Caractérisation par spectroscopie et analyse compositionnelle des formes du phosphore dans des sols agricoles canadiens
|Advisor:||Parent, Léon-Étienne; Ziadi, Noura|
|Abstract:||Understanding of phosphorus (P) forms dynamics and changes in agro-ecosystems is essential for the development of best management practices to maintain soil productivity and surface water quality. The objective of this thesis was to develop and use innovative methods to characterize soil P forms and their changes under different management practices. We examined the potential of near infrared spectroscopy (NIRS) to predict soil total P (TP), soil P extracted by Mehlich-3 solution (M3P) and by water (Cp), and soil organic P (OP) for soil samples taken from two sites with different P content located at Quebec and Saskatchewan. The results showed that the prediction of TP and M3P in the site of Quebec were moderately useful and not acceptable, respectively. However, the opposite was found in the site of Saskatchewan. The prediction of OP was moderately useful to moderately successful in experimental site of Saskatchewan. The potential of NIRS to predict P depends to the soil texture, to P soil content variation and to the relation of P to organic matter. Furthermore, contradictory results of variance and correlations analyses were found for the raw and ordinary log transformed molecular P species expressed as proportions or concentrations, indicating spurious correlations. Using compositional analysis with centred log ratio or isometric log ratio transformations avoid the methodological biases and allow coherent interpretation. Finally, phosphorus-31 nuclear magnetic resonance spectroscopy was used to characterize P species for soil samples collected from a long-term corn-soybean rotation experiment in Quebec. Results showed an accumulation of TP (1326 mg kg-1) on the top 5 cm of P fertilized soil under no-till primarily due to orthophosphate ions accumulation (49.7% of TP). However, the organic P forms of inositol monoesters and nucleotides had accumulated in the deep layer; indicating a potential loss through different hydrological pathways. Overall, these studies allow us to improve our understanding of P forms and to better monitor them under different agro-ecosystems using the best management practices.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||23 April 2018|
|Collection:||Thèses et mémoires|
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