Abstract
Dye tracers provide a direct means in which to visualise flow paths and interpret active wetting mechanisms in soil. Until recently it had been assumed that rewetting in milled peat took place by surface wetting front advance, but recent laboratory and field evidence has indicated that by-pass flow readily occurs. In order to investigate the mechanisms of rewetting in milled peat, a laboratory-based morphological assessment of selected milled peats was conducted using a dye tracer to examine flow paths at different water contents. The outflow/inflow ratio from specially prepared columns was recorded and thin sections of samples from selected depths produced. The staining process in peat was found to be different from that documented for mineral soil because staining of the internal peat fabric as opposed to pore/particle interfaces typically took place. This prevented accurate digital image analysis, hence point counting techniques were used to provide quantitative measures of staining. By-pass flow was identified in all milled peat types and a relationship between initial water content and percent stain was identified, although the nature of by-pass was found to be unpredictable. Pore shapes and milled peat components associated with staining were also documented.
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References
Aeby P, Forrer J, Steinmeier C and Flühler H 1997 Image analysis for determination of dye tracer concentrations in sand columns. Soil Sci. Soc. Am. J. 61, 33-35.
Anderson J L and Bouma J 1977 Water movement through pedal soils: I. Saturated Flow. Soil Sci. Soc. Am. J. 41, 413-418.
Beven K and Germann P 1982 Macropores and water flow in soils. Water Resour. Res. 18, 1311-1325.
Bord na Móna 1997.The peatlands of Ireland. Factsheet 1. Bord na Móna, Newbridge, Co. Kildare, Ireland. 4 pp.
Bouma J, Jongerius A, Boersma O, Jager A and Schoonderbeek D 1977 The function of different types of macropores during saturated flow through four swelling soil horizons. Soil Sci. Soc. Am. J. 41, 945-950.
Bouma J and Dekker LW1978 A case study on infiltration into dry clay soil. I. Morphological observations. Geoderma 20, 27-40.
Bouma J, Dekker L W and Muilwijk C J 1981 A field method for measuring short-circuiting in clay soils. J. Hydrol. 52, 347-354.
Daniel O, Kretzschmar A, Capowiez L. Kohli L and Zeyer J 1997 Computer-assisted tomography of macroporosity and its application to study the activity of the earthworm Aporrectodea nocturna. Euro. J. Soil Sci. 48, 727-737.
Dexter A R 1993 Heterogeneity of unsaturated, gravitational flow of water through beds of large particles. Water Resour. Res. 29, 1859-1862.
Droogers P, Stein A, Bouma J and de Boer G 1998 Parameters for describing soil macroporosity derived from staining patterns. Geoderma 83, 293-308.
Dykes M G, Ward S M, Holden N M and Lynch J 1997 Wetting of milled peat during storage. Int. Peat J. 7, 11-13.
FitzPatrick E A 1984 Micromorphology of Soils. Chapman & Hall, London. Germann P and Beven K 1981 Water flow in soil macropores. I. An experimental approach. J. Soil Sci. 32, 1-13.
Holden N M 1998 By-pass of water through laboratory columns of milled peat. Int. Peat J. (in press: expected Feb 1999).
Holden N M and Ward S M 1997 The physical properties of stockpiled milled peat from midland production bogs. Irish J Agric. & Food Res. 36, 205-218.
Holden N M and Ward S M 1998 Rewetting of milled peat: laboratory investigation of water movement and storage. Soil Use Manage. 14, 149-154.
Leinonen A, Ward S M and Larsson L E 1997 Evaluation of the Fuel Peat Industry in the Enlarged E.U. Vol. 1. E.U. contract No 4.1040/E/96-001.
Mooney S J, Holden N M, Ward S M and Collins J F 1998a The rapid preparation of structural images from undisturbed, non-cohesive material (milled peat). Geoderma 86, 159-168.
Mooney S J, Holden N M, Ward S M and Collins J F 1998b The identification and quantification of preferential flow paths in columns of milled peat. Proc.World Cong. Soil Sci. Montpellier, France, 1998 (CD rom).
Mooney S J, Holden N M, Ward S M and Collins J F 1999 The Micromorphology of Selected Irish Milled Peats. In press: Irish J Agric. Food Res. (expected 1999).
Omoti U and Wild A 1979 Use of fluorescent dyes to mark the pathways of solute movement through soils under leaching conditions. 2. Field experiments. Soil Sci. 128, 98-104.
Pettijohn F H 1957 Sedimentary Rocks. Harper & Row, New York.
Ringrose-Voase A J 1996 Measurement of soil macropore geometry by image analysis of sections through impregnated soil. Plant & Soil, 183, 27-47.
Smettem K R J and Trudgill S T 1983 An evaluation of some fluorescent and non-fluorescent dyes in the identification of water transmission routes in soils. J. Soil Sci. 34, 45-56.
Vepraskas M J, Hoover M T and Bouma J 1991 Sampling strategies for assessing hydraulic conductivity and water-conducting voids in saprolite. Soil Sci. Soc. Am. J. 55, 165-170.
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Mooney, S., Holden, N., Ward, S. et al. Morphological observations of dye tracer infiltration and by-pass flow in milled peat. Plant and Soil 208, 167–178 (1999). https://doi.org/10.1023/A:1004538207229
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DOI: https://doi.org/10.1023/A:1004538207229