Comparing Field Methods that Estimate Mobile–Immobile Model Parameters Casey, F. Jaynes, D. B. Horton, Robert Horton, R. Logsdon, S. D.
dc.contributor.department Agronomy 2018-01-30T22:44:40.000 2020-06-29T23:05:05Z 2020-06-29T23:05:05Z 1999
dc.description.abstract <p>Recent studies have used field techniques that estimate soil hydraulic and solute transport parameters. These methods utilize a tension infiltrometer to infiltrate either a single tracer or a series of tracers in order to estimate immobile water content (θ<sub>im</sub>) and mass exchange coefficient (α) of the mobile–immobile solute transport model. The objective of this study was to compare two single tracer methods (basic and variance) with one multiple tracer method for estimating θ<sub>im</sub> and α from data obtained on the same field soil location. Hydraulic conductivity (<em>K</em>(<em>h</em> <sub>0</sub>)) was also estimated using these methods. Research was done at five interrow sites in a ridge-tilled corn (<em>Zea mays</em> L.) field, and the soil was mapped as a Nicollet series (fine-loamy, mixed, superactive, mesic, Aquic Hapludoll). The values of θ<sub>im</sub> and α estimated by the multiple tracer method compared well with previously measured values using the same technique on the same field. The θ<sub>im</sub> values for the multiple tracer technique were larger than values derived from the basic single tracer technique. The basic single tracer technique did not take into consideration a mass exchange between θ<sub>im</sub> and the mobile water domain (θ<sub>m</sub>). The α values were less variable for the multiple tracer method than for the single tracer-variance method. Values of immobile water fraction (θ<sub>im</sub>/θ) for the multiple and basic single tracer techniques ranged from 0.30 to 0.52 and from 0.24 to 0.35, respectively. The values of α for the multiple and single tracer-variance techniques ranged from 0.06 to 0.9 d<sup>−1</sup> and from 0.03 to 60 d<sup>−1</sup>, respectively. The volumetric water content (θ) changed considerably over the course of the experiment for the estimation of α using the single tracer-variance method; thus, the assumptions of this technique were compromised. The measured values of <em>K</em>(<em>h</em> <sub>0</sub>) at the five sites ranged from 0.47 to 1.66 μm s<sup>−1</sup> There was evidence that the basic single tracer method underestimated θ<sub>im</sub> and overestimated θ<sub>m</sub>, because this method considers α = 0 during the tracer application.</p>
dc.description.comments <p>This article is published as Casey, F. X. M., D. B. Jaynes, R. Horton, and S. D. Logsdon. "Comparing field methods that estimate mobile–immobile model parameters." Soil Science Society of America Journal 63, no. 4 (1999): 800-806. doi; <a href="" target="_blank" title="Comparing Field Methods that Estimate Mobile–Immobile Model Parameters ">10.2136/sssaj1999.634800x</a>. Posted with permission.</p>
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dc.identifier archive/
dc.identifier.articleid 1469
dc.identifier.contextkey 11445388
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath agron_pubs/420
dc.language.iso en
dc.source.bitstream archive/|||Sat Jan 15 00:13:01 UTC 2022
dc.source.uri 10.2136/sssaj1999.634800x
dc.subject.disciplines Agriculture
dc.subject.disciplines Hydrology
dc.subject.disciplines Soil Science
dc.title Comparing Field Methods that Estimate Mobile–Immobile Model Parameters
dc.type article
dc.type.genre article
dspace.entity.type Publication
relation.isAuthorOfPublication d3fb0917-6868-417e-9695-a010896cfafa
relation.isOrgUnitOfPublication fdd5c06c-bdbe-469c-a38e-51e664fece7a
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