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Use of time domain reflectometry for continuous monitoring of nitrate-nitrogen in soil and water

Payero, J.O. and Tarkalson, D.D. and Irmak, S. (2006) Use of time domain reflectometry for continuous monitoring of nitrate-nitrogen in soil and water. Applied Engineering in Agriculture. 22(5):689-700.

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Nitrate-Nitrogen (NO3 -N) losses to ground and surface water are an environmental and agronomic concern in
modern crop production systems in the Central Great Plains. Monitoring techniques for nitrogen use in agricultural
production are needed to increase crop yield, optimize nitrogen use, and reduce NO 3 -N leaching. Time domain reflectometry
(TDR) could potentially be calibrated to continuously measure NO3 -N in soil and water. The objectives of this study were to:
(1) evaluate the effect of different factors affecting the response of the bulk electrical conductivity (ECb) sensed by TDR, (2)
compare the sensitivity and differences between vertically-installed and horizontally-installed probes for measuring NO3 -N
leaching in the soil profile, and (3) evaluate the feasibility of using TDR to measure changes in NO 3 -N concentration in an
irrigated agricultural soil. Studies were conducted in the laboratory and in the field at the University of Nebraska West
Central Research and Extension Center in North Platte, Nebraska. Temperature of the medium (Ts), solute concentration,
TDR cable length, and volumetric soil water content (O p) all influenced and were linearly related to the bulk electrical
conductivity (ECb) sensed by the TDR probes. In the field, measured soil NO3 -N correlated well with values estimated using
TDR measurements of ECb, corrected for changes in CC and Ts. These results indicated that TDR, if properly calibrated for
a particular soil, could be used to continuously monitor NO3-N in soil, and should also be well-suited for monitoring NO3-N
in groundwater and surface water. It is, however, important to perform the calibration over a long enough period of time to
include the expected range of 0v, Ts, and NO3-N values to obtain adequate accuracy.

Item Type: Article
NWISRL Publication Number: 1221
Subjects: Soil > Chemistry > Nitrogen
Research methodology
Mass Import - autoclassified (may be erroneous)
Depositing User: Dan Stieneke
Date Deposited: 20 Nov 2010 21:49
Last Modified: 31 Oct 2016 17:18
Item ID: 60