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1.
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
2.
An examination of potential extraction methods to assess plant-available organic phosphorus in soil 总被引:1,自引:0,他引:1
The role of soil organic phosphorus (P) in plant nutrition was assessed using data from a glasshouse pot experiment carried
out on seven soil types using two contrasting plant species (Lolium perenne, Pinus radiata) and 12 different extractants (five salts (0.025 M ethylenediaminetetraacetic acid (EDTA), 0.025 M EDTA pH 7, Olsen, Mehlich-III,
and 6% NaOCl pH 7.5) and seven exchange resins (Hampton chelating resin, Bio-Rad Chelex-100, Dow MAC-3, Amberlite IRC76, Diaion
WT01S, Lewatit MP500A, Diaion WA30)). The contribution from mineralization of soil organic P was inferred by consistent increases
in correlation coefficients between extractable P and plant P uptake when organic P was considered in addition to inorganic
P. The best correlated extractants for combined inorganic and organic P were NaOCl (r = 0.84), Hampton chelating resin (r = 0.78), and MP500A resin (r = 0.73), which compared favorably with Olsen P (r = 0.66) and EDTA (r = 0.72). 31P nuclear magnetic resonance analysis of selected extracts from two soils confirmed that the Hampton-chelating-resin-extractable
P was mainly monoester and diester forms of organic P, while there was no monoester or diester organic P in the IRC76 resin
extract—poorly correlated with plant uptake. The findings of this study suggest that readily extractable forms of organic
P in soil contribute to short-term plant P uptake, and this P should be considered for inclusion in routine tests for soil
P availability. 相似文献
3.
A study was conducted to investigate the effects of cow manure and sewage sludge application on the activity and kinetics
of soil l-glutaminase. Soil samples were collected from a farm experiment in which 0, 25, and 100 Mg ha−1 of either cow manure or sewage sludge had been applied annually for 4 consecutive years to a clay loam soil (Typic Haplargid).
A chemical fertilizer treatment had also been applied. Results indicated that the effects of chemical fertilizer and the solid
waste application on pH in the 18 surface soil (0–15 cm) samples were not significant. The organic C content, however, was
affected significantly by the different treatments, being the greatest in soils treated with 100 Mg ha−1 cow manure, and the least in the control treatment. l-Glutaminase activity was generally greater in solid-waste applied soils and was significantly correlated (r = 0.939, P < 0.001) with organic C content of soils. The values of l-glutaminase maximum velocity (Vmax) ranged from 331 to 1,389 mg NH4
+–N kg−1 2 h−1. Values of the Michaelis constant (K
m) ranged from 35.1 to 71.7 mM. Organic C content of the soils were significantly correlated with V
max (r = 0.919, P < 0.001) and K
m (r = 0.763, P < 0.001) values. These results demonstrate the considerable influence that solid waste application has on this enzymatic
reaction involved in N mineralization in soil. 相似文献
4.
This study aims to determine leaf litter preference, consumption rate, growth rate, food conversion efficiency, and quality
of fecal pellets of two endemic pill millipedes (Arthrosphaera dalyi and Arthrosphaera davisoni) of the Western Ghats of India by laboratory microcosm experiments. Among seven combinations of three plantation leaf litters
offered in 4-day trial, top three preferred combinations were selected for 4-week trial. In 4-week trial, preference of mixed
litter diet was higher than single litter diet, which resulted in enhanced growth as well as food conversion efficiency of
millipedes. Among Hopea
,
Pongamia
, and Areca litters, A. dalyi preferred Hopea + Pongamia, and its consumption was significantly correlated with contents of organic carbon (P < 0.05; r = –0.97) and nitrogen (P < 0.01; r = 0.99), while growth rate with phosphorus content (P < 0.05; r = 0.97) and food conversion efficiency with contents of organic carbon (P < 0.05; r = 0.98) and calcium (P < 0.01; r = –0.99). Among Areca
,
Elettaria
, and Coffea litters, Areca + Elettaria
+ Coffea was most preferred by A. davisoni, which was significantly correlated with organic carbon content (P < 0.05; r = 0.98) and food conversion efficiency with calcium content (P < 0.0001; r = 0.99). The food conversion efficiency, however, was the highest in millipedes fed with Areca
+
Elettaria. The present study demonstrated increased nitrogen and phosphorus contents and decreased phenolic content and C/N ratio in
fecal pellets of pill millipedes fed with plantation litter, and thus, these millipedes play an important role in leaf litter
mineralization and soil enrichment in plantations Western Ghats. 相似文献
5.
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
6.
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
7.
Use of Ozonization for the Treatment of Dye Wastewaters Containing Rhodamine B in the Agate Industry
Machado Ênio Leandro de Sales Dambros Vagner Kist Lourdes Teresinha Alcayaga Lobo Eduardo Alexis Tedesco Solange Bosio Moro Celso Camilo 《Water, air, and soil pollution》2012,223(4):1753-1764
The industrial processing of precious stones is a source of revenue for several Brazilian towns, especially in the state of
Rio Grande do Sul. Given the growing number of small-sized companies that process precious stones, wastewater production is
inevitable and is a cause for concern inasmuch as preservation of nature is considered. The present study investigates the
detoxification of the wastewater produced by the process of rhodamine B dyeing using oxidation processes. Ozonization (O3), ultraviolet irradiation (UV), and O3/UV methods were assessed. Some of the parameters used to measure the efficiency of the analyzed treatments included COD,
ecotoxicity (Daphnia magna), cytotoxicity, and genotoxicity assays (Allium cepa assays). Results show predominance of negative and local environmental impacts, which are reversible in more than 70% of
cases. The major proposed reversibility measures were the change in the process layout and dye wastewater segregation. Among
the analyzed methods, ozonization proved to be more efficient in decolorization, with 60 min of treatment, pH = 9 and dosage
of 5.705 mg O3/mg of rhodamine B. A pseudo first-order reaction, with a kinetic constant of 7.5 × 10−2 min−1, was observed. The cytotoxic and genotoxic effects were assessed for both raw and treated wastewaters. Despite complete decolorization,
cytotoxicity and genotoxicity assays revealed an EC50 of 28.6, in addition to chromosome aberrations in 40% of dividing cells for the treated wastewater. 相似文献
8.
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
9.
This study examines the effects of atrazine on both microbial biomass C and C mineralization dynamics in two contrasting agricultural
soils (organic C, texture, and atrazine application history) located at Galicia (NW Spain). Atrazine was added to soils, a
Humic Cambisol (H) and a Gleyic Cambisol (G), at a recommended agronomic dose and C mineralization (CO2 evolved), and microbial biomass measurements were made in non-treated and atrazine-treated samples at different time intervals
during a 12-week aerobic incubation. The cumulative curves of CO2–C evolved over time fit the simple first-order kinetic model [Ct = Co (1 − e
−kt
)], whose kinetic parameters were quantified. Differences in these parameters were observed between the two soils studied;
the G soil, with a higher content in organic matter and microbial biomass C and lower atrazine application history, exhibited
higher values of the total C mineralization and the potentially mineralizable labile C pool than those for the H soil. The
addition of atrazine modified the kinetic parameters and increased notably the C mineralized; by the end of the incubation
the cumulative CO2–C values were 33–41% higher than those in the corresponding non-added soils. In contrast, a variable effect or even no effect
was observed on the soil microbial biomass following atrazine addition. The data clearly showed that atrazine application
at normal agricultural rates may have important implications in the C cycling of these two contrasting acid soils. 相似文献
10.
Arylsulfatase activity of microbial biomass in soils as affected by cropping systems 总被引:5,自引:0,他引:5
The impacts of crop rotations and N fertilization on different pools of arylsulfatase activity (total, intracellular, and
extracellular) were studied in soils of two long-term field experiments in Iowa to assess the contibution of the microbial
biomass to the activity of this enzyme. Surface-soil samples were taken in 1996 and 1997 in corn, soybeans, oats, or meadow
(alfalfa) plots that received 0 or 180 kg N ha–1 before corn, and an annual application of 20 kg P ha–1 and 56 kg K ha–1. The arylsulfatase activity in the soils was assayed at optimal pH (acetate buffer, pH 5.8) before and after chloroform fumigation;
microbial biomass C (Cmic) and N (Nmic) were determined by chloroform-fumigation methods. All pools of arylsulfatase activity in soils were significantly affected
by crop rotation and plant cover at sampling time, but not by N fertilization. Generally, the highest total, intracellular,
and extracellular arylsulfatase activities were obtained in soils under cereal-meadow rotations, taken under oats or meadow,
and the lowest under continuous cropping systems.Total, intracellular, and extracellular arylsulfatase activities were significantly
correlated with Cmic (r>0.41, P<0.01) and Nmic (r>0.38, P<0.01) in soils. The averages of specific activity values, i.e., of arylsulfatase activity of the microbial biomass, expressed
per milligram Cmic, ranged from 315 to 407 μg p-nitrophenol h–1. The total arylsulfatase activity was significantly correlated with the intracellular activity, with r values >0.79 (P<0.001). In general, about 45% of the total arylsulfatase activity was extracellular, and 55% was associated with the microbial
biomass in soils, indicating the importance of the microflora as an enzyme source in soils.
Received: 23 April 1998 相似文献
11.
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
12.
Conservation tillage, and especially no-tillage, induce changes in the distribution of organic pools in the soil profile.
In long-term field experiments, marked stratification of the total soil microbial biomass and its activity have been observed
as consequence of the application of no-tillage to previously tilled soils. Our objective was to study the evolution of the
total and active soil microbial biomass and mineralized C in vitro during the first crop after the introduction of no-tillage
to an agricultural soil. The experiment was performed on a Typic Hapludoll from the Argentinean Pampa. Remaining plant residues,
total and active microbial biomass and mineralized C were determined at 0–5 cm and 5–15 cm depths, at three sampling times:
wheat tilling, silking and maturity. The introduction of no-tillage produced an accumulation of plant residues in the soil
surface layer (0–5 cm), showing stratification with depth at all sampling dates. Active microbial biomass and C mineralization
were higher under no-tillage than under conventional tillage in the top 5 cm of the profile. The total soil microbial biomass
did not differ between treatments. The active soil biomass was highly and positive correlated with plant residues (r
2=0.617;P<0.01) and with mineralized C (r
2=0.732;P<0.01). Consequently, the active microbial biomass and mineralized C reflected immediately the changes in residue management,
whereas the total microbial biomass seemed not to be an early indicator of the introduction of a new form of soil management
in our experiment.
Received: 23 February 1999 相似文献
13.
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
14.
Nitrogen and carbon mineralization of cattle manure (N=6 g kg–1; C:N=35), pressmud (N=17.4 g kg–1; C:N=22), green manure (N=26.8 g kg–1; C:N=14) and poultry manure (N=19.5 g kg–1; C:N=12) and their influence on gaseous N losses via denitrification (using the acetylene inhibition technique) in a semiarid subtropical soil (Typic Ustochrepts) were investigated in a growth chamber simulating upland, nearly saturated, and flooded conditions. Mineralization of N started quickly in all manures, except pressmud where immobilization of soil mineral N was observed for an initial 4 days. Accumulation of mineral N in upland soil plus denitrified N revealed that mineralization of cattle manure-, pressmud-, poultry manure- and green manure-N over 16 days was 12, 20, 29 and 44%, respectively, and was inversely related to C:N ratio (R 2=0.703, P=0.05) and directly to N content of organic manure (R 2=0.964, P=0.01). Manure-C mineralized over 16 days ranged from 6% to 50% in different manures added to soil under different moisture regimes and was, in general, inversely related to initial C:N ratio of manure (R 2=0.690, P=0.05). Cumulative denitrification losses over 16 days in control soils (without manure) under upland, nearly saturated, and flooded conditions were 5, 23, and 24 mg N kg–1, respectively. Incorporation of manures enhanced denitrification losses by 60-82% in upland, 52–163% in nearly saturated, and 26–107% in flooded soil conditions over a 16-day period, demonstrating that mineralized N and C from added manures could result in 2- to 3-fold higher rate of denitrification. Cumulative denitrification losses were maximal with green manure, followed by poultry manure, pressmud and cattle manure showing an increase in denitrification with increasing N content and decreasing C:N ratio of manure. Manure-amended nearly saturated soils supported 14–35% greater denitrification than flooded soils due to greater mineralization and supply of C. 相似文献
15.
The impacts of crop rotations and N fertilization on different pools of urease activity were studied in soils of two long-term
field experiments in Iowa; at the Northeast Research Center (NERC) and the Clarion-Webster Research Center (CWRC). Surface
soil samples (0–15 cm) were taken in 1996 and 1997 in corn, soybeans, oats, or meadow (alfalfa) plots that received 0 or 180 kg
N ha–1, applied as urea before corn and an annual application of 20 kg P and 56 kg K ha–1. The urease activity in the soils was assayed at optimal pH (THAM buffer, pH 9.0), with and without toluene treatment, in
a chloroform-fumigated sample and its nonfumigated counterpart. The microbial biomass C (Cmic) and N (Nmic) were determined by chloroform fumigation methods. The total, intracellular, extracellular and specific urease activities
in the soils of the NERC site were significantly affected by crop rotation, but not by N fertilization. Generally, the highest
total urease activities were obtained in soils under 4-year oats–meadow rotations and the lowest under continuous corn. The
higher total activities under multicropping systems were caused by a higher activity of both the intracellular and extracellular
urease fractions. In contrast, the highest values for the specific urease activity, i.e. of urease activity of the microbial
biomass, were found in soils under continuous soybean and the least under the 4-year rotations. Total and extracellular urease
activities were significantly correlated with Cmic (r>0.30* and >0.40**) and Nmic (r>0.39** and >0.44**) in soils of the NERC and CWRC sites, respectively. Total urease activity was significantly correlated
with the intracellular activity (r>0.73***). About 46% of the total urease activity of the soils was associated with the microbial biomass, and 54% was extracellular
in nature.
Received: 25 May 1999 相似文献
16.
Soil microbial biomass (SMB) activity was investigated in a long-term experiment in which grazed swards received annual inputs
of 200 N kg ha–1. SMB total C and total N, specific respiration, ammonification and nitrification were examined over a 10 week period, following
the first and the second seasonal applications of N. Whilst there was no effect on biomass C and N, additions of N appeared
to increase biomass activity. Nitrification was weakly correlated with ammonification (r
2=0.413) and the latter was stimulated by the addition of N (P<0.05), suggesting a ‘priming’ effect.
Received: 28 February 1997 相似文献
17.
This study was conducted to investigate the effect of inorganic nitrogen (N) and root carbon (C) addition on decomposition
of organic matter (OM). Soil was incubated for 200 days with nine treatments (three levels of N (no addition (N0) = 0, low
N (NL) = 0.021, high N (NH) = 0.083 mg N g−1 soil) × three levels of C (no addition (C0) = 0, low C (CL) = 5, high C (CH) = 10 mg root g−1 soil)). The carbon dioxide (CO2) efflux rates, inorganic N concentration, pH, and potential activities of β-glucosidase and oxidative enzyme were measured
during incubation. At the beginning and the end of incubation, the native soil organic carbon (SOC) and root-derived SOC were
quantified by using a natural labeling technique based on the differences in δ
13C between C3 and C4 plants. Overall, the interaction between C and N was not significant. The decomposition of OM in the NH
treatment decreased. This could be attributed to the formation of recalcitrant OM by N because the potentially mineralizable
C pool was significantly lower in the NH treatment (3.1 mg C g−1) than in the N0 treatment (3.6 mg C g−1). In root C addition treatments, the CO2 efflux rate was generally in order of CH > CL > C0 over the incubation period. Despite no differences in the total SOC concentration
among C treatments, the native SOC in the CH treatment (18.29 mg C g−1) was significantly lower than that in the C0 treatment (19.16 mg C g−1). 相似文献
18.
Abbas Biabani Lynne Carpenter-Boggs Clarice J. Coyne Lisa Taylor Jeffrey L. Smith Stewart Higgins 《Biology and Fertility of Soils》2011,47(6):679-685
Biological nitrogen fixation (BNF) is a sustainable alternative for nitrogen supply to agriculture worldwide. One approach
to increasing BNF in agriculture is to breed and use legumes with greater BNF capacity. To assess the capacity for BNF in
chickpea (Cicer arietinum) global germplasm, a genetically diverse subset from the USDA global chickpea core collection was assayed for BNF potential.
The greenhouse experiment assayed 39 global accessions and commercial cultivar UC-5, inoculated with Mesorhizobium ciceri. Plant height, branch number, nodule number, shoot weight, root weight, nodule weight, proportion of nitrogen fixed, and total
nitrogen fixation were determined. All characteristics varied significantly among the accessions. Proportion of plant nitrogen
fixed ranged from 47% to 78% and was correlated with shoot weight (r = 0.21, P < 0.01) and total plant weight (r = 0.20, P < 0.01), but not with nodule number or weight. Accession 254549 from Iraq produced the greatest total fixed nitrogen, more
than any other accession and 121% more than that fixed by UC-5. The variation among BNF capacities of the accessions supports
the preservation and use of global germplasm resources and suggests that nitrogen fixation in commercial chickpea varieties
may be improved by introgressing positive alleles from the global chickpea germplasm collections. 相似文献
19.
Sulfate adsorption by variable charge soils: Effect of low-molecular-weight organic acids 总被引:1,自引:0,他引:1
C. E. Martinez A. W. Kleinschmidt M. A. Tabatabai 《Biology and Fertility of Soils》1998,26(3):157-163
Sulfate (SO4
2–) movement and transport in soils has received considerable attention in recent years. In most soils, SO4
2– coexists with a variety of natural organic compounds, especially organic acids. Studies were conducted to assess the effect
of low-molecular-weight organic acids (eight aliphatic and five aromatic acids) on SO4
2– adsorption by variable charge soils from Chile and Costa Rica. The effects of type of organic acid, pH, type of soil, and
organic acid concentration were investigated. In one experiment, a 1.0 g soil sample was equilibrated with 25 ml 0, 0.5, 1.0,
2.0, 4.0, or 6.0 mM K2SO4 in 1 mM NaCl in the presence or absence of 5 mM citric acid. In the second set of experiments, the adsorption of 2 mM SO4
2– in soils at pH 4 or pH 5 in the presence or absence of one of 13 organic acids at a concentration of 2 mM or 5 mM was studied. Results showed that citric acid significantly decreased SO4
2– adsorption by the two soils. Sulfate adsorption decreased with increasing pH of the equilibrium solution. Aliphatic acids,
with the exception of cis-aconitic acid, decreased the amount of SO4
2– adsorbed by the two soils, with oxalic, tartaric, and citric acid showing the greatest effect. The differences in pH values
of the equilibrium solutions in the presence and absence of organic acids were significantly, but negatively, correlated with
the amount of SO4
2– adsorbed, suggesting chemisorption of SO4
2– and the release of hydroxide ions. The ionization fraction values of the organic acids at the equilibrium pH were correlated
with the amounts of SO4
2– adsorbed, suggesting that the protonation of surface hydroxyl groups of the mineral phase increased as the strength of the
ionization of the acid increased, thus creating more positively charged surfaces.
Received: 12 February 1997 相似文献
20.
Jianping Luo Mei Ma Cao Liu Jinmiao Zha Zijian Wang 《Journal of Soils and Sediments》2009,9(3):180-187
Background, aim, and scope The potential of wetlands for controlling point- and nonpoint-source pollution in surface water has attracted increasing interest.
The partitioning process of organic contaminants between water, particulate organic carbon (POC) and dissolved organic carbon
(DOC), impacts their behaviors in the aquatic environments. Meantime, the partitioning process of organic contaminants is
closely related to their physicochemical properties, such as hydrophobicity (or K
ow), and their fates in wetlands may vary greatly depending on physicochemical properties. The aim of this study was to examine
fates and removals of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and nonylphenols (NPs) in
a wetland in Beijing, China, and provide useful information for ecological remediation.
Materials and methods Water samples, collected at five sites from inlet to outlet of the wetland once a month in summer 2006, were immediately filtered
within 2 days through 0.45-μm glass fiber prefilters and enriched by solid-phase extraction. The filtered particulates were
collected as the total suspended particulates (TSPs), freeze-dried, and Soxhlet-extracted. After extraction, samples were
purified following a clean-up procedure and analyzed by GC-MS.
Results TSPs could be removed efficiently with a removal rate of 97.4%, and DOC could be moderately removed with a removal rate of
44.7% from inlet to outlet. The total removals of target contaminants varied widely from null to 82.0%. A good correlation
between logK
ow and logK
oc (organic-carbon-normalized suspended-particulate partition coefficient) was observed (r
2 = 0.84 for PAHs and r
2 = 0.86 for OCPs, p < 0.01). Ratios of the POC-bound fraction of target contaminants (or DOC-bound fraction) to the freely dissolved fraction
increased with their K
ow values. The removal of the POC fraction contributed more than 50% to the total removal for the contaminants with logK
ow > 5.0. Only a small portion of the removal was attributed to the removal of the freely dissolved fraction.
Discussion Hydrophobic compounds such as PAHs and OCPs with higher K
ow values would show stronger POC or DOC preference. Their removal depended greatly on their K
ow values and the removal of total suspended particulates. On the other hand, concentrations of NPs decreased little in the
wetland, probably due to their production through degradation of their precursors and relatively low hydrophobicity.
Conclusions POC and DOC play essential roles on the fates and removals of hydrophobic organic contaminants in the wetland. The removal
of target contaminants with a high K
ow should be mainly through association with the suspended particulates which were precipitated and retained in the wetland.
The fates of the organic contaminants in the wetland greatly depended on their hydrophobicities.
Recommendations and perspectives Further work should be done to study the influence of hydraulic retention time and some other environmental factors, e.g.,
temperature, on removals and fates of organic contaminants. Behavior of NPs and their precursors in the wetland should also
be investigated more thoroughly. 相似文献