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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Water Quality and Ecology Research » Research » Publications at this Location » Publication #410389
Research Project: Enhancing Long-Term Agroecosystem Sustainability of Water and Soil Resources Through Science and Technology

Location: Water Quality and Ecology Research

Title: Phosphorus distributions in alluvial soils of the Lower Mississippi River Basin: A case of dual legacies

Author
item Witthaus, Lindsey
item PAWLOWSKI, ETHAN - Orise Fellow
item Stevens, Eric
item Chatterjee, Amitava
item Locke, Martin
item McNamara, Sarah
item Moore, Matthew

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Phosphorus is a critical nutrient needed for adequate crop production. In excess, phosphorus can cause environmental problems by increasing algal growth in aquatic ecosystems. Successful phosphorus management is dependent on knowing phosphorus concentrations in soils and understanding potential pathways for phosphorus transport to waterbodies. In the Lower Mississippi Alluvial Plain (MAP), soil phosphorus concentrations are higher than expected, considering low phosphorus fertilizer application rates. This study evaluated phosphorus concentrations across dominant soil types in both cropland and forest land uses. We found phosphorus concentrations were relatively similar across soil types and land uses. These results suggest there is a naturally high level of phosphorus in soils of this region. Understanding phosphorus sources and dynamics will be helpful to guide management decisions and to improve watershed modeling simulations in the region.

Technical Abstract: Legacies can become intertwined; none more so than the body of work that Dr. Andrew Sharpley produced over his career examining agricultural nutrient delivery to waterbodies and the phosphorus (P) accumulation in agricultural soils, or “legacy P”. Although Sharpley’s work focused on the anthropogenic influence of P storage in soils, results of our study suggest soils of the Lower Mississippi Alluvial Plain (MAP) represent a natural legacy with relatively high levels of available P resulting from minimal anthropogenic input. In 2019 we collected surface soil samples from four regionally dominant soil series (Alligator, Dundee, Forestdale, and Sharkey) in either cropland or forested land uses, spanning 76 locations within the Mississippi portion of the MAP. Soil chemical and physical properties were measured utilizing a suite of extractions and texture analysis to correlate properties with soil P values. Total soil P did not vary between land uses. Mehlich-3 extractable P was slightly higher in cropland soils due to higher concentrations in Forestdale and Sharkey soils. Dundee, Forestdale, and Sharkey cropland soils showed significant associations between Mehlich-3-extractable iron (Fe) and P. Ratios of carbon (C) to nitrogen (N) and C to P were consistent across all sampled soil series but differed between forest and cropland soils. These ratios are critical for establishing baseline soil nutrient values in simulation models and can be used to improve water quality model simulations that help guide P management in the MAP. As Sharpley routinely demonstrated, understanding sources of P is critical for developing an appropriate management strategy. This study will provide critical knowledge on soil P dynamics in the MAP region.