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1.
Fragipan is a widely distributed subsoil horizon that induces severe limitations to plant growth and land use, mainly because of its high bulk density. In this work, we evaluated the pore‐size distribution through the analysis of the cumulative curve of intruded mercury volume in some soils with fragipan horizons. This approach provides information also about the arrangement of particles, thus we compared the results obtained for fragipan and nonfragipan horizons to relate porosity and particle arrangement with the specific physical properties of fragipans. The total volume of intruded mercury did not allow to discriminate between fragipan and nonfragipan horizons. However, from the variation of the pore volume as a function of the radius, two modal classes of pores were found, coarse and fine, respectively. The fine‐pore class arose from the arrangement of clay particles, and its volume was correlated to clay contents (r = 0.787) and to clay packing density (r = –0.621). The clay fractions in fragipans were less densely packed than in the other B horizons, even if they had similar clay contents. The coarser‐pore modal class is known to arise from the interactions between clay, silt, and sand particles, and its volume was different among horizons. Fragipan had a low volume of this modal pore class. In addition, a packing density for the coarser phase of 0.74, corresponding to a rhombohedral packing, was found only in fragipans. Thus, the low permeability and high bulk density of fragipans are linked to specific arrangements of the particles: an open packing of the clay phase is associated to an extremely dense packing of silt and sand. This combination is not present in any other soil horizon.  相似文献   

2.
Crop yields and yield potentials on Danish coarse sandy soils are strongly limited due to restricted root growth and poor water and nutrient retention. We investigated if biochar amendment to subsoil can improve root development in barley and significantly increase soil water retention. Spring barley (Hordeum vulgare cv. Anakin) was grown in soil columns (diameter: 30 cm) prepared with 25 cm topsoil, 75 cm biochar‐amended subsoil, and 30 cm un‐amended subsoil lowermost placed on an impervious surface. Low‐temperature gasification straw‐biochar (at 0, 0.50, 1.0, 2.0, and 4.0 wt%) and slow pyrolysis hardwood‐biochar (at 2 wt%) were investigated. One wt% can be scaled up to 102 Mg/ha of char. After full irrigation and drainage, the in‐situ moisture content at 30‐80 cm depth increased linearly (R2 = 0.99) with straw‐biochar content at a rate corresponding to 0.029 m3/m3/%. The lab determined wilting point also increased linearly with char content (R2 = 0.99) but at a much lower rate (0.003 m3/m3/%). Biochar at concentrations up to 2% significantly increased the density of roots in the 40–80 cm depth interval. Addition of 1% straw‐biochar had the most positive effect on root penetration resulting in the highest average root density (54% coverage compared to 33% without biochar). This treatment also resulted in the greatest spring barley grain yield increase (22%). Improving the quality of sandy subsoils has global potentials, and incorporation of the right amount of correctly treated residues from bioenergy technologies such as straw‐biochar is a promising option.  相似文献   

3.
Appropriate soil amendments may increase plant available water and crop yields on coarse sandy soils under drought conditions. In this study, we applied straw ash or straw biochar from gasification to a Danish coarse sandy subsoil to assess the effects on soil water retention, evapotranspiration and crop yields. Spring barley (2016, 2017) and winter wheat (2018) were grown over three years in columns containing 25cm of organic matter-rich topsoil, 80 cm of amended coarse sandy soil (1.5%, 3%, 6% wt. ash or 1% wt. biochar or control soil) and 45 cm of un-amended subsoil. Precipitation, evaporative demands and soil moisture were recorded across the growth seasons, with 2018 having severe drought conditions. This year evapotranspiration levels increased with increasing ash and biochar content (by 54% and 33% for the 6% ash- and 1% biochar-amended soils, respectively), and plant dry matter increased by 18% in both the 1% biochar- and 6% ash-treated soils compared to the untreated control. A linear relationship was established between in situ field capacity and ash dosage (R= .96), showing an increase of 2.2% per percentage (wt.) of ash added, while the 1% biochar treatment increased the capacity by 3.5%, indicating a higher efficiency than for ash. However, we did not find significant positive effects on grain yields. The results show that ash and biochar have the potential to significantly increase soil water retention, evapotranspiration and total dry matter yield in drought conditions, but that this may not correspond to an increase in grain yield.  相似文献   

4.
试验研究了添加生物炭对砂壤土团聚体分布、稳定性及其碳、氮分布的影响,为生物炭的农业利用和土壤培肥提供理论依据。设置生物炭用量4个水平(0、10、20、30 t/hm2)、氮肥用量2个水平(0、150 kg/hm2),通过2年的田间定位试验,对土壤团聚体及其碳、氮含量进行分析。结果表明:不同处理团聚体分布均以>5、2~5 mm粒级团聚体为主,其中单施生物炭20 t/hm2时,>5、2~5 mm粒级团聚体占比最大,总占比为58%,与不添加生物炭相比,增幅为20%;施用生物炭20 t/hm2时土壤团聚体平均重量直径及几何重量直径增幅最为显著(P<0.05),与不施生物炭处理相比分别增加了17.6%和24.3%;有机碳和全氮变化趋势一致,添加生物炭后,土壤有机碳、氮含量均增加,不同粒级团聚体有机碳、氮含量均不同程度地升高,分别较对照显著提升27.9%和28.9%,<0.25 mm粒级团聚体有机碳、氮含量较高。添加生物炭显著增加土壤大团聚体含量,并提高了土壤团聚体稳定性;土壤碳、氮含量及各粒级土壤团聚体碳、氮含量均显著提升,提高了>5 mm粒级团聚体有机碳、氮的贡献率。在本试验条件下,当生物炭添加量为20 t/hm2时有利于北疆灌区麦田土壤培肥改良。  相似文献   

5.
Urinations of ruminants on grazed pastures increase the risk of nitrate leaching. The study investigated the effect of reducing the length of the grazing season on nitrate leaching from a coarse sandy, irrigated soil during 2006–2007 and 2007–2008. In both years, precipitation was above the long‐term mean. The experiment was initiated in a 4‐yr‐old grass‐clover sward in south Denmark. Three treatments were as follows grazing only (G), spring cut followed by grazing (CG) and both spring and autumn cuts with summer grazing (CGC). Nitrate leaching was calculated by extracting water isolates from 80 cm depth using ceramic suction cups. Because of considerable variation in measured nitrate concentrations, the 32 installed suction cups per treatment were insufficient to reveal differences between treatments. However, weighted nitrate leaching estimations for G, CG and CGC showed estimated mean nitrate N concentrations of 23, 19 and 13 mg/L for an estimated proportion area occupied by urine patches of 0.33, 0.26 and 0.16, respectively. Thus, N concentrations in G and CG exceeded the EU limit of 11.3 mg N/L. Under the prevailing conditions, the time of urination did not appear important. The estimated background leaching calculated from suction cups presumably not situated under urine patches resulted in mean nitrate N concentrations of 2.6 mg/L.  相似文献   

6.
A laboratory column experiment was conducted to investigate the effects of 400°C biochar at application rate of 15 g kg?1 (21.9 t ha?1) with different particle sizes (<0.5 mm (S1), 0.5–1 mm (S2) and 1–2 mm (S3)) and application depths (0–2 cm depth (D0), 4–6 cm depth (D5) and 8–10 cm depth (D10)) on hydro-physical properties of sandy loam soil. The results indicated that applying biochar decreased the waterfront and saturated hydraulic conductivity of sandy loam soil. The cumulative evaporation was the highest and amounted to 40.9 mm in the non-treated soil, but it recorded the lowest amount of 32.2–35.5 mm in the biochar-treated soil. Applying biochar caused significant increases in the amount of conserved and retained water with the highest amount of water conserved in soil treated with S2 biochar at D5. Moreover, the cumulative water infiltration through the soil was significantly reduced by S1 and S2 biochars at D0. The values of saturated hydraulic conductivity for biochar treatments were significantly lower than those for the control, with the lowest values for S1 at D0 and D5. These results suggest positive improvement for the hydro-properties of coarse-textured soils following biochar addition, especially with finer particles of biochar.  相似文献   

7.
The original light‐brown sandy seam filling of pavements in urban areas turns dark and changes its properties by the time due to various inputs of urban dust. Deposited Corg inputs do mostly not have natural characteristics but are man‐made, e.g., diesel dust. Thus, properties of the seam material are not predictable from experiences with forest or agricultural soils. Semiperviously sealed urban areas are sites of contaminant deposition as well as groundwater recharge. For an assessment of the resulting groundwater‐contamination risk in these areas, the properties of the seam material, which influences transport processes, must be known. The aim of this study was to investigate the pore‐system build‐up, which includes size distribution and fractal character in the seam material of urban sites. The investigated samples were taken from pavements adjacent to roads in Berlin and Warsaw. The micropore parameters (nanometer range) were characterized using water‐vapor desorption isotherms, mesopore parameters (micrometer range) were estimated from mercury‐intrusion porosimetry and macropore parameters (millimeter range) from water‐retention curves. Particle density, dry bulk density, and particle‐size distribution were measured using standard methods. Volumes of micro‐ and mesopores as well as particle densities and dry bulk densities correlated with Ctot contents. However, no such relation was found for macropore volumes. Compared to the original sandy seam filling, the altered seam material shows significantly higher Corg contents and higher amounts of micro‐ and mesopores. Therefore, the available water capacity increases by 0.05–0.11 m3 m–3, as compared to the original sandy seam filling. Compared to natural sandy soils having similar Corg contents, the seam material shows similar macropore volumes, but the volume of mesopores and micropores is a few times smaller. That is mainly because of the particulate character of the organic matter.  相似文献   

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11.
The choice of analytical method and sample pretreatment has significant consequences for the shape of particle‐size distribution (PSD) frequency curves, and therefore for the evaluation of soil textural parameters. Here, the comparison of several granulometric methods based on different physical principles is presented: wet sieving (WS), based on gravity and the mechanical force of water, was combined with pipette (PP) sedimentation/settling velocity, Micromeritics SediGraph (MS) sedimentation/x‐ray attenuation and Coulter Counter (CC) electroresistance particle counting. The Malvern Mastersizer (MM), an instrument based on laser diffraction, was used without WS. Twelve typical temperate‐region soil types were chosen for this study on the basis of their mineral composition, organic matter content, conductivity and magnetic susceptibility. The modalities of PSD frequency curves obtained by different methods were compared. The results showed considerably larger clay‐fraction contents determined with the sedimentation techniques, PP and MS, than that obtained by CC or MM. Statistical correlation and regression models were used to compare the fractions of clay, silt and sand obtained with different methods. Linear correlations were found in almost all cases, except those comparing clay fractions obtained by CC with those obtained by MM, PP and MS methods. These correlations were non‐linear. The observed difference was attributed to the presence of aggregates and/or magnetic properties of soil particles. However, more data are needed to verify this hypothesis. The implications of sample pre‐treatment with dispersant and hydrogen peroxide (H2O2) were evaluated by the MS and CC techniques and observed by the scanning electron microscope. H2O2 was found to be an efficient disaggregating agent. The use of dispersant resulted in the increased amount of the clay fraction measured by the MS method.  相似文献   

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13.
Numerous studies conducted so far have shown that biochar has a significant effect on physical, chemical and biological properties of soils. Biochar can be used to alleviate the effects of soil contamination with organic and inorganic compounds, for instance, to reduce the mobility of heavy metals. The aim of the research was to evaluate the effect of pig manure and poultry litter, as well as biochars produced from these materials at a temperature of 300 °C on Cu, Cd, Pb and Zn contents in mobile and organic matter‐bound forms in soil. The research was conducted under laboratory conditions. The materials were introduced into sandy acid soil in doses of 0.5, 1.0 and 2.0% w/w. The application of pig manure‐derived biochar (BPM) and poultry litter‐derived biochar (BPL), depending on the amount added, reduced the mobility of copper from 28 to 69%, from 77 to 100% in the case of cadmium, from 94 to 99% in the case of lead, and from 15 to 97% in the case of zinc. The 2% amendment of pig manure (PM) and poultry litter (PL) caused an increase in the content of Cu extracted with NH4NO3 in comparison with the control treatment. A similar situation was observed in the case of zinc after the application of 0.5 and 1% amendments of pig manure (PM). Cu, Cd, Pb and Zn contents extracted with 0.025 mol C10H22N4O8 were higher than contents of these elements extracted with 1 m NH4NO3, mainly due to different extraction force of the extractants. The obtained results indicate that, compared with the content determined in soil from the control treatment, 1 and 2% amendments of both unconverted and thermally converted materials to the soil had a greater effect on contents of Cu, Pb and Zn in the organic matter‐bound fraction than the 0.5% amendment. The organic materials applied did not affect the content of cadmium in organic matter‐bound fraction.  相似文献   

14.
风沙土是我国重要耕地之一,具有土质瘠薄、漏水漏肥等特点,易造成肥料利用率低、产量低等问题,急需对其改良,以提高其保水保肥能力。以风沙土为研究对象,采用玉米秸秆生物炭(BM)、水稻秸秆生物炭(BR)及花生壳生物炭(BP),设置生物炭两个不同施用量:0.5%土重和1%土重。采用盆栽试验,研究添加不同来源和数量生物炭对土壤养分和氮素利用率的影响。结果表明:不同种类生物炭均可以提高风沙土土壤pH、有机碳、速效钾含量。随着生物炭用量的增加,增加效果越明显;与未施生物炭处理(CK)相比,高量水稻秸秆生物炭处理对土壤有机碳、全氮、有效磷、速效钾含量提升效果最显著,分别提高了101.70%、20.30%、14.92%、88.36%;高量花生壳生物炭处理对土壤pH提升效果最显著,提高了0.46个单位。不同种类的生物炭均提高了土壤氮素残留率和利用率,随着生物炭用量的增加,土壤氮残留率提高,其中以高量水稻秸秆生物炭处理和高量花生壳生物炭处理提升幅度最大,与CK相比,分别提高了45.47%、36.10%。而氮素利用率随着生物炭用量的增加却出现降低趋势,低量玉米秸秆生物炭的处理氮素利用率最高,为51.32%。土壤氮残留率与花生籽粒产量、土壤pH、有机碳、有效磷、速效钾呈显著正相关关系,与氮肥利用率呈显著负相关关系。综上所述,施加生物炭能显著改变风沙土土壤有效养分含量。高量水稻秸秆生物炭和花生壳生物炭短期内可以显著提高氮残留率,而在氮肥利用率提升方面不如玉米秸秆生物炭,高量花生壳生物炭增产效果最好。  相似文献   

15.
We examined the possibility of an environment‐friendly slow‐release fertilizer (SRF) made of biochar impregnated by anaerobically digested slurry. The biochar materials were produced from three types of feedstocks (orange peel, residual wood, water‐treatment sludge) at different temperatures of 300°C, 500°C, and 700°C via pyrolysis. The release behaviors of the water‐soluble K+, Ca2+, and Mg2+ were similar for all impregnated biochars and the commercial SRF used. The water‐retention capacity was greatly improved by mixing the biochar‐SRF with the soil. The yield of lettuce was lower for the biochar‐SRF applications of 3.7 to 34.2 t ha–1 than for the commercial SRF application of 51.4 t ha–1. This might be due to excessive increase of soil pH for the biochar‐SRF application. Based on these results, the authors concluded that the biochar impregnated with nutrients could become an effective slow‐release K+ fertilizer.  相似文献   

16.
Soil applications of recalcitrant biochar offer the possibility of mitigating climate change effects through long‐term carbon sequestration and potentially also by reducing emissions of the potent greenhouse gas nitrous oxide (N2O). This laboratory study examined the effect of combining a fast‐pyrolysis biochar at small (1% by mass) and large (3%) concentrations with anaerobically digested slurry on soil N2O and carbon dioxide (CO2) emissions over a period of 55 days. The results showed that fast‐pyrolysis biochar applied on its own increased N2O emissions from soil. However, when biochar was applied together with slurry, the larger biochar concentration decreased N2O emissions by 47%, relative to those from the slurry treatment with the smaller biochar concentration. Reduced N2O emissions coincided with enhanced soil microbial activity and immobilization of nitrogen. A combined application of biochar and anaerobic digested slurry could therefore be beneficial for cropping systems in terms of soil nitrogen retention while concurrently mitigating N2O fluxes and sequestering carbon in soil.  相似文献   

17.
Anthropogenic sandy soils in Scotland, Denmark and The Netherlands were studied to determine the extent to which they had been influenced by inputs of materials and current land management. Particle size distribution, pH, loss on ignition, ECEC, base saturation and total P were determined for eight profiles under different land uses (arable, meadow and woodland). Inputs of materials were identified by comparison of particle size distributions of the deepened cultivated horizons with those of parent materials. At all three sites turf derived from local sources was the main input though there were other mineral additions including an aeolian component. Overall, the anthropogenic soils are remarkably similar in field and some analytical properties, though land use has influenced pH, base saturation and total P.  相似文献   

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Non‐essential silicon (Si) is beneficial to plants. It increases the biomass of Si‐accumulator plants by improving photosynthetic activity and alleviating stresses. Desilication, however, takes place because of natural soil weathering and removal of harvested biomass. Pyrolysis transforms Si‐rich biomass into biochar that can be used to supply bioavailable Si. Here, we applied two biochar materials differing in Si content on soils differing in weathering stage: a young Cambisol and a highly weathered Nitisol. We studied the impact of biochar supply on the bioavailability of Si, cotton biomass, and Si mineralomass. The biochar materials derived from, respectively: Miscanthus × giganteus (Mi; 34.6 g Si kg?1 in biochar) and soft woody material (SW; 0.9 g Si kg?1 in biochar). They were compared to conventional Si fertilizer wollastonite (Wo; CaSiO3). Amendments were incorporated in soils at the rate of 3% (w/w). The content of bioavailable Si in soil was determined through 0.01 M CaCl2 extraction. In the Cambisol, the proportion (CaCl2 extractable Si: total Si content) was significantly smaller for Mi (0.9%) than for Wo (5.2%). In the Nitisol, this proportion was much larger for Mi (1.4%) than for Wo (0.7%). Mi‐biochar significantly increased Si‐mineralomass relatively to SW‐biochar in both soils. This increase was, however, much larger in the Nitisol (5.9‐fold) than in the Cambisol (2.2‐fold). Mi biochar is thus an alternative Si fertilizer to Wo to supply bioavailable Si, increase plant biomass, and promote the biological cycle of Si in the soil‐plant system in the Nitisol. Besides, it increased soil fertility and soil organic carbon content.  相似文献   

20.
This paper presents the influence of selected methodological aspects on the results of particle‐size distribution (PSD) as measured by the laser diffraction method (LDM). The investigations were carried out using the Mastersizer 2000 with Hydro MU attachment (Malvern Ltd., UK). It was found that for the investigated soils: (1) optimal speed of pump and stirrer was 2500 rpm, (2) optimal measurement time was ≈ 1 min, (3) there are two, practically equivalent methods for soil‐sample dispersion: chemical (with the use of a solution of sodium hexametaphosphate) or physical (by means of ultrasound application for 4 min at a maximum power of 35W), (4) one must not use the chemical and physical dispersing methods simultaneously, because this can lead to aggregation (not dispersion) of soil particles, (5) the Fraunhofer theory (physical models) can be used to convert scattered‐light data to PSD. In the case of the Mie theory, the best results were obtained for a refractive index (RI) in the range of 1.5–1.6 and an absorption index (AI) of 1.0. It was also found that most of the discussed parameters depend on design of the measuring device and on the type and volume of the investigated suspensions. It is necessary, therefore, to explain how the data was obtained every time and to specify the details in the methodological part of the paper.  相似文献   

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