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  • Sinaj, Sokrat  (14)
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  • 1
    Language: English
    In: Geoderma, May, 2014, Vol.219-220, p.125(11)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.geoderma.2013.12.015 Byline: Emmanuel Frossard, Paolo Demaria, Sokrat Sinaj, Michael Scharer Abstract: Controlling phosphate (P) release from agricultural soils to water while maintaining optimal plant growth conditions remain a major challenge for the development of sustainable agricultural systems. To achieve this, it is important to have a proper knowledge of the amount of soil P that can be mobilized by water and of the kinetics of P release. We evaluated the ability of a flow-through reactor in which.sup.33P labeled soils can be inserted and leached continuously with deionized water, to assess P release. The experiment was conducted on five grassland soils presenting a large range in P availability. The availability of P in these soils was further modified by submitting them to 0 to 3 plant growth cycles with Italian ryegrass (Lolium multiflorum) with three levels of P added (0, 20 and 40mgPkgsoil.sup.-1). The P input-output balance, water and oxalate extractable P, the degree of P saturation of the soil and the amount of isotopically exchangeable P (E value) were assessed in all samples. A subset of these soil samples was labeled with.sup.33P, introduced in a flow-through reactor and the release of P and.sup.33P measured over 14days. The cumulated amount of P released after 14days was strongly correlated to the amount of oxalate extractable P, isotopically exchangeable P (E value), and water extractable P. The P release kinetics was modeled with a 2 pools model with each pool following first order kinetics. Plants were able to take up P from both pools. Assuming that the leached P had the same isotopic composition as the pool of soil P it came from it became possible to quantify the amount of isotopically exchangeable remaining in the soil which was called the D value. D decreased during the three first days of the flow-through experiment and then increased linearly with time reaching a maximum after 14days. This maximum remained lower than the oxalate extractable P. Processes contributing to this increase were isotopic exchange and possibly also some organic P mineralization. The D value was strongly linearly correlated to E values measured after different exchange times, but for a given exchange time, the D value was lower than the E value, whereas equality could have been expected. This difference was related to the high rate of.sup.33P export from the soil at the beginning of the flow-through experiment. The D value was also strongly correlated to the oxalate and water extractable P. In conclusion, we suggest that the use of the flow-through reactor yields relevant information on the amount of P that can be leached from a given soil, and that the D value delivers information on the amount of isotopically exchangeable P remaining in the soil and therefore which could still be leached if sufficient time would be given. Article History: Received 24 July 2013; Revised 7 December 2013; Accepted 11 December 2013
    Keywords: Oxalic Acid -- Evaluation ; Oxalic Acid -- Analysis ; Soils -- Analysis ; Phosphates -- Evaluation ; Phosphates -- Analysis ; Oxalates -- Evaluation ; Oxalates -- Analysis
    ISSN: 0016-7061
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Geoderma, April, 2014, Vol.217-218, p.26(11)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.geoderma.2013.11.001 Byline: Aurelien Roger, Zamir Libohova, Nicolas Rossier, Stephane Joost, Alexandra Maltas, Emmanuel Frossard, Sokrat Sinaj Abstract: Phosphorus (P) is the second essential nutrient for plant growth but can become an ecological and economical concern in case of over-fertilization. Soil P dynamic is influenced by many parameters like soil physical-chemical properties and farming practices. A better understanding of the factors controlling its distribution is required to achieve best management of P in cropping systems. In Switzerland, the FRIBO network was launched in 1987 and consists of 250 sites covering a wide diversity of soils (Cambisols, Gleysols, Rendzinas, Lithosols, Luvisols, Fluvisols) and three different land uses (cropland, grassland and mountain pasture) across the Fribourg canton. A spatial investigation of the different P forms (total, organic and available) for the FRIBO network led to the following main conclusions: (i) The P status in agricultural soils was significantly different among the three land uses encountered, with the highest mean values of available P found in croplands, from 2.12 (CO.sub.2 saturated water extraction) to 81.3mg.kg.sup.-1 (acetate ammonium+EDTA extraction); whereas total P was more abundant in permanent grasslands (1186mg.kg.sup.-1), followed by mountain pastures (1039mg.kg.sup.-1) and croplands (935mg.kg.sup.-1). This full characterization of the soil P status provides important data on P distribution related to soil properties and land use. (ii) Environmental variables such as altitude, slope, wetness index or plan curvature, derived from the digital elevation model (DEM) only explained a small part of the spatial variation of the different P forms (20 to 25%). Thus, the geostatistical analyses revealed that land use plays a significant role in soil P distribution. Improved predictions of the spatial distribution of P-related forms at landscape scales are needed and would require additional data points and variables such as parent material, soil types and terrain attributes. Article History: Received 2 July 2013; Revised 31 October 2013; Accepted 8 November 2013
    Keywords: Soil Phosphorus -- Chemical Properties ; Soil Phosphorus -- Analysis
    ISSN: 0016-7061
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Geoderma, May 2014, Vol.219-220, pp.125-135
    Description: Controlling phosphate (P) release from agricultural soils to water while maintaining optimal plant growth conditions remain a major challenge for the development of sustainable agricultural systems. To achieve this, it is important to have a proper knowledge of the amount of soil P that can be mobilized by water and of the kinetics of P release. We evaluated the ability of a flow-through reactor in which P labeled soils can be inserted and leached continuously with deionized water, to assess P release. The experiment was conducted on five grassland soils presenting a large range in P availability. The availability of P in these soils was further modified by submitting them to 0 to 3 plant growth cycles with Italian ryegrass ( ) with three levels of P added (0, 20 and 40 mg P kg soil ). The P input–output balance, water and oxalate extractable P, the degree of P saturation of the soil and the amount of isotopically exchangeable P ( value) were assessed in all samples. A subset of these soil samples was labeled with P, introduced in a flow-through reactor and the release of P and P measured over 14 days. The cumulated amount of P released after 14 days was strongly correlated to the amount of oxalate extractable P, isotopically exchangeable P ( value), and water extractable P. The P release kinetics was modeled with a 2 pools model with each pool following first order kinetics. Plants were able to take up P from both pools. Assuming that the leached P had the same isotopic composition as the pool of soil P it came from it became possible to quantify the amount of isotopically exchangeable remaining in the soil which was called the value. decreased during the three first days of the flow-through experiment and then increased linearly with time reaching a maximum after 14 days. This maximum remained lower than the oxalate extractable P. Processes contributing to this increase were isotopic exchange and possibly also some organic P mineralization. The value was strongly linearly correlated to values measured after different exchange times, but for a given exchange time, the value was lower than the value, whereas equality could have been expected. This difference was related to the high rate of P export from the soil at the beginning of the flow-through experiment. The value was also strongly correlated to the oxalate and water extractable P. In conclusion, we suggest that the use of the flow-through reactor yields relevant information on the amount of P that can be leached from a given soil, and that the value delivers information on the amount of isotopically exchangeable P remaining in the soil and therefore which could still be leached if sufficient time would be given.
    Keywords: Desorption ; Flow-through Reactor ; Isotopic Exchange ; Kinetics ; Phosphate ; Soil ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 4
    Language: English
    In: Communications in Soil Science and Plant Analysis, 01 January 2013, Vol.44(1-4), pp.287-300
    Description: Isotopically exchangeable phosphate (P) is the main source of P for most crops. The amount of P that is located on the solid phase of a soil and that can exchange with P in the soil solution can be calculated knowing the concentration of water-extractable P (C P...
    Keywords: Isotopically Exchangeable Phosphate ; Pedotransfer Function ; Soil Properties ; Statistical Models ; Temperate Soils ; Agriculture
    ISSN: 0010-3624
    E-ISSN: 1532-2416
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  • 5
    Language: English
    In: Geoderma, April 2014, Vol.217-218, pp.26-36
    Description: Phosphorus (P) is the second essential nutrient for plant growth but can become an ecological and economical concern in case of over-fertilization. Soil P dynamic is influenced by many parameters like soil physical–chemical properties and farming practices. A better understanding of the factors controlling its distribution is required to achieve best management of P in cropping systems. In Switzerland, the FRIBO network was launched in 1987 and consists of 250 sites covering a wide diversity of soils (Cambisols, Gleysols, Rendzinas, Lithosols, Luvisols, Fluvisols) and three different land uses (cropland, grassland and mountain pasture) across the Fribourg canton. A spatial investigation of the different P forms (total, organic and available) for the FRIBO network led to the following main conclusions:
    Keywords: Soil Phosphorus ; Soil Properties ; Land Use ; Spatial Variability ; Geostatistics ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 6
    Language: English
    In: Soil Biology, Phosphorus in Action: Biological Processes in Soil Phosphorus Cycling, pp.59-91
    Description: The use of tracers is relevant to study the transformations of phosphorus (P) in the soil–plant system because (a) only a small fraction of the total soil P is rapidly circulating in this system, (b) P participates in many reactions in the soil, some occurring within a few seconds, others over years, and (c) P is distributed in many pools in the soil. This review presents the use of P radioisotopes (a) to probe pools and to study P transformations in soils, (b) to trace the fate of fertilizers in soil–plant systems, and (c) to assess the foraging strategies of arbuscular mycorrhizal fungi for P. Finally, we discuss the potential of analyzing the oxygen isotopes bound to P to study soil P dynamics and the research needed to achieve this aim.
    Keywords: Life Sciences ; Biochemistry, General ; Plant Physiology ; Microbiology ; Agriculture ; Soil Science & Conservation ; Agriculture ; Biology ; Chemistry
    ISBN: 9783642152702
    ISBN: 3642152708
    Source: SpringerLink Books
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  • 7
    In: Soil Science, 2001, Vol.166(6), pp.365-373
    Description: The loss of phosphorus (P) on overland flow and subsurface drainage from soils receiving long-term applications of fertilizer and manure has been linked to the accelerated eutrophication of fresh waters. This loss is initiated by the release of P from soil to solution, which for overland flow can be estimated by water extraction and for subsurface drainage waters by 0.01 M CaCl2 extraction. Although this release is rapid, the information available on the kinetics of P loss is insufficient to support improved soil P management. In this study, an isotopic exchange kinetics (IEK) approach was used to assess the effect of two solutions (water and 0.01 M CaCl2) and different soil-to-solution ratios on soil isotopically exchangeable P (Et). Results are described by a compartmental analysis that quantified the amount of P isotopically exchangeable within 1 min (E1min), 30 min (E30min), 24 hr (E24hr), and between 24 hr and 3 months (E24hr-3mo). The quantity of P in each compartment was then compared with the concentration of P in overland flow and subsurface drainage waters. Isotopically exchangeable soil P within 1 min (1:5 soil to solution ratio) was correlated most closely with the concentration of P in overland flow (r = 0.84 with water) and subsurface drainage waters (r = 0.93 with 0.01 M CaCl2). For overland flow, a significant correlation was maintained at a soil-to-solution ratio of 1:100 for more exchangeable P pools than at other ratios (1:5 or 1:10). Similarly, the relationship between isotopically exchangeable P in 0.01 M CaCl2 (but not Et in water) and subsurface drainage waters P was maintained for exchange times up to 24 hr, reflecting the greater contact period of subsurface drainage water with soil compared with overland flow. The results suggest that the concentration of P in overland flow and subsurface drainage waters is dependent on the rapid or short-term (1 min and 〈24 hr) kinetics of soil exchangeable P and that the IEK approach can explain, and with further work may predict, the amount of P that can potentially move from agricultural soils to overland flow and subsurface drainage waters.
    Keywords: Isotopes ; Eutrophication ; Pollution (Nonpoint Sources) ; Kinetics ; Runoff (Agricultural) (See Also Return Flows) ; Groundwater Flow ; Phosphorus ; Runoff ; Soil Contamination ; Water Pollution Sources ; Eutrophication ; Drainage ; Nonpoint Pollution Sources ; Phosphorus ; Groundwater Pollution ; Isotope Studies ; Overland Flow ; Sources and Fate of Pollution ; Water Quality;
    ISSN: 0038-075X
    E-ISSN: 15389243
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  • 8
    Language: English
    In: Journal of Plant Nutrition and Soil Science, February 2005, Vol.168(1), pp.89-93
    Description: Isotopically exchangeable phosphate (P) is a major source of P for plants. In practice, however, plant‐available P is assessed by chemical extractions solubilizing a mixture of P forms the availability of which is ill defined. We undertook an isotopic approach to assess the exchangeability of P extracted by (1) CO‐saturated water (P‐CO), (2) ammonium acetate EDTA (P‐AAEDTA), and (3) sodium bicarbonate (P‐NaHCO) compared to the exchangeability of P extracted by water. Five topsoils with similar P‐fertilization histories but different soil properties were studied. Phosphorus was extracted from soils labeled with carrier‐free P after 1 week of incubation, and the specific activity (SA = P / P) of the extracts was compared with the SA of P extracted by water to calculate the amount of P isotopically exchangeable that had been solubilized during the extraction. P‐CO extracted between 20 and 100 times less P than P‐AAEDTA and P‐NaHCO. The SA of P‐CO was not different from the SA of water‐extractable P, showing that P‐CO solubilized similar forms of P as water and that these forms can be considered as available. The SA of P extracted by the two other methods ranged between 25% and 63% for P‐AAEDTA and 66% and 92% for P‐NaHCO of the SA of water‐extractable P. The fraction of exchangeable P extracted by AAEDTA decreased linearly with increasing soil pH, suggesting that this method dissolves slowly or non‐exchangeable P from calcium phosphates. Phosphataustauschbarkeit, bestimmt mittels vier chemischer Extraktionsmethoden Isotopisch austauschbares Phosphat (P) ist eine der Haupt‐P‐Quellen für Pflanzen. In der Praxis wird pflanzenverfügbares P mittels chemischer Extraktionen ermittelt. Dabei werden unterschiedliche P‐Formen extrahiert, deren Verfügbarkeit nur ungenügend definiert ist. Mittels der Isotopentechnik verglichen wir die Austauschbarkeit von P, das extrahiert wurde durch 1) CO‐gesättigtes Wasser (P‐CO), 2) Ammoniumacetat EDTA (P‐AAEDTA) und 3) Natrium‐Bicarbonat (P‐NaHCO), mit der Austauschbarkeit von mit Wasser extrahiertem P. Dabei wurden fünf Oberböden mit gleicher P‐Düngung, aber unterschiedlichen Bodeneigenschaften untersucht. Die Böden wurden während einer Inkubationszeit von einer Woche mit P‐trägerfreiem P markiert. Um die Menge an isotopisch austauschbarem P, welches während der Extraktion aus dem Boden gelöst wurde, zu bestimmen, wurde die spezifische Aktivität (SA = P / P) der Extrakte mit der SA von P, das mit Wasser extrahiert wurde, verglichen. Die Extraktion mit CO‐gesättigtem Wasser setzte 20‐ bis 100mal weniger P frei als diejenige mit AAEDTA oder NaHCO. Die SA von P‐CO unterschied sich nicht von derjenigen von mit Wasser extrahierbarem P. Das weist was darauf hin, dass mit P‐CO dieselben P‐Formen gelöst werden wie mit Wasser; diese P‐Formen können als pflanzenverfügbar angesehen werden. Die SA von P, das mit AAEDTA bzw. NaHCO extrahiert wurde, machte 25–64% bzw. 66–92% der SA von mit Wasser extrahierbarem P aus. Die mit AAEDTA extrahierte austauschbare P‐Fraktion nahm linear mit ansteigendem Boden‐pH ab, was darauf hindeutet, dass mit dieser Methode langsam oder nicht austauschbares P aus Calcium‐Phosphaten gelöst werden kann.
    Keywords: Extractable Phosphate ; Isotopically Exchangeable Soil Phosphate ; Plant‐Available Phosphorus
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 9
    Language: English
    In: Journal of Plant Nutrition and Soil Science, 13 October 2003, Vol.166(5), pp.557-567
    Description: Residual fertilizer phosphorus (residual P) may significantly contribute to crop P nutrition. To test this hypothesis, a pot experiment was conducted with ryegrass and clover grown separately on three different soils which either had not received P fertilizer for at least nine years () or had received P fertilizer equivalent to crop P off‐take (). Soils in the pot experiment were given either none () or a single rate of 15 mg P (kg soil) as diammonium phosphate (). In the treatments and DAP had been labeled with PO while in the treatments and the pool of available soil P had been labeled with carrier‐free PO. This allowed estimating the quantities of P in plant dry matter that derived from native soil P, residual fertilizer P or fresh fertilizer P. Fourteen to 62 % of the P in the above ground biomass of white clover or perennial ryegrass were derived from residual P whereas 7 to 28 % were derived from freshly applied DAP. The proportion of P derived from residual P was correlated to the total amount of P fertilizer added to the soils, while the proportion of P derived from DAP was correlated to the concentration of P in the soil solution of the and soils. Aufnahme von Phosphat aus Rückständen von früherer Düngung und aus frisch ausgebrachtem Diammoniumphosphat durch Lolium perenne und Trifolium repens In Düngerrückständen enthaltener Phosphor (P) kann möglicherweise signifikant zur P‐Ernährung von Kulturpflanzen beitragen. Um diese Hypothese zu prüfen, wurde im Topfversuch die P‐Aufnahme durch und untersucht. Als Substrat dienten drei Böden, die entweder seit mindestens 1989 keine P‐Gabe mehr erhalten hatten () oder die jährlich P‐Gaben im Umfang der P‐Entzüge durch die vorgängigen Kulturen erhalten hatten und deshalb P‐Rückstände enthielten (). Es ergaben sich folgende Verfahren: : ohne P aus Düngerrückständen und frischer Düngung; : mit P aus frischer Düngung (Diammoniumphosphat, 15 mg P (kg Boden)); : mit P aus Düngerrückständen; : mit P aus Düngerrückständen und frischer Düngung. In den Verfahren und war DAP mit PO markiert. In den Verfahren und war der verfügbare P des Bodens mit carrier‐freiem PO markiert. Dies ermöglichte die Erfassung der Aufnahme von P durch die Pflanzen differenziert nach Herkunft aus Boden, Düngerrückständen und frischem Dünger. Von Düngerrückständen stammten 14–62 %, von frischem Dünger 7–28 % des in den Sprossen der Pflanzen gefundenen P. Der von Düngerrückständen stammende Anteil P in den Pflanzensprossen war korreliert mit dem gesamten Gehalt an P das dem Boden als Dünger zugeführt worden war. Der von frischem DAP stammende Anteil war korreliert mit der P‐Konzentration in der Bodenlösung.
    Keywords: Lolium Perenne ; Trifolium Repens ; Association / ; Phosphorus ; Fresh Fertilization ; Residual Fertilization 7 Isotopic Methods
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 10
    Language: German
    In: Journal of Plant Nutrition and Soil Science, December 2003, Vol.166(6), pp.782-782
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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