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Berlin Brandenburg

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  • 1
    Language: English
    In: Plant and Soil, 2010, Vol.330(1), pp.481-501
    Description: A modelling approach was used to extend the knowledge about the processes that affect the availability of the nutrient P and the toxic agent As V in the rhizosphere in the presence of a strong sorbent. Based on compartment system experiments in which Zea mays was grown the following hypothesis were assumed: a) measured P concentration gradients can be explained by the mobilisation of P by the root exudate citrate, and b) measured As V concentration gradients can be explained by the simultaneous effect of the competitive sorption of As V and P and the competitive uptake of As V and P. First, the feasibility of the applied description of soil chemical processes was justified. Then competitive uptake was implemented in the computer code using two different mathematical approaches. Our model calculation provided support for hypothesis a) and suggested that hypothesis b) has to be extended. The results show that the competitive uptake of As V and P has an influence on As V concentrations in the rhizosphere, but including competitive uptake was not sufficient to predict observed As V concentration profiles. Recent results on plant As-metabolism like As III efflux and Si As III interaction probably have to be included in addition for simulation of measured As V concentration profiles.
    Keywords: Rhizosphere ; Modelling ; Speciation ; Phosphate ; Arsenate ; Goethite
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 2
    Language: English
    In: Plant and Soil, 2013, Vol.371(1), pp.267-279
    Keywords: Exchangeable K ; Non-exchangeable K ; Subsoil ; Illite ; Soil solution ; Ca
    ISSN: 0032-079X
    E-ISSN: 1573-5036
    Source: Springer Science & Business Media B.V.
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  • 3
    Language: English
    In: Geochimica et Cosmochimica Acta, 15 August 2018, Vol.235, pp.89-102
    Description: Ferric iron (Fe ) solid phases serve many functions in soils and sediments, which include providing sorption sites for soil organic matter, nutrients, and pollutants. The reactivity of Fe solid phases depends on the mineral structure, including the overall crystallinity. In redox-active soils and sediments, repeated reductive dissolution with subsequent exposure to aqueous ferrous iron (Fe ) and oxidative re-precipitation can alter Fe phase crystallinity and reactivity. However, the trajectory of Fe mineral transformation under redox fluctuations is unclear and has been reported to result in both increases and decreases in Fe phase crystallinity. Several factors such as water budget, organic matter input, redox dynamics as well as the initial Fe phase composition might play a role. The objective of our study was to examine if Fe minerals in soils that differ in porosity-dependent water leaching rate and initial Fe phase crystallinity, demonstrate distinct mineral transformations when subjected to redox fluctuations. We sampled paired plots of two soil types under similar management but with different water leaching rates and contrasting Fe oxide crystallinity — an Alisol rich in crystalline Fe phases and an Andosol rich in short-range-ordered (SRO) Fe phases. The two soils were either exposed to several decades of redox fluctuations during rice paddy cultivation (paddy) or to predominantly oxic conditions in neighboring vegetable gardens (non-paddy). Paddy soils are uniquely suited for this type of study because they are regularly submerged and develop regular redox fluctuations. We also incubated the non-paddy soils in the laboratory for one year through eight anoxic/oxic cycles and monitored the aqueous soil geochemistry. Mössbauer spectroscopy was then used to evaluate Fe mineral speciation in field soils (paddy and non-paddy) and laboratory incubations. In the field soils, we found that redox fluctuation had contrasting effects on Fe oxide crystallinity, with crystallinity being lower in the Alisol paddy soil and higher in the Andosol paddy soil than in their corresponding non-paddy controls. In the laboratory incubation experiment, Eh, pH and dissolved Fe responded as anticipated, with elevated Fe concentrations during the anoxic periods as well as low Eh and high pH. Mössbauer measurements suggest the fluctuating redox incubation was beginning to alter Fe oxide crystallinity along the same trajectory as observed in the field, but the changes were within the range of fitting errors. We propose that reductive dissolution of crystalline Fe oxides prevails in the soil rich in crystalline Fe oxides (Alisol) and that re-precipitation as SRO Fe oxides is favored by constrained leaching, which leads to the observed decrease in Fe oxide crystallinity. In the soil rich in SRO Fe phases (Andosol), preferential reductive dissolution of SRO Fe oxides coupled with stronger leaching of dissolved Fe causes the observed relative increase in crystallinity of the remaining Fe oxides. The observed increase in Fe oxide crystallinity may further be a result of Fe(II)-catalyzed re-crystallization of SRO Fe oxides. These findings indicate that, besides other factors, the Fe mineral composition of the initial soil or sediment as well as the leaching rate likely influence the trajectory of Fe oxide evolution under alternating redox-conditions.
    Keywords: Fe Oxides ; Redox Fluctuation ; Paddy Soils ; Mössbauer Spectroscopy ; Alisol ; Andosol ; Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 4
    In: Global Change Biology, January 2018, Vol.24(1), pp.e183-e189
    Description: Current climate and land‐use changes affect regional and global cycles of silicon (Si), with yet uncertain consequences for ecosystems. The key role of Si in marine ecology by controlling algae growth is well recognized but research on terrestrial ecosystems neglected Si since not considered an essential plant nutrient. However, grasses and various other plants accumulate large amounts of Si, and recently it has been hypothesized that incorporation of Si as a structural plant component may substitute for the energetically more expensive biosynthesis of lignin. Herein, we provide evidence supporting this hypothesis. We demonstrate that in straw of rice () deriving from a large geographic gradient across South‐East Asia, the Si concentrations (ranging from 1.6% to 10.7%) are negatively related to the concentrations of carbon (31.3% to 42.5%) and lignin‐derived phenols (32 to 102 mg/g carbon). Less lignin may explain results of previous studies that Si‐rich straw decomposes faster. Hence, Si seems a significant but hardly recognized factor in organic carbon cycling through grasslands and other ecosystems dominated by Si‐accumulating plants. The key role of silicon in marine ecology by controlling algae growth is well recognized but research on terrestrial ecosystems neglected Si since not considered an essential plant nutrient. However, many plants accumulate large amounts of Si, and recently it has been hypothesized that incorporation of Si as a structural component may substitute for the energetically more expensive biosynthesis of lignin. Herein, we provide evidence supporting this hypothesis. We demonstrate that in rice straw deriving from a large geographic gradient across South‐East Asia, the Si concentrations are negatively related to the concentrations of carbon and lignin‐derived phenols. Our data offer an explanation for previous findings of faster decomposition of Si‐rich rice straw as lignin regulates plant litter decomposition rates. Hence, Si seems a significant but hardly recognized factor in carbon cycling through ecosystems dominated by grass species and/or other Si‐accumulating plants.
    Keywords: Carbon Cycle ; Lignin ; Litter Decomposition ; Rice ; Silicon ; Structural Plant Components
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 5
    Language: English
    In: Plant and Soil, 2004, Vol.258(1), pp.307-327
    Description: Soil solution composition changes with time and distance from the root surface as a result of mass flow, diffusion, plant nutrient uptake and root exudation. A model system was designed, consisting of a root compartment separated from the bulk soil compartment by a nylon net (30 μm mesh size), which enabled independent measurements of the change of soil solution composition and soil water content with increasing distance from the root surface (nylon net). K + concentration in the rhizosphere soil solution decreased during the initial growth stage (12 days after planting, DAP). Thereafter K + accumulated with time, due to mass flow as the dominating process. The extend of K + accumulation depended on the initial fertiliser application. As K + concentrations in soil solution increase, not only as a result of transport exceeding uptake, but also as a result of decreasing soil water content, it is hypothesised that K concentration in soil solution is not the only trigger for the activity of K transporters in membranes, but ABA accumulation in roots induced by decreasing soil matric potentials may add to the regulation. A strong decrease of rhizosphere pH with time is observed as a result of H + efflux from the roots in order to maintain cation-anion balance. In addition the K + to Ca 2+ ratio was altered continuously during the growing period, which has an impact on Ca 2+ uptake and thus firmness of cell walls, apoplast pH, membrane integrity and activity of membrane transporters. The value of osmotic potential in the rhizosphere soil solution increased with time indicating decreasing soil water availability. Modelling approaches based on the data obtained with the system might help to fill in the time gaps caused by the low temporal resolution of soil solution sampling method.
    Keywords: K ; matric potential ; osmotic potential ; pH ; rhizosphere ; soil solution
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 6
    In: Global Change Biology, April 2013, Vol.19(4), pp.1107-1113
    Description: More than 50% of the world's population feeds on rice. Soils used for rice production are mostly managed under submerged conditions (paddy soils). This management, which favors carbon sequestration, potentially decouples surface from subsurface carbon cycling. The objective of this study was to elucidate the long‐term rates of carbon accrual in surface and subsurface soil horizons relative to those of soils under nonpaddy management. We assessed changes in total soil organic as well as of inorganic carbon stocks along a 2000‐year chronosequence of soils under paddy and adjacent nonpaddy management in the angtze delta, hina. The initial organic carbon accumulation phase lasts much longer and is more intensive than previously assumed, e.g., by the ntergovernmental anel on limate hange (). Paddy topsoils accumulated 170–178 kg organic carbon ha a in the first 300 years; subsoils lost 29–84 kg organic carbon ha a during this period of time. Subsoil carbon losses were largest during the first 50 years after land embankment and again large beyond 700 years of cultivation, due to inorganic carbonate weathering and the lack of organic carbon replenishment. Carbon losses in subsoils may therefore offset soil carbon gains or losses in the surface soils. We strongly recommend including subsoils into global carbon accounting schemes, particularly for paddy fields.
    Keywords: Carbon Sequestration ; Inorganic Carbon ; Land Use ; Organic Carbon ; Paddy ; Rice Cultivation ; Soils ; Subsoils
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 7
    Language: English
    In: Journal of Plant Nutrition and Soil Science, December 2010, Vol.173(6), pp.811-821
    Description: Natural mineral dust has manifold environmental effects reaching from fertilizing aquatic and terrestrial ecosystems to affecting the earth's radiation balance and thus impacting on climate. The Sahara is considered the largest source of natural mineral dust on the globe, so much research attention has been paid to source identification, dust mobilization, transport, and effects in the sink areas. This paper gives a review of the research results concerning these topics emphasizing soil‐science‐related aspects of the last 20 y and the identification of knowledge gaps.
    Keywords: Dust Properties ; Soil Formation ; Mineralogy ; Wind Erosion ; Eolian Deposit
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 8
    Language: English
    In: Catena, January 2014, Vol.112, pp.1-3
    Keywords: Soil Geography ; Palaeopedology ; Soil Landscapes ; Palaeosols ; Soil Archives ; Sciences (General) ; Geography ; Geology
    ISSN: 0341-8162
    E-ISSN: 1872-6887
    Source: ScienceDirect Journals (Elsevier)
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  • 9
    Language: English
    In: Plant and Soil, 1 October 2013, Vol.371(1/2), pp.267-279
    Description: Aims and background Release of 'non-exchangeable' potassium (K) from interlayers of illite is diffusioncontrolled and has been shown to depend on the solution concentration of Ê and other cations (Ca²⁺, Mg²⁺, NH₄⁺). Methods We analysed changes in soil solution concentrations of K and competing cations in situ at different distances from the root surface over time and related them to the transformation of illite, as revealed by X-ray diffraction, and chemical measures of differently bound K. Results and Conclusions Within 49 and 98 days, respectively, 6.4 and 14.4 % of the illite's total K was released upon contact with the root system. Mixed layered minerals increased from 33 (0 d) to 35 (49 d) to 40 % (98 d). Release of K from interlayers and the transformation of illite occurred at soil solution K concentrations close to the threshold of 80 µM suggested earlier. Concentrations of Ca and Mg increased with decreasing distance from the root surface, promoting the release of K. The NaBPh₄ method supposed to determine 'non-exchangeable' K extracted only 1/3 of the total K from illite.
    Keywords: Physical sciences -- Earth sciences -- Geology ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Biology -- Botany ; Physical sciences -- Earth sciences -- Geology ; Physical sciences -- Chemistry -- Chemical elements ; Biological sciences -- Biology -- Botany ; Biological sciences -- Agriculture -- Agricultural sciences ; Physical sciences -- Earth sciences -- Geology
    ISSN: 0032079X
    E-ISSN: 15735036
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  • 10
    Language: English
    In: Soil Biology and Biochemistry, February 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. ► Subsoil is relevant for nutrient acquisition by plants especially in the long term. ► Biopores in the subsoil can be hot spots for nutrient acquisition. ► A conceptual model of nutrient acquisition from the subsoil is presented.
    Keywords: Structure Dynamics ; Biopore Formation ; Root Growth ; Drilosphere ; Rhizodeposition ; Microbial Activity ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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