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  • 1
    Electronic Resource
    Electronic Resource
    Soil phosphorus management and water quality: a UK perspective (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 14 (1998), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. An increasing proportion of P reaching surface waters appears to be derived from agricultural land; apportioning the relative contribution to particular farming systems is not straightforward. The majority of farms in the UK operate on the basis of an annual agricultural P surplus, the size of which varies across different farm types. Particularly high values (〉20kg ha-1) are commonly associated with intensive-livestock production and the lower values (〈10kg P ha-1) with arable farms. The geographical divide between the predominance of arable cropping in the east and livestock enterprises in the west of the UK should result in an uneven pattern to the distribution of annual P surplus. The expected cumulative effects of this surplus should be a noticeable increase in total and extractable soil P concentrations, but this is not readily apparent. While evidence from experimental plots suggests a relationship between the concentration of available soil P and that present in drainage waters, extrapolating this information so that it can be useful at the scale of a whole catchment is difficult. The loss of P from agricultural land is controlled by factors which are independent of the size of the annual P surplus. The pattern of P cycling, together with the dominant loss pathways, differ greatly between livestock and arable farming systems. Proportioning the contributions that either increased soil erosion arising from changing agricultural practices or the cumulative effect of a P surplus have had upon P loss is a necessary prerequisite to effective management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1998.tb00630.x
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  • 2
    Electronic Resource
    Electronic Resource
    Reactions of phosphorus with sediments in fresh and marine waters (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 14 (1998), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The interactions of P with soils and sediments are examined in the context of transport processes from land, through rivers to estuaries and coastal waters. In soil erosion, selective size fractionation and preferential sorption to finer solids is crucial in the transport of P to water courses. Problems in quantifying the sorption affinity and equilibrium phosphate concentration (EPC) of mixtures of different soils and sediments are identified. Riverine transport of P by suspended solids is usually very important and examples of the changes in the amount and composition of particulate P (PP) concentration during storm events are discussed. Increased P content of solids during the first autumn storms, probably reflect the resuspension of accumulated stream bed-deposits. The fate of P in estuaries and their importance as possible long-term sinks of P are discussed. The relatively high concentrations of dissolved P associated with riverine inputs are to some extent buffered by the relatively high concentrations of suspended sediments resulting from tidal flows. Phosphorus may be released during transport to the sea due to decreases in the EPC, increases in salinity and release from bottom sediments as a result of low oxygen conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1998.tb00632.x
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  • 3
    Electronic Resource
    Electronic Resource
    The phosphorus composition of soil solutions and soil leachates: Influence of soil:solution ratio (1997)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 48 (1997), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Compositional differences between soil solutions obtained by different methods have frequently been reported; variations in the soi1: solution ratio may explain these results. In this study we compared the amount and composition of phosphorus (P) in soil leachates and soil solutions from a temperate grassland soil in northeast Scotland and determined the influence of soi1:solution ratio on P fractions in soil water extracts. Leachates were collected from intact soil cores over 6 months, the cores were then destructively sampled, and soil solutions obtained by centrifuging. Molybdate reactive P (MRP) represented 71% of the total dissolved P (TDP) in soil leachates but only 54% in soil solutions. The MRP component in soil water extracts increased from 71% to 92% as the soi1:solution ratio increased from 1:15 to 1:15·4, while the dissolved organic P (DOP) component decreased from 26% to 6%. As the soil:solution ratio increased the amount of MRP extracted increased; by contrast the amount of DOP and dissolved condensed P (DCP) extracted remained constant. While the MRP component is regulated by soil sorption processes, the supply and amount of DOP and DCP is probably related to biological activity. Dissolved organic carbon (DOC) extracted at wide soi1:solution ratios contained a smaller proportion of P than that extracted at narrower ratios. The results indicate differences in the behaviour of P fractions in the soil at various soi1:solution ratios and that these are reflected in the P composition of soil solution and leachate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1997.tb00570.x
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of reducing conditions on the solubility of phosphorus in a diverse range of European agricultural soils (2002)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 53 (2002), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of reducing conditions on solubility of phosphorus (P) can directly influence water quality. The release of P is enhanced although the P is not directly involved in reduction processes. We here compare the responses to flooding of 12 overfertilized agricultural soils in widely varying pedological and management regimes, belonging to seven World Reference Base groups. The redox potential initially ranged from 305 to 515 mV and decreased to −157 to −195 mV within 32 days. The onset of reducing conditions led to an increase in the concentration of soluble P. The maximum rate of solubilization occurred within 1–3 weeks under reducing conditions, and the steady-state concentrations of P never exceeded 200 μmol dm−3. Four stages in the development of the reduction process are identified, and a simple empirical model describes the change in concentrations of soluble P. The potential of P release under reduction is positively correlated with the soil saturation with P. Flooding over a few weeks triggered the release of large amounts of P. Constant pe + pH is related to constant concentration of molybdate-reactive P, suggesting that soluble P is effectively buffered so that P will be immobilized. In general the solubilization of P under reducing conditions is likely to be aggravated by the increased soil P status that has resulted from overfertilization of agricultural land with P. These findings bear on the establishment and long-term effectiveness of riparian buffer zones where phosphorus is likely to accumulate by the interception of drainage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2002.00462.x
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  • 5
    Electronic Resource
    Electronic Resource
    Measuring bioavailable trace metals by diffusive gradients in thin films (DGT): soil moisture effects on its performance in soils (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: Conventional methods of measuring labile chemical species of trace metals in soil solutions, such as chemical competition following centrifuging, are inadequate if the speciation changes during sampling and extraction. A new technique, diffusive gradients in thin films (DGT), measures labile species of trace metals in natural waters and sediments in situ. A well-defined diffusive gel layer distinguishes it from other resin-based techniques. It perturbs the soil in a controlled way by introducing an in situ local sink for metal ions. Resulting fluxes to the device are quantitatively measured, allowing assessment of re-supply kinetics and in some cases measurement of in situ soil solution concentrations. We used DGT to measure fluxes of Cd, Co, Cu, Ni, Pb and Zn in a sludge-treated soil at various moisture contents (27–106%). Replicate measurements showed that the precision of DGT-measured fluxes was within 10%. For moisture contents exceeding the field capacity (42%), the DGT response reflected soil water concentrations. At smaller moisture contents, changes related to tortuosity and dilution were reflected in the measurements. This technique has the potential for in situ measurements in the field where it should provide quantitative flux data on individual soils and provide a good surrogate for bioavailable metal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.1999.00226.x
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular size distribution and enzymatic degradation of organic phosphorus in root exudates of spring barley (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 285-290 
    Details
    ISSN: 1432-0789
    Keywords: Exudates ; Hordeum vulgare ; Gel filtration ; Phosphatases ; Phytase ; Phosphorus ; Roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seeds from two varieties of spring barley (Prisma and Camorgue) were grown axenically in water. After 14 days, the culture solutions contained organic P substances (about 4 μg P per plant) derived from root exudation, representing about 3% of the total P found in the seed. Gel filtration, separated the organic P into two well defined peaks, one with a high molecular weight (〉45000 daltons) and the other with a low molecular weight (〈500 daltons). The bioavailability of the soluble organic P released was assessed enzymatically and chemically. At the optimum pH of 5.0, phytase and acid phosphatase hydrolysed about 80% and 65%, respectively of the organic P in the exudate after 24 h whereas at the optimum pH of 9.8, alkaline phosphatase hydrolysed up to 40% P after the same length of time. In a pH 5.0 buffer, up to 10% of the organic P was hydrolysed compared with up to 45% in a pH 9.8 buffer. The high molecular weight organic P fraction recovered from the G-75 Sephadex behaved similarly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570630
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  • 7
    Electronic Resource
    Electronic Resource
    High pressure basic inclusions from the Kayrunnera kimberlitic diatreme in New South Wales, Australia (1979)
    Springer
    Contributions to mineralogy and petrology 69 (1979), S. 185-192 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Basic inclusions of two types occur in a kimberlitic diatreme at Kayrunnera in northwestern New South Wales. Type I inclusions comprise assemblages of clinopyroxene+garnet+rutile±plagioclase ±quartz±K-feldspar±scapolite±sphene±apaite. Type II inclusions have assemblages of clinopyroxene +garnet+kyanite+quartz±plagioclase and are lower in Ti, total Fe, and higher in Al and have a higher Mg/Mg+gSFe ratio than the Type I inclusions. Experimental and theoretical data indicate that both inclusion types equilibrated at between 850–900 ° C and 18–23 kb. Due to their low concentrations of incompatible elements, the Type I inclusions are considered to represent a basaltic melt derived from an Fe-rich mantle source rock, and not to be the product of fractionation. The Type II inclusions are believed to represent cumulates which formed from a basaltic magma. The presence of sulphur rich scapolite in the Type I inclusions extends the range of P-T conditions from which this mineral has been reported thus adding further credence to the hypothesis that it may act as a stable repository for S and CO2 in the crust and upper mantle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371861
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  • 8
    Electronic Resource
    Electronic Resource
    Extraction, molecular fractionation and enzyme degradation of organically associated phosphorus in soil solutions (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 196-200 
    Details
    ISSN: 1432-0789
    Keywords: Phosphorus ; Fractionation ; Phosphatase ; Hydrolysis ; Organic phosphorus ; Hordeum vulgare
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The concentrations and chemical composition of water-extractable P were compared in four soil types from NE Scotland. All sites were sampled during the early establishment phase of a spring barley (Hordeum vulgare) crop. The quantity of total soluble P extracted ranged from 〈2.0 to 10 mg P kg soil-1, of which up to 50% was classified as being organically associated. Sample fractionation showed that both orthophosphate inorganic P and organic P were associated with a wide molecular-size range of organic material. A strong positive correlation was readily apparent between P and the sum of Fe + Al in the fractionated samples. The extent of enzymatic hydrolysis of organic P varied between soil samples and the type of enzyme. Phytase consistently produced the greatest degree of hydrolysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336322
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  • 9
    Electronic Resource
    Electronic Resource
    Role of proteinaceous amino acids released in root exudates in nutrient acquisition from the rhizosphere (1994)
    Springer
    Plant and soil 158 (1994), S. 183-192 
    Details
    ISSN: 1573-5036
    Keywords: amino acids ; nutrient acquisition ; rhizosphere ; root exudates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The role of proteinaceous amino acids in rhizosphere nutrient mobilization was assessed both experimentally and theoretically. The degree of adsorption onto the soil's solid phase was dependent on both the amino acid species and on soil properties. On addition of amino acids to both soil and freshly precipitated Fe(OH)3, no detectable mobilization of nutrients (K, Na, Ca, Mg, Cu, Mn, Zn, Fe, S, P, Si and Al) was observed, indicating a very low complexation ability of the acidic, neutral and basic amino acids. This was supported by results from a solution equilibria computer model which also predicted low levels of amino acid complexation with solutes present in the soil solution. On comparison with the Fe(OH)3 and equilibria data obtained for the organic acid, citrate, it was concluded that amino acids released into the rhizosphere have a limited role in the direct acquisition of nutrients by plants. The effectiveness of root exudates such as amino acids, phytosiderophores and organic acids in nutrient mobilization from the rhizosphere is discussed with reference to rhizosphere diffusion distances, microbial degradation, rate of complexation and the root's capacity to recapture exudate-metal complexes from the soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009493
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of polysulfone hollow fibres and ceramic suction samplers as devices for the in situ extraction of soil solution (1993)
    Springer
    Plant and soil 150 (1993), S. 157-165 
    Details
    ISSN: 1573-5036
    Keywords: ceramic samplers ; extraction ; polysulfone fibres ; soil solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An investigation was carried out to assess the potential of using polysulfone hollow fibres for the extraction of soil solution. In comparison to ceramic suction samplers the fibres were shown to contain very low levels of potential contaminants and a low exchange capacity. Carry over between individual samples was negligible permitting the accurate monitoring of temporal changes in solution chemistry. Their flexible and root sized nature makes them ideal for sampling small soil volumes. Some concern however remains about retention of colloidal Fe at the fibre interface. When comparing the soil solution of samples extracted with polysulfone fibres with those extracted by ceramic suction samplers, no significant differences in solute concentrations were observed. No sample contamination resulting from dissolution of Al or Si from the ceramic cup was detected. Analysis of soil solutions collected over a number of extractions, and during and after a rainfall event showed concentrations of elements in solution to remain relatively constant with time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00013013
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