Skip to main content
ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #417492
Research Project: Sustainable Intensification in Agricultural Watersheds through Optimized Management and Technology

Location: Agroecosystems Management Research

Title: USDA LTAR Common Experiment measurement: Total nitrogen (TN) and total dissolved nitrogen (TDN) concentration

Author
item Malone, Robert - Rob
item Morrow, Amy
item Pisani, Oliva
item Kovar, John
item HAMILTON, STEPHEN - Michigan State University
item Cole, Kevin

Submitted to: Protocols.io
Publication Type: Research Notes
Publication Acceptance Date: 9/7/2024
Publication Date: 9/7/2024
Citation: Malone, R.W., Morrow, A.J., Pisani, O., Kovar, J.L., Hamilton, S.K., Cole, K.J. 2024. USDA LTAR Common Experiment measurement: Total nitrogen (TN) and total dissolved nitrogen (TDN) concentration. Protocols.io. https://doi.org/10.17504/protocols.io.5jyl82rkrl2w/v1.
DOI: https://doi.org/10.17504/protocols.io.5jyl82rkrl2w/v1

Interpretive Summary: This protocol is part of a set of protocols for the Long-Term Agroecosystem Research (LTAR) network Cropland Common Experiment. This protocol outlines the measurement of Total nitrogen (TN) and total dissolved nitrogen (TDN) concentration in water samples. TDN can originate from sources such as municipal effluent and agricultural runoff and is composed of dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen (DON). DON is the N-containing component of dissolved organic matter (DOM) and part of the biologically reactive N pool in aquatic ecosystems that can degrade water quality and can contribute to harmful algal blooms. The goal of this protocol is to provide repeatable guidelines to LTAR scientists to achieve consistent data collection, instrument maintenance, data processing, and quality control for obtaining these data at established or new sites.

Technical Abstract: Total dissolved nitrogen (TDN) is composed of dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen (DON). DON is the N-containing component of dissolved organic matter (DOM) and part of the biologically reactive N pool in aquatic ecosystems that can degrade water quality in N-sensitive waters. Evidence suggests that DON may be important in triggering harmful algal blooms, particularly the DON from synthetic urea fertilizers. TDN measurements therefore contribute to an estimate of the N most available to phytoplankton. DIN export from agroecosystems is reasonably well characterized, but the factors that regulate spatial and temporal patterns of DON are not as well understood. Although the export of DON into groundwater has received recognition for more than 100 years and the contribution of DON to total nitrogen (TN) is often significant, leaching losses of N from agricultural systems are often assumed to be dominated by DIN and uninfluenced by DON. The most widely recognized N digestion method is total Kjeldahl N (TKN), whereby organic N is converted to ammonia-N, followed by titrimetric or colorimetric detection. The measurement of TDN at moderate to high concentrations (i.e., >0.5 mg N/L) using the high-temperature combustion method is recommended.