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  • 11
    Language: English
    In: Journal of Plant Nutrition and Soil Science, June 2006, Vol.169(3), pp.462-463
    Keywords: Resin‐Film Method ; Soil Profile ; History Of Soil Science
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 12
    Language: English
    In: Soil biology & biochemistry, 2013, Vol.57, pp.1003-1022
    Description: In arable farming systems, the term ‘subsoil’ refers to the soil beneath the tilled or formerly tilled soil horizon whereas the latter one is denoted as ‘topsoil’. To date, most agronomic and plant nutrition studies have widely neglected subsoil processes involved in nutrient acquisition by crop roots. Based on our current knowledge it can be assumed that subsoil properties such as comparatively high bulk density, low air permeability, and poverty of organic matter, nutrients and microbial biomass are obviously adverse for nutrient acquisition, and sometimes subsoils provide as little as less than 10% of annual nutrient uptake in fertilised arable fields. Nevertheless, there is also strong evidence indicating that subsoil can contribute to more than two-thirds of the plant nutrition of N, P and K, especially when the topsoil is dry or nutrient-depleted. Based on the existing literature, nutrient acquisition from arable subsoils may be conceptualised into three major process components: (I) mobilisation from the subsoil, (II) translocation to the shoot and long-term accumulation in the Ap horizon and (III) re-allocation to the subsoil. The quantitative estimation of nutrient acquisition from the subsoil requires the linking of field experiments with mathematical modelling approaches on different spatial scales including Process Based Models for the field scale and Functional–Structural Plant Models for the plant scale. Possibilities to modify subsoil properties by means of agronomic management are limited, but ‘subsoiling’ – i.e. deep mechanical loosening – as well as the promotion of biopore formation are two potential strategies for increasing access to subsoil resources for crop roots in arable soils. The quantitative role of biopores in the nutrient acquisition from the subsoil is still unclear, and more research is needed to determine the bioaccessibility of nutrients in subsoil horizons. ; p. 1003-1022.
    Keywords: Topsoil ; Bulk Density ; Roots ; Bioavailability ; Mathematical Models ; Field Experimentation ; Microbial Biomass ; Organic Matter ; Farming Systems ; Subsoiling ; Nutrients ; Poverty ; Nutrient Uptake ; Shoots ; Air ; Arable Soils ; Permeability ; Plant Nutrition
    ISSN: 0038-0717
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 13
    Language: English
    In: Catena, 2012, Vol.88(1), pp.57-67
    Description: The motivation for this article results from the fact that conceptual soil maps show oftentimes inaccuracies with regard to soil unit boundaries or misfits between original paper and actual soil-related information. Using the example of a German conceptual soil map (CSM), we introduce a procedure which could be considered as a framework for testing the terrain-related plausibility applied within a genetic based soil-ordering system. Framework means that all tests and the underlying methods can be adapted to specific targets. The procedure enables both reproducible integration of expert knowledge and application of statistically sound methods. The CSM of the German Federal State of Saxony-Anhalt was tested regarding the plausibility of colluvial and fluvial process domains. The plausibility test consists of four steps and was exemplified on a study area of 100 km . First, basic relief parameters were combined to the explaining relief parameters and enabling a classification of process domains by relative descriptions. Second, relief parameters and aggregated CSM soil units were integrated to soil-terrain objects (STO) executing a region-growing segmentation algorithm. In the third step, the one-dimensional or feature space of STO entities were clustered by using the K-means algorithm. The fourth step comprises the expert-based selection of reference clusters (RC) representing colluvial and fluvial process domains accepted as being true. Then, empirical cumulative distribution functions (ECDF) of RC and remaining soil unit-related STO clusters were compared by a traditional goodness-of-fit test whose suitability for estimation of terrain-related CSM plausibility is shown. Finally, the resulting ECDF distances were visualized. The testing procedure could also be used for the supervised selection of appropriate samples for automatic classification algorithms. The data integration approach is generally suitable for adopting existing data in computer-based systems. ► Integration of statistically sound DSM techniques and expert knowledge. ► Framework for basic tests of conceptual and legacy soil maps regarding terrain-related process domains. ► Usage of a goodness-of-fit measure for the comparison of soil-terrain-related distributions.
    Keywords: Digital Soil Mapping ; Terrain Analysis ; Segmentation ; Expert Knowledge ; Cluster Analysis ; Kolmogorov Smirnov Test ; Sciences (General) ; Geography ; Geology
    ISSN: 0341-8162
    E-ISSN: 1872-6887
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  • 14
    Language: English
    In: 한국토양비료학회 학술발표회 초록집, 2014, Vol.2014(6), pp.422-423
    Keywords: Silicon ; Rice ; Paddy Soils ; Straw Residue Management ; Phytoliths
    Source: DBpia - 디비피아 (Nurimedia)
    Source: DBpia (Nurimedia)
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  • 15
    Language: English
    In: Environmental Pollution, 2009, Vol.157(11), pp.3016-3024
    Description: is known to hyperaccumulate As but the mechanism is poorly understood. We found an increase of As concentration with increasing soil solution As concentrations, but P application had no impact, although plant P concentrations responded to different rates of P supply. As in fronds was dominantly (82–89%) present in the form of AsIII. In roots we detected 45% as AsIII which is higher than reported in previous studies and supports substantial As-reduction to take place in roots. We detected PC2/3GS–AsIII, PC2–GS–AsIII and (PC2)2–AsIII in increasing amounts with application of As. The total amount of PC was in the range reported previously and far too small to assign a significant role in As detoxification to PCs. The close correlation between S and As in fronds and the lack of data on sulphur uptake and metabolism indicates the need for a detailed investigation on sulphur nutritional status and As metabolism in . As–PC complexes were detected in increasing amounts with increasing As availability, but total amounts were small and do not explain the close correlation between S and As in fronds.
    Keywords: Arsenic Detoxification ; Arsenic Speciation ; Hyperaccumulator ; PC–As Complexes ; P Uptake ; Sulphur Metabolism ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
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  • 16
    Language: English
    In: 한국토양비료학회 학술발표회 초록집, 2014, Vol.2014(6), pp.418-419
    Keywords: Silicon ; Rice ; Fertilizer ; Harvest Residue Management ; Southeast Asia
    Source: DBpia - 디비피아 (Nurimedia)
    Source: DBpia (Nurimedia)
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  • 17
    Language: English
    In: Geochimica et Cosmochimica Acta, 2007, Vol.71(10), pp.2569-2590
    Description: Mineral-associated organic matter (OM) represents a large reservoir of organic carbon (OC) in natural environments. The factors controlling the extent of the mineral-mediated OC stabilization, however, are poorly understood. The protection of OM against biodegradation upon sorption to mineral phases is assumed to result from the formation of strong bonds that limit desorption. To test this, we studied the biodegradation of OM bound to goethite (α-FeOOH), pyrophyllite, and vermiculite via specific mechanisms as estimated from OC uptake in different background electrolytes and operationally defined as ‘ligand exchange’, ‘Ca bridging’, and ‘van der Waals forces’. Organic matter extracted from an Oa forest floor horizon under Norway spruce ( (L.) Karst) was reacted with minerals at dissolved OC concentrations of ∼5–130 mg/L at pH 4. Goethite retained up to 30.1 mg OC/g predominantly by ‘ligand exchange’; pyrophyllite sorbed maximally 12.5 mg OC/g, largely via ‘van der Waals forces’ and ‘Ca bridging’, while sorption of OM to vermiculite was 7.3 mg OC/g, mainly due to the formation of ‘Ca bridges’. Aromatic OM components were selectively sorbed by all minerals (goethite ≫ phyllosilicates). The sorption of OM was strongly hysteretic with the desorption into 0.01 M NaCl being larger for OM held by ‘Ca bridges’ and ‘van der Waals forces’ than by ‘ligand exchange’. Incubation experiments under aerobic conditions (initial pH 4; 90 days) revealed that OM mainly bound to minerals by ‘ligand exchange’ was more resistant against mineralization than OM held by non-columbic interactions (‘van der Waals forces’). Calcium bridges enhanced the stability of sorbed OM, especially for vermiculite, but less than the binding via ‘ligand exchange’. Combined evidence suggests that the extent and rate of mineralization of mineral-associated OM are governed by desorption. The intrinsic stability of sorbed OM as related to the presence of resistant, lignin-derived aromatic components appears less decisive for the sorptive stabilization of OM than the involved binding mechanisms. In a given environment, the type of minerals present and the solution chemistry determine the operating binding mechanisms, thereby the extent of OM sorption and desorption, and thus ultimately the bioavailability of mineral-associated OM.
    Keywords: Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 18
    Language: English
    In: Paddy and Water Environment, 2018, Vol.16(2), pp.243-252
    Description: Silicon (Si) mitigates abiotic and biotic stresses for rice plants ( Oryza sativa L.). Here, we test relationships between Si cycling, plant growth, and pest and fungal attacks in rice agroecosystems. We conducted a plot experiment on Si fertilization in a Southern Vietnamese paddy, where plant-available Si was inherently low. For two cropping seasons, we investigated the temporal dynamics of Si in soil solution, plant Si uptake, and the occurrence of leaf folders ( Cnaphalocrocis medinalis ) and rice blast caused by the fungus Magnaporthe oryzae . Silicon application increased Si concentrations in soil solutions collected in the field as expected from previous laboratory experiments. Soil solution Si concentrations were furthermore affected by Si uptake by plants and by recycling Si with rice straw ash. Silicon concentrations in rice leaves at tillering stage increased with increasing Si application. However, surprisingly, no relationship between Si in soil solution and Si concentration in straw at maturity stage was found. The occurrences of leaf folders and rice blast disease were mitigated by increased Si uptake. However, rice biomass production was not affected, probably because the biotic stress level was generally low. Our field data emphasize the importance of recycling crop residues in rice fields for the Si supply to plants, especially in regions with low Si availability. They furthermore show that under field conditions, the relationship between dissolved Si in soil solution and Si uptake by rice plants is not as straightforward as expected and thus needs to be further investigated.
    Keywords: Dissolved silicon ; Leaf folder ; Rice ; Rice blast ; Silicon fertilization
    ISSN: 1611-2490
    E-ISSN: 1611-2504
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  • 19
    Language: English
    In: Vadose Zone Journal, 2014, Vol.13(8), p.0
    Description: Root system architecture and associated root–soil interactions exhibit large changes over time. Nondestructive methods for the quantification of root systems and their temporal development are needed to improve our understanding of root activity in natural soils. X-ray computed tomography (X-ray CT) was used to visualize and quantify growth of a single Vicia faba L. root system during a drying period. The plant was grown under controlled conditions in a sandy soil mixture and imaged every second day. Minkowski functionals and Euclidean distance transform were used to quantify root architectural traits. We were able to image the root system with water content decreasing from 29.6 to 6.75%. Root length was slightly underestimated compared with destructive measurements. Based on repeated measurements over time it was possible to quantify the dynamics of root growth and the demography of roots along soil depth. Measurement of Euclidean distances from any point within the soil to the nearest root surface yielded a frequency distribution of travel distances for water and nutrients towards roots. Our results demonstrate that a meaningful quantitative characterization of root systems and their temporal dynamics is possible.
    Keywords: Agriculture;
    ISSN: Vadose Zone Journal
    E-ISSN: 1539-1663
    Source: CrossRef
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  • 20
    Language: English
    In: Clays and Clay Minerals, 2010, Vol.58(5), pp.707-716
    Description: Allophane is a very fine-grained clay mineral which is especially common in Andosols. Its importance in soils derives from its large reactive surface area. Owing to its short-range order, allophane cannot be quantified by powder X-ray diffraction (XRD) directly. It is commonly dissolved from the soil by applying extraction methods. In the present study the standard extraction method (oxalate) was judged to be unsuitable for the quantification of allophane in a soil/clay deposit from Ecuador, probably because of the large allophane content (〉60 wt.%). This standard extraction method systematically underestimated the allophane content but the weakness was less pronounced in samples with small allophane contents. In the case of allophane-rich materials, the Rietveld XRD technique, using an internal standard to determine the sum of X-ray amorphous phases, is recommended if appropriate structural models are available for the other phases present in the sample. The allophane (+imogolite) content is measured by subtracting the amount of oxalate-soluble phases (e.g. ferrihydrite). No correction would be required if oxalate-soluble Fe were incorporated in the allophane structure. The present study, however, provides no evidence for this hypothesis. Mössbauer and scanning electron microscopy investigations indicate that goethite and poorly ordered hematite are the dominant Fe minerals and occur as very fine grains (or coatings) being dispersed in the cloud-like allophane aggregates. Allophane is known to adsorb appreciable amounts of water, depending on ambient conditions. The mass fraction of the sample attributed to this mineral thus changes accordingly; the choice of a reference hydration state is, therefore, a fundamental factor in the quantification of allophane in a sample. Results from the present study revealed that (1) drying at 105ºC produced a suitable reference state, and (2) water adsorption has no effect on quantification by XRD analysis.
    Keywords: Allophane ; Chemical Extraction Methods ; Differential Thermal Analysis ; Ecuador ; Mössbauer Spectroscopy ; Quantification ; X-ray Diffraction
    ISSN: 0009-8604
    E-ISSN: 1552-8367
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