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Title: Persistence and surface transport of urea-nitrogen: A rainfall simulation study

Author
item KIBET, LEONARD - University Of Maryland Eastern Shore (UMES)
item Bryant, Ray
item Buda, Anthony
item Kleinman, Peter
item Saporito, Louis - Lou
item ALLEN, ARTHUR - University Of Maryland Eastern Shore (UMES)
item HASHEM, FAWZY - University Of Maryland Eastern Shore (UMES)
item MAY, ERIC - University Of Maryland Eastern Shore (UMES)

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2016
Publication Date: 4/25/2016
Citation: Kibet, L.C., Bryant, R.B., Buda, A.R., Kleinman, P.J., Saporito, L.S., Allen, A.L., Hashem, F.M., May, E.B. 2016. Persistence and surface transport of urea-nitrogen: A rainfall simulation study. Journal of Environmental Quality. 45:1062–1070. doi:10.2134/jeq2015.09.0495.

Interpretive Summary: Urea is an organic nitrogen compound that has been linked to the expansion of harmful algal blooms around the globe and is also one of the major nitrogen fertilizers used in agriculture. We sought to assess the potential for different nitrogen fertilizers to contribute to urea in runoff. Results point to the potential, under worst case conditions, for urea from some forms of commercial fertilizers and manures to wash off of agricultural soils. Results also highlight the potential for simple management options to curtail urea loss in runoff.

Technical Abstract: Studies of harmful algal blooms and associated urea concentrations in the Chesapeake Bay and in coastal areas around the globe strongly suggest that elevated urea concentrations are associated with harmful algal blooms. The observed increased frequency and toxicity of harmful algal blooms in recent decades has been correlated with increased agricultural use of nitrogen inputs and increased use of urea as a preferred form of commercial nitrogen (N). This study sought to assess the potential for different nitrogen fertilizers and manures to contribute to urea in runoff from a Coastal Plain soil on the Eastern Shore of Maryland. Under worst case conditions, approximately 1% of urea-N applied as commercial fertilizer and surface applied poultry litter was lost in runoff in a rainfall event 12 hours after application. Cumulative urea-N losses, including four subsequent weekly rainfall events, approached 1.7% from urea-N fertilizer containing a urease inhibitor. Urea-N loss from incorporated poultry litter was negligible, and losses from dairy manure were intermediate. These losses are likely confined to hydrological contributing areas that extend several meters from a drainage ditch or stream for storms with frequent recurrence intervals. Cumulative dissolved N losses in runoff (urea-N + ammonium-N + nitrate-N) as a proportion of total applied N were less than 5%, suggesting that most of the applied N was lost by other pathways or was immobilized in soil. Results also highlight the potential for simple management options to curtail urea loss in runoff.