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Title:The assessment of physicochemical factors influencing phosphorus mineralization and immobilization in an Illinois floodplain soil
Author(s):Arenberg, Mary
Director of Research:Arai, Yuji
Doctoral Committee Chair(s):Mulvaney, Richard
Doctoral Committee Member(s):Matthews, Jeffrey W; Chu, Maria L
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Soil Chemistry
Nutrient Cycling
Abstract:Persistent losses of phosphorus (P) from soil to aquatic environments, provoked by human activity, degrade downstream water quality. Thus, it is critical to gain a deeper understanding of the biogeochemical processes that govern P bioavailability/mobility in the soil, including P mineralization and immobilization. Through microbially mediated immobilization, inorganic P is transformed into an organic form while during mineralization, organic P is converted into a labile, inorganic form, which is more susceptible to loss. In this study, the occurrence of mineralization/immobilization in Illinois floodplain soils was thoroughly examined. First, a comprehensive examination of mineralization and immobilization parameters in a floodplain and its adjacent upland was carried out. Due to higher total organic P and microbial P relative to the upland soil, it was concluded that the floodplain soil buffers P in part through microbial immobilization (Chapter 2). However, the degree of P immobilization varied throughout the floodplain, which motivated further investigation of physicochemical parameters that may be influencing the process, namely organic C and inorganic N. The following objectives were subsequently developed: 1) to evaluate the influence of native leaf residue on P reaction dynamics as a function of the C composition of the residue and the soil organic C:P ratio and 2) to investigate if the P mineralization rates vary as a function of inorganic nitrogen (N) species. Separately, floodplain soils were amended with 1) three species of native leaf residue with varying C compositions and 2) nitrate (NO3-N) and ammonium (NH4-N). Phosphorus mineralization/immobilization dynamics (i.e., wet chemistry analysis and NMR spectroscopy) were examined during long-term laboratory incubations. In the C study, residues with low aromaticity promoted P mineralization, and residues with high aromaticity and hydrophobicity led to P immobilization (Chapter 3). In the N study, NH4-N was more effective at boosting phosphatase activity and P mineralization rates than NO3-N (Chapter 4). It was concluded that both C and N have a large influence on P mineralization and immobilization in floodplain soil. On one hand, the incorporation of vegetation that specifically produces litter with more recalcitrant C compounds could optimize soil P sequestration in constructed floodplain buffers and improve downstream water quality. On the other hand, excess inorganic N, especially NH4-N, could promote mineralization and reduce P sequestration. These conclusions should be considered in the management of floodplains, wetlands, and P rich agricultural soils to minimize the release of P to aquatic environments.
Issue Date:2021-03-18
Rights Information:Copyright 2021 Mary Arenberg
Date Available in IDEALS:2021-09-17
Date Deposited:2021-05

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