Tuesday, November 14, 2006

MLRA Based Soil-Landscape Studies: A Central USA Example.

S.J. Indorante1, M.A. Wilson2, L.R. Follmer3, J.M. Kabrick4, B.D. Lee5, and R.L. McLeese2. (1) USDA-NRCS, MLRA Office, 148 E Pleasant Hill Rd, Suite 105, Carbondale, IL 62903, (2) USDA-NRCS, National Soil Survey Center, 5111 W Sumner Circle, Lincoln, NE 68522, (3) Illinois State Geological Survey, 204 Natural Resources Bldg, 615 E Peabody Dr, Champaign, IL 61820, (4) USDA Forest Service, 202 Natural Resources Bldg, Columbia, MO 65211-7260, (5) Agronomy Dept, Purdue Univ, 915 W State, West Lafayette, IN 47907

The National Cooperative Soil Survey has been conducting soil surveys by MLRA’s (Major Land Resource Areas) for nearly two decades. During this time soil surveys have been initiated and/or updated on natural rather than political (e.g. county and state), boundaries. An essential component of MLRA soil surveys are carefully planned soil- landscape studies. The emphases of these studies are the determination and documentation of important soil-landscape relationships within the MLRA. The objective of this central USA study is to develop a regional soil-landscape model and to show the utility of soil-landscape models in soil surveys occurring in MLRA’s 114, 115,120 and 131. The study is being conducted on a forested and a cultivated first order watershed in Union and Alexander Counties (Illinois) that represent the catena of soils ranging from a Typic Hapludalf on ridge tops to Oxyaquic Eutrudepts in lower landscape positions. Detailed (0.5 m contour) topographic and geomorphic component maps were completed, followed by a first order soil survey of each site. Pedons were selected and sampled for laboratory characterization to represent dominant soil-landscape relationships. Further satellite sampling was carried out to characterize horizontal and vertical soil variation within soil-landscape units and soil map units. These types of studies will improve the accuracy and precision of soil maps and interpretations within an MLRA by understanding soil distribution relative to hydrology and landscape/pedogenic processes. Other long term benefits of these studies are: documenting important and extensive MLRA benchmark soil-landscapes, providing hands-on field experience (mapping and sampling) to soil scientists with carefully planned field studies, and establishing and documenting areas to encourage further interdisciplinary research (e.g. pedology, forestry, geomorphology, ecology, hydrology, agronomy etc.) on important soils.