This project was designed to determine the effects of nitrogen fertilization on the quality and quantity of streamflow eminating from an eastern hardwood forest watershed. A 40.67 ha watershed, located in mountainous eastern Kentucky, was aerially fertilized in late April 1975. The forest stand was principally oak, hickory, and yellow poplar, 50 - 55 years of age and in a relatively undisturbed condition. A helicopter applied anunonium nitrate at a rate of 504 kg/ha. Because a large part of applied nitrogen fertilizer ends up in the highly mobile nitrate nitrogen.form, this is the principal ion monitored in this study. No effort was made to avoid live streams during application and, consequently, very high levels of nitrate nitrogen were detected (640 mg/1) in streamfiow within the watershed. Levels potentially toxic to humans and animals persisted in the streamflow for several days following application. Although elevated concentrations of nitrate nitrogen persisted in streamflow leaving the watershed over a two year period no algal blooms or excessive growth of aquatic plants were noted. Rather high concentrations of nitrate nitrogen were found in the soils of the watershed, with greatest concentrations in the surface layer (0 - 5 cm), intermediate amounts at 15 - 20 cm, and the lowest concentrations at the 41 - 46 cm depth. The effects of the fertilizer application on soils persisted less than one year in the 0 - 46 cm depth sampled. Analysis of streamf1ow records indicated a reduction in water yield the first and second growing seasons after treatment. Gross budgeting of nitrate nitrogen inputs vs. outputs suggests this anion accumulates on these relatively undisturbed watersheds at an annual rate of 3 to 5 kg/ha.
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The work on which this report is based was supported in part by funds provided by the Office of Water Research and Technology, United States Department of the Interior, as authorized under the Water Resources Research Act of 1964.
Considerable financial and facilities support was provided by the Kentucky Agricultural Experiment Station.
Coltharp, George B.; Shearer, Michael T.; Springer, Everett P.; and Wittwer, Robert F., "Influence of Nitrogen Fertilization on the Quality and Quantity of Streamflow from a Forested Watershed" (1978). KWRRI Research Reports. 87.