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. Conversely, organic P can be mineralized into labile, inorganic P, which is more susceptible to loss. A preliminary study revealed that floodplain soil buffers P in part through microbial immobilization. However, the degree of P immobilization varied throughout the floodplain, which motivated further investigation of other macronutrients that may be influencing the process, namely organic carbon (C) and inorganic nitrogen (N). The following objectives were subsequently developed: 1) to evaluate the influence of C composition of native leaf residue on P reaction dynamics 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. In the N study, NH4-N was more effective at boosting phosphatase activity and P mineralization rates than NO3-N. It was concluded that both C and N have a large influence on P mineralization and immobilization in floodplain soil. 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.

Inherent macronutrient influence on phosphorus immobilization in floodplain soils

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.