Contrasting nitrogen fate in watersheds using agricultural and water quality information

Journal of Environmental Quality
By: , and 

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Abstract

Surplus nitrogen (N) estimates, principal component analysis (PCA), and end-member mixing analysis (EMMA) were used in a multisite comparison contrasting the fate of N in diverse agricultural watersheds. We applied PCA-EMMA in 10 watersheds located in Indiana, Iowa, Maryland, Nebraska, Mississippi, and Washington ranging in size from 5 to 1254 km2 with four nested watersheds. Watershed Surplus N was determined by subtracting estimates of crop uptake and volatilization from estimates of N input from atmospheric deposition, plant fixation, fertilizer, and manure for the period from 1987 to 2004. Watershed average Surplus N ranged from 11 to 52 kg N ha−1 and from 9 to 32% of N input. Solute concentrations in streams, overland runoff, tile drainage, groundwater (GW), streambeds, and the unsaturated zone were used in the PCA-EMMA procedure to identify independent components contributing to observed stream concentration variability and the end-members contributing to streamflow and NO3 load. End-members included dilute runoff, agricultural runoff, benthic-processing, tile drainage, and oxic and anoxic GW. Surplus N was larger in watersheds with more permeable soils (Washington, Nebraska, and Maryland) that allowed greater infiltration, and oxic GW was the primary source of NO3 load. Subsurface transport of NO3 in these watersheds resulted in some removal of Surplus N by denitrification. In less permeable watersheds (Iowa, Indiana, and Mississippi), NO3 was rapidly transported to the stream by tile drainage and runoff with little removal. Evidence of streambed removal of NOby benthic diatoms was observed in the larger watersheds.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Contrasting nitrogen fate in watersheds using agricultural and water quality information
Series title Journal of Environmental Quality
DOI 10.2134/jeq2016.02.0071
Volume 45
Issue 5
Year Published 2016
Language English
Publisher Alliance of Crop, Soil, and Environmental Science Societies
Contributing office(s) National Research Program - Western Branch
Description 11 p.
First page 1616
Last page 1626
Country United States
State Indiana, Iowa, Maryland, Nebraska, Mississippi, Washington
Online Only (Y/N) N
Additional Online Files (Y/N) N