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1.
Crop residues and fertilizer nitrogen influence residue decomposition and nitrous oxide emission from a Vertisol 总被引:2,自引:0,他引:2
Wisal Muhammad Sarah M. Vaughan Ram C. Dalal Neal W. Menzies 《Biology and Fertility of Soils》2011,47(1):15-23
Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching,
denitrification, and nitrous oxide (N2O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content
55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral
N addition, on N mineralization–immobilization and N2O emission. Residues were added at the rate of 3 t C ha−1 to soil with, and without, 150 kg urea N ha−1. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of
soil N. Amended soil had significantly (P < 0.05) lower NO3−–N, which reached minimum values of 2.8 mg N kg−1 for sugarcane (at day 28), 10.3 mg N kg−1 for maize (day 7), and 5.9 mg N kg−1 for sorghum (day 7), compared to 22.7 mg N kg−1 for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased
by 45 mg N kg−1 in sugarcane, 34 mg kg−1 in maize, 29 mg kg−1 in sorghum, and 16 mg kg−1 in cotton amended soil compared to soil + N fertilizer, although soil NO3−–N increased by 7 mg kg−1 in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum
emissions of N2O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the
cumulative N2O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N2O emission was significantly and positively correlated with NO3−–N (r = 0.92, P < 0.01) and total mineral N (r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO2 in the first 3 and 5 days of incubation (r = 0.59, P < 0.05). 相似文献
2.
Ignacio A. Ciampitti Esteban A. Ciarlo Marta E. Conti 《Biology and Fertility of Soils》2008,44(4):581-588
The purpose of this study was to evaluate, during the phenological stages of inoculated soybean crop [Glycine max (L.) Merrill], the effect of different N fertilization levels and inoculation with Bradyrhizobium japonicum on N2O emissions from the soil. Gas emissions were evaluated at field conditions by the static-chamber method. Nitrogen fertilization
increased N2O emissions significantly (P < 0.05). The variable that best explained cumulative N2O emissions during the whole soybean growing season was the soil nitrate level (r
2 = 0.1899; P = 0.0231). Soil moisture presented a greater control on N2O emissions between the grain-filling period and the crop commercial maturity (r
2 = 0.5361; P < 0.0001), which coincided with a positive balance of the available soil N, as a consequence of the decrease in crop requirements
and root and nodular decomposition. Only soil soluble carbon (r
2 = 0.29; P = 0.019) and moisture (r
2 = 0.24; P = 0.039) were correlated with N2O emissions during the residue decomposition period. The relationship between soil variables and N2O emissions depended on crop phenological or stubbles decomposition stages. 相似文献
3.
Mohammad Mofizur Rahman Jahangir Dries Roobroeck Oswald Van Cleemput Pascal Boeckx 《Biology and Fertility of Soils》2011,47(7):753-766
Nitrous oxide (N2O) emissions, soil microbial community structure, bulk density, total pore volume, total C and N, aggregate mean weight diameter
and stability index were determined in arable soils under three different types of tillage: reduced tillage (RT), no tillage
(NT) and conventional tillage (CT). Thirty intact soil cores, each in a 25 × 25-m2 grid, were collected to a depth of 10 cm at the seedling stage of winter wheat in February 2008 from Maulde (50°3′ N, 3°43′ W),
Belgium. Two additional soil samples adjacent to each soil core were taken to measure the spatial variance in biotic and physicochemical
conditions. The microbial community structure was evaluated by means of phospholipid fatty acids analysis. Soil cores were
amended with 15 kg NO3−-N ha−1, 15 kg NH4+-N ha−1 and 30 kg ha−1 urea-N ha−1 and then brought to 65% water-filled pore space and incubated for 21 days at 15°C, with regular monitoring of N2O emissions. The N2O fluxes showed a log-normal distribution with mean coefficients of variance (CV) of 122%, 78% and 90% in RT, NT and CT, respectively,
indicating a high spatial variation. However, this variability of N2O emissions did not show plot scale spatial dependence. The N2O emissions from RT were higher (p < 0.01) than from CT and NT. Multivariate analysis of soil properties showed that PC1 of principal component analysis had
highest loadings for aggregate mean weight diameter, total C and fungi/bacteria ratio. Stepwise multiple regression based
on soil properties explained 72% (p < 0.01) of the variance of N2O emissions. Spatial distributions of soil properties controlling N2O emissions were different in three different tillages with CV ranked as RT > CT > NT. 相似文献
4.
A 15N dilution experiment was carried out to investigate effects of cultivation on the gross N transformation rate in coastal
wetland zone. Microbial community composition was estimated by phospholipid fatty acid (PLFA) analysis and abundance of soil
ammonia-oxidizing bacteria (AOB) was quantified by real-time polymerase chain reaction (PCR). Soil salinity decreased significantly,
while total N increased after coastal wetland was cultivated. Microbial biomass (total PLFA), bacterial biomass, fungal biomass,
and actinomycete biomass of the native coastal wetland soils were significantly (p < 0.05) lower than those of the cultivated soils whereas AOB population size also significantly increased after coastal wetland
cultivation. Multiple regression analysis showed that total PLFA biomass and soil total N (TN) explained 97% of the variation
of gross N mineralization rate in the studied soils (gross mineralization rate = 0.179 total PLFA biomass + 5.828TN − 2.505,
n = 16, p < 0.01). Gross nitrification rate increased by increasing the soil AOB population size and gross mineralization rate (M) (gross nitrification rate = 3.39AOB + 0.18 M − 0.075, R
2 = 0.98, n = 16, p < 0.01). Management of salt discharge and mineral N fertilization during the cultivation of wetland soils might have changed
composition of soil microflora and AOB population size, thus influencing mineralization and nitrification. Probably, the cultivation
of coastal wetland soils increased the risk of N losses from soil through nitrate leaching and gas emission (e.g., N2O and NO). 相似文献
5.
Manuel Aira Niall P. McNamara Trevor G. Piearce Jorge Domínguez 《Journal of Soils and Sediments》2009,9(1):54-61
Background, aim, and scope Earthworms make a major contribution to decomposition in ecosystems where they are present, mainly acting in the drilosphere,
that is, galleries, burrows, casts, and middens. Earthworm middens are hot-spots of microbial activity and nutrient dynamics
and represent a suitable model for studying earthworm-mediated influences on soil microbial communities by alteration of the
patch structure of the microbial environment. We studied the structure and activity of the microbial communities in the soil
system formed by middens of Lumbricus terrestris and the soil below and surrounding them and the role of earthworms in maintaining these structures through time.
Material and methods We set up an experiment in which middens were either left (control) or removed from their original place (translocated) and
left in a nearby area free of earthworm activity for 2 months. After 1 and 2 months we sampled middens, soil below them, and
surrounding soil. We analyzed the phospholipid fatty acid (PLFA) profiles and measured respiratory fluxes of CO2 and CH4.
Results Microbial communities of middens clearly differed from those of soil below and surrounding soil samples, showing higher bacterial
and fungal PLFAs (p < 0.0001 and p < 0.01, respectively); furthermore, changes in microbial communities were stronger in control middens than in translocated
middens. Moreover, gram positive and negative bacterial PLFAs were greater in translocated than control middens (p < 0.0001 and p < 0.001, respectively), as well as total organic carbon (p < 0.001). Microbial activity was higher in middens than in soil below and surrounding soil samples both for CO2 (p < 0.0001) and CH4 (p < 0.0001).
Discussion Soil bioturbation by the earthworm L. terrestris was strong in their middens, but there was not any effect on soil below and surrounding soil. Microbial communities of middens
maintain their biomass and activity when earthworms were not present, whereas they decreased their biomass and increased their
activity when earthworms were present.
Conclusions Earthworms strongly enhanced microbial activity measured as CO2 production in middens, which indicates that there are hot spots for soil microbial dynamics and increasing habitat heterogeneity
for soil microorganisms. Moreover, our data strongly support the fact that the impact of this earthworm species in this soil
is restricted to their middens and increasing soil heterogeneity.
Recommendations and perspectives Our data indicate that it is not clear if earthworms enhance or depress microbial communities of middens since the microbial
activity increased, but did not modify their biomass and this was not dependent on soil organic C content. These results indicate
no competence for C pools between this anecic earthworm and microorganisms, which has been found for other earthworm species,
mainly endogeics. Conversely, they suggest some type of facilitation due to the release of additional nutrient pools in middens
when earthworms are present, through the digestion of middens' material or the addition of casts produced from other food
sources. 相似文献
6.
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
7.
P. Houngnandan R. G. H. Yemadje S. O. Oikeh C. F. Djidohokpin P. Boeckx O. Van Cleemput 《Biology and Fertility of Soils》2008,45(2):175-183
Biological nitrogen fixation (BNF) of 17 soybean cultivars was comparatively estimated by the δ15N natural abundance technique using two non-nodulation soybeans (Clay and Chippewa) as reference plants. A field study was
established on the experimental farm of the University of Abomey-Calavi, Benin on a typical “terre de barre” soil classified
by Food and Agriculture Organization-United Nations Educational, Scientific and Cultural Organisation as Rhodic Ferralsol.
A nitrogen-free pot trial was also carried out using soil substrate sampled from the Atlantic Ocean beach. In the N-free medium,
N content of the whole soybean cultivars ranged from 2.6 to 8.1 mg N per plant compared with an average of 1.8 mg N per plant
observed with the non-fixing soybeans. Plant δ15N of the nodulating soybeans ranged from −2.7756‰ (Jupiter) to 0.1951‰ (Conquista), while the non-nodulating cultivars Chippewa
and Clay had 2.67‰ and 9.30‰, respectively. Percentage and amount of N derived from air (Ndfa) were significantly different
(P < 0.01) among soybean cultivars, and values depended highly on the selected reference plants. When Clay was used as the reference
plant, the average percentage Ndfa was 1.4 times higher than when Chippewa was the reference plant. Both reference plants
consistently ranked promiscuous soybean cvs. TG× 1894 3F and TG× 1908 8F as the best cultivars and cv. TG× 1888 29F as the
least in percentage Ndfa, suggesting that any of the reference plants could be used in δ15N method for assessing N2-fixation. The two identified promiscuous soybean cultivars with greatest capacity to fix N could be included in a soybean
extension program for West African farming systems. 相似文献
8.
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
9.
Karoline D’Haene Annemie Van den Bossche Jeroen Vandenbruwane Stefaan De Neve Donald Gabriels Georges Hofman 《Biology and Fertility of Soils》2008,45(2):213-217
The effect of reduced tillage (RT) on nitrous oxide (N2O) emissions of soils from fields with root crops under a temperate climate was studied. Three silt loam fields under RT agriculture
were compared with their respective conventional tillage (CT) field with comparable crop rotation and manure application.
Undisturbed soil samples taken in September 2005 and February 2006 were incubated under laboratory conditions for 10 days.
The N2O emission of soils taken in September 2005 varied from 50 to 1,095 μg N kg−1 dry soil. The N2O emissions of soils from the RT fields taken in September 2005 were statistically (P < 0.05) higher or comparable than the N2O emissions from their respective CT soil. The N2O emission of soils taken in February 2006 varied from 0 to 233 μg N kg−1 dry soil. The N2O emissions of soils from the RT fields taken in February 2006 tended to be higher than the N2O emissions from their respective CT soil. A positive and significant Pearson correlation of the N2O–N emissions with nitrate nitrogen (NO3
−–N) content in the soil was found (P < 0.01). Leaving the straw on the field, a typical feature of RT, decreased NO3
−–N content of the soil and reduced N2O emissions from RT soils. 相似文献
10.
Shixue Yin Yuanhua Dong Yangchun Xu Qiwei Huang Qirong Shen 《Biology and Fertility of Soils》2011,47(3):303-313
Rice seedling wilt frequently occurs in upland nurseries under well-aerated conditions and causes considerable economic loss.
Whether the wilt is pathogenic or edaphic is not known. We hypothesize the use of composts to alleviate seedling wilt. The
severity level of upland rice seedling wilt was significantly (p < 0.05) positively correlated with soil pH (r = 0.499; n = 19), but negatively correlated with soil organic matter (r = −0.745), microbial biomass C (r = −0.669), activities of dehydrogenase (r = −0.589), arylsulfatase (r = −0.272), fluorescein diacetate hydrolysis (r = −0.466), and β-glucosidase (r = −0.280). Correlations between severity level and soil inorganic N and exchangeable potassium K were not significant. Contents
of Fe, Zn, Cu, and Mn in healthy seedlings were not significantly (p < 0.05) different from those in infected seedlings. These data suggest that seedling wilts are not associated with nutrient
constraints. Compost amendment at the rate of 3% or above in pot experiments significantly improved seedling growth and reduced
the wilt symptoms. Field trials further showed that aboveground weight of seedlings in compost-amended treatment ranged from
11.5 to 14.9 mg per plant, significantly higher than the range from 6.38 to 12.1 mg per plant in the control treatment; in
addition to rice growth compost significantly increased microbial biomass and enzyme activities of soils. Soil fumigation
significantly increased rice growth and alleviation symptoms in 11 out of 19 soils, suggesting the involvement of pathogens.
It is concluded that upland seedling wilt is a pathogen-associated disease. Probably high soil pH and low soil biochemical
activities may favor pathogen activities. 相似文献
11.
Effects of moisture and temperature on greenhouse gas emissions and C and N leaching losses in soil treated with biogas slurry 总被引:1,自引:0,他引:1
The objective of this study was to examine the effects of soil moisture, irrigation pattern, and temperature on gaseous and
leaching losses of carbon (C) and nitrogen (N) from soils amended with biogas slurry (BS). Undisturbed soil cores were amended
with BS (33 kg N ha−1) and incubated at 13.5°C and 23.5°C under continuous irrigation (2 mm day−1) or cycles of strong irrigation and partial drying (every 6 weeks, 1 week with 12 mm day−1). During the 6 weeks after BS application, on average, 30% and 3.8% of the C and N applied with BS were emitted as carbon
dioxide (CO2) and nitrous oxide (N2O), respectively. Across all treatments, a temperature increase of 10°C increased N2O and CO2 emissions by a factor of 3.7 and 1.7, respectively. The irrigation pattern strongly affected the temporal production of CO2 and N2O but had no significant effect on the cumulative production. Nitrogen was predominantly lost in the form of nitrate (NO3−). On average, 16% of the N applied was lost as NO3−. Nitrate leaching was significantly increased at the higher temperature (P < 0.01), while the irrigation pattern had no effect (P = 0.63). Our results show that the C and N turnovers were strongly affected by BS application and soil temperature whereas
irrigation pattern had only minor effects. A considerable proportion of the C and N in BS were readily available for soil
microorganisms. 相似文献
12.
In industrial areas, heavy metals may accumulate in forest soil organic horizons, affecting soil microorganisms and causing
changes in the chemical composition of the accumulated organic matter. The objectives of this study were to test the ability
of near-infrared spectroscopy (NIRS) to detect heavy metal effects on the chemical composition of forest soil O horizons and
to test whether NIRS may be used to quantitatively determine total and exchangeable concentrations of Zn and Pb (Znt, Pbt, Znex, Pbex) and other chemical and microbial properties in forest soil O horizons polluted with heavy metals. The samples of O horizons
(n = 79) were analyzed for organic C (Corg), total N and S (Nt, St), Znt, Pbt, Znex, Pbex, basal respiration (BR), microbial biomass (Cmic) and Cmic-to-Corg ratio. Spectra of the samples were recorded in the Vis-NIR range (400–2,500 nm). To detect heavy-metal-induced changes in
the chemical composition of O horizons principal components (PC1–PC7) based on the spectral data were regressed against Znt + Pbt values. A modified partial least squares method was used to develop calibration models for prediction of various chemical
and microbial properties of the samples from their spectra. Regression analysis revealed a significant relationship between
PC3 and PC5 (r = −0.27 and −0.34, respectively) and Znt + Pbt values, indicating an effect of heavy metal pollution on the spectral properties of the O horizons and thus on their chemical
composition. For quantitative estimations, the best calibration model was obtained for Corg-to-Nt ratio (r = 0.98). The models for Corg, Nt, and microbial properties were satisfactory but less accurate. NIRS failed to accurately predict St, Corg-to-St, Znt, Pbt, Znex, and Pbex. 相似文献
13.
Ana María Gagneten Georgina Tumini Alba Imhof Susana Gervasio 《Water, air, and soil pollution》2012,223(2):617-624
Lead (Pb) is known as an important aquatic contaminant with different toxic effects on various organisms. Until now, only
few quantitative investigations have been published comparing Pb content in different organs of adult freshwater crabs. Their
capacity to bioaccumulate other heavy metals is already known, and they can potentially transfer Pb to the terrestrial systems,
as they are frequent trophic items of reptiles and birds, even humans. The objectives of this study were to assess Pb accumulation
in the gills, carapace, digestive gland, and quela muscle of the freshwater crab Zilchiopsis oronensis, and to correlate bioaccumulation with morphometric data and sex. The crabs were manually caught in unpolluted ponds of the
middle Paraná River alluvial valley (Santa Fe, Argentina). After the acclimation period, they were individually and randomly
exposed per quadruplicate to three Pb experimental doses: 20, 40, and 80 mg Pb/L, in plastic cages during 15 days. After dissecting
the crabs, the tissues were analyzed for lead in a Perkin Elmer Analyst 800 atomic absorption spectrometer. We found significant
differences (p < 0.05) between the control and each one of the treatments but not between treatments (p > 0.05) and highly significant differences (p < 0.0001) between Pb concentration in organs. The Tukey posttest showed significant differences (p < 0.05) between gills–carapace, gills–digestive gland, and gills–quela muscle. The weight of the crabs only showed a negative
correlation with Pb in the quela muscle (r = −0.53; p = 0.03). Pb in the carapace (but not in the other tissues) was positively correlated with the width (p = 0.571) and length (p = 0.616). Males accumulated more Pb than females, though not significantly. The present paper is aimed to contribute to our
knowledge on Pb accumulation in freshwater crabs and select the better indicator organisms for biomonitoring. 相似文献
14.
A 3-year field study in southeast China was performed to examine the relationship between N2O emission and winter wheat production. Over the 2002–03, 2003–04 and 2004–05 wheat-cropping seasons, N2O emissions depended on nitrogen addition, plowing practice, and preceding crop type treatments, and showed a pronounced inter-annual
variation. N2O–N emission factor, the proportion of fertilizer N released as N2O–N from the wheat field, varied from 1.33% to 2.97%. The relationship between N2O emission (y) and crop yield (x) was well explained by the function y = 3.773Ln(x) + 1.46. Similarly, the function y = 4.445Ln(x) − 3.52 can be employed to address the relationship between N2O emission (y) and above ground biomass (x). About 84% and 87% of variation in seasonal N2O emission were explained by the two functions, while only 66% of the variation was represented by the N input with a linear
relationship. The results of this study suggest that seasonal N2O emission of soil under winter wheat could be better predicted by crop yield and biomass than by N input.
Submitted to Biology and Fertility of Soils. 相似文献
15.
Balaji Anandha Rao Cameron P. Wake Todd Anderson William Andrew Jackson 《Water, air, and soil pollution》2012,223(1):181-188
Temporal depositional rates are important in order to understand the production and occurrence of perchlorate (ClO4−) as limited information exists regarding the impact of anthropogenic production or atmospheric pollution on ClO4− deposition. Perchlorate concentrations in discrete ice core samples from the Eclipse Icefield (Yukon Territory, Canada) and
Upper Fremont Glacier (Wyoming, USA) were analyzed using ion chromatography tandem mass spectrometry to evaluate temporal
changes in the deposition of ClO4
− in North America. The ice core samples cover a time period from 1726 to 1993 and 1970 to 2002 for the Upper Fremont Glacier
(UFG) and Eclipse ice cores, respectively. The average ClO4
− concentration in the Eclipse ice core for the time period from 1970 to 1973 was 0.6 ± 0.3 ng L−1, with higher values of 2.3 ± 1.7 and 2.2 ± 2.0 ng L−1 for the periods 1982–1986 and 1999–2002, respectively. All pre-1980 ice core samples from the UFG had ClO4
− concentrations <0.2 ng L−1, and the post-1980 samples ranged from <0.2 ng L−1 to a maximum of 2.6 ng L−1 for the year 1992. A significant positive correlation (R = 0.75, N = 15, p < 0.001) of ClO4− with SO42− was found for the annual UFG ice core layers and of ClO4
− with SO42− and NO3− in sub-annual Eclipse ice samples (R > 0.3, N = 121, p < 0.002). The estimated yearly ClO4− depositional flux for the Eclipse ice core ranged from 0.6 (1970) to 4.7 μg m−2 year−1 (1982) and the UFG from <0.1 (pre-1980) to 1.4 μg m−2 year−1 (1992). There was no consistent seasonal variation in the ClO4− depositional flux for the Eclipse ice core, in contrast to a previous study on the Arctic region. The presence of ClO4− in these ice cores might correspond to an intermittent source such as volcanic eruptions and/or any anthropogenic forcing
that may directly or indirectly aid in atmospheric ClO4− formation. 相似文献
16.
Emission of N2O from rye grass (Lolium perenne L.) 总被引:6,自引:0,他引:6
The possibility of an additional N2O emission pathway via plants was investigated in a soil-rye-grass (Lolium perenne L.) system. The N2O emission rate of the system varied between 0.8 and 13.3 mg N2O-N m–2 day–1. Comparing the N2O emission rate of the system before and immediately after cutting the rye grass allowed us to calculate the contribution
of the rye grass to the N2O emission from the soil-plant system. It was found that, depending on the type of fertilization and the growing period of
the plants, the N2O released from the rye grass varied between 0 and 2.8 mg N2O-N m–2 day–1. N
2
O emission mediated by the rye grass increased towards the end of the growing period. An exponential correlation [R2=0.93, y=(8×10–6 x
2
)–(2×10–5 x)+0.21] was observed between the N2O emission (y) from the rye grass and its NO3
––N content (x). However, it was not clear whether N2O was produced by the plants themselves or whether the rye grass served as a conduit for N2O produced in the soil.
Received: 18 March 1998 相似文献
17.
The effect of soil freeze–thaw cycles on the denitrification potential was examined based on the C2H2 inhibition method. The gross N2O production curve of the soil sample (incubation with C2H2) showed minor changes between the freeze–thaw treatment and the unfrozen control. However, kinetics analysis revealed that
the initial production rate, an indicator of the population density of denitrifying communities, decreased (P = 0.043) and the specific growth rate constant, an indicator of the activity of denitrifying communities, increased (P = 0.039) as a result of the freeze–thaw cycles in five of six soil samples examined. The increase in the specific growth
rate constant suggested the stimulation of the activity of denitrifying communities that survived after the freeze–thaw cycles
and may explain the minor suppression on the gross N2O production in spite of decreasing the population density of denitrifying communities that was suggested by the initial production
rate. The net N2O production curve of the soil sample (incubation without C2H2) showed a remarkable change in one out of six soil samples, and in that one soil sample, N2O release to the atmosphere was largely stimulated (7.6 times) by the freeze–thaw cycles. However, the stimulation of the
N2O release by the freeze–thaw cycles was even observed in two other selected soil samples (4.6 and 1.8 times), suggesting that
an imbalance in the N2O-producing and N2O-reducing activities of denitrifying communities might complementally explain the N2O release stimulated by the freeze–thaw cycles. 相似文献
18.
Simple and rapid chemical indices of soil nitrogen (N)-supplying capacity are necessary for fertilizer recommendations. In
this study, pot experiment involving rice, anaerobic incubation, and chemical analysis were conducted for paddy soils collected
from nine locations in the Taihu Lake region of China. The paddy soils showed large variability in N-supplying capacity as
indicated by the total N uptake (TNU) by rice plants in a pot experiment, which ranged from 639.7 to 1,046.2 mg N pot−1 at maturity stage, representing 5.8% of the total soil N on average. Anaerobic incubation for 3, 14, 28, and 112 days all
resulted in a significant (P < 0.01) correlation between cumulative mineral NH4+-N and TNU, but generally better correlations were obtained with increasing incubation time. Soil organic C, total soil N,
microbial C, and ultraviolet absorbance of NaHCO3 extract at 205 and 260 nm revealed no clear relationship with TNU or cumulative mineral NH4+-N. Soil C/N ratio, acid KMnO4-NH4+-N, alkaline KMnO4-NH4+-N, phosphate–borate buffer extractable NH4+-N (PB-NH4+-N), phosphate–borate buffer hydrolyzable NH4+-N (PBHYDR-NH4+-N) and hot KCl extractable NH4+-N (HKCl−NH4+-N) were all significantly (P < 0.05) related to TNU and cumulative mineral NH4+-N of long-term incubation (>28 days). However, the best chemical index of soil N-supplying capacity was the soil C/N ratio,
which showed the highest correlation with TNU at maturity stage (R = −0.929, P < 0.001) and cumulative mineral NH4+-N (R = −0.971, P < 0.001). Acid KMnO4-NH4+-N plus native soil NH4+-N produced similar, but slightly worse predictions of soil N-supplying capacity than the soil C/N ratio. 相似文献
19.
Gang Xin Gengyun Zhang Jun Won Kang James T. Staley Sharon L. Doty 《Biology and Fertility of Soils》2009,45(6):669-674
An endophytic bacterium, wild poplar strain B (WPB), isolated from stems of wild cottonwood (Populus trichocarpa) was identified to Burkholderia vietnamiensis by analyzing the recA and rDNA genes. Phylogenetic analysis of the nifHDK cluster indicates that the WPB isolate shares high sequence similarity with known B. vietnamiensis strains. The nitrogenase activity of WPB was determined by a 15N2 incorporation assay and an acetylene reduction assay. WPB was also monitored for production of indole-3-acetic acid (IAA),
a phytohormone which can promote plant growth, when incubated with l-tryptophan. In addition, its plant growth promotion capacity was assessed by inoculating the WPB strain onto Kentucky bluegrass
in nitrogen-free medium. Compared to uninoculated control plants, the plants inoculated with WPB gained more dry weight (42%,
p = 0.01) and more nitrogen content (37%, p = 0.04) in 50 days. 相似文献
20.
Long-term winter cover cropping effects on corn (Zea mays L.) production and soil nitrogen availability 总被引:1,自引:0,他引:1
This study was conducted to determine effects of long-term winter cover cropping with hairy vetch, cereal rye and annual
ryegrass on soil N availability and corn productivity. From 1987 to 1995, with the exception of the first year of the study,
the cover crops were seeded each year in late September or early October after the corn harvest and incorporated into the
soil in late April or early May. Corn was seeded 10 days to 2 weeks after the cover crop residues had been incorporated, and
N fertilizer was applied as a side-dressing at rates of 0, 67, 134, or 201 kg N ha–1 each year. While the average annual total N input from the above-ground biomass of the cover crops was highest for hairy
vetch (72.4 kg N ha–1), the average annual total C input was highest for cereal rye (1043 kg C ha–1) compared with the other cover crops. Hairy vetch was the only cover crop that significantly increased pre-side-dressed NO3
–-N (Ni) corn biomass and N uptake at 0 N. At an N fertilizer rate of 134 kg N ha–1 or higher, the cover crops had a minimal effect on corn biomass. This indicated that even after 9 years of winter cover cropping,
the effect of the cover crops on corn growth resulted primarily from their influence on soil N availability. The amount of
available N estimated from the cover crops (Nac) was significantly correlated with relative corn biomass production (r
2=0.707, P<0.001). The total amount of available N, comprising Nac and N added from fertilizer (Nf), was strongly correlated (r
2=0.820, P<0.001)) with relative corn biomass production. The correlation was also high for the available N comprising Ni and Nf (r
2=0.775, P<0.001). Although cereal rye and annual ryegrass did not improve corn biomass production in the short term, they benefited
soil organic N accumulation and gradually improved corn biomass production compared with the control over the long term.
Received: 10 August 1999 相似文献