Degree Type

Dissertation

Date of Award

2004

Degree Name

Doctor of Philosophy

Department

Agricultural and Biosystems Engineering

Major

Water Resources

First Advisor

James L. Baker

Abstract

Two experiments were performed to evaluate NO3-N leaching features using tracer anions combined with use of non-destructive time domain reflectometry (TDR) techniques. A laboratory experiment was conducted to study the effects of different soil bulk density (1.10, 1.33, 1.57, and 1.81 g/cm 3) in the zone of N application and antecedent soil moisture by mass (10 and 15%) on NO3-N leaching during rainfall simulation (6.5 cm/h for 70 min to runoff/drainage pans with 7.6 cm soil layer). Surface runoff, subsurface drainage, and soil extract samples were analyzed for NO3-N, Br (added with rainfall), and Cl (added uniformly to soil) concentrations. TDR probes were horizontally installed either beneath the zone of NO 3-N applied in a line sources for determination of resident solute transport from measured soil bulk electrical conductivity (ECb), or just 1 cm below the soil surface to estimate solute concentrations in the "mixing zone". It was found that the 15% soil moisture content treatment had a longer time to the beginning of drainage and less drainage volume compared to 10% soil moisture. Greater compaction caused lower concentrations and losses of NO3-N in subsurface drainage. A second experiment was outdoor rainfall simulation (5 cm/h for 60 min to lysimeters), using two tillage practices (no-till and tillage) and two methods of N-fertilizer applications (local soil compaction and no compaction as a line source). The results showed that local compaction in the zone of application reduced NO3-N leaching significantly; however, tillage did not have a significant effect. In both studies, soil ECb and volumetric water content, measured by TDR, beneath the fertilizer line sources provided "real-time" information; it was found that NO3-N in top soil has a curvilinear relationship to ECb beneath line sources that had the potential to simultaneously indicate solute leaching and water infiltration/movement in that zone. This study could provide new information for improving N fertilizer applicators.

DOI

https://doi.org/10.31274/rtd-180813-2080

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu

Copyright Owner

Jian Zhou

Language

en

Proquest ID

AAI3145697

File Format

application/pdf

File Size

151 pages

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