Nitrogen balance and use efficiency in the Calapooia River Watershed, Oregon, United States

Jiajia Lin1, Jana Compton2, George Mueller-Warrant3, William Matthews4, Scott Leibowitz5

1 National Research Council, based at US Environmental Protection Agency, Western Ecology Division, 200 SW 35th St, Corvallis, OR 97333,

2 US Environmental Protection Agency, Western Ecology Division, 200 SW 35th St, Corvallis, OR 97333,

3 US Department of Agriculture, Agricultural Research Service, 3420 NW Orchard Ave, Corvallis, OR 97331,

4 Oregon Department of Agriculture, Natural Resources Division, 635 Capitol St NE, Salem, OR 97301,

5 US Environmental Protection Agency, Western Ecology Division, 200 SW 35th St, Corvallis, OR 97333,


Reducing nitrogen (N) released into the environment through greater N use efficiencies (NUE) is a current challenge in watershed management. Examining N sources and sinks at local scales allows for better watershed-scale N use. We use data on land-use, CAFOs, N deposition, stream chemistry, and crop-level and county-level fertilizer use to assess the N inputs, exports and retention in the Calapooia River Watershed (CRW).  The CRW is influenced by intensive agricultural activities, mostly in grass seed crops. Our results demonstrate that fertilizer is the dominant N input on agricultural land, with an average rate of 130 kg N/ha/yr on these subwatersheds.  Deposition and alder fixation are the two main sources of N on forested land, with an average rate of <10 kg N/ha/yr.  About 50-60% of the annual hydrologic N yield occurs during wet winter and reaches 40 kg N/ha per season.  Summer TN yield is minimum, as low as <1 kg N/ha per season.  At the CRW scale, annual stream export is 19% of the total N inputs.  On average, about 41% of total N input is removed annually via crop harvest among the 58 subwatershed.  The proportion of net N input that is “retained” in Calapooia is within the same range of estimates of northeastern watersheds.  Our analysis also shows that runoff alone explains 62% of the variance in fractional N export in the U.S. watersheds.


Determining nitrogen removal in US sewage treatment

Lia R. Cattaneo1, Robert Bastian2, Lisa M. Colosi1, Allison M. Leach3, James N. Galloway1

 1University of Virginia, 291 McCormick Road, Charlottesville, VA, 22904 USA,

2United States Environmental Protection Agency, 1200 Pennsylvania Ave., NW, Washington, D.C. 20460

3University of New Hampshire, 131 Main Street, 107 Nesmith Hall, Durham, NH, 03824 USA


Most of the nitrogen (N) in food passes through the human body, is excreted, and enters the wastewater stream. This sewage N is an important component of the food consumption N footprint. The US N-Calculator (a per capita nitrogen footprint tool) calculates N removal from sewage by estimating the proportion of homes connected to wastewater treatment plants (WWTPs) with tertiary treatment N removal technologies. However, this assumes that no N is removed in WWTPs with primary or secondary treatment or in WWTPs with tertiary treatment processes other than nitrogen removal. This paper uses a mass balance approach to revise the factor used in the US N-Calculator to better represent the N removal from sewage treatment in the US. N in wastewater can have several fates: release to the environment through septic systems, release to the environment through WWTPs, release to the environment in disposed sludge, conversion to N2 in WWTPs, and beneficial use as land-applied sludge. The national average N removal factor (55%) represents N converted to N2 or used as beneficial sludge compared with the N in wastewater. The removal from just WWTPs was 73%. The new total removal reduces the average US per capita food consumption N footprint by 2.63 kg N, resulting in a total footprint decrease of 6.7%.

Evaluation of historical global gaseous nitrogen emissions from croplands considering NH4+ and NO3- forming fertilizer species in global fertilizer dataset

Kazuya NISHINA, Akihiko ITO, Seiji HAYASHI

1 National Institute for Environmental Studies 16-2, Onogawa, Tsukuba, 305-8506, JAPAN,,


We developed a new historical global N fertilizer map (half degree resolution) during 1961-2010 based on FAOSTAT and various global dataset. This new map incorporated the fraction of NH4+ (and NO3) into N fertilizer inputs by utilizing fertilizer species information in FAOSTAT. In the data processing, we applied a statistical data imputation method for the missing data in FAOSTAT. The multiple imputation method enabled to fill gaps of the time-series data by the plausible values. In this study, we evaluated NH3, NO, and N2O emissions from agricultural soils with biogeochemical model “VISIT” using the developed map. During 1961-2010, synthetic fertilizer consumption increased from 15 Tg-N to 110 Tg-N at global. In this period, the global average fraction of NH4+ was about 80% to synthetic N fertilizer consumption. The most countries showed NH4+ based fertilizer are dominant, however, the ratio NH4+:NO3 in N fertilizer inputs shows clear differences among countries and periods. Considering the ratio NH4+:NO3 in N fertilizer inputs, the simulated NH3 volatilization were generally reduced, compared to N fertilizer input dealt as only NH4+input assumption. On the other hand, NO and N2O emissions shows both positive and negative impacts using the NH4+:NO3 fertilizer map. Our new map can be utilized and bring new insights in the global model studies for the assessment of historical terrestrial N cycling changes.