed for the direct measurement of denitrification, considering also the
N2O entrapped in the soil. Taking into account the N2O evolved from soil cores and that entrapped in the soil, a total of 65.7 kg N ha–1 and 64.4 kg N ha–1 was lost due to denitrification during the 1995 and 1996 cotton-growing seasons, respectively. Most (>70%) of the denitrification
loss occurred during June–August, a period characterized by high soil temperatures and heavy monsoon rains. On average, 35%
of the denitrification-N2O was found entrapped in the soil and the amount of entrapped N2O was significantly correlated with head space N2O concentration and with water-filled pore space. 15N-balance during the 1996 growing season revealed a loss of 71.8 kg N ha–1. It was concluded that a substantial proportion of the fertilizer-N applied to irrigated cotton is lost under the semiarid
subtropical climatic conditions prevailing in the Central Punjab region of Pakistan and that denitrification is the major
N loss process under irrigated cotton in this region.
Received: 8 March 1999 相似文献
2.
Nitrous oxide (N2O) emissions via the nitrification (I
nit) and denitrification (I
den) pathways were successfully measured with in-field incubation of soil cores in preserving jars at 0 Pa and 5–10 Pa acetylene.
From the incubations, fractions of nitrification – N2O over total N2O (I
nit / I
tot) – and denitrification – N2O over total N2O (I
den / I
tot) – were obtained. Actual field emissions of N2O via nitrification (F
nit) and denitrification (F
den) were calculated by multiplying the fractions from the incubation technique with the daily N2O emission (F
day) determined with a direct soil cover method. The approach presented here was successful for a whole range of soil moisture
conditions in intensive grassland. F
nit and F
den followed the trends of soil ammonium and soil nitrate.
Received: 31 October 1997 相似文献
3.
Denitrification measurements by means of the acetylene inhibition method require a continuous presence of acetylene to block the microbial reduction of N20 to N2. To examine the effect of such steady exposures on the growth of plants, roots of cucumber and tomato seedlings were treated with different acetylene concentrations. Acetylene concentrations of 1 vol% in the gas phase, which were necessary for complete inhibition of N2 formation, led to a significant retardation of root growth. This was partly due to trace amounts of ethylene contained in the acetylene gas which could not be removed with the usual prescrubbing through a sulfuric acid train. As a result of the growth impairment, oxygen consumption in the root zone decreased after 4 days of exposure. In order to avoid these side effects, the denitrification measurements in soilless cultures were performed on individual plants over a limited period of 2–3 days. The flow-through chamber method proved to be suitable for determining the gaseous N losses in a closed-loop system. It avoided greater air variations from the environmental conditions (substrate temperature, airflow and plant composition) and excluded errors in measurement caused by injury to roots and spatial variability of denitrification activity in the root medium. For exact estimation of the gaseous N losses, preceding 24-h acetylene fumigation was necessary. Subsequently at least three gas samples had to be taken throughout the day, because the N2O+N2 emissions were subject to a pronounced diurnal variability. 相似文献
4.
Nitrous oxide emissions from an irrigated sandy-clay loam cropped to maize and wheat 总被引:4,自引:0,他引:4
Nitrous oxide (N2O) emissions were measured from an irrigated sandy-clay loam cropped to maize and wheat, each receiving urea at 100 kg N ha–1. During the maize season (24 August–26 October), N2O emissions ranged between –0.94 and 1.53 g N ha–1 h–1 with peaks during different irrigation cycles (four) ranging between 0.08 and 1.53 g N ha–1 h–1. N2O sink activity during the maize season was recorded on 10 of the 29 sampling occasions and ranged between 0.18 and 0.94 g
N ha–1 h–1. N2O emissions during the wheat season (22 November–20 April) varied between –0.85 and 3.27 g N ha–1 h–1, whereas peaks during different irrigation cycles (six) were in the range of 0.05–3.27 g N ha–1 h–1. N2O sink activity was recorded on 14 of the 41 samplings during the wheat season and ranged between 0.01 and 0.87 g N ha–1 h–1. Total N2O emissions were 0.16 and 0.49 kg N ha–1, whereas the total N2O sink activity was 0.04 and 0.06 kg N ha–1 during the maize and wheat seasons, respectively. N2O emissions under maize were significantly correlated with denitrification rate and soil NO3
–-N but not with soil NH4
+-N or soil temperature. Under wheat, however, N2O emissions showed a strong correlation with soil NH4
+-N, soil NO3
–-N and soil temperature but not with the denitrification rate. Under either crop, N2O emissions did not show a significant relationship with water-filled pore space or soil respiration.
Received: 11 June 1997 相似文献
5.
A method of selective inhibition to distinguish between nitrification and denitrification as sources of nitrous oxide in soil 总被引:4,自引:0,他引:4
Summary Nitrapyrin and C2H2 were evaluated as nitrification inhibitors in soil to determine the relative contributions of denitrification and nitrification to total N2O production. In laboratory experiments nitrapyrin, or its solvent xylene, stimulated denitrification directly or indirectly and was therefore considered unsuitable. Low partial pressures of C2H2 (2.5–5.0 Pa) inhibited nitrification and had only a small effect on denitrification, which made it possible to estimate the contribution of denitrification. The contribution of nitrification was estimated by subtracting the denitrification value from total N2O production (samples without C2H2). The critical C2H2 concentrations needed to achieve inhibition of nitrification, without affecting the N2O reductase in denitrifiers, must be individually determined for each set of experimental conditions. 相似文献
6.
Nitrous oxide emissions from a fallow and wheat field as affected by increased soil temperatures 总被引:8,自引:0,他引:8
T. Kamp H. Steindl R. E. Hantschel F. Beese J.-C. Munch 《Biology and Fertility of Soils》1998,27(3):307-314
In order to determine the effects of increased soil temperature resulting from global warming on microbiological reactions,
a 21-month field experiment was carried out in the Bavarian tertiary hills. The major objective was to focus on N2O releases as either a positive or negative feedback in response to global warming. The soils of a fallow field and a wheat
field were heated 3 °C above ambient temperature and N2O fluxes were measured weekly from June 1994 to March 1996. During the experimental period, measured temperature differences
between the control plots and the heated plots were 2.9±0.3 °C at a depth of 0.01 m and 1.0–1.8 °C at a depth of 1 m. Soil
moisture decreased with the elevated soil temperatures of the heated plots. The mean differences in soil moisture between
the treatments were 6.4% (fallow field) and 5.2%DW (wheat field dry weight, DW), respectively. Overall N2O releases during the experimental period from the fallow field were 4.8 kg N2O–N ha–1 in the control plot against 5.0 kg N2O–N ha–1 in the heated plot, and releases from the wheat field were 8.0 N2O–N ha–1 in the control plot and 7.6 N2O–N kg ha–1 in the heated plot. However, on a seasonal basis, cumulated N2O emissions differed between the plots. During the summer months (May–October), releases from the heated fallow plot were
3 times the rates from the control plot. In the winter months, N2O releases increased in both the fallow and wheat fields and were related to the number of freezing and thawing cycles.
Received: 1 December 1997 相似文献
7.
The NO turnover in soils was measured in two different experimental set-ups, a flow-through system, which is very time-consuming
and needs rather sophisticated equipment, and a closed system using serum bottles. We compared the NO turnover parameters
(NO consumption rate constant, NO production rate, NO compensation concentration) that were measured with both systems in
different soils, under different conditions and in the presence of 10 Pa acetylene to inhibit nitrification. The values of
the NO turnover parameters that were measured with the two systems under oxic conditions were usually comparable. The addition
of acetylene did not affect the NO consumption rate constants of the soils with the exception of soil G1. However, the NO
production rates and the NO compensation concentrations decreased significantly in the presence of acetylene, indicating that
nitrification was the main source of NO in these soils. Only one soil (Bol) showed no nitrifying activity. Increasing soil
moisture content resulted in decreasing NO consumption rate constants and NO production rates. Even at a high soil moisture
content of 80% water holding capacity, nitrification was the main source of NO. The values of the NO turnover parameters that
were measured with the two systems were not comparable under anoxic conditions. The NO consumption rate constants and the
NO production rates were much lower in the closed than in the flow-through system, indicating that the NO consumption activity
became saturated by the high NO concentrations accumulating in the closed system. Under oxic conditions, however, closed serum
bottles were a cheap, easy and reliable tool with which to determine NO turnover parameters and to distinguish between nitrification
and denitrification as sources of NO.
Received: 21 April 1998 相似文献
8.
Estimation of simultaneous nitrification and denitrification in grassland soil associated with urea-N using 15N and nitrification inhibitor 总被引:1,自引:0,他引:1
A low efficiency of use of N fertilisers has been observed in mid-Wales on permanent pasture grazed intensively by cattle.
Earlier laboratories studies have suggested that heterogeneity in redox conditions at shallow soil depths may allow nitrification
and denitrification to occur concurrently resulting in gaseous losses of N from both NH4
+ and NO3
–. The objective of the investigation was to test the hypothesis that both nitrification and denitrification can occur simultaneously
under simulated field capacity conditions (∼5 kPa matric potential). Intact soil cores were taken from grassland subjected
to both grazing and amenity use. The fate of applied NH4
+ was examined during incubation. 15N was used as a tracer. Nitrapyrin was used as a nitrification inhibitor and acetylene was used to block N2O reductase. More than 50% of N applied as NH4
+ disappeared over a period of 42 days from the soil mineral-N pool. Some of this N was evolved as N2O. Accumulation of NO3
––N in the surface 0–2.5 cm indicated active nitrification. Addition of nitrapyrin increased N recovery by 26% and inhibited
both the accumulation of NO3–N and emission of N2O. When intact field cores were incubated after addition of 15N-urea, all of the N2O evolved was derived from added urea-N. It was concluded that nitrification and denitrification do occur simultaneously in
the top 7.5 cm or so, of the silty clay loam grassland topsoils of mid-Wales at moisture contents typical of field capacity.
The quantitative importance of these concurrent processes to N loss from grassland systems has not yet been assessed.
Received: 15 December 1998 相似文献
9.
In a field experiment, the effect of animal slurry, (with and without the nitrification inhibitor dicyandiamide on total denitrification losses estimated by the C2H2 inhibition technique was measured over 2 years (1989–1990). During this period, four different plots (each with four replicates) were fertilized six times with 150 kg N ha-1 in the form of cattle-pig slurry or NH4NO3. Soil samples (0–20 cm) were analysed at regular intervals for NH
inf4
sup+
and NO
inf3
sup–
concentrations. The soil water content was determined gravimetrically. During the first year (1989) total denitrification losses from unfertilized, mineral-fertilized, and animal slurry-amended plots (with or without dicyandiamide) were estimated as 0.2, 3.1, 0.7, and 0.6 kg N ha-1, respectively. During the second year (1990) the denitrification losses were 0.4, 1.3, 0.7, and 0.7 kg N ha-1, respectively. There was a clear relationship between the NO
inf3
sup–
concentration or soil water content and the denitrification rate. The results are siteund experiment-specific and cannot be generalized so far. 相似文献
10.
Our objective was to assess the effect of anaerobic conditioning in the presence of acetylene on subsequent aerobic respiration and N2O emission at the scale of soil aggregates. Nitrous oxide production was measured in intact soil aggregates Δ (compacted aggregates without visible porosity) and Γ (aggregates with visible porosity) incubated under oxic conditions, with or without anaerobic conditioning for 6 d. N2O emissions were much higher in aggregates that had been submitted to anaerobic conditioning than in aggregates that did not experience this conditioning, although very little NO3− remained in soil after the anaerobic period. 15N isotope tracing technique was used to check whether N2O came from nitrification or denitrification. The results showed that denitrification was the major process responsible for N2O emissions. The aerobic CO2 production rate was also measured in intact soil aggregates. It was greater in aggregates submitted to anaerobic conditioning than in those that were not, suggesting that the anaerobic conditioning lead to an accumulation of small compounds including fatty acids that are readily available for microbial decomposition in aerobic conditions. This process increases the aerobic CO2 production and favours the N2O emissions through denitrification. 相似文献
11.
There has been concern that the measurement of gas emissions from a soil surface may not accurately reflect gas production
within the soil profile. But, there have been few direct assessments of the error associated with the use of surface emissions
for estimating gas production within soil profiles at different water contents. To determine the influence of air porosity
on the distribution of gases within soil profiles, denitrification assays were performed using soil columns incubated with
different water contents to provide air porosities of 18%, 13%, and 0% (equivalent to 62%, 73%, and 100% water-filled pore
space, respectively). The soil columns were formed by packing sieved soil into cylinders which could be sealed at the top
to form a headspace for the measurement of surface emissions of soil gases. Gas-permeable silicone tubing was placed at three
depths (4.5, 9, and 13.5 cm) within each soil core to permit the measurement of gas concentration gradients within the soil
core. Assays for denitrification were initiated by the addition of acetylene (5 kPa) to the soil column, and gas samples were
taken from both the headspace and gas-permeable tubing at various times during a 46-h incubation. The results showed that
at 18% air porosity, the headspace gases were well equilibrated with pore-space gases, and that gas emissions from the soil
could provide good estimates of N2O and CO2 production. At air porosities of 13% and 0%, however, substantial storage of these gases occurred within the soil profiles,
and measurements of surface emissions of gas from the soils greatly underestimated gas production. For example, the sole use
of N2O emission measurements caused three to five fold underestimates of N2O production in soil maintained at 13% air porosity. It was concluded that the confounding influence of soil moisture on gas
production and transport in soil greatly limits the use of surface emissions as a reliable indicator of gas production. This
is particularly pertinent when assessing processes such as denitrification in which N gas production is greatly promoted by
the conditions that limit O2 influx and concurrently limit N gas efflux.
Received: 15 January 1999 相似文献
12.
We evaluated a new method to measure in situ denitrification under field conditions in a number of water-saturated subsoils that had a broad range of biogeochemical properties. A test solution containing 15NO3− and/or C2H2 was introduced to the subsoil and the subsequent production of dissolved denitrification products was measured to quantify denitrification activity. The method showed a clear production of denitrification products over time. Results were compared to laboratory-based measurements from the same soil incubated as anaerobic slurries with added 15NO3−. Rates of denitrification with the in situ and the laboratory methods ranged from 1-2800 and 1-1700 μg N kg−1 d−1, respectively. Generally the methods gave good agreement and we consider both to be valid. However, there were some significant deviations, which we attribute to spatial heterogeneity and laboratory effects. Because the laboratory method is so much easier to perform, we suggest it should be the preferred method for large-scale studies of denitrification from the soil types we investigated. However, the two methods showed poor agreement in determining the proportion of N2O in the total denitrification output. This was because this proportion is subject to delicate and complex control. We conclude that neither method was suitable for quantifying N2O emission from the denitrification measurements. 相似文献
13.
Acetylene, dimethyl ether (DME) and 2-chloro-6-trichloromethyl pyridine (nitrapyrin) were used as inhibitors to study the
contributions of nitrification and denitrification to the production of N2O and nitric oxide (NO) in samples taken from the soil profile of a peatland drained for forestry. Acetylene and DME inhibited
60–100% of the nitrification activity in field-moist samples from the 0–5 cm and 5–10 cm peat layers, whereas nitrapyrin had
no inhibitory effect. In the 0–5 cm peat layer the N2O production could be reduced by up to 90% with inhibitors of nitrification, but in the 5–10 cm peat layer this proportion
was 20–30%. All the inhibitors removed 96–100% of the nitrification potential in peat-water slurries from the 0–5 cm peat
layer, but the 5–10 cm layer had a much lower nitrification activity, and here the efficiency of the inhibitors was more variable.
Litter was the main net source of NO in the peat profile. NO3
– production was lower in the litter layer than in the peat, whereas N2O production was much higher in the litter than in the peat. Denitrification was the most probable source of N2O and NO in the litter, which had a high availability of organic substrates.
Received: 14 July 1997 相似文献
14.
P. Laville S. LehugerB. Loubet F. ChaumartinP. Cellier 《Agricultural and Forest Meteorology》2011,151(2):228-240
Quantifying the nitrous oxide (N2O) and nitric oxide (NO) fluxes emitted from croplands remains a major challenge. Field measurements in different climates, soil and agricultural conditions are still scarce and emissions are generally assessed from a small number of measurements. In this study, we report continuously measured N2O and NO fluxes with a high temporal resolution over a 2-year crop sequence of barley and maize in northern France. Measurements were carried out using 6 automatic chambers at a rate of 16 mean flux measurements per day. Additional laboratory measurements on soil cores were conducted to study the response of NO and N2O emissions to environmental conditions.The detection limit of the chamber setup was found to be 3 ng N m−2 s−1 for N2O and 0.1 ng N m−2 s−1 for NO. Nitrous oxide fluxes were higher than the threshold 37% of the time, while they were 72% of the time for NO fluxes.The cumulated annual NO and N2O emissions were 1.7 kg N2O-N ha−1 and 0.5 kg NO-N ha−1 in 2007, but 2.9 kg N2O-N ha−1 and 0.7 kg NO-N ha−1 in 2008. These inter-annual differences were largely related to crop types and to their respective management practices. The forms, amounts and timing of nitrogen applications and the mineralization of organic matter by incorporation of crop residues were found to be the main factor controlling the emissions peaks. The inter-annual variability was also due to different weather conditions encountered in 2007 and 2008. In 2007, the fractioned N inputs applied on barley (54 kg ha−1 in March and in April) did not generate N2O emissions peaks because of the low rainfall during the spring. However, the significant rainfall observed in the summer and fall of 2007, promoted rapid decomposition of barley residues which caused high levels of N2O emissions. In 2008, the application of dairy cattle slurry and mineral fertilizer before the emergence of maize (107 kg Nmin ha−1 or 130 kg Ntot ha−1 in all) coincided with large rainfalls promoting both NO and N2O emissions, which remained high until early summer.Laboratory measurements corroborated the field observations: NO fluxes were maximum at a water-filled pore space (WFPS) of around 27% while N2O fluxes were optimal at 68% WFPS, with a maximum potentially 14 times larger than for NO. 相似文献
15.
T.J. van der Weerden R. R. Sherlock P. H. Williams K. C. Cameron 《Biology and Fertility of Soils》2000,31(3-4):334-342
N2O emissions were measured from three contrasting onion (Allium cepa L.) production systems over an 8.5-month period. One system was established on soil where a clover sward had 3 months earlier
been ploughed in (ploughed clover site). This production system followed conventional production management practices. The
other two systems were established on soil where a mixed herb ley had 3 months earlier been either ploughed or rotovated.
These last two production systems followed the guidelines of the International Federation of Organic Agriculture Movements
(IFOAM). Cumulative N2O emissions were significantly greater from the ploughed clover site compared to the ploughed ley site (3.8 and 1.6 kg N2O-N ha–1, respectively), while cumulative N2O emissions from the ploughed ley and rotovated ley sites were not significantly different from each other. Emissions from
all sites were dominated by episodes of high N2O flux activity following seedbed preparation and drilling, when soil water suction (SWS) was shown to be the rate-controlling
variable. The decline in the N2O fluxes after these peak emissions followed clear exponential relationships of the form F=Ae–
kt
(r≥0.91), where F is the daily flux and A is the y-intercept. First-order decay constants (k) during these periods of declining N2O fluxes (corresponding to half-lives of 2.6–3.0 days) were not significantly different in magnitude from the first-order
rate constants that characterised the increasing SWS. Gross differences in cumulative emissions between the clover and ley
sites were attributed to the influence of differing soil pHs at the two sites on the N2O:(N2O+N2) ratio in the denitrification products. It also appeared that fertiliser applications to the clover site had both direct
and indirect effects on N2O emissions by: (1) enhancing N2O emissions via potential nitrification, (2) increasing the NO3
– supply for enhanced N2O emissions via denitrification, and (3) influencing the N2O:(N2O+N2) ratio by lowering soil pH and increasing NO3
– concentrations. Onion crop yields were greater at the clover site, mainly due to the higher density of planting made possible
under a conventional production philosophy. Expressing the yield on the basis of net N2O emissions, 23 t onions kg–1 N2O-N was obtained from the ploughed clover, which was double that obtained for the two systems based on the ley site. However,
when the N2O emissions from the cultivation of the soils prior to the sowing of the onions was included, all three systems produced a
similar yield per kilogram of N2O-N emitted, averaging 10 t kg–1.
Received: 6 January 1999 相似文献
16.
Summary In model experiments with a silty loam soil the effect of different C : NO
inf3
sup-
-N ratios on the reliability of C2H2 (1% v/v) in blocking N2O-reductase activity was examined. The soil was carefully mixed with different amounts of powdered lime leaves (Tilia vulgaris) to obtain organic C contents of about 1.8, 2.3, and 2.8%, and of NO
inf3
sup-
solution to give C : NO
inf3
sup-
-N ratios of 84, 107, 130, 156, 200, and 243. The soil samples were incubated in specially modified anaerobic jars (22 days, 25°C, 80% water-holding capacity, He atmosphere) and the atmosphere was analysed for N2, N2O, CO2, and C2H2 by gas chromatography at regular intervals. Destruction jars were used to analyse soil NO
inf3
sup-
, NH
4
+
and C. The results clearly showed that N2O-reductase activity was completely blocked by 1% (v/v) C2H2 only as long as NO
inf3
sup-
was present. In the presence of C2H2, NO
inf3
sup-
was apparently entirely converted into N2O. The C2H2 blockage of N2O-reductase activity ceased earlier in soils with a wide C : NO
inf3
sup-
-N ratio (156, 200, and 243) than in those with closer C : NO
inf3
sup-
-N ratios (84, 107, and 130). As soon as NO
inf3
sup-
was exhausted, N2O was reduced to N2 in spite of C2H2. The wider the C : NO
inf3
sup-
-N ratio, the earlier the production of N2 and the less the reliability of the C2H2 blockage. In the untreated control complete inhibition of N2O-reductase activity by C2H2 lasted for 7–12 days. In the field, estimates of total denitrification losses by the C2H2 inhibition technique should be considered reliable only as long as NO
inf3
sup-
is present. Consequently, NO
inf3
sup-
monitoring in the field is essential, particularly in soils supplied with easily decomposable organic matter. 相似文献
17.
Soils are a major source of atmospheric NO and N2O. Since the soil properties that regulate the production and consumption of NO and N2O are still largely unknown, we studied N trace gas turnover by nitrification and denitrification in 20 soils as a function
of various soil variables. Since fertilizer treatment, temperature and moisture are already known to affect N trace gas turnover,
we avoided the masking effect of these soil variables by conducting the experiments in non-fertilized soils at constant temperature
and moisture. In all soils nitrification was the dominant process of NO production, and in 50% of the soils nitrification
was also the dominant process of N2O production. Factor analysis extracted three factors which together explained 71% of the variance and identified three different
soil groups. Group I contained acidic soils, which showed only low rates of microbial respiration and low contents of total
and inorganic nitrogen. Group II mainly contained acidic forest soils, which showed relatively high respiration rates and
high contents of total N and NH4
+. Group III mainly contained neutral agricultural soils with high potential rates of nitrification. The soils of group I produced
the lowest amounts of NO and N2O. The results of linear multiple regression conducted separately for each soil group explained between 44–100% of the variance.
The soil variables that regulated consumption of NO, total production of NO and N2O, and production of NO and N2O by either nitrification or denitrification differed among the different soil groups. The soil pH, the contents of NH4
+, NO2
– and NO3
–, the texture, and the rates of microbial respiration and nitrification were among the important variables.
Received: 28 October 1999 相似文献
18.
Comparison of different methodologies for field measurement of net nitrogen mineralization in pasture soils under different soil conditions 总被引:3,自引:0,他引:3
D. J. Hatch A. Bhogal R. D. Lovell M. A. Shepherd S. C. Jarvis 《Biology and Fertility of Soils》2000,32(4):287-293
Net mineralization was measured in free-draining and poorly drained pasture soils using three different field incubation
methodologies. Two involved the use of enclosed incubation vessels (jar or box) containing C2H2 as a nitrification inhibitor. The third method confined soil cores in situ in an open tube in the ground, with an anion-exchange
resin at the base to retain leached NO3
– (resin-core technique, RCT). Measurements were made on three occasions on three free-draining pastures of different ages
and contrasting organic matter contents. In general, rates of net mineralization increased with pasture age and organic matter
content (range: 0.5–1.5 kg N ha–1 day–1) and similar rates were obtained between the three techniques for a particular pasture. Coefficients of variation (CVs) were
generally high (range: 10.4–98.5%), but the enclosed incubation methods were rather less variable than the RCT and were considered
overall to be the more reliable. The RCT did not include C2H2 and, therefore, newly formed NO3
– may have been lost through denitrification. In a poorly drained pasture soil, there were discrepancies between the two enclosed
methods, especially when the soil water content approached field capacity. The interpretation of the incubation measurements
in relation to the flux of N through the soil inorganic N pool is discussed and the drawbacks of the various methodologies
are evaluated.
Received: 18 November 1999 相似文献
19.
Nitrous oxide emission from wetland rice soil as affected by the application of controlled-availability fertilizers and mid-season aeration 总被引:5,自引:0,他引:5
N2O emission from a wetland rice soil as affected by the application of three controlled-availability fertilizers (CAFs) and
urea was investigated through a pot experiment. N2O fluxes from the N fertilized paddy soil averaged 44.8–69.3 μg N m–2 h–1 during the rice growing season, accounting for 0.28–0.51% of the applied N. The emission primarily occurred during the mid-season
aeration (MSA) and the subsequent re-flooding period. Fluxes were highly correlated with the NO3
– and N2O concentrations in the soil water. As there were relatively large amounts of NH4
+-N present in the soil of the CAF treatments at the beginning of MSA, leading to large amounts of NO3
–-N during the MSA and the subsequent re-flooding period, the tested CAFs were not effective in reducing N2O emission from this paddy soil. The potential of applied CAFs to reduce N2O emissions from paddy soil is discussed.
Received: 25 May 1999 相似文献
20.
The use of zootechnical slurries in agriculture can increase N losses as N2O by direct emission and by denitrification. The aim of this research was to determine the influence of pig slurry, as well
as its combination with mineral N, on N2O emissions in the field and their relationships with some fractions of soil organic matter, with soil moisture and with rainfall.
In spite of varying amounts of organic substance applied, the diverse agronomic treatments did not produce substantial differences
in N losses due to denitrification. Wide variations between the slurry fertilized and the urea-fertilized plots were not found,
whereas the combination of pig slurry with urea usually produced an increase both in N2O emissions due to denitrification and in direct N2O emissions (N losses corresponding to about 50% of those due to denitrification). The greatest losses of N2O-N occurred in the first month following fertilizer administration. N2O emissions due to denitrification were highest in the days immediately following the administration of fertilizers and lowest
in a later period. N2O emissions due to nitrification occurred later. Therefore, N2O emission via nitrification differed from N2O losses via denitrification which, under optimal conditions, presented peaks of activity during the whole growth cycle. The
N2O-N losses were highly influenced by physical parameters, particularly rain. An increase in micropore water creates conditions
of scarce oxygenation or of anaerobiosis which influence oxidation-reduction processes and, at the same time, can limit the
diffusion of bacteria-produced gas towards the soil surface.
Received: 14 January 1998 相似文献