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Impact of Preferential Flow at Varying Irrigation Rates by Quantifying Mass Fluxes
Author(s) -
Gish T. J.,
Kung K.J. S.,
Perry D. C.,
Posner J.,
Bubenzer G.,
Helling C. S.,
Kladivko E. J.,
Steenhuis T. S.
Publication year - 2004
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.1033
Subject(s) - loam , irrigation , flux (metallurgy) , outflow , mass flux , tile , tile drainage , chemistry , volumetric flow rate , environmental science , soil science , effluent , hydrology (agriculture) , soil water , environmental engineering , materials science , geology , mechanics , geotechnical engineering , ecology , physics , organic chemistry , composite material , biology , oceanography
Solute concentration and soluble dye studies inferring that preferential flow accelerates field‐scale contaminant transport are common but flux measurements quantifying its impact are essentially nonexistent. A tile‐drain facility was used to determine the influence of matrix and preferential flow processes on the flux of mobile tracers subjected to different irrigation regimes (4.4 and 0.89 mm h −1 ) in a silt loam soil. After tile outflow reached steady state either bromide (Br; 280 kg ha −1 ) or pentafluorobenzoic acid (PFBA; 121 kg ha −1 ) was applied through the irrigation system inside a shed (3.5 × 24 m). Bromide fluxes were monitored at an irrigation rate of 4.4 mm h −1 while PFBA fluxes were monitored at an irrigation rate of 0.89 mm h −1 At 4.4 mm h −1 nearly one‐third of the surface‐applied Br was recovered in the tile line after only 124 mm of irrigation and was poorly fit by the one‐dimensional convective–dispersive equation (CDE). On the other hand, the one‐dimensional CDE fit the main PFBA breakthrough pattern almost perfectly, suggesting the PFBA transport was dominated by matrix flow. Furthermore, after 225 mm of water had been applied, less than 2% of the applied PFBA had been leached through the soil compared with more than 59% of the applied Br. This study demonstrates that the methodology of applying a narrow strip of chemical to a tile drain facility is appropriate for quantifying chemical fluxes at the small‐field scale and also suggests that there may be a critical input flux whereby preferential flow is initiated.