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1.
The leachability of B and salts from two fly ash-amended soils was conducted in a column leaching experiment. Fly ash was applied to the surface 3 cm of a Baywood (acid) sand and an Arizo (calcareous) sandy, loam at 5% by weight; the columns were continously leached with Colorado River water at two different pH's. Boron from fly ash was solubilized more readily in the Baywood than in the Arizo soil. Addition of fly ash increased B levels in the leachates from 0.25 to 2.35 μg ml?1 (Baywood) and 0.93 μg ml?1 (Arizo). Acidified leaching water had no significant effect on B leaching patterns but resulted in leaching higher soluble salts. Approximately 348 and 161 cm of water for the Arizo and the Baywood soils respectively, would be required to reduce the B concentration below a critical limit for B sensitive crops. It is suggested that crops planted when fly ash is applied for disposal/recycling on land should be both salt and B tolerant.  相似文献   

2.
Fly ash was collected from a coal-fired power plant in and near the U.S. Department of Energy Savannah River Site to study the feasibility of the application of fly ash compost mixture to soils for the availability and uptake of various elements by corn (Zea mays L.). The crop was grown in potted Ogeechee sandy loam soil using eight treatments: soil alone, soil amended with 15% compost, and soil amended with 2, 5, 10, 15, 20 and 25% of fly ash-amended compost. It was observed that 20–25% fly ash and compost soil ratio treatments generally increased plant growth and the yield. The plant uptake of K, Mn, and Cu increased with increasing percentages (2–25%) of fly ash+compost: soil ratios. The total content of K in plants was positively correlated with the dry matter yield of corn. This study indicates that the application of fly ash blended with compost to soil is beneficial to corn production without causing any deleterious effects on plant growth and plant composition.  相似文献   

3.
Crop yields in the Atlantic Coastal Plain of the U.S.A. are limited by the low moisture-holding capacities of the sandy soils common to the region. Corn was grown in a Hammonton loamy sand soil amended with fly ash (0, 5, 10, 20, 30, and 40%) to determine if the ash rates required to improve soil moisture holding capacity would adversely affect plant growth, or soil and plant levels of nutrients and heavy metals. Fly ash increased soil test levels of P, K, Ca, Mg, Mn, Cu, Zn, B, Cd, Cr, Ni, and Pb. Nutrient concentrations in plants grown in the ash-amended soils, except P, Mn, and B, remained within established sufficiency ranges. The 20 and 40% ash rates increased soil soluble salt (EC) levels from 0.2 to 1.1–1.5 and 1.7–2.1 mmho cm?1, soil pH from 5.6 to 6.0–6.4 or 6.3–6.9, and extractable B from 0.2 to 2.2–5.9 and 2.2–9.0 mg kg?1. Fly ash reduced corn germination, delayed seedling emergence, and reduced root and shoot dry weights. Plant B concentrations at the 40% ash rate were in the phytotoxic range (136–189 mg kg?1). Management practices that allow for pre-leaching of B and soluble salts will likely be required to attain satisfactory corn growth in ash-amended soils.  相似文献   

4.

Purpose

Fly ash can reduce CO2 emission from soils via biochemical (i.e., inhibition of microbial activity) and physicochemical (i.e., carbonation) mechanisms. This study investigated the effects of fly ash amendment on biochemical and physicochemical reduction in CO2 emission from normal and saline soils.

Materials and methods

The physicochemical mechanisms of reduction in CO2 emission by fly ash were estimated in a batch experiment with carbonate solution as a CO2 source by the scanning electron microscope (SEM) and inductively coupled plasma analyses. Biochemical mechanisms of reduction in CO2 emission by fly ash were investigated in a 3-day laboratory incubation experiment with normal and saline soils in the absence and presence of fly ash. Finally, the effects of fly ash amendment at a variety rate from 2 to 15?% (w/w) on CO2 emission from normal and saline soils in the presence of additional organic carbon source (glucose) were investigated through a 15-day laboratory incubation study.

Results and discussion

In the batch experiment with carbonate solution, both the SEM image of fly ash and changes in soluble Ca and Mg concentrations during reaction with carbonate suggested that the formation of CaCO3 and MgCO3 via carbonation was the principal physicochemical mechanism of carbonate removal by fly ash. In the 3-day incubation study conducted to examine biochemical mechanisms of reduction in CO2 emission by fly ash, microbial respiration of saline soil was inhibited (P?<?0.05) by fly ash due to high pH, salinity, and boron concentration of fly ash; meanwhile, for normal soil, there was no inhibitory effect of fly ash on microbial respiration. In the 15-day incubation with glucose, fly ash application at a variety rates from 2 to 15?% (w/w) reduced CO2 emission by 3.6 to 21.4?% for normal and by 19.8 to 30.3?% for saline soil compared to the control without fly ash. For saline soil, the reduction in CO2 emission was attributed primarily to inhibition of microbial respiration by fly ash; however, for normal soil in which suppression of microbial respiration by fly ash was not apparent, carbonation was believed to play an important role in reduction of CO2 emission.

Conclusions

Therefore, fly ash may be helpful in reducing CO2 emission from normal soils via carbonation. For saline soil, however, fly ash needs to be carefully considered as a soil amendment to reduce CO2 emission as it can inhibit soil microbial activities and thus degrade soil quality.  相似文献   

5.
Mineralization of organic matter and microbial activities in an intensively cultivated acid, N-rich peat soil planted with Salix sp. cv. aquatica were examined for 3 yr. The soil was amended with wood ash or NPK fertilizers providing N as ammonium nitrate or urea. The wood ash amendment (10 tons ha?1) increased soil pH from 4.6 to 5.5 and increased markedly all microbial activities measured, resulting in increased mineralization and N availability, and in loss of 9% total soil N during the first year. The addition of ammonium nitrate caused a corresponding though less pronounced increase in N mineralization. Cellulose decomposition increased in all amended soils, reaching rates 53–86% higher than in non-amended soil. Potential N2 fixation (C2H2 reduction) by free-living organisms was increased by the ash-amendment. Potential denitrification rates were positively correlated (r = 0.98) with the presence of water-soluble organic-C, which was more abundant in ash-amended and non-amended soils than in the soils fertilized with N.  相似文献   

6.
Wood ash is a residual material produced during biomass burning. In the northeastern United States up to 80 % of the ash is spread on agricultural lands as a liming amendment with the remainder being disposed of in landfills. As well as raising soil pH, wood ash also adds plant nutrients to soil. This study is an examination of the plant availability of the P in 8 different soils amended with one wood ash. Plant availability was assessed by measuring the biomass and P concentration of corn (Zea mays) L.) plants grown in the greenhouse for 28 d in soil amended with either CaCO3 (control), wood ash to supply 200 mg kg?1 total P, or monocalcium phosphate (MCP) to supply 200 mg kg?1 total P and CaCO3. Both corn growth and P uptake were highest in the MCP treatments, intermediate in the wood ash treatments, and lowest in the controls for all soil types. The soil property which seemed to have the greatest influence on P availability was pH buffer capacity. The soils with the greatest capacity to buffer OH additions also tended to exhibit the greatest absolute P uptake from wood ash-amended soils and the greatest P uptake relative to that from MCP-amended soils. The ability of soil test extractants to predict uptake of P in the three soil treatments was examined. A buffered ammonium acetate extradant overestimated P availability in the ash-amended soils relative to the MCP-amended soils. An unbuffered, acid, fluoride-containing extract provided a measure of P levels that was consistent with P uptake from all soil treatments. In this study the predictive relationship was as follows: P uptake = 0.017× (Bray P, mg kg?1) + 1.19; r = 0.81.  相似文献   

7.
With the increasing use of conservation tillage, many questions about the long-term effects of tillage system on soil physical properties have been raised. Studies were conducted to evaluate saturated hydraulic conductivity (KSAT), macropore characteristics and air permeability of two silty soils as affected by long-term conservation tillage systems in the state of Indiana. Measurements were taken during the tenth year of a tillage study on a Chalmers silty clay loam (Typic Haplaquoll) and the fifth year of a study on a Clermont silt loam (Typic Ochraqualf). Tillage systems were moldboard plow, chisel, ridge till-plant, and no-till in a rotation of corn (Zea mays L.) and soya beans (Glycine max L.). Saturated hydraulic conductivity was measured on large soil columns (25 × 25 × 40 cm) before spring tillage, and macropore size and continuity were assessed with staining techniques. Intact soil cores (8 cm diam × 10 cm) were collected in early July in the row and non-trafficked interrow at three depths (10–20, 20–30, and 30–40 cm) and were analyzed for air permeability (Kair), air-filled porosity and bulk density. Saturated hydraulic conductivity values were in the order plow > chisel > ridge till > no-till for the Chalmers soil and were significantly greater in the plow treatment than in the other 3 tillage systems on the Clermont soil. Differences in KSAT between the 2 soils were generally greater than differences among tillage systems, and coefficients of variation were lower for treatments that did not include may fall tillage operations. At the 10-cm depth on the Chalmers soil, the chisel treatment had the greatest number of stained cylindrical channels, whereas for the Clermont soil the ridge till had the greatest number at this depth. Although the no-till treatment had similar or fewer total channels, it had the most continuous channels from the 10-cm depth to the 20- and 30-cm depths on both soils. Tillage system, row position and depth all affected Kair. On the Chalmers soil, plow, chisel and ridge systems had lower Kair between rows than in the row at the 10–20-cm depth, whereas no-till had constant Kair in the row and between the row. On the Clermont soil, ridge till had the highest Kair of all treatments at the 10–20-cm depth, and no-till had the highest Kair of all treatments at the 20–30-cm depth.  相似文献   

8.
Fang  M.  Wong  J. W. C. 《Water, air, and soil pollution》2000,124(3-4):333-343
The thermophilic bacteria in compost made from coal flyash-amended sewage sludge were isolated and identified using theBiolog system to investigate the effect of coal fly ash on thethermophilic decomposition of sewage sludge during composting. Atotal of 8 species of Bacillus were isolated from thecompost and Bacillus brevis was the dominant speciesduring the entire composting process. The present resultsdemonstrate that the Biolog system is a fast and simple methodfor identifying bacterial species in compost, provided thatoptimum conditions could be achieved for the Bacillusculture. Adding coal fly ash as an amendment did not change thedominant bacteria species during composting, but decreased thepopulation and diversity of thermophilic bacteria species due tothe high alkalinity and salinity. Fewer thermophilic bacteriawere detected in ash-amended sewage sludge compost than insludge compost. There was also reduced metabolic activityobserved in the ash-amended sludge compost from the data ofCO2 evolution and weight loss. Although ash amendmentdemonstrated a negative effect on the population and diversityduring thermophilic phase, it did not cause any significanteffect on compost maturity.  相似文献   

9.
Application of fine-textured and Ca-rich fly ash may be helpful in enhancing soil carbon content via protecting soil organic C (SOC) by organo-mineral complexation and via reducing CO2 emission by carbonation (e.g. formation of CaCO3). However, very limited information is available on the effects of fly ash application on gases loss of C and soil C content. In this study, to estimate the potential use of fly ash as a soil amendment for SOC enhancement purposes, the effects of fly ash application (0, 5, and 10 w/w %) on microbial biomass C (MBC), CH4 and CO2 emissions, and on soil C content were investigated. A 60-days incubation experiment was conducted with an acidic soil in the presence of organic input (pig manure compost, PMC; hairy vetch, HV) with contrasting substrate quality under changing water regime from water-logged to unsaturated via a transition period. Fly ash application did not affect MBC under water-unsaturated conditions, but reduced (P < 0.01) microbial growth under water-logged conditions, probably due to the increased solubility of a certain toxic element such as arsenic under the anaerobic conditions. Across the 60 days of incubation, the CO2 emission was reduced by fly ash regardless of organic input by 20.5–41.3%; meanwhile, a decline of CH4 emission by fly ash application was significant (P < 0.05) only in the HV treatment. Overall, fly ash application slowed down gases C loss and increased soil C content, probably due to the retardation of CH4 and CO2 emission as well as the addition of C contained in the fly ash. Biochemical (inhibition of microbial activity), chemical (formation of CaCO3 via carbonation), and physical (restriction of gas diffusion) mechanisms were suggested for the fly ash effects.  相似文献   

10.
《CATENA》2004,58(2):183-213
Standard field indicators, currently used for hydric soil delineations [USDA-NRCS, 1998. Field indicators of hydric soils in the United States, Version 4.0. In: G.W. Hurt et al. (Ed.), United States Department of Agriculture-NRCS, Fort Worth, TX], are useful, but in some cases, they can be subjective, difficult to recognize, or time consuming to assess. Magnetic susceptibility (MS) measurements, acquired rapidly in the field with a portable meter, have great potential to help soil scientists delineate and map areas of hydric soils more precisely and objectively. At five sites in Illinois (from 5 to 15 ha in area) with contrasting soil types and glacial histories, the MS values of surface soils were measured along transects, and afterwards mapped and contoured. The MS values were found to be consistently higher in well-drained soils and lower in hydric soils, reflecting anaerobic deterioration of both detrital magnetite and soil-formed ferrimagnetics. At each site, volumetric MS values were statistically compared to field indicators to determine a critical MS value for hydric soil delineation. Such critical values range between 22×10−5 and 33×10−5 SI in silty loessal or alluvial soils in Illinois, but are as high as 61×10−5 SI at a site with fine sandy soil. A higher magnetite content and slower dissolution rate in sandy soils may explain the difference. Among sites with silty parent material, the lowest critical value (22×10−5 SI) occurs in soil with low pH (4.5–5.5) since acidic conditions are less favorable to ferrimagnetic mineral neoformation and enhance magnetite dissolution. Because of their sensitivity to parent material properties and soil pH, critical MS values must be determined on a site specific basis.The MS of studied soil samples (0–5 cm depth) is mainly controlled by neoformed ultrafine ferrimagnetics and detrital magnetite concentrations, with a minor contribution from anthropogenic fly ash. Neoformed ferrimagnetics are present in all samples but, based on high χFD% (∼5% to 10%), are most prevalent in high pH Mollisols of northeastern Illinois. Scanning electron microscope images display significantly more detrital magnetite alteration in hydric soils, substantiating that reductive dissolution of magnetite (aided by microorganisms) is a primary cause for lower MS. Fly ash comprises 8–50% of the >5 μm strongly magnetic particles and typically accounts for 5–15% of the total MS signal. The proportion of fly ash in >5 μm strongly magnetic fractions is greater in hydric soils because of lower natural magnetite contents, possibly combined with historical topsoil accumulation in lower landscapes. Magnetic fly ash particles are also more altered in low MS soils, implying that significant magnetite dissolution can occur in less than 150 years.  相似文献   

11.
A field experiment was conducted at ICAR-Indian Institute of Sugarcane Research, Lucknow, with three tillage practices (T1: Control- two times ploughing with harrow and cultivator, each followed by planking before sugarcane planting; T2: Deep tillage with disc plough (depth 25–30 cm) before planting followed by harrowing, cultivator, and planking; and T3: Subsoiling at 45–50 cm and deep tillage with disc plough/moldboard plough (depth 25–30 cm) followed by harrowing, cultivator, and planking before planting, two soil moisture regimes (M1: 0.5 irrigation water (IW)/cumulative pan evaporation (?CPE) ratio and M2: 0.75 IW/CPE ratio) at 7.5 cm depth of IW, and four N levels (N1- 0, N2- 75, N3- 150, and N4-225 kg N ha?1) in sugarcane plant crop. Deep tillage and subsoiling increased porosity and reduced bulk density in surface/subsurface soil. Further, these physical changes also improved soil biological and chemical properties responsible for higher crop growth and yield. Deep tillage and subsoiling reduced the compaction by 6.12% in 0–15 cm depth in sugarcane plant crop at maximum tillering stage. The highest N uptake (158.5 kg ha?1) was analyzed with deep tillage and subsoiling compared to all other tillage practices. Maintaining suboptimal moisture regime with deep tillage and subsoiling showed the highest IW use efficiency (157.16 kg cane kg?1 N applied). Mean soil microbial biomass carbon (SMBC) in ratoon crop was higher compared to plant crop. During initial tillering stage, ratoon crop showed higher SMBC with application of deep tillage and subsoiling (1209 mg CO2-C g?1 soil day?1) at 0–15 cm depth and 1082.9 mg CO2-C g?1 soil day?1 at 15–30 cm depth. Thus, it could be concluded that besides improving sugarcane yield, soil health could be sustained by adopting subsoiling (45–50 cm depth) and deep tillage (20–25 cm depth), with soil moisture regime of 0.75 IW/CPE and application of 150 kg N ha?1 in sugarcane (plant crop).  相似文献   

12.
Fly ash‐enriched soils occur widely throughout the industrial regions of eastern Germany and in other heavily industrialized areas. A limited amount of research has suggested that fly ash enrichment alters the water repellency (WR) characteristics of soil. This study concentrates on the influence of fly ash enrichment on WR of forest soils with a focus on forest floor horizons (FFHs). The soils were a Technosol developed from pure lignite fly ash, FFHs with lignite fly ash, and FFHs without lignite fly ash enrichment. Three different methods (water drop penetration time, WDPT, test; water and ethanol sorptivity measurement and the derived contact angle, θR; and the Wilhelmy‐plate method contact angle, θwpm) were used to characterize soil WR. Additionally, carbon composition was determined using 13C‐NMR spectra to interpret the influence of the organic matter. This study showed that the actual WR characteristics of undisturbed, fly ash‐enriched soils can be explained in terms of the composition of soil organic matter, with the fly ash content playing only a minimal role. Regardless of the huge amounts of mainly mineral fly ash enrichment, all undisturbed FFHs were comparable in their WR characteristics and their carbon compositions, which were dominated by recently‐formed organic substances. The pure fly ash deposit was strongly influenced by lignite remains, with the topsoil having a greater content of recent plant residues. Thus, the undisturbed topsoil was more repellent than the subsoil. When homogenized samples were used, we found a distinct effect of fly ash enrichment and structure on WR. Water repellency of the pure fly ash horizons did not differ distinctly, while the fly ash enrichment in the FFHs caused a significant reduction in WR. The methods used (WDPT, θR and θwpm) identified these differences similarly. These results led to the assumption that water‐repellent structures of the topsoils were probably the result of hydrophobic coatings of recently formed organic substances, whereby the initially high wettability of the mainly mineral, hydrophilic fly ash particles was reduced.  相似文献   

13.
Tillage depth influences the soil–water–plant ecosystem, thereby affecting crop yield and quality. The effects of tillage depth on soil physical properties and sugarbeet (Beta vulgaris L.) yield and quality were evaluated. A field study composed of two tillage depths [10 cm, referred to as shallow (ST), and 20 cm, referred to as deep (DT)] was conducted on a Lihen sandy loam soil in spring 2007 at the Agricultural Research Service (ARS) irrigated research farm near Williston, North Dakota. Soil bulk density (ρb), gravimetric water content (θw), and saturated hydraulic conductivity (Ks) were measured three times during the growing season at four depth increments to 40 cm deep. Samples were taken approximately 0.5 m apart within the crop row of irrigated sugarbeet. Soil air-filled pore volume (εa) was calculated from soil bulk density and water content data. Soil penetration resistance (PR) was also measured in 2.5-cm increments to a depth of 35 cm. Roots were hand-harvested from each plot, and each sample consisted of the roots within an area consisting of two adjacent rows 1.5 m long. Soil ρb was greater in ST than in DT, whereas Ks was greater with DT than with ST. Soil PR was significantly greater in ST than in DT at the 0- to 20-cm depth. Soil θw and εa were slightly greater in DT than those under ST. Although tillage depth had no significant effect on sugarbeet population, root yield, or sucrose content, a small difference in sucrose yield between two depths of tillage may be attributed to reduced ρb, increased water intake, improved aeration, and increased response to nitrogen uptake under DT than under ST. It was concluded that tillage depth enhanced soil physical quality and had little effect on sugarbeet yield or quality.  相似文献   

14.
Abstract

Fly ash from the coal‐burning industry may be a potential inorganic soil amendment to increase rice productivity and to restore the soil nutrient balance in paddy soil. In this study, fly ash was applied at rates of 0, 40, 80, and 120 Mg ha?1 in two paddy soils (silt loam in Yehari and loamy sand in Daegok). During rice cultivation, available phosphorus (P) increased significantly with fly ash application, as there was high content of P (786 mg kg?1) in the applied fly ash. In addition, high content of silicon (Si) and high pH of fly ash contributed to increased available‐P content by ion competition between phosphate and silicate and by neutralization of soil acidity, respectively. With fly‐ash application, water‐soluble P (W‐P) content increased significantly together with increasing aluminum‐bound P (Al‐P) and calcium‐bound P (Ca‐P) fractions. By contrast, iron‐bound P (Fe‐P) decreased significantly because of reduction of iron under the flooded paddy soil during rice cultivation. The present experiment indicated that addition of fly ash had a positive benefit on increasing the P availability.  相似文献   

15.
An experiment was conducted to determine the effect of four tillage systems (moldboard plow, chisel plow, Paraplow and no-till) on soil aggregate shear strength and bulk density. Two soils, a Canisteo clay loam (fine-loamy, mixed (calcareous), mesic, Typic Haplaquoll) and a Haig silt loam (fine, montmorillonitic, mesic, Typic Argiaquoll) were used in this study. Soil samples were collected from the 0.075–0.15-m-depth increment in 1983 and the 0.075–0.15- and 0.225–0.30-m-depth increments in 1985. Shear strength of soil aggregates 0.02–0.03 m in diameter was measured by a fall-cone penetrometer and bulk density of the same aggregates was measured by gamma-ray attenuation. Aggregates were tested at soil water matric potentials (ψm) of −0.2, −1.1 and −4.0 kPa in 1983 and at ψm of −0.2, −1.1, −4.0 and −7.9 kPa in 1985. Tillage for the 1983 growing season was conducted under very wet conditions, whereas tillage for the 1985 growing season was conducted under much drier conditions. Samples collected in 1983 showed little tillage effect on shear strength or bulk density. In 1985, tillage had an effect on shear strength and bulk density for the Haig soil, but not for the Canisteo soil. Much of the tillage effect on soil aggregate shear strength could be explained by tillage-induced changes in the aggregate bulk density. As bulk density decreased, soil aggregate shear strength decreased.Sampling depth had no effect on soil aggregate shear strength or bulk density. Matric potential had an effect on soil aggregate shear strength and bulk density. As matric potential decreased, both shear strength and bulk density increased.  相似文献   

16.
Fly ash and biosolid wastes can be mixed and applied to soil as a means of disposal. A significant decline in soil respiration following waste application indicates restricted activities of functional microbial populations. Weathering decreases salinity and neutralizes alkalinity in fly ash, but there is little information on the effects of unweathered fly ash and biosolid mixtures on soil carbon (C) mineralization. The objective of this study was to determine the effects of a weathered fly ash–limestone scrubber residue (LSR) mixed with an aerobically digested biosolid on soil respiration in a laboratory incubation study. Biosolids significantly increased carbon dioxide (CO2) production (p < 0.05), but up to 6.75% (w/w) fly ash did not. Mean total C mineralization was 770 mg CO2‐C kg?1 soil in the control and 3,810 mg CO2‐C kg?1 soil in the 6.75% (w/w) biosolid treatment. Fly ash with neutral pH and low salinity appears unlikely to affect soil and biosolid C mineralization.  相似文献   

17.
Agronomic use of coal combustion by-products is often associated with boron (B) excess in amended soils and subsequently in plants. A greenhouse study with corn (Zea mays L.) as test plant was conducted to determine safe application rates of five fly ashes and one flue gas desulfurization gypsum (FDG). All by-products increased soil and corn tissue B concentration, in some cases above toxicity levels which are 5 mg hot water soluble B (hwsB) kg?1 soil and 100 mg B kg?1 in corn tissue. Acceptable application rates varied from 4 to 100 Mg ha? for different by-products. Leaching and weathering of a high B fly ash under ponding conditions decreased its B content and that of corn grown in fly ash amended soil, while leaching of the same fly ash under laboratory conditions increased fly ash B availability to corn in comparison to the fresh fly ash. Hot water soluble B in fly ash or FDG amended soil correlated very well with corn tissue B. Hot water soluble B in fly ash amended soil could be predicted based on soil pH and B solubility in ash at different pH values but not so in the case of FDG. Another greenhouse study was conducted to compare the influence of FDG and Ca(OH)2 on B concentration in spinach (Spinacia oleracea L.) leaves grown in soil amended with the high B fly ash. The Ca(OH)2 significantly decreased tissue B content, while FDG did not affect B uptake from fly ash amended soil.  相似文献   

18.
Unweathered, acidic fly ash from a coal-fired power plant was applied to alfalfa meal-amended agricultural soil at levels equivalent to 0, 100, 400, and 700 tonne ha?1. Amended soils were placed in respirometer jars and monitored for C02-C evolution over a 37-day period. Fly ash applications of 400 and 700 tonne ha?1 reduced C02-C production significantly compared to 0 and 100 tonne ha?1 treatments. Carbon dioxide-carbon from all treatments was considerably greater than that from soil treated with 1000 ppm CdCl2. The results suggest that soil heterotrophic microbial activity may be impacted minimally by relatively low levels of fly ash application, but may be inhibited by higher levels of fly ash. Several metals were present at potentially toxic levels in the fly ash employed and may have accounted for the inhibition of CO2 C evolution. The availability of some of these metals was indicated in companion plant uptake experiments.  相似文献   

19.
Differences in the mechanisms of storage and decomposition of organic matter (OM) between minimum tillage (MT) and conventional tillage (CT) are generally attributed to differences in the physical impact through tillage, but less is known about the effects of residue location. We conducted an incubation experiment at a water content of 60% of the maximum water‐holding capacity and 15°C with soils from CT (0–25 cm tillage depth) and MT fields (0–5 cm tillage depth) with 15N‐labeled maize straw incorporated to different depths (CT simulations: 0–15 cm; MT simulations: 0–5 cm) for 28 d in order to determine the effects of the tillage simulation on (1) mineralization of recently added residues, (2) the dynamics of macroaggregate formation and physical protection of OM, and (3) the partitioning of maize‐derived C and N within soil OM fractions. The MT simulations showed lower relative C losses, and the amount of maize‐C mineralized after 28 d of incubation was slightly but significantly lower in the MT simulations with maize added (MTmaize) than in the respective CT (CTmaize) simulations. The formation of new water‐stable macroaggregates occurred during the phase of the highest microbial activity, with a maximum peak 8 d after the start of incubation. The newly formed macroaggregates were an important location for the short‐term stabilization of C and N with a higher importance for MTmaize than for CTmaize simulations. In conclusion, our results suggest that a higher amount of OM in MT surface soils compared with CT surface soils may not only result from decreased macroaggregate destruction under reduced tillage but also from a higher efficiency of C retention due to a more concentrated residue input.  相似文献   

20.
Diffusion coefficients (D) of CO2 at 0–10 cm layers in undisturbed and tilled soil conditions were estimated using the Penman (Penman HL. 1940. Gas and vapor movement in soil, 1. The diffusion of vapours through porous solids. J Agric Sci. 30:437–463), Millington–Quirk (Millington RJ, Quirk JP. 1960. Transport in porous media. In: Van Baren FA, editor. Transactions of the 7th International Congress of Soil Science. Vol. 1. Amsterdam: Elsevier. p. 97–106), Ridgwell et al. (Ridgwell AJ, Marshall SJ, Gregson K. 1999. Consumption of atmospheric methane by soils: A process-based model. Global Biogeochem Cy. 13:59–70), Troeh et al. (Troeh FR, Jabro JD, Kirkham D. 1982. Gaseous diffusion equations for porous materials. Geoderma. 27:239–258) and Moldrup et al. (Moldrup P, Kruse CW, Rolston DE, Yamaguchi T. 1996. Modeling diffusion and reaction in soils: III. Predicting gas diffusivity from the Campbell soil–water retention model. Soil Sci. 161:366–375) models. Soil bulk density and volumetric soil water content (θv) at 0–10 cm were measured on 14 April, 2 June and 12 July 2005 at 0–10 cm depth in no-till (NT) and conventional till (CT) malt barley and undisturbed soil grass–alfalfa (UGA) systems. Air-filled porosity (ε) was calculated from total soil porosity and θv measurements. Both soil air porosity and estimated CO2 diffusivity at the 0–10 cm depth were significantly affected by tillage. Results of CO2 diffusion coefficients in the soil followed trends similar to those for soil ε data. The CT tended to have significantly greater estimated soil CO2 diffusion coefficients than the NT and UGA treatments. The relationship between D/D 0, and air-filled porosity was well described by a power (R 2 = 0.985) function. The model is useful for predicting CO2 gas-diffusion coefficients in undisturbed and tilled soils at various ranges of ε where actual gas D measurements are time-consuming, costly and infeasible.  相似文献   

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