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  • 11
    Electronic Resource
    Electronic Resource
    Fixation of radiocaesium traces in a weathering sequence mica → vermiculite → hydroxy interlayered vermiculite (1999)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 50 (1999), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Radiocaesium fixation in soils is reported to occur on frayed edge sites of micaceous minerals. The weathering of mica in acid soils may therefore influence the Cs+ fixation process and thereby the mobility of the radiopollutant. We produced a laboratory weathering model biotite → trioctahedral vermiculite → oxidized vermiculite → hydroxy interlayered vermiculite (HIV) and quantified the Cs+ fixation of each mineral both in a fixed K+–Ca2+ background and in acid conditions. The transformation process was achieved through K depletion by Na-tetraphenylboron, oxidation with Br2 and Al-intercalation using NaOH and AlCl3. In a constant K+–Ca2+ background, vermiculite fixed 92–95% of the initial 137Cs+ contamination while biotite and HIV fixed only 18–33%. In acid conditions, the interlayer occupancy by either potassium (biotite) or hydroxy-Al groups (HIV) strongly limited Cs+ fixation to 1–4% of the initial 137Cs+ contamination. Cs+ fixation occurred on vermiculitic sites associated with micaceous wedge zones. Though both oxidized and trioctahedral vermiculites fixed similar Cs+ amounts in a constant K+–Ca2+ background (92–95%), the oxidized vermiculite retained much more radiocaesium in acid conditions (78–84% against 54–59%), because of its dioctahedral character.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.1999.00223.x
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  • 12
    Electronic Resource
    Electronic Resource
    Fixation of radiocaesium in an acid brown forest soil (1998)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 49 (1998), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The OAh and Ah horizons of acid brown and podzolic forest soils are reported to fix more radiocaesium than the mineral B horizons beneath them. We determined the respective influence of organic matter and clay minerals on the magnitude of Cs+ retention in a strongly acid brown forest soil in Belgium. The soil contained mica throughout the profile. Vermiculite was identified in the OAh and Ah horizons, and hydroxy interlayered vermiculite (HIV) in the Bw horizon. The OAh and Ah clay fraction retained much more Cs+ than the Bw horizon. The extraction of Al interlayers by Na-citrate resulted in a marked increase in Cs+ fixation in the Bw clays as well as the collapse of the vermiculitic layers after K+ saturation. Organic matter had a strong but indirect effect on Cs+ fixation. In the Bw horizon, acid weathering of layer silicates releases free Al and produces HIV minerals in which Al polymers block the access of radiocaesium onto Cs+-specific sites. In OAh and Ah horizons, free Al is complexed by organic acids. Consequently, the interlayer specific sites remain accessible for Cs+ fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.1998.00139.x
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  • 13
    Electronic Resource
    Electronic Resource
    Cation exchange resin and test vermiculite to study soil processes in situ in a toposequence of Luvisol and Cambisol on loess (2001)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 52 (2001), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Both the ion accumulation on cation exchange resin and the transformation of test vermiculite in situ have been used to identify current processes in acid forest soils. We used such test materials to study weathering in a toposequence Dystric Luvisol–Spodo-Dystric Cambisol on loess under deciduous forest in Belgium. The resin and a trioctahedral vermiculite were inserted for 2 years in the major horizons, down to a depth of 60 cm. The cation accumulation on the resin revealed that four main acid-consuming systems are currently active in the toposequence. With decreasing acid neutralizing capacity, these systems are in the Luvisols: (i) the pool of exchangeable bases, (ii) the Al-bearing minerals controlling the Al concentration in the liquid phase; and in the podzolized Cambisols: (iii) the less weatherable K-bearing minerals, (iv) the Mg-bearing phyllosilicates made free of Al interlayers in complexing conditions. The loss of cation exchange capacity in the test vermiculite is related to Al interlayering. However, this process masks a significant interlayer accumulation of magnesium, which is generated by the weathering of the test mineral itself. The largest interlayer accumulation of Mg occurs in the podzolized Cambisol, suggesting more intense weathering of the test vermiculite in this soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2001.00401.x
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  • 14
    Electronic Resource
    Electronic Resource
    Estimation of soil weathering stage and acid neutralizing capacity in a toposequence Luvisol–Cambisol on loess under deciduous forest in Belgium (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 51 (2000), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Soils derived from loess are extensive in Europe and are well suited for forestry. They are suspected to be poor acid buffers, however. We have estimated the weathering stage and acid neutralizing capacity of acid soils under forest in a toposequence on loess in the Belgian silt belt. The soils vary distinctly in morphology and physico-chemical properties according to their topographic position. Dystric Cambisols have developed in colluvial deposits in the dry valley floors, whereas Dystric Luvisols have formed on the slopes in a rejuvenated material. The Cambisols are more acid and less saturated in bases than are Luvisols. They are strongly depleted of clay and contain less weatherable minerals. Easily weatherable minerals are concentrated mainly in the clay fraction of both soil types. Clay minerals of size 〈 2 μm therefore act as major sinks for protons in these soils. A simplified expression taking into account the total reserve in bases, total aluminium and iron occluded in silicates is used to estimate acid neutralizing capacity. Our estimates confirm that these acid loessic soils are indeed poor acid buffers. They show that the Dystric Cambisols depleted of clay are sensitive to potential acidification, whether natural or man-made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2000.00285.x
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  • 15
    Electronic Resource
    Electronic Resource
    Effects of arbuscular mycorrhizal fungi on severity of root rot of bananas caused by Cylindrocladium spathiphylli (2002)
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 51 (2002), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The interaction between four arbuscular mycorrhizal (AM) fungi, Glomus sp., G. proliferum, G. intraradices and G. versiforme, and the root-rot fungus Cylindrocladium spathiphylli, and subsequent effects on growth and phosphorus nutrition of banana (Musa acuminata, AAA, cv. Grande Naine) were investigated under glasshouse conditions. Overall, root infection by C. spathiphylli reduced the growth of banana plants, but preinoculation with AM fungi significantly attenuated this detrimental effect. Lower disease severity, stimulation of growth and increase of shoot P content were observed for the plants inoculated with one of the four AM fungi. Glomus sp. and G. proliferum induced the largest increase in growth parameters and shoot P content as compared to G. intraradices and G. versiforme, in the presence as well as in the absence of C. spathiphylli. Root damage caused by C. spathiphylli was decreased in the presence of AM fungi, but the inoculation of mycorrhizal plants with C. spathiphylli also decreased the intensity of AM fungal root colonization, indicating a clear interaction between the two organisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0032-0862.2001.656.x
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  • 16
    Electronic Resource
    Electronic Resource
    Potassium exchange behaviour in Carribean volcanic ash soils under banana cultivation (1989)
    Springer
    Plant and soil 120 (1989), S. 283-290 
    Details
    ISSN: 1573-5036
    Keywords: allophane ; banana crop ; fertilization ; halloysite ; ion exchange ; potassium ; volcanic ash soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ca−K exchange isotherms of samples from carribean (Martinique island) volcanic soils differing in the weathering stage and in the nature of cation-exchange material were studied. Allophanic soils high in organic matter (Troporthents, Hydrandepts) exhibit a low selectivity for K-ions. Potassium is adsorbed specifically in the halloysitic soils (Humitropepts). A positive relationship exists between the affinity for K+ and the halloysite content. This relation is most likely due to the close association of 1∶1 hydrated phyllosilicates with 2∶1 smectitic clay minerals. A lower selectivity for K was observed in the kaolinitic soil materials (Dystropepts). Because parent rocks are very low in K, these exchange properties strongly influence their K status, through differences in susceptibility to K leaching losses and K availability to banana plants in intensive cropping systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02377078
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  • 17
    Electronic Resource
    Electronic Resource
    Iron toxicity and other chemical soil constraints to rice in highland swamps of Burundi (1994)
    Springer
    Plant and soil 166 (1994), S. 109-115 
    Details
    ISSN: 1573-5036
    Keywords: Fe toxicity ; highland swamp ; Histosol ; Mn ; leaf mineral content ; organic carbon ; peat ; rice ; soil pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Iron toxicity is suspected to be a major nutritional disorder in rice cropping systems established on flooded organic soils that contain reductible iron. A pot trial was carried out to assess Fe toxicity to rice in flooded Burundi highland swamp soils with a wide range of organic carbon contents. Soil and leaf analyses were performed and total grain weight was determined. Clear Fe toxicity was diagnosed, based on leaf Fe content at panicle differentiation. Leaf Fe contents higher than 250 μg g−1 dry matter induced lower Mg (and probably Mn) uptake, and a 50% total grain weight reduction. These features were associated with exchangeable Fe equivalent fractions higher than 86%. Besides, several non-Fe toxic soils exhibited an Mg-Mn imbalance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185487
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  • 18
    Electronic Resource
    Electronic Resource
    Redox conditions and iron chemistry in highland swamps of Burundi (1994)
    Springer
    Plant and soil 166 (1994), S. 165-171 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; exchange complex ; highland swamp ; Histosol ; iron oxides ; iron toxicity ; peat ; redox potential ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Iron toxicity is a major soil constraint to rice (Oryza sative L.) cropping in highland swamps of Burundi. These swamps have a wide range of carbon content. This study aims at determining the influence of carbon content and redox conditions on the release of iron from Fe-bearing minerals. The pe-pH pairs distribution and oxalate dissolution data strongly suggest a control of Fe2+ activity by a pool of poorly crystallized ferric oxides. Flooding results in high values of KCl-extractable Fe (up to 22 cmolc kg-1) being released from that pool. The iron release is positively correlated with organic matter. On the other hand, highly organic, peaty soils have large CEC and their adsorbed Fe fraction remains relatively low. As the exchangeable Fe fraction has previously been correlated with Fe toxicity to rice, we may conclude that very organic (〉 25% C), peaty soils exhibit a lower Fe toxicity hazard than soils with intermediate carbon content (10–25%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008329
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