The environmental footprint of inorganic nitrogen application

Ryan Deany’23 is an Environmental Geology major working with thesis advisor Jim Rougvie. He studies the impact of long-term manure application on potentially mineralizable nitrogen in soil and reducing the environmental footprint of inorganic nitrogen application.

My thesis project focuses on identifying the amount of potentially mineralizable nitrogen in agricultural fields with a history of manure application across North Carolina. Potentially mineralizable nitrogen is a measure of the pool of organic nitrogen that is readily mineralized into inorganic nitrogen (ammonium and nitrate) that is available for crop use. By understanding the nitrogen-supplying capability in fields with manure application history, the recommendations for inorganic nitrogen fertilizer application can be adjusted. Reducing inorganic nitrogen fertilizer use is crucial to the sustainability and ecosystem health of many North Carolina waterways. Nitrogen runoff into local waterways that feed into the sounds of North Carolina has created harmful eutrophication events and major fish kills which economically hurt the regions that rely so heavily on their fishing and tourism industries. Additionally, smaller farming operations could save thousands of dollars a year by reducing inorganic fertilizer application.

Through the North Carolina State University REU program, I conducted an incubation study that held soil samples at constant temperatures and moisture levels for the 28-day incubation period in order to ensure proper microbial activity in the soils being tested. Samples were taken from 12 counties and 18 farms. The manure types that were examined were swine, poultry, and dairy. The change in total inorganic nitrogen from day 0 to day 28 is determined to be the potentially mineralizable nitrogen. My initial findings were presented at the North Carolina State University Summer Symposium. To date, my evidence suggests that long-term manure application can reduce inorganic nitrogen recommendations by nearly half, which can save growers money and protect the environment and ecosystems of North Carolina.

By: Ryan Deany'23
January 20, 2023

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