Resumo: A área experimental foi instalada na Fazenda de Ensino e Pesquisa da Faculdade de Ciências Agrárias e Veterinárias, UNESP, Campus de Jaboticabal, SP, localizada a uma altitude de 610m e com as seguintes coordenadas geográficas: 21°15'22" S e 48°15'18" W. O clima é do tipo Cwa, segundo a classificação de Köppen, isto é, subtropical, temperado, seco no inverno, com temperatura média máxima superior a 22°C. O experimento foi instalado com o objetivo de estudar o comportamento de diferentes doses de biossólidos aplicadas, comparadas à fertilização mineral, sobre formas de fósforo no solo, bem como distribuição do nutriente no perfil até a profundidade de 0,60m. Utilizou-se a cultura do milho nos anos agrícolas 1997/1998, 1998/1999 e 1999/2000, utilizando-se um solo latossolo vermelho distroférrico, em delineamento de blocos ao acaso, com quatro tratamentos e cinco repetições. Os tratamentos utilizados foram: sem qualquer tipo de fertilização (no ano agrícola 1997/98) e apenas com fertilização mineral (nos anos subseqüentes) (T); aplicação de 2,5 t ha-1 de biossólido (base seca) e complementação mineral de P e K, quando necessário (L1), aplicação de 5,0 t ha-1 de biossólido (base seca) e complementação mineral de P e K, quando necessário (L2), aplicação de 10 t ha-1 de biossólido (base seca) e complementação mineral de P e K, quando necessário (L3). Avaliou-se a distribuição do P total e P das frações substâncias humicas (P-SH), ácido fúlvico (P-AF), acido humico (P-AH) e humina (P-HN), P inorgânico, P orgânico, P Total(i+o), P extraível no perfil até a profundidade de 0,60m, bem como suas inter-relações... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work was carried out in Experimental and Research Farm of FCAV - UNESP, Jaboticabal county, São Paulo State, located at 610m altitude and geographic coordinates: 21°15'22" S and 48°15'18" W. The climate is Cwa by Kopen classification, sub tropical, temperate dry winter, with average maximum temperature of 22°C. The experiment was carried out with the objective to study the comportment of different biossolid ratio applications, compared with mineral fertilization, on P forms and distribution in soil layers from surface to 0,60m. The Maize was utilized at tree years (1997/98, 1998/99 and 1999/00) using an Oxisol in randomized blocks, with four treatments and five replications, cultivating maize without mineral fertilization (1997/98) and only mineral fertilization in the following years (T); 2.5 t biosolid ha-1 (dry basis) (L1), 5 t biosolid ha-1 (dry basis) (L2), 10 t biosolid ha-1 (dry basis) (L3). The treatments with biosolid was amended with mineral fertilizer (P and K) whenever necessary. The area was prepared and biossolid was applied and then incorporated at 0,05-0,10m. Phosphorus in nitric percloric acid (PNP), humic substances fractions (P-SH), fulvic acid (P-AF), humic acid (P-AH), humin (P-HN), inorganic phosphorus (Pi), total phosphorus (total P), organic phosphorus (Po) and resin phosphorus (P res) was evaluated in 0-0.05m, 0.05-0.10m, 0.10-0.20m, 0.20-0.40m and 0.40-0.60m layers. Phosphatase activity was evaluated at 0-0.05m and 0.05-0.10m. The data showed that the application of 5 t ha-1 biosolid was the best treatment, considering the amound of total P and labile fractions (P-SH) and less labile fractions (P-AF) in the upper layers. Dose that showed the best total P and P-HN contents is 7 t ha-1; non labile P forms (P-AH) was detected bellow the 0.20m layers including when mineral fertilizer was applied... (Complete abstract, click eletronic address below) / Orientador: Wanderley José de Melo / Coorientador: Marcos Omir Marques / Banca: Mara Cristina Pessôa da Cruz / Banca: Takashi Muraoka / Banca: Ronaldo Severiano Berton / Banca: José Carlos Barbosa / Doutor

This thesis presents an experimental study, both in the field and laboratory to cast more light on the primary role of the river floodplains in releasing and/or removing total-P to/from the in-stream load, under high runoff and flood conditions, by investigating the soil total-P spatial and vertical deposition patterns and topsoil erodibility, along the three (3) main river sections (e.g., headwaters, transfer and deposition zones) of an agricultural watershed, such as the Turkey River (TR). In soils, phosphorus, P, primarily exists as sediment-bound and less often as dissolved. During wet hydrological years, soil erosion and surface runoff are the main P release and transport mechanisms, while during dry hydrological years, P leaches to the deeper soil levels and is transported to freshwaters through groundwater discharge. In between the upland areas and the river network, there is a buffer zone, known as floodplain that regulates the flux exchanges between these two watershed components. Floodplains play an essential role in the riverine system health by supporting important physical and biochemical processes and improving the water quality downstream. These characteristics have led to the conclusion that floodplains primarily act as sinks for P. However, floodplains are subject to erosion as well, where soil particles along with the attached P are removed from the topsoil or enter re-suspension, under high runoff and flood conditions. The study provides an insight into the soil total-P deposition patterns across the floodplains of five (5) identified field sites and couples them with topsoil erodibility to eventually address the research objectives, which can be summarized as follows: (i) investigation of the soil total-P spatial and vertical variability across the floodplains along the main river zones and development of relationships between P variability and soil physical properties (e.g., soil texture); (ii) identification and characterization of the soil total-P deposition patterns across the floodplains (e.g., short- vs. long-term P deposition areas); and (iii) comparisons of the soil total-P concentrations and critical shear stresses among the main river zones and determination of their primary function either as P sources or sinks, under high runoff and flood conditions. Following that line of thinking, this research results comprise of three (3) parts, each one addressing a specific objective. The first part of the results includes the soil texture and total-P concentration analyses of the extracted soil profiles to identify the soil total-P spatial and vertical deposition patterns across the floodplains, as well as, to investigate the total-P variability with respect to soil physical properties (e.g., soil texture). The second part of the results focuses on investigating the role of topography (e.g., flat vs. ridge vs. swale land surfaces) and flood characteristics (e.g., frequency, magnitude, duration) in soil total-P spatial and vertical deposition patterns across the river floodplains to understand the time-scale nature of the P storage. The last part of the results presents the experimentally determined topsoil critical shear stress values and erodibility rates to characterize the floodplains’ primary function, based on their location along the three (3) main river zones, either as sources or sinks for total-P, during high runoff and flood conditions. Overall, the results of this research show that (i) the total-P concentration in soils is tightly related to the fine particle content and monotonic linear relationships can be established between the two variables. In other words, the higher the fine particle content, the higher the total-P concentration in soils; (ii) a mixture of two normal distributions fit the log-transformed soil total-P concentration data of each field site considered in this study. The fitted distributions successfully capture the two peaks of the soil total-P concentration data correspond to the lower and upper floodplain terraces; (iii) the lower floodplain terraces (e.g., 2- and 5-year floodplains) are characterized by significantly lower soil fine particle percentage contributions and total-P concentrations compared to the upper floodplain terraces, at a 5% confidence level. These patterns can be attributed to the fact that the lower floodplain terraces are frequently flooded and/or under inundation compared to the upper floodplain terraces and thus part of the fine particles along with the attached P are regularly winnowed away. Therefore, the lower floodplain terraces can be considered as short-term P storage means, in between two consecutive major flood events, while the upper floodplain terraces act more as long-term P storage means; (iv) there is a longitudinal increase in the topsoil critical shear stress values, which follows the increase in the fine particle content reconfirming the principle that the more the fine particle content in soils, along with the existence of vegetation with dense, well-developed root systems, the more resistant to erosion are the soils. From a soil erodibility perspective, the floodplains along the headwaters zone can be considered as major fine sediment and total-P sources contributing to the in-stream loads, while the floodplains along the deposition zone primarily act as sinks for fine sediment and total-P. As far as the role of the floodplains along the transfer zone, they can be considered as sinks for fine sediment and total-P during low magnitude runoff and flood events (e.g., 2-; 5-; and 10-year return periods), while during higher magnitude events, they act as sources releasing fine sediment and total-P; and (v) topsoil samples characterized by dense, well-developed root systems fall approximately along a trend line that follows almost a parallel pattern with the trend line for the topsoil samples without dense and/or well-developed root systems. The existence of dense, well-developed vegetation root systems to topsoil consistently increases its critical shear stress threshold (e.g., > 1 Pa) and thus its ability to resist erosion.

Charwell Basin is a 6 km-wide structural depression situated at the boundary between the axial ranges and faulted and folded Marlborough Fault Zone of north-eastern South Island, New Zealand. The basin contains the piedmont reach of the Charwell River, and a series of late Quaternary loess-mantled alluvial terraces and terrace remnants that have been uplifted and translocated from their sediment source due to strike-slip motion along the Hope Fault which bounds the basin to its immediate north. The aim of this study was to provide an interdisciplinary, integrated and holistic analysis of late Quaternary landscape evolution and environmental change in Charwell Basin using terrain analysis, loess stratigraphy, soil chemistry and paleoecological data. The study contributes new understanding of New Zealand landscape and ecosystem responses to regional and global climatic change extending to Marine Isotope Stage (MIS) 6, and shows that climatically-forced shifts in biogeomorphic processes play a significant role in lowland landscape evolution. Morphometric analysis of alluvial terraces and terrace remnants of increasing age demonstrated geomorphic evolution through time, with a decrease in extent of original planar terrace tread morphology and an increase in frequency of steeper slopes and convexo-concave land elements. Paleotopographic analysis of a &gt150 ka terrace mantled by up to three loess sheets revealed multiple episodes of alluvial aggradation and degradation and, subsequent to river abandonment, gully incision prior to and coeval with loess accumulation. Spatial heterogeneity in loess sheet preservation showed a complex history of loess accumulation and erosion. A critical profile curvature range of -0.005 to -0.014 (d2z/dx2, m-1) for loess erosion derived from a model parameterised in different ways successfully predicted loess occurrence on adjacent slope elements, but incorrectly predicted loess occurrence on an older terrace remnant from which all loess has been eroded. Future analyses incorporating planform curvature, regolith erosivity and other landform parameters may improve identification of thresholds controlling loess occurrence in Charwell Basin and in other South Island landscapes. A loess chronostratigraphic framework was developed for, and pedogenic phases identified in, the three loess sheets mantling the &gt150 ka terrace. Except for one age, infrared-stimulated luminescence dates from both an upbuilding interfluve loess exposure and colluvial gully infill underestimated loess age with respect to the widespread Kawakawa/Oruanui Tephra (KOT; 27,097 ± 957 cal. yr BP), highlighting the need for improvements in the methodology. Onset of loess sheet 1 accumulation started at ca. 50 ka, with a break at ca. 27 ka corresponding to the extended Last Glacial Maximum (eLGM) interstadial identified elsewhere in New Zealand. Loess accumulation through MIS 3 indicates a regional loess flux, and that glaciation was not a necessary condition for loess generation in South Island. Loess accumulation and local alluvial aggradation are decoupled: the youngest aggradation event only covers ~12 kyr of the period of loess sheet 1 accumulation. Older local aggradation episodes could not be the source because their associated terraces are mantled by loess sheet 1. In the absence of numerical ages, the timing of L2 and L3 accumulation is inferred on the basis of an offshore clastic sediment record. The upbuilding phase of loess sheet 2 occurred in late MIS 5a/MIS 4, and loess sheet 3 accumulated in two phases in MIS 5b and late MIS 6. Biogenic silica data were used to reconstruct broad shifts in vegetation and changes in gully soil saturation status. During interglacial/interstadial periods (MIS 1, early MIS 3, MIS 5) Nothofagus¬-dominated forest covered the area in association with Microlaena spp grasses. Lowering of treeline altitude during glacial/stadial periods (MIS 2, MIS 3, MIS 5b, late MIS 6) led to reduction in forest cover and a mosaic of shrubs and Chionochloa spp, Festuca spp and Poa spp tussock grasses. Comparison of interfluve and gully records showed spatial heterogeneity in vegetation cover possibly related to environmental gradients of exposure or soil moisture. A post-KOT peak in gully tree phytoliths corresponds to the eLGM interstadial, and a shift to grass-dominated vegetation occurred during the LGM sensu stricto. Diatoms indicated the site became considerably wetter from ca. 36 ka, with peak wetness at ca. 30, 25 and 21 ka, possibly due to reduced evapotranspiration and/or increased precipitation from a combination of strengthened westerly winds and increased cloudiness, or strengthened southerly flow and increased precipitation. Human influence after ca. 750 yr BP led to re-establishment of grassland in the area, which deposited phytoliths mixed to 30 cm depth in the soil. A coupled gully colluvial infilling/vegetation record showed that sediment flux during the late Pleistocene was ~0.0019 m3 m-1 yr-1 under a shrubland/grassland mosaic, and Holocene sediment flux was ~0.0034 m3 m-1 yr-1 under forest. This increase of 60% through the last glacial-interglacial transition resulted from increased bioturbation and down-slope soil transport via root growth and treethrow, which formed a biomantle as evidenced by slope redistribution of the KOT. These results contrast with sediment transport rates and processes hypothesised to occur contemporaneously in adjacent mountain catchments. This suggests that intraregional biogeomorphic processes can differ significantly depending on topography and geological substrate, with different landscapes responding in unique ways to the same climate shifts. Analysis of Quaternary terrestrial landscape evolution in non-glaciated mountainous and lowland areas must therefore consider spatial and temporal heterogeneity in sediment fluxes and underlying transport processes.

No description available.

Diferentes metodologias de determinação de fósforo no solo (P total, Bray 1, Mehlich 1, Mehlich 3, Olsen modificado, Resina de troca iônica, H3A-1 modificado e H3A-2 modificado) foram avaliadas e calibradas para seu uso em três distintas ordens de solos (Andisols, Inceptisols e Ultisols) coletados em diferentes lugares da Costa Rica. Aos resultados das análises de P e às outras variáveis químicas dos solos foram aplicadas análises de correlação, nas quais resaltam o teor de Ca, Mg e Al como fatores relacionados ao P recuperado pelos diferentes extratores. Entre os resultados destacam as calibrações de uma modificação nas metodologias H3A-1 e H3A-2 com a resposta das plantas de arroz, metodologias que tinham sido testadas unicamente contra os resultados de outros extratores. Ao nível geral as metodologias Olsen modificada e à resina de troca iônica apresentaram-se como os extratores mais adequados quando não se faz distinção por tipo de solo ou ordem, mas foram encontradas diferenças no comportamento dos diferentes métodos de extração segundo o tipo de solo, podendo variar a conveniência de utilizar um método ou outro. Em geral as metodologias P total, Bray 1 e Mehlich 1 foram as que representaram em menor medida a resposta das plantas de arroz à condição de P nos solos do experimento de calibração. As metodologias de avaliação de P apresentaram correlação entre si, apresentando também variações se avaliadas para uma condição geral (todos os solos) ou diferenciando por ordens. / Different soil phosphorus extraction methodologies (total phosphorus, Bray 1, Mehlich 1, Mehlich 3, modified Olsen, ion exchange resin, modified H3A-1 and modified H3A-2) were assessed and calibrated to evaluate its suitability to determinate the plant available phosphorus in different Costa Rican soils (Andisols, Inceptisols and Ultisols). The phosphorus results of these analyses were correlated against other soil chemical characteristics like pH, Ca, Mg and Al, in order to determinate which of these characteristics are related to the soil phosphorus content determined by the different extractants, were founded correlations of P with Al, Ca and Mg. As a results are presented for the first time the calibrations of the methodologies H3A-1 and H3A-2 (a modification) against phosphorus plant absorption and relative plant yield. In general conditions (all the soil orders) the modified Olsen method and the ion exchange resin method, resulted in better correlations with plant responses, therefore its seems to be the more suitable methods in this conditions. The analysis of the data by soil order, demonstrate some differences among extractants, that suggest the selective use of the methodologies and interpretation of results in accordance with soil order. In general total P, Bray 1 and Mehlich 1 were the less reliable methods to represent the rice plants response to the condition of soil phosphorus in this greenhouse calibration. Some of the assessed phosphorus methodologies present correlation among themselves, in both conditions (all soil orders in a group, or fractionated by soil order).

Diferentes metodologias de determinação de fósforo no solo (P total, Bray 1, Mehlich 1, Mehlich 3, Olsen modificado, Resina de troca iônica, H3A-1 modificado e H3A-2 modificado) foram avaliadas e calibradas para seu uso em três distintas ordens de solos (Andisols, Inceptisols e Ultisols) coletados em diferentes lugares da Costa Rica. Aos resultados das análises de P e às outras variáveis químicas dos solos foram aplicadas análises de correlação, nas quais resaltam o teor de Ca, Mg e Al como fatores relacionados ao P recuperado pelos diferentes extratores. Entre os resultados destacam as calibrações de uma modificação nas metodologias H3A-1 e H3A-2 com a resposta das plantas de arroz, metodologias que tinham sido testadas unicamente contra os resultados de outros extratores. Ao nível geral as metodologias Olsen modificada e à resina de troca iônica apresentaram-se como os extratores mais adequados quando não se faz distinção por tipo de solo ou ordem, mas foram encontradas diferenças no comportamento dos diferentes métodos de extração segundo o tipo de solo, podendo variar a conveniência de utilizar um método ou outro. Em geral as metodologias P total, Bray 1 e Mehlich 1 foram as que representaram em menor medida a resposta das plantas de arroz à condição de P nos solos do experimento de calibração. As metodologias de avaliação de P apresentaram correlação entre si, apresentando também variações se avaliadas para uma condição geral (todos os solos) ou diferenciando por ordens. / Different soil phosphorus extraction methodologies (total phosphorus, Bray 1, Mehlich 1, Mehlich 3, modified Olsen, ion exchange resin, modified H3A-1 and modified H3A-2) were assessed and calibrated to evaluate its suitability to determinate the plant available phosphorus in different Costa Rican soils (Andisols, Inceptisols and Ultisols). The phosphorus results of these analyses were correlated against other soil chemical characteristics like pH, Ca, Mg and Al, in order to determinate which of these characteristics are related to the soil phosphorus content determined by the different extractants, were founded correlations of P with Al, Ca and Mg. As a results are presented for the first time the calibrations of the methodologies H3A-1 and H3A-2 (a modification) against phosphorus plant absorption and relative plant yield. In general conditions (all the soil orders) the modified Olsen method and the ion exchange resin method, resulted in better correlations with plant responses, therefore its seems to be the more suitable methods in this conditions. The analysis of the data by soil order, demonstrate some differences among extractants, that suggest the selective use of the methodologies and interpretation of results in accordance with soil order. In general total P, Bray 1 and Mehlich 1 were the less reliable methods to represent the rice plants response to the condition of soil phosphorus in this greenhouse calibration. Some of the assessed phosphorus methodologies present correlation among themselves, in both conditions (all soil orders in a group, or fractionated by soil order).

Charwell Basin is a 6 km-wide structural depression situated at the boundary between the axial ranges and faulted and folded Marlborough Fault Zone of north-eastern South Island, New Zealand. The basin contains the piedmont reach of the Charwell River, and a series of late Quaternary loess-mantled alluvial terraces and terrace remnants that have been uplifted and translocated from their sediment source due to strike-slip motion along the Hope Fault which bounds the basin to its immediate north. The aim of this study was to provide an interdisciplinary, integrated and holistic analysis of late Quaternary landscape evolution and environmental change in Charwell Basin using terrain analysis, loess stratigraphy, soil chemistry and paleoecological data. The study contributes new understanding of New Zealand landscape and ecosystem responses to regional and global climatic change extending to Marine Isotope Stage (MIS) 6, and shows that climatically-forced shifts in biogeomorphic processes play a significant role in lowland landscape evolution. Morphometric analysis of alluvial terraces and terrace remnants of increasing age demonstrated geomorphic evolution through time, with a decrease in extent of original planar terrace tread morphology and an increase in frequency of steeper slopes and convexo-concave land elements. Paleotopographic analysis of a >150 ka terrace mantled by up to three loess sheets revealed multiple episodes of alluvial aggradation and degradation and, subsequent to river abandonment, gully incision prior to and coeval with loess accumulation. Spatial heterogeneity in loess sheet preservation showed a complex history of loess accumulation and erosion. A critical profile curvature range of -0.005 to -0.014 (d²z/dx², m⁻¹) for loess erosion derived from a model parameterised in different ways successfully predicted loess occurrence on adjacent slope elements, but incorrectly predicted loess occurrence on an older terrace remnant from which all loess has been eroded. Future analyses incorporating planform curvature, regolith erosivity and other landform parameters may improve identification of thresholds controlling loess occurrence in Charwell Basin and in other South Island landscapes. A loess chronostratigraphic framework was developed for, and pedogenic phases identified in, the three loess sheets mantling the >150 ka terrace. Except for one age, infrared-stimulated luminescence dates from both an upbuilding interfluve loess exposure and colluvial gully infill underestimated loess age with respect to the widespread Kawakawa/Oruanui Tephra (KOT; 27,097 ± 957 cal. yr BP), highlighting the need for improvements in the methodology. Onset of loess sheet 1 accumulation started at ca. 50 ka, with a break at ca. 27 ka corresponding to the extended Last Glacial Maximum (eLGM) interstadial identified elsewhere in New Zealand. Loess accumulation through MIS 3 indicates a regional loess flux, and that glaciation was not a necessary condition for loess generation in South Island. Loess accumulation and local alluvial aggradation are decoupled: the youngest aggradation event only covers ~12 kyr of the period of loess sheet 1 accumulation. Older local aggradation episodes could not be the source because their associated terraces are mantled by loess sheet 1. In the absence of numerical ages, the timing of L2 and L3 accumulation is inferred on the basis of an offshore clastic sediment record. The upbuilding phase of loess sheet 2 occurred in late MIS 5a/MIS 4, and loess sheet 3 accumulated in two phases in MIS 5b and late MIS 6. Biogenic silica data were used to reconstruct broad shifts in vegetation and changes in gully soil saturation status. During interglacial/interstadial periods (MIS 1, early MIS 3, MIS 5) Nothofagus-dominated forest covered the area in association with Microlaena spp grasses. Lowering of treeline altitude during glacial/stadial periods (MIS 2, MIS 3, MIS 5b, late MIS 6) led to reduction in forest cover and a mosaic of shrubs and Chionochloa spp, Festuca spp and Poa spp tussock grasses. Comparison of interfluve and gully records showed spatial heterogeneity in vegetation cover possibly related to environmental gradients of exposure or soil moisture. A post-KOT peak in gully tree phytoliths corresponds to the eLGM interstadial, and a shift to grass-dominated vegetation occurred during the LGM sensu stricto. Diatoms indicated the site became considerably wetter from ca. 36 ka, with peak wetness at ca. 30, 25 and 21 ka, possibly due to reduced evapotranspiration and/or increased precipitation from a combination of strengthened westerly winds and increased cloudiness, or strengthened southerly flow and increased precipitation. Human influence after ca. 750 yr BP led to re-establishment of grassland in the area, which deposited phytoliths mixed to 30 cm depth in the soil. A coupled gully colluvial infilling/vegetation record showed that sediment flux during the late Pleistocene was ~0.0019 m³ m⁻¹ yr⁻¹ under a shrubland/grassland mosaic, and Holocene sediment flux was ~0.0034 m³ m⁻¹ yr⁻¹ under forest. This increase of 60% through the last glacial-interglacial transition resulted from increased bioturbation and down-slope soil transport via root growth and treethrow, which formed a biomantle as evidenced by slope redistribution of the KOT. These results contrast with sediment transport rates and processes hypothesised to occur contemporaneously in adjacent mountain catchments. This suggests that intraregional biogeomorphic processes can differ significantly depending on topography and geological substrate, with different landscapes responding in unique ways to the same climate shifts. Analysis of Quaternary terrestrial landscape evolution in non-glaciated mountainous and lowland areas must therefore consider spatial and temporal heterogeneity in sediment fluxes and underlying transport processes.

No description available.

No description available.

Diffuse Phosphor (P)-Austräge aus der Landwirtschaft tragen zur Gewässereutrophierung bei. Der Phosphorsättigungsgrad (DPS) ist ein etablierter Parameter, um das P-Austragsrisiko aus Böden zu erfassen. Ein bodentypunabhängiger Ansatz, der die Abschätzung des DPS durch eine einfache Standardmethode wasserlöslichen P (WSP) ermöglicht (WSP-DPS-Ansatz), wurde an europäischen Böden entwickelt. In der Dissertation wurde dieser Ansatz erstmalig: i) an tropischen Böden getestet und ii) dazu verwendet P-Austragsrisiken von Boden-P-Monitoringdaten und von landwirtschaftlichen Institutionen empfohlenen P-Gehalten abzuleiten. Neben dem DPS wurde der Einfluss der in Brasilien gängigen anorganischen Oberflächendüngung auf das Austragsrisiko mittels Laboranalysen und Feldstudien erfasst. Die Bodentypunabhängigkeit des WSP-DPS-Ansatzes wurde für Böden Brasiliens bestätigt. Infrarotspektroskopische Analysen lieferten eine Erklärung für relativ niedrige gelöste P-Konzentrationen im Oberflächenabfluss von Oxisols. Pedotransferfunktionen zwischen WSP und Methoden, die in Brasilien und Deutschland zur Abschätzung pflanzenverfügbaren P verwendet werden, ermöglichten die Berechnung von DPS-Werten aus Monitoringdaten. Erste DPS-Karten zeigten relative geringe Austragsrisiken für das Untersuchungsgebiet in Brasilien und hohe Risiken für Deutschland, die teilweise durch unterschiedliche empfohlene Boden-P-Gehalte erklärbar waren. Um mit einer einfachen und kosteneffizienten Methode sowohl die landwirtschaftliche Produktion als auch den Gewässerschutz zu berücksichtigen, wurden die Wasser- und CaCl2-Methode zur Abschätzung von pflanzenverfügbarem P mit dem WSP-DPS-Ansatz kombiniert. Dieser Ansatz könnte helfen die Herausforderungen zu lösen mit denen die Menschheit in den nächsten Jahrzehnten bezüglich P in der Landwirtschaft konfrontiert sein wird: Einer effizienten Nutzung der limitierten Ressource P und dem Schutz der Gewässer vor diffusen P-Einträgen. / Diffuse phosphorus (P) losses from agriculture contribute to the eutrophication of surface waters. The degree of P saturation (DPS) is an established parameter for assessing the risk of P loss from agricultural soils. A soil type-independent approach for estimating the DPS by a simple standard method of water-soluble phosphorus (WSP; the WSP-DPS approach) was developed on European soils. In the thesis, the WSP-DPS approach was for the first time: i) tested on tropical soils and ii) used to derive P loss risks from soil P monitoring data and from recommended soil P levels by agricultural institutions. In addition to DPS, laboratory analyses and field studies were combined to assess the risk of P loss associated with the superficial application of inorganic fertilizer, which is commonly used in Brazil. The soil type-independency of the WSP-DPS approach was confirmed for soils of Brazil. Infrared spectroscopic analyses provided an explanation for the relatively low dissolved P concentrations in the surface runoff of Oxisols. Pedotransfer functions were determined between WSP and methods used to estimate plant-available P in Brazil and Germany and allowed for the transformation of soil P monitoring data into DPS values. The first DPS maps revealed relatively low P loss risks for the investigation area in Brazil and high risks for Germany. This difference was partly explainable by the recommended soil P levels in the two countries. To consider both agricultural production and the protection of surface waters in soil P management with a simple and cost-effective method, the soil test methods of using water and CaCl2 to estimate plant-available P and the WSP-DPS approach were combined. This approach could help to solve the challenges humanity faces regarding P in agriculture in the coming decades: An efficient use of the limited resource P and the protection of surface waters from diffuse P losses.