Illinois and Missouri
28,570 km² (11,030 mi²)

    Land use: Nearly all this MLRA is in farms, and about 60 percent is cropland. Corn, soybeans, other feed grains, and hay for cattle and other livestock are the main crops. About 10 percent is in permanent introduced and native grasses. An additional 20 percent, mainly on the steeper slopes and on wet bottom land, is forested. About 5 percent is used for urban development; the remainder is used for miscellaneous purposes. Wetness is the major land use problem.
    Elevation and topography: Elevation ranges from 200 to 300m in Missouri and is about 200m in Illinois, increasing gradually from south to north in both states. This MLRA consists of nearly level to gently sloping silt-mantled old till plains. Stream valleys are shallow, and most of them are narrow. Local relief is mainly a few meters.
    Climate: Average annual precipitation-About 1,025 mm. About 60 percent of the precipitation falls during the freeze-free period. Average annual temperature-13°C. Average freeze-free period-180 to 190 days.
    Water: In most years the moderate precipitation is adequate for crops. Small to moderate quantities of water are available from ground water. A few large perennial streams are potential sources of water, but they are little used for this purpose. Most of the soils are somewhat poorly drained to poorly drained, and claypans prevent effective artificial drainage on most of them.
    Soils: Most of the soils are Aqualfs. They have a deep, medium textured surface layer and a fine textured and moderately fine textured subsoil. These soils have a mesic temperature regime, an aquic moisture regime, and montmorillonitic mineralogy. In areas in Missouri are nearly level, poorly drained Albaqualfs (Putnam series) and gently sloping, somewhat poorly drained Ochraqualfs (Mexico and Leonard series). On some sites in Illinois are nearly level Albaqualfs (Cisne, Cowden, and Wynoose series). Somewhat poorly drained, nearly level and gently sloping Hapludalfs (Bluford and Hoyleton series) and moderately well drained, nearly level and gently sloping Fragiudalfs (Ava series) are on loess-covered old till plains. Well drained and moderately well drained, moderately sloping to steep Hapludalfs (Armstrong, Gara, Keswick, Lindley, and Weller series in Missouri and Hickory series in Illinois) are on side slopes. Fluvaquents (Belknap, Piopolis, and Westerville series) and Udifluvents (Sharon series) are in silty alluvium. Haplaquolls (Wabash series) are in clayey alluvium on narrow flood plains of small extent.
    Potential natural vegetation: When this MLRA was settled, most of the level upland soils supported tall grass prairie vegetation characterized by big bluestem, indiangrass, prairie dropseed, and switchgrass. The present potential for natural vegetation on the level upland soils is unknown. Forests of post oak, swamp white oak, blackjack oak, and pin oak grow on poorly drained soils. White oak, shingle oak black oak, hickory, white ash, basswood, sugar maple elm, and walnut grow on the better drained soils. Silver maple, willows, cottonwood, sycamore, elm pin oak, white oak, hickory, and ash grow on floodplains.

Data Source:
U. S. Department of Agriculture, Soil Conservation Service. 1981.
       Land Resource Regions and Major Land Resource Areas of the United States.
       Agriculture Handbook 296.U. S. Government Printing Office, Washington, D. C.

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