High Levels of Phosphorus in North Carolina Agricultural Soils Pose Environmental Risks

Strategic Insights -

Agricultural researchers in North Carolina have found high levels of available phosphorus in soils across the state, highlighting the need for improved management practices to mitigate environmental risks. The study, published in the Journal of Environmental Quality, analyzed soil samples from 57 counties across three regions and identified significant differences in phosphorus fractions between different soil types. The research suggests that excessive phosphorus fertilization and limited adoption of conservation practices are contributing to the problem.

Key Takeaways:

  • Most agricultural soils in North Carolina have high levels of available phosphorus, with 75% of evaluated counties presenting a high risk of phosphorus contamination.
  • Phosphorus fractions were characterized through sequential chemical fractionation of 391 soil samples from three regions: Tidewater, Coastal Plain, and Piedmont + Mountains.
  • The highest phosphorus fraction was occluded phosphorus (39%), followed by inorganic phosphate (26%), Mehlich-3 phosphorus (17%), and organic phosphorus (11%).
  • Coastal Plain soils exhibited the highest degree of phosphorus saturation (29%), followed by Piedmont + Mountains (24%) and Tidewater (15%).
  • Minimal differences in phosphorus fractions were found between different tillage systems, highlighting the need for improved phosphorus management.
  • Financial supporters for the research included the CAPES/PRINT Program, Corn Growers Association of North Carolina, and Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES).

Statistics:

  • 391 soil samples were analyzed from 57 counties across three regions.
  • 75% of evaluated counties presented a high risk of phosphorus contamination.
  • Coastal Plain soils exhibited the highest degree of phosphorus saturation (29%).
  • Occluded phosphorus (39%) was the highest phosphorus fraction.
  • Mehlich-3 phosphorus (81 mg kg-1) was the highest phosphorus content in Coastal Plain soils.

Sources:

  • Phosphorus Fractions Status of Representative Agricultural Fields In North Carolina. Journal of Environmental Quality, 2025.
  • NewsRx. Investigators at North Carolina State University (NC State) Discuss Findings in Agriculture (Phosphorus Fractions Status of Representative Agricultural Fields In North Carolina). Agriculture Week. July 31, 2025; p 1418.
  • North Carolina State University (NC State) and Luke Gatiboni (Dept. of Crop and Soil Sciences, Raleigh, NC 27695, United States)
  • Andria Paula Lima, Tales Tiecher, and Dionata Filippi (authors)