<" ~" Ii ELSEVIER Catena 25 (1995) 21-32 CATENA Rain infiltration into loess soils from different geographic regions M.J.M. R~Smkens a S.H. Luk b, J.W.A. Poesen c, A.R. Mermut d a USDA-ARS National Sedimentation Laboratory, P.O. Box 1157, Oxford, MS 38655, USA b Department of Geography, University of Toronto, Erindale College, Mississauga, Ont. L5L IC6, Canada c National Fund for Scientific Research, Laboratory for Experimental Geomorphology, K.U. Leuven, Redingenstraat 16bis, 3000 Leuven, Belgium d Department of Soil Science, Univ. of Saskatchewan, Saskatoon, Sask. S7N OWO, Canada Received 2 May 1993; accepted after revision 5 January 1994 Abstract Loess soils are among the most erodible soils. Therefore, evaluating and enhancing infiltration is paramount in controlling soil loss. A laboratory study was conducted to evaluate the relative difference in infiltration among selected loess surface and subsurface soils from Belgium, Canada, China, and the United States, representing the major loess belts of the Northern Hemisphere. Soils were subjected to simulated rainstorms of constant intensity (I= 41.1 mm-h-l), duration (2 hours), and energy rate (27.0 J • m -2 per mm of rain). Infiltration, runoff, and soil water pressure were continuously monitored. Infiltration was described by a linear relationship for the pre-pond- ing period and by a power series for the post-ponding period. Differences in infiltration response were attributed to differences in soil properties such as differences in organic matter, particle size, swelling clay content, Fe-oxyhydroxides, and carbonates. Despite the high organic carbon content and coarser texture of the Canadian loess surface soil, the presence of highly expansive smectitic clay caused a rapid reduction in infiltration rates indicating the importance of soil mineralogical constituents in surface seal development. 1. Introduction Infiltration is a much studied subject, that is of interest to hydrologists, agronomists, soil erosion specialists, environmentalists, and others who are concerned with water requirements and water quality. Erosion specialists are primarily concerned with excess rain water, that accumulates on the soil surface, collects in depressions, and concentrates as runoff in rills, gullies, streams, and channels. In fact, most dynamic soil erosion models are driven by hydrologic considerations in which the generation of excess rain 0341-8162/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0341-8162(94)00039-5