CAREER: Influence of soil phosphorus on soil organic matter dynamics

Phosphorus is finite rock-derived nutrient required by all life on Earth. In natural soils, the breakdown of bedrock controls the amount of phosphorus available. Similar processes are also important for accumulating soil organic matter, which is a major reservoir of nutrients, supporting soil health and capturing atmospheric carbon. As humans expand efforts to accumulate more soil organic matter, they also capture phosphorus, but how phosphorus is involved in soil organic matter stabilization remains a significant knowledge gap. The goal of this project is to understand the role of phosphorus in the stabilization and persistence of soil organic matter. This project will use laboratory and field experiments, spectroscopic, and microscopic tools, to assess the ability of phosphorus on mineral surfaces to bind soil organic matter. The outcomes of this research will provide benefits that support agricultural productivity by providing the basis for future strategies such as targeted plant breeding and soil microbe manipulation that can access the phosphorus within soil organic matter. This research integrates the education goals of improving public understanding of soils and improving soil science education. These education activities will provide continuing adult education through citizen science projects as well as open pathways to careers in science and natural resources for undergraduate students by infusing statistics and data literacy into soil science curricula. The proposed research addresses this central question: what role does phosphorus play in stabilizing soil carbon? To address this question, the specific aims are: 1) Describe the mechanisms by which organic and inorganic phosphorus control mineral associated organic matter adsorption and stabilization by loading common soil minerals with various phosphorus molecules and comparing adsorption of organic matter under laboratory conditions, 2) Determine the phosphorus forms that exist in and relate to soil organic matter in phosphorus-rich and phosphorus-limited ecosystems by performing a series of physical and chemical phosphorus and soil organic matter fractionations in natural soils, and 3) Quantify organic and inorganic phosphorus control of mineral associated organic matter dynamics within phosphorus-rich and phosphorus-limited ecosystems by deploying minerals loaded with common phosphorus molecules in the field. This project will demonstrate how phosphorus acts as an anchor for soil organic matter to stabilize on mineral surfaces, fundamentally controlling soil organic matter persistence, and linking the carbon and phosphorus cycles. This proposal is supported by the Life & Environments through Time (LET) program, the Ecosystem Science (ES) program and The Water, Landscape, and Critical Zone Processes (WaLCZ) program. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.