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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 (CO 2) and nitrous oxide (N 2O), respectively. Across all treatments, a temperature increase of 10°C increased N 2O and CO 2 emissions by a factor of 3.7 and 1.7, respectively. The irrigation pattern strongly affected the temporal production of CO 2 and N 2O but had no significant effect on the cumulative production. Nitrogen was predominantly lost in the form of nitrate (NO 3−). On average, 16% of the N applied was lost as NO 3−. 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
2.
During the intensive flood in May–June 2010, the floodplains in Little Poland Vistula Gap, used mostly for agriculture, were
waterlogged for a period of over 1 month. The aim of the study was to assess the effect of the flood on the level of contamination
of the soils in this region. The analysis included basic physicochemical soil properties, contents of ten metals, and concentrations
of 16 polycyclic aromatic hydrocarbons (PAHs). The studies cover two territories on opposite sites of the river Vistula (Wilkow
and Janowiec) differing in their areas (70 and 4.6 km 2) and time of water logging (30 and 10 days). Forty soil samples were collected from both areas immediately after the flood
event from the upper (0–30 cm) soil layer together with four samples from the 30–60-cm depth layer. This was supplemented
by eight samples from the flood-deposited sediment layer (thickness, 2 cm). The concentrations of identified metals (As, Ba,
Cr, Sn, Zn, Cd, Co, Cu, Ni, Pb) at all the sampling points were below the Polish legal limits for the upper layer of soils
for agriculture use. The same regarded the median contents of nine PAHs compounds specified in the Polish regulations. In
both areas, the median contents of Σ16 PAHs (0.21–0.35 mg kg −1), Zn (10.3–10.6 mg kg −1), Pb (9.2–10.7 mg kg −1), and Cd (0.03 mg kg −1) were much below the mean concentrations of those contaminants in arable soils on the national and European levels. The results
show that this severe flooding episode in “clean” agricultural area had no immediate negative impact on the soils as regards
the basic physicochemical properties (organic matter content, acidity, nitrogen content) and did not result in excessive soil
contamination. 相似文献
3.
Secondary soil salinilization is a big problem in irrigated agriculture. We have studied the effects of irrigation-induced
salinity on microbial biomass of soil under traditional cotton ( Gossypium hirsutum L.) monoculture in Sayhunobod district of the Syr-Darya province of northwest Uzbekistan. Composite samples were randomly
collected at 0–30 cm depth from weakly saline (2.3 ± 0.3 dS m −1), moderately saline (5.6 ± 0.6 dS m −1), and strongly saline (7.1 ± 0.6 dS m −1) replicated fields, 2-mm sieved, and analyzed for pH, electrical conductivity, total C, organic C (C Org), and extractable C, total N and P, and exchangeable ions (Ca 2+, Mg 2+, K +, Na +, Cl −, and CO 32−), microbial biomass (C mic). The Na + and Cl − concentrations were 36-80% higher in strongly saline compared to weakly saline soil. The C Org concentration was decreased by 10% and C Ext by 40% by increasing soil salinity, whereas decrease in C mic ranged from 18-42% and the percentage of C Org present as C mic from 8% to 26%. We conclude that irrigation-induced secondary salinity significantly affects soil chemical properties and
the size of soil microflora. 相似文献
4.
We compared, from 2004 through 2006, rates of soil–atmosphere CH 4 exchange at permanently established sampling sites in a temperate forest exposed to ambient (control plots; ∼380 μL L −1) or elevated (ambient + 200 μL L −1) CO 2 since August 1996. A total of 880 observations showed net atmospheric CH 4 consumption (flux from the atmosphere to the soil) from all static chambers most of the time at rates varying from 0.02 mg m −2 day −1 to 4.5 mg m −2 day −1. However, we infrequently found net CH 4 production (flux from the soil to the atmosphere) at lower rates, 0.01 mg m −2 day −1 to 0.08 mg m −2 day −1. For the entire study, the mean (±SEM) rate of net CH 4 consumption in control plots was higher than the mean for CO 2-enriched plots, 0.55 (0.03) versus 0.51 (0.03) mg m −2 day −1. Annual rates of 184, 196, and 197 mg m −2 for net CH 4 consumption at control plots during the three calendar years of this study were 19, 10, and 8% higher than comparable values
for CO 2 enriched plots. Differences between treatments were significant in 2004 and 2005 and nearly significant in 2006. Volumetric
soil water content was consistently higher at CO 2-enriched sites and a mixed-effects model identified a significant soil moisture x CO 2 interaction on net atmospheric CH 4 consumption. Increased soil moisture at CO 2-enriched sites likely increases diffusional resistance of surface soils and the frequency of anaerobic microsites supporting
methanogenesis, resulting in reduced rates of net atmospheric CH 4 consumption. Our study extends our observations of reduced net atmospheric CH 4 consumption at CO 2-enriched plots to nearly five continuous years, suggesting that this is likely a sustained negative feedback to increasing
atmospheric CO 2 at this site. 相似文献
5.
Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching,
denitrification, and nitrous oxide (N 2O) 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 N 2O 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 NO 3−–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 NO 3−–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 N 2O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the
cumulative N 2O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N 2O emission was significantly and positively correlated with NO 3−–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 CO 2 in the first 3 and 5 days of incubation ( r = 0.59, P < 0.05). 相似文献
6.
In this study, the effects of 1 h aeration, nitrogen gas N 2(g) sparging (15 and 30 min) and increasing ferric ions (Fe +3) as FeSO 4 (10, 20 and 50 mg L −1) and Fe 3O 4 nanoparticles (1, 2 and 4 g L −1) concentrations on three less hydrophobic and three more hydrophobic polycyclic aromatic hydrocarbons (PAHs) and toxicity
removals from a petrochemical industry in Izmir (Turkey) were investigated in a sonicator with a power of 650 W and an ultrasound
frequency of 35 kHz; 1 h aeration increased the yields in benzo[ b]fluoranthene, benzo[ k]fluoranthene and benzo[ a]pyrene PAHs (less hydrophobic) from 62% to 67% to around 95–97% after 150 min sonication at 60°C. However, 1 h aeration did
not contribute to the yields of more hydrophobic PAHs (indeno[1,2,3- cd]pyrene, dibenz[ a, h]anthracene, benzo[ g, h, i]perylene). The maximum yields were obtained at acidic and alkaline pH for more and less hydrophobic PAHs, respectively, after
60 and 120 min sonication at 30°C; 30 min N 2(g) sparging, 50 mg L −1 Fe +3 increased the yields of less hydropobic PAHs after 150 min sonication at 60°C. Two milligrams per liter of Fe 3O 4 nanoparticles increased both less (87–88%) and more (96–98%) hydrophobic PAH yields. The Daphnia magna acute toxicity test showed that the toxicity decreased significantly with an hour aeration, 30 min N 2(g) sparging, 50 mg L −1 Fe +3 and 2 g L −1 Fe 3O 4 nanoparticles at 60°C after 120 and 150 min sonications. Vibrio fischeri was found to be more resistant to the sonicated samples than D. magna. Significant correlations were found between the physicochemical properties of sonicated PAHs and acute toxicities both organisms. 相似文献
7.
We studied soil moisture dynamics and nitrous oxide (N 2O) fluxes from agricultural soils in the humid tropics of Costa Rica. Using a split-plot design on two soils (clay, loam) we compared two crop types (annual, perennial) each unfertilized and fertilized. Both soils are of andic origin. Their properties include relatively low bulk density and high organic matter content, water retention capacity, and hydraulic conductivity. The top 2–3 cm of the soils consists of distinct small aggregates (dia. <0.5 cm). We measured a strong gradient of bulk density and moisture within the top 7 cm of the clay soil. Using automated sampling and analysis systems we measured N 2O emissions at 4.6 h intervals, meteorological variables, soil moisture, and temperature at 0.5 h intervals. Mean daily soil moisture content at 5 cm depth ranged from 46% water filled pore space (WFPS) on clay in April 1995 to near saturation on loam during a wet period in February 1996. On both soils the aggregated surface layer always remained unsaturated. Soils emitted N 2O throughout the year. Mean N 2O fluxes were 1.04±0.72 ng N 2O-N cm −2 h −1 (mean±standard deviation) from unfertilized loam under annual crops compared to 3.54±4.31 ng N 2O-N cm −2 h −1 from the fertilized plot (351 days measurement). Fertilization dominated the temporal variation of N 2O emissions. Generally fluxes peaked shortly after fertilization and were increased for up to 6 weeks (‘post fertilization flux’). Emissions continued at a lower rate (‘background flux’) after fertilization effects faded. Mean post-fertilization fluxes were 6.3±6.5 ng N 2O-N cm −2 h −1 while the background flux rate was 2.2±1.8 ng N 2O-N cm −2 h −1. Soil moisture dynamics affected N 2O emissions. Post fertilization fluxes were highest from wet soils; fluxes from relatively dry soils increased only after rain events. N 2O emissions were weakly affected by soil moisture during phases of low N availability. Statistical modeling confirmed N availability and soil moisture as the major controls on N 2O flux. Our data suggest that small-scale differences in soil structure and moisture content cause very different biogeochemical environments within the top 7 cm of soils, which is important for net N 2O fluxes from soils. 相似文献
8.
Red lead (Pb 3O 4) has been used extensively in the past as an anti-corrosion paint for the protection of steel constructions. Prominent examples
being some of the 200,000 high-voltage pylons in Germany which have been treated with red lead anti-corrosion paints until
about 1970. Through weathering and maintenance work, paint compounds and particles are deposited on the soils beneath these
constructions. In the present study, six such “pylon soils” were investigated in order to characterize the plant availability
and plant uptake of Pb, Cd, and Zn. For comparison, three urban soils with similar levels of heavy metal contamination were
included. One phase extractions with 1 M NH 4NO 3, sequential extractions (seven steps), and extractions at different soil pH were used to evaluate the heavy metal binding
forms in the soil and availability to plants. Greenhouse experiments were conducted to determine heavy metal uptake by Lolium multiflorum and Lactuca sativa var. crispa in untreated and limed red lead paint contaminated soils. Concentrations of Pb and Zn in the pylon soils were elevated with
maximum values of 783 mg Pb kg −1 and 635 Zn mg kg −1 while the soil Cd content was similar to nearby reference soils. The pylon soils were characterized by exceptionally high
proportions of NH 4NO 3-extractable Pb reaching up to 17% of total Pb. Even if the relatively low pH of the soils is considered (pH 4.3–4.9), this
appears to be a specific feature of the red lead contamination since similarly contaminated urban soils have to be acidified
to pH 2.5 to achieve a similarly high Pb extractability. The Pb content in L. multiflorum shoots reached maximum values of 73 mg kg −1 after a cultivation time of 4 weeks in pylon soil. Lime amendment reduced the plant uptake of Pb and Zn significantly by
up to 91%. But L. sativa var. crispa cultivated on soils limed to neutral pH still contained critical Pb concentrations (up to 0.6 mg kg −1 fresh weight). Possible mechanisms for the exceptionally high plant availability of soil Pb derived from red lead paint are
discussed. 相似文献
9.
PurposeThe purpose of this study is to study the major sources, concentrations, and distributions of polycyclic aromatic hydrocarbons (PAHs) in three different types of green space in Shanghai. In addition, we will quantitatively assess the burden of PAHs in the soil, as well as the potential carcinogenic risk of PAHs in humans. These results will provide valuable information for soil remediation and human health risk management. Materials and methodsA total of 166 surface soil samples were collected in parks, greenbelts, and woodlands. Soils were extracted using accelerated solvent extraction (ASE). PAHs were analyzed by gas chromatography-mass spectrometry (GC-MS). The positive matrix factorization (PMF) model was used to identify major PAH emission sources and quantitatively assess their contributions to PAHs. The incremental lifetime cancer risk (ILCR) was used to quantify the potential health risk of PAHs. Results and discussionThe average concentrations of ∑15 PAHs are 227?±?95 ng g?1, 1632?±?251 ng g?1, and 1888?±?552 ng g?1 in the woodland, park, and greenbelt soils, respectively. The PMF results show that biomass (33%), coal (21%), vehicles (17%), natural gas (14%), oil (9%), and coke (7%) are the dominant sources of PAHs in the park soils. Diesel (40%), tire debris (30%), biomass (15%), gasoline (9%), and oil (5%) are the main sources in the greenbelt soils. Biomass (48%), vehicles (37%), and coal (15%) are the main sources in the woodland soils. The ILCRs of adults and children who are exposed to PAHs in soils range from 9.53?×?10?8~1.42?×?10?5. ConclusionIn three types of green space in Shanghai, the dominant PAHs are high–molecular weight (HMW) compounds (≥?4 rings). This may be due to the proximity of the sampling site to emission sources. In addition, low–molecular weight (LMW) PAHs (with 2–3 rings) are relatively unstable, and these compounds are prone to volatilization and degradation. Source identification indicates that biomass combustion is the most dominant PAH source in the park and woodland soils, while vehicles are the dominant PAH source in the greenbelt soils. The ILCRs of adults and children indicate potential health risks, and children have a greater health risk than adults. 相似文献
10.
Water quantity and quality were monitored for 3 years in a 360-m-long wetland with riparian fences and plants in a pastoral
dairy farming catchment. Concentrations of total nitrogen (TN), total phosphorus (TP) and Escherichia coli were 210–75,200 g N m −3, 12–58,200 g P m −3 and 2–20,000 most probable number (MPN)/100 ml, respectively. Average retentions (±standard error) for the wetland over 3 years
were 5 ± 1%, 93 ± 13% and 65 ± 9% for TN, TP and E. coli, respectively. Retentions for nitrate–N, ammonium–N, filterable reactive P and particulate C were respectively −29 ± 5%,
32 ± 10%, −53 ± 24% and 96 ± 19%. Aerobic conditions within the wetland supported nitrification but not denitrification and
it is likely that there was a high conversion rate from dissolved inputs of N and P in groundwater, to particulate N and P
and refractory dissolved forms in the wetland. The wetland was notable for its capacity to promote the formation of particulate
forms and retain them or to provide conditions suitable for retention (e.g. binding of phosphate to cations). Nitrogen retention
was generally low because about 60% was in dissolved forms (DON and NO X–N) that were not readily trapped or removed. Specific yields for N, P and E. coli were c. 10–11 kg N ha −1 year −1, 0.2 kg P ha −1 year −1 and ≤10 9 MPN ha −1 year −1, respectively, and generally much less than ranges for typical dairy pasture catchments in New Zealand. Further mitigation
of catchment runoff losses might be achieved if the upland wetland was coupled with a downslope wetland in which anoxic conditions
would promote denitrification. 相似文献
11.
The following six pig slurries obtained after acidification and/or solid/liquid separation were used in the research: original
(S) and acidified (AS) pig slurry, nonacidified (LF) and acidified (ALF) pig slurry liquid fraction, and nonacidified (SF)
and acidified (ASF) pig slurry solid fraction. Laboratory incubations were performed to assess the effect of the application
of these slurries on N mineralization and CO 2 and N 2O emissions from a sandy soil. Acidification maintained higher NH 4
+-N contents in soil particularly in the ALF-treated soil where NH 4
+-N contents were two times higher than in LF-treated soil during the 55–171-day interval. At the end of the incubation (171 days),
32.9 and 24.2 mg N kg −1 dry soil were mineralized in the ASF- and SF-treated soils, respectively, but no mineralization occurred in LF- and S-treated
soils, although acidification decreased N immobilization in ALF- (−25.3 mg N kg −1 soil) and AS- (−12.7 mg N kg −1 soil) compared to LF- (−34.4 mg N kg −1 soil) and S-treated (−18.6 mg N kg −1 soil) soils, respectively. Most of the dissolved CO 2 was lost during the acidification process. More than 90% of the applied C in the LF-treated soil was lost during the incubation,
indicating a high availability of the added organic compounds. Nitrous oxide emissions occurred only after day 12 and at a
lower rate in soils treated with acidified than nonacidified slurries. However, during the first 61 days of incubation, 1,157 μg N
kg −1 soil was lost as N 2O in the AS-treated soil and only 937 in the S-treated soil. 相似文献
12.
The effect of reduced tillage (RT) on nitrous oxide (N 2O) 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 N 2O emission of soils taken in September 2005 varied from 50 to 1,095 μg N kg −1 dry soil. The N 2O emissions of soils from the RT fields taken in September 2005 were statistically ( P < 0.05) higher or comparable than the N 2O emissions from their respective CT soil. The N 2O emission of soils taken in February 2006 varied from 0 to 233 μg N kg −1 dry soil. The N 2O emissions of soils from the RT fields taken in February 2006 tended to be higher than the N 2O emissions from their respective CT soil. A positive and significant Pearson correlation of the N 2O–N emissions with nitrate nitrogen (NO 3
−–N) content in the soil was found ( P < 0.01). Leaving the straw on the field, a typical feature of RT, decreased NO 3
−–N content of the soil and reduced N 2O emissions from RT soils. 相似文献
13.
Seasonal drought in tropical agroecosystems may affect C and N mineralization of organic residues. To understand this effect,
C and N mineralization dynamics in three tropical soils (Af, An 1, and An 2) amended with haricot bean (HB; Phaseolus vulgaris L.) and pigeon pea (PP; Cajanus cajan L.) residues (each at 5 mg g −1 dry soil) at two contrasting soil moisture contents (pF2.5 and pF3.9) were investigated under laboratory incubation for 100–135 days.
The legume residues markedly enhanced the net cumulative CO 2–C flux and its rate throughout the incubation period. The cumulative CO 2–C fluxes and their rates were lower at pF3.9 than at pF2.5 with control soils and also relatively lower with HB-treated than
PP-treated soil samples. After 100 days of incubation, 32–42% of the amended C of residues was recovered as CO 2–C. In one of the three soils (An 1), the results revealed that the decomposition of the recalcitrant fraction was more inhibited by drought stress than easily
degradable fraction, suggesting further studies of moisture stress and litter quality interactions. Significantly ( p < 0.05) greater NH 4+–N and NO 3−–N were produced with PP-treated (C/N ratio, 20.4) than HB-treated (C/N ratio, 40.6) soil samples. Greater net N mineralization
or lower immobilization was displayed at pF2.5 than at pF3.9 with all soil samples. Strikingly, N was immobilized equivocally
in both NH 4+–N and NO 3−–N forms, challenging the paradigm that ammonium is the preferred N source for microorganisms. The results strongly exhibited
altered C/N stoichiometry due to drought stress substantially affecting the active microbial functional groups, fungi being
dominant over bacteria. Interestingly, the results showed that legume residues can be potential fertilizer sources for nutrient-depleted
tropical soils. In addition, application of plant residue can help to counter the N loss caused by leaching. It can also synchronize
crop N uptake and N release from soil by utilizing microbes as an ephemeral nutrient pool during the early crop growth period. 相似文献
14.
Cattle feedyards can impact local environments through emission of ammonia and dust deposited on nearby land. Impacts range
from beneficial fertilization of cropland to detrimental effects on sensitive ecosystems. Shortgrass prairie downwind from
an adjacent feedyard on the southern High Plains of Texas, USA changed from perennial grasses to annual weeds. It was hypothesized
that N enrichment from the feedyard initiated the cascade of negative ecological change. Objectives were to determine the
distribution of soil nitrogen and estimate N loading to the pasture. Soil samples were collected from 119 locations across
the pasture and soil total N (TN), nitrate-N and ammonium-N (AN) determined in the top 30 cm. Soil TN concentration decreased
with distance downwind from the feedyard from 1.6 ± 0.2 g kg −1 at 75 m to 1.2 ± 0.05 g kg −1 at 582 m. Nitrate-N concentration decreased within 200 m of the feedyard and changed little at greater distances. Ammonium-N
concentration decreased linearly ( P < 0.001) with increasing distance from the feedyard from 7.9 ± 1.7 mg kg −1 within 75 m from the feedyard to 5.8 ± 1.5 mg kg −1 at more than 550 m from the feedyard; however, distance only explained 12% of the variability in AN concentration. Maximum
nitrogen loading, from 75 to 106 m from the feedyard, was 49 kg ha −1 year −1 over 34 years and decreased with distance from the feedyard. An estimate of net dry deposition of ammonia indicated that
it contributed negligibly to N loading to the pasture. Nitrogen enrichment that potentially shifted vegetation from perennial
grasses to annual weeds affected soil N up to 500 m from the feedyard; however, measured organic and inorganic N beyond that
returned to typical and expected levels for undisturbed shortgrass prairie.
相似文献
15.
The organophosphorus insecticide, chlorpyrifos, has been widely applied in agriculture; in veterinary, against household pests;
and in subterranean termite control. Due to its slow rate of degradation in soil, it can persist for extended periods in soil
with a significant threat to environment and public health. The mixed and pure fungi were isolated from three soils by enrichment
technique. The enriched mixed fungal cultures were capable of biodegrading chlorpyrifos (300 mg L −1) when cultivated in Czapek Dox medium. The identified pure fungal strain, Acremonium sp., utilized chlorpyrifos as a source of carbon and nitrogen. The highest chlorpyrifos degradation (83.9%) by Acremonium sp. strain GFRC-1 was found when cultivated in the nutrient medium with full nutrients. Desdiethyl chlorpyrifos was detected
as a major biodegradation product of chlorpyrifos. The isolated fungal strain will be used for developing bioremediation strategy
for chlorpyrifos-polluted soils. 相似文献
16.
Little information is available about the effects of cover crops on soil labile organic carbon (C), especially in Australia.
In this study, two cover crop species, i.e., wheat and Saia oat, were broadcast-seeded in May 2009 and then crop biomass was
crimp-rolled onto the soil surface at anthesis in October 2009 in southeastern Australia. Soil and crop residue samples were
taken in December 2009 to investigate the short-term effects of cover crops on soil pH, moisture, NH 4+–N, NO 3−–N, soluble organic C and nitrogen (N), total organic C and N, and C mineralization in comparison with a nil-crop control
(CK). The soil is a Chromic Luvisol according to the FAO classification with 48.4 ± 2.2% sand, 19.5 ± 2.1% silt, and 32.1 ± 2.1%
clay. An exponential model fitting was employed to assess soil potentially labile organic C ( C
0) and easily decomposable organic C for all treatments based on 46-day incubations. The results showed that crop residue biomass
significantly decreased over the course of 2-month decomposition. The cover crop treatments had significantly higher soil
pH, soluble organic C and N, cumulative CO 2–C, C
0, and easily decomposable organic C, but significantly lower NO 3−–N than the CK. However, no significant differences were found in soil moisture, NH 4+–N, and total organic C and N contents among the treatments. Our results indicated that the short-term cover crops increased
soil labile organic C pools, which might have implications for local agricultural ecosystem managements in this region. 相似文献
17.
Background, aim, and scope In the soil environment, polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) are of great environmental and human
health concerns due to their widespread occurrence, persistence, and carcinogenic properties. Bioremediation of contaminated
soil is a cost-effective, environmentally friendly, and publicly acceptable approach to address the removal of environmental
contaminants. However, bioremediation of contaminants depends on plant–microbe interactions in the rhizosphere. The microorganisms
that can mineralize various PAHs have PAH dioxygenase genes like nahAc, phnAc, and pdo1. To understand the fate of pyrene in rhizospheric and non-rhizospheric soils in the presence or absence of Pb, pyrene biodegradation,
bacterial community structure, and dioxygenase genes were investigated in a pot experiment. 相似文献
18.
Long-term effects of mineral fertilization on microbial biomass C (MBC), basal respiration ( R
B), substrate-induced respiration ( R
S), β-glucosidase activity, and the r– K-growth strategy of soil microflora were investigated using a field trial on grassland established in 1969. The experimental
plots were fertilized at three rates of mineral N (0, 80, and 160 kg ha −1 year −1) with 32 kg P ha −1 year −1 and 100 kg K ha −1 year −1. No fertilizer was applied on the control plots (C). The application of a mineral fertilizer led to lower values of the MBC
and R
B, probably as a result of fast mineralization of available substrate after an input of the mineral fertilizer. The application
of mineral N decreased the content of C extracted by 0.5 M K 2SO 4 ( C
ex). A positive correlation was found between pH and the proportion of active microflora ( R
S/MBC). The specific growth rate ( μ) of soil heterotrophs was higher in the fertilized than in unfertilized soils, suggesting the stimulation of r-strategists, probably as the result of the presence of available P and rhizodepositions. The cessation of fertilization with
320 kg N ha −1 year −1 (NF) in 1989 also stimulated r-strategists compared to C soil, probably as the result of the higher content of available P in the NF soil than in the C
soil. 相似文献
19.
Carbon flux represents carbon uptake from or release to the atmosphere in desert ecosystems, yet the changing pattern of carbon flux in desert ecosystems and its dependence on soil cover type and rainfall amount are poorly understood. We measured net carbon fluxes (NCF) in soil with four cover types (moss crusted soil, cyanobacteria/lichen crusted soil, bareland and semishrub Ephedra distachya-inhabited site) from April to October of 2010 and 2011, and NCF and dark respiration (DR) after four rainfall amounts (0, 2, 5, and 15 mm) in cyanobacteria/lichen crusted soil, bareland and the E. distachya-inhabited site. NCF in the E. distachya-inhabited site differed significantly from those of the other three soil cover types, while no difference was observed between the moss and cyanobacteria/lichen crusted soils or between the two crusted soils and bareland on most measurement occasions. NCF ranged from −0.28 ± 0.14 to 1.2 ± 0.07 μmol m −2 s −1 in the biologically crusted soils, and from −2.2 ± 0.27 to 0.46 ± 0.03 μmol m −2 s −1 at the E. distachya-inhabited site. Daily NCF in the biologically crusted soils and bareland showed carbon release at most times and total carbon production ranged from 48.8 ± 5.4 gC m −2 yr −1 to 50.9 ± 3.8 gC m −2 yr −1, while the E. distachya-inhabited site showed a total carbon uptake of −57.0 ± 9.9 gC m −2 yr −1. Daily variances in NCF were well-explained by variances in surface soil temperature, and seasonal NCF showed a significant linear relationship with soil moisture in the two biologically crusted soils and bareland when soil volumetric water content was less than 3%. Rainfall elicited intense carbon release in cyanobacteria/lichen crusted soil, bareland and at the E. distachya-inhabited site, and both NCF and DR were positive in the first two days after rainfall treatments. Mean NCF and DR were not different between rainfall amounts of 2, 5 and 15 mm in cyanobacteria/lichen crusted soil and bareland, while they were significantly higher after 15 mm rainfall treatment compared with 2 mm and 5 mm treatments at the E. distachya-inhabited site. Mean NCF and DR in the first two days increased logistically with rainfall amount. Based on our findings, we suggest that E. distachya-inhabited sites contribute to carbon uptake in the Gurbantunggute Desert, while biologically crusted soils exhibit carbon release for most of the year. Even though photosynthesis immediately following rainfall can be stimulated, carbon uptake effect in biologically crusted soil is likely intermittent and confined to periods when moisture is available. 相似文献
20.
Pot experiments were carried out over two growing periods to assay the biocontrol efficacy and rhizosphere colonization of
Trichoderma harzianum SQR-T037 (SQR-T037) applied as SQR-T037 conidia suspension (TCS), SQR-T037 conidia suspension blended with organic fertilizer
(TBF), or SQR-T037 fermented organic fertilizer (TFF). Each formulation had three T. harzianum numbers. In two experiments, Percent Disease Indexes (PDIs) decreased with the increase of SQR-T037 number added to soils.
The TFF treatment consistently exhibited the lowest PDIs at same amendment rate of SQR-T037 and 0–8.9%, 25.6–78.9%, and 4.4–50.0%
of PDIs were found in TFF, TCS, and TBF treatment, respectively. Soils treated with TFF showed the highest SQR-T037 population
in rhizosphere and bulk soil. Decrease of Fusarium oxysporum population in both bulk and rhizosphere soils occurred in the treatment SQR-T037 at 10 5 and 10 6 cfug −1 soil rate. The TFF treatment at the SQR-T037 rate of 10 3 cfug −1 soil significantly ( p < 0.05) increased SQR-T037 population within the rhizoplane but had no effect on F. oxysporum population when compared to TCS and TBF. Generally, TFF treatments were superior to TCS and TBF treatments on disease control
by sustaining colonization of SQR-T037 and decreasing F. oxysporum abundance in the rhizosphere soil. We propose that TFF treatment at SQR-T037 rate of 10 7 cfug −1 (i.e., 10 5 cfug −1 soil after applied to soil) was the best formulation for controlling Fusarium wilt of cucumber. 相似文献
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