Evaluating the Transport and Fate of Nutrients in Large Scale River Basins Using an Integrated Modeling System - Landscape Ecology for Sustainable Environment and Culture - page 183

Soil type in the UMRB ranges from heavy, poorly drained clay soil to light, well-
drained sands. Mollisols dominate but there are also Alfisols that have high clay
subhorizons and lower amounts of organic matter and clay in the surface horizons.
These soils are highly productive but have poor internal drainage. Subsurface tile
drainage of soils in this region is necessary for crop production. Corn and soybean
require a well-drained warm soil for optimum growth. In most parts of the basin,
agriculture is the dominant land use (Fig. 10.2 ). This figure indicates that over 60 %
of total land is used for agriculture and pasture. Corn, soybeans, and alfalfa are the
major crops in the basin. The UMRB encompasses most of the Corn Belt region of
the U.S. Nitrogen and phosphorus are abundant in the UMRB because of the
widespread use of commercial and animal-manure fertilizers. In fact, the quantity

Fig. 10.2 UMRB soil types