Ground Beef: Human Impact on Soil Nutrients in Eastern California and Central North Carolina (2023)

Undergraduates: Isabel Lucas, Kinsley Huskey, Nathalie Ramirez, Molly Zolotor

Faculty Advisor: Drew Coleman
Department: Earth, Marine, and Environmental Sciences

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Nitrogen, phosphorus, and potassium nutrients are key to fertile soil. They often enter the environment through livestock manure and agriculture. Since agriculture and grazing cause higher nutrient content in the soil, then areas with greater human impact should have higher nutrient levels. Two regions were examined: Eastern California and Central North Carolina. In California, samples were taken at sites with varying land management strategies to see if greater conservation corresponded with lower nutrient levels. In North Carolina, samples were taken at two nearby sites, where just one had a history of agriculture. After three soil samples were randomly collected at each site, the samples were dried, and excess organic materials and rocks were removed. Next, samples were mixed vigorously with water and centrifuged. Afterward, water without sediment was separated and tested for nitrogen, phosphorus, and potassium density categories. In California, samples taken in a human-developed city park had significantly higher nitrogen levels than other city sites, illustrating how recent human development can increase soil fertility. In North Carolina, potassium levels were higher in soil that had not been used historically for agriculture compared to land that had been used, demonstrating how historically fertile soil can deplete current soil fertility. In the future, quantitative analysis of soil samples could provide further insight into the nuances of the relationship between human impact and soil fertility.

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