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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Impact of fertilizer placement on phosphorus in crop, soil, and run-off water in a brown Chernozem in south-central Saskatchewan.

2015 November 1900 (has links)
Fertilizer phosphorus (P) application rate and method are anticipated to have important influences on crop utilization and concentration and distribution of residual P in soil. This, in turn, can influence the amount of P removed in run-off water. The objective of this thesis work was to assess the influence of fertilizer P application method and rate on soybean (Glycine max (L.)) emergence, yield, and P uptake. Additionally, the forms and distribution of residual soil P following a season of crop growth, and the off-site export of applied P in simulated snowmelt run-off water was assessed. In a controlled environment study, soybean could tolerate up to 20 kg P2O5 ha-1 placed in the seed-row without significant reduction in emergence. Soybean was grown in a field study in 2014 in south-central Saskatchewan. Two sites were utilized within the same wheat stubble field (Downslope and Upslope) where fertilizer P was soil applied in the spring (seed-placed, deep band, and broadcast and incorporated) at 20 kg P2O5 ha-1 and broadcast at three rates (20, 40, and 80 kg P2O5 ha-1), along with a control treatment receiving no fertilizer P. At the Downslope position, in-soil application of fertilizer P resulted in a greater soybean yield and P uptake than broadcast application. After harvest, higher labile P concentrations were found in the zone of fertilizer P placement in the soil. Elevated concentrations of water soluble P were noted near the soil surface with broadcast P application compared to in-soil placement methods, attributed to immobility of P and lower plant utilization. A simulated snowmelt run-off event was conducted on intact soil slabs removed from the Upslope position treatments. Fertilizer P application method had a significant influence on P export with the greatest export occurring with broadcast application. Phosphorus XANES spectroscopy provided further evidence that, qualitatively, fertilizer P application method influenced speciation of fertilizer P reaction products in calcareous soil common to the Canadian prairies. Overall, it is concluded that in-soil placement of P fertilizer is a beneficial management practice in a prairie soil to maximize agronomic benefit while minimizing potential transport of fertilizer P off the field in snowmelt run-off water.
2

Phosphorus Management: An Analysis of the Virginia Phosphorus Index

Jesiek, Julie B. 12 March 2003 (has links)
Excess phosphorus (P) that is transported into water bodies can cause water quality problems. A high potential for P delivery occurs when there is a high transport potential from erosion, runoff, and/or leaching coupled with high soil test P and/or high rate of fertilizer P application. A management tool is needed to identify those fields that have a high transport and source potential to deliver P to surface water. The Virginia P-Index is a mass-based tool that estimates the annual risk of delivery of P from a given field to surface water. Guidelines on P application rates are then given based on the level of risk. This is a new tool and additional research and testing are needed to determine the dependability and validity of the index. The overall goal of the research was to contribute to the continued development of the Virginia P-Index as an effective P management tool. A sensitivity analysis was completed to identify the parameters to which the P-Index was most sensitive under a range of conditions. In low erosion and runoff conditions, the P-Index was most sensitive to P management factors including application rate. As erosion and runoff potential increased, the P-Index was most sensitive to the erosion risk factors including soil loss. Under conditions with subsurface leaching, the P-Index was most sensitive to the subsurface leaching factors and Mehlich I soil test P. A stochastic analysis was also conducted to determine the effects of parameter variability. Variability of the P-Index output was greater as the risk of P delivery increased and this could affect management recommendations. A survey was completed to determine expert opinion as to the appropriateness of parameter estimation methods used in the Virginia P-Index. Thirty-eight surveys were returned, representing a diverse range of participants within and outside of Virginia. Comments from the respondents were used to evaluate the appropriateness of the parameter methods. All factors were determined to be appropriate given the state of the science. Estimation methods for the following factors were determined to be less appropriate than the other sub-factors by the survey respondents: soil texture/drainage class, subsurface dissolved reactive orthophosphate (DRP), runoff delivery, and sediment delivery. The Virginia P-Index was determined to be a well thought out management tool and implementation should identify fields with the greatest risk of P delivery to surface water. Recommendations for improvement were identified including a need for additional analysis and studies. / Master of Science
3

Sustainable Phosphorus Management in Sweden : A study of phosphorus recycling from wastewater sludge in several municipalities of the Östergötland County

Haile, Henok Debessai January 2015 (has links)
The Swedish Environmental Agency (SEPA) proposed a national target to increase the rate of phosphorus recycling from wastewater sludge in 2013. Reusing phosphorus from wastewater sludge by spreading it on arable lands raises the risk of contamination and substance deposition in soils. In addition to quantifying the targeted rate of recycling, the proposal has also introduced new thresholds that limit the concentrations of undesired substances in wastewater sludge. This thesis assesses the potential challenges and opportunities in implementing the proposed measure in the Swedish municipality settings. Both qualitative and quantitative data have been gathered from three selected mid-sized Swedish municipalities in the Östergötland County and other data sources. The analytical framework of the thesis is based on the Systems Framework for Phosphorus Recovery and Reuse. Several discrepancies between the national goal to increase phosphorus recycling and local circumstances that affect local decision-making have been identified in this thesis. Reducing the flow of undesired substances into the wastewater stream raises goal conflict and is an enormous challenge which requires regulating the way chemicals are consumed in society. From the policy perspective, the national environmental objectives framework is ambiguous with regards to how local decisions should be directed in line with the national goals. The proposed measure should hierarchically be unequivocal and its implementation needs to be coordinated across all geographical scales. The thesis also highlights that there are significant local opportunities for addressing other sustainability goals through phosphorus recycling measures. Sweden’s commitment to creating a resource-efficient phosphorus cycle affirms that the key for a sustainable phosphorus management is the transformation of path-dependent social and technical systems.
4

Phosphorus Management in the Agroecosystem: An analysis of knowledge and perceived risk

Ferry, Joshua David 31 March 2011 (has links)
No description available.
5

Evaluating the Effects of Legacy Phosphorus on Dissolved Reactive Phosphorus Losses in Tile-Drained Systems

Pauline Kageha Welikhe (8803301) 07 May 2020 (has links)
<p>Eutrophication due to phosphorus (P) enrichment continues to be a primary water quality concern affecting freshwater and marine estuaries around the world. Excessive anthropogenic P inputs, driven by the need to meet the rising food and energy demands of a growing and increasingly urbanized population, have resulted in the buildup of P creating legacy (historical) P pools in agricultural landscapes. There is growing evidence that remobilization of accumulated legacy P can interfere with conservation efforts aimed at curbing eutrophication and improving water quality. Less is known about the magnitude and effects of these legacy P pools on dissolved reactive P (DRP) losses in tile-drained systems. This dissertation consists of three separate inquiries into how legacy P may affect DRP losses in tile drains. In the first inquiry, we examined the possibility of developing a suitable pedo-transfer function (pedoTF) for estimating P sorption capacity (PSC). Subsequent PSC-based indices (Phosphorus Saturation Ratio (PSR) and Soil Phosphorus Storage Capacity (SPSC)) were evaluated using daily water quality data from an in-field laboratory. The pedoTF derived from soil aluminum and organic matter accurately predicted PSC (R<sup>2</sup> = 0.60). Segmented-line models fit between PSR and soluble P (SP) concentrations in both desorption assays (R² = 0.69) and drainflows (R² = 0.66) revealed apparent PSR thresholds in close agreement at 0.21 and 0.24, respectively. Linear relationships were observed between negative SPSC values and increasing SP concentrations (R² = 0.52 and R<sup>2</sup> =0.53 respectively), and positive SPSC values were associated with very low SP concentrations in both desorption assays and drainflows. Zero SPSC was suggested as a possible environmental threshold. Thus, PSC-based indices determined using a pedoTF could estimate the potential for SP loss in tile drains. Also, both index thresholds coincided with the critical soil test P level for agronomic P sufficiency (22 mg kg<sup>-1</sup> Mehlich 3 P) suggesting that the agronomic threshold could serve as an environmental P threshold. In the second inquiry, PSC- based indices in addition to other site characteristics present in a P index (PI), were used as inputs in the development of a multi-layer feed-forward artificial neural network (MLF-ANN). The MLF-ANN was trained, tested, and validated to evaluate its performance in predicting SP loss in tile drains. Garson’s algorithm was used to determine the weight of each site characteristic. To assess the performance of ANN-generated weights, empirical data from an in-field laboratory was used to evaluate the performance of an unweighted PI (PI<sub>NO</sub>), a PI weighted using Lemunyon and Gilbert weights (PI<sub>LG</sub>), and an ANN-weighted PI (PI<sub>ANN</sub>) in estimating SP losses in tile effluent. The MLF-ANN provided reliable predictions of SP concentrations in tile effluent (R<sup>2</sup> = 0.99; RMSE = 0.0024). Soil test P, inorganic fertilizer application rate (FPR), SPSC, PSR, and organic P fertilizer application rate (OPR), with weights of 0.279, 0.233, 0.231, 0.097, and 0.084, respectively, were identified as the top five site characteristics with the highest weights explaining SP loss in tile discharge. These results highlighted the great contribution of both contemporary and legacy P sources to SP concentrations in tile discharge. Also, PI<sub>ANN </sub>was the only PI with a significant exponential relationship with measured annual SP concentrations (R<sup>2 </sup>= 0.60; p < 0.001). These findings demonstrated that MLF-ANNs coupled with Garson’s algorithm, can accurately quantify weights for individual site characteristics and develop PIs with a strong correlation with measured SP in tile discharge. Finally, in the third inquiry, we compared DRP loads and flow-weighted mean DRP (FDRP) concentrations in P source and P sink soils and evaluated the predominant DRP concentration – discharge (C-Q) behavior in these soils on a daily and event scale. At the daily scale, C-Q patterns were linked to the soil P status whereby a chemostatic and dilution behavior was observed for P source and P sink soils, respectively. At the event scale, C-Q patterns were linked to soil P status, flow path connectivity, and mixing of event water, matrix water, and rising shallow groundwater. The predominant anti-clockwise rotational pattern observed on P source soils suggested that, as the discharge event progressed, contributions from P poor waters including matrix and shallow groundwater resulted in lower DRP concentrations on the rising limb compared to the falling limb. However, the variable flushing and dilution behavior observed on the rising limb suggested that, in addition to discharge and soil P status, rapid exchanges between P pools, the magnitude of discharge events (Q), and the relative number of days to discharge peak (D<sub>rel</sub>) also regulated DRP delivery. On the other hand, the predominant non-hysteretic C-Q behavior in P sink soils suggest that DRP loss from these soils can be discounted. Our collective results highlight the need for nutrient and conservation practices focused on P drawdown, P sequestration, and P supply close to the crop needs, which will likely be required to convert P sources to sinks and to avoid the conversion of P sinks to sources. </p>
6

Regional phosphorus management in Berlin-Brandenburg

Theobald, Tim 08 March 2017 (has links)
Phosphor (P) ist ein für alles Leben notwendiges essentielles Nährelement. Die heutige globalisierte und intensivierte agrarische Produktion benötigt daher die Anwendung großer Mengen Phosphatgesteins, welches eine endliche Ressource darstellt. Gleichzeitig ist der intensive P Gebrauch mit der Eutrophierung von Gewässern verbunden. Es besteht daher Forschungsbedarf um die landwirtschaftliche Produktion zu erhalten. Ziel dieser Arbeit ist die in der Region Berlin-Brandenburg nach Ansatzpunkten für ein verbessertes P Management zu suchen. Hierfür wurde für 2011 eine Substanzflussanalyse (SFA) für P erstellt und Pflanzenproduktion der Jahre 2005-2012 genauer untersucht. Mit Hilfe einer Briefumfrage wurde Daten von 119 Bauernhöfen ausgewertet und mit dem pflanzenverfügbaren P Gehalt (PVP) der landwirtschaftlichen Nutzfläche abgeglichen (LNF). Im Ergebnis zeigt sich für die Region eine negative P Bilanz der LNF(-3.617 t P) und ein hohes Recyclingpotential in Abfall (933 t P) und Abwasser (3.921 t P). P in mineralischen Düngemitteln belief sich auf 4.447 t. Der Gesamtentzug über die Ernte ohne Stroh betrug 15.283 t P und war vergleichbar zu 2006, das Jahr des geringsten P-Entzugs. P-Entzug durch die Ernte schwankte um 7.069 t P/a von 2005 bis 2013, abhängig vom Ertrag der Hauptfeldfrüchte, welche durch die Wetter- und Bodenbedingungen bestimmt wurde. Hieraus ergeben sich mögliche Konsequenzen für P-Flüsse in Bezug auf den Klimawandel, die an den Wasserhaushalt und die Temperatur gekoppelt sind. Die Analyse der Umfrage ergab, dass die kleinen und mittgroßen Einzelunternehmen höhere PVP Werte in der LNF aufwiesen. Die größeren Unternehmensformen regierten empfindlich auf Faktoren, die niedrige PVP-Werte begünstigten. Pacht, Grünland, extensive Rinderhaltung, und viehlose ökologische Landwirtschaft waren mit niedrigen PVP-Werten assoziiert. Biogasanlagen und intensive Tierhaltung, zum Teil auch in Kombination miteinander standen im Zusammenhang mit hohen PVP-Werten. / Phosphorus (P) is an essential nutrient for all life on earth and it is thus needed in agricultural production. Today’s globalized and intensified agricultural production has led to the dependency on P inputs which are fed by phosphate rock, being a finite resource. In contrast, excessive P is a major driver in eutrophication. To sustain agricultural production, there is a need to address this problem. The aim of this thesis was to identify points at which P management could be improved for the region Berlin-Brandenburg. To analyze the system and screen for improvement, a substance flow analysis (SFA) for P for the year 2011 was compiled and for crop production the years 2005-2012 were analyzed. Also, data from 119 farms was obtained by a letter survey and relations between farm structural factors and soil test P (STP) were drawn. The results showed a negative balance for agricultural soils (-3,617 t P) and a considerable recycling potential in waste (933 t P) and wastewater (3,921 t P). Mineral fertilizer inputs amounted to 4,447 t P. P removal by crops was 15,283 t without straw and residues, being almost as low as in 2006; the year with the lowest removal by main crops. P removal by harvest varied significantly (7,069 t P/yr from 2005 to 2013) and depended on the performance of main crops which in turn is influenced by weather and soil. As a result of this, climate change may interact significantly with P flows in agriculture. Here, important variables are connected to conditions in P uptake and plant growth in general (e.g. water supply and temperature). The analyses of farms in the region showed that individual farms of small to medium size had more land with (very) high STP. Larger partnerships and companies/cooperatives were susceptible to factors causing low STP. Tenancy, grassland, extensive cattle and stockless organic farming had a lowering effect on STP. Biogas plants and intensive (cattle) farming, partly combined, were connected to a rise in STP.
7

The degree of phosphorus saturation of agricultural soils in Brazil and Germany: New approaches for risk assessment of diffuse phosphorus losses and soil phosphorus management

Fischer, Peter 30 November 2018 (has links)
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.

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