![]() Precipitation governs water movement in the soil. Temperature fluctuations increase physical weathering of rocks. The warmer the temperature, the faster reactions occur. Temperature directly influences the speed of chemical reactions. Temperature and precipitation influence how fast parent materials weather and, thus, soil properties such as mineral composition and organic matter content. These soils tend to be shallow and aren’t extensively used for crop production.įigure 2: Normal annual precipitation in Minnesota. There are also significant areas of soils formed directly from bedrock. Materials from the glacier were deposited over bedrock, similar to south-central Minnesota but with material from different glacial ice. Till bedrock deposits occur in northeastern Minnesota. Examples of Minnesota areas with soils formed in outwash include the Anoka Sand Plain, North Central Sands and Bonanza Valley regions in east-central, north-central and central Minnesota, respectively. Soils formed in outwash are excessively well-drained and have sand and sandy loam textures. This includes rocks, gravel, sand and other materials large enough to drop out of the water flow, as the river current continued transporting smaller particles. Outwash is material deposited on the edges of fast-running rivers from the melting ice of receding glaciers. Many soils in northwestern Minnesota were formed in lacustrine material. Soils formed in lacustrine deposits have clay, clay loam and silty clay loam textures, poor internal drainage and no rocks. The lakes existed long enough that the large particles, such as rocks and sand, were deposited immediately after the lake was formed, while the smaller clay-sized particles were deposited later.Īn example is the soil formed under Glacial Lake Agassiz in northwestern Minnesota and eastern North Dakota (Red River Valley of the North). ![]() Lacustrine parent materials result from sediment deposited in lakes formed by glacial meltwater. Residue management becomes an important factor in maintaining high productivity. Erosion is a major concern for these soils because of the silt loam texture. Soils formed in this material are generally poorly drained and behave similarly to soils formed in glacial till. Loess in southwestern Minnesota is deposited over glacial till. Because of the porous state of the underlying materials in southeastern Minnesota, the soils are generally well-drained. Most soils formed in loess occur in southeastern Minnesota where the loess deposits are on top of limestone or sandstone. Soils formed in loess generally have silt loam textures and no rocks. These silt deposits can range in depth from a few inches to many feet. Loess is windblown, silt-sized material deposited after the glacier melted. The poor drainage has a large influence on nitrogen management and cultural practices. Soils formed in this material generally have silty clay loam to silty clay textures, many different rock sizes and poor internal drainage. As the last glacier was melting, these materials were deposited. Till is predominant in the south-central, west-central and southwestern parts of the state. Figure 1 lists five major parent materials: Till, loess, lacustrine, outwash and till over bedrock. This may seem like a long time but is considered recent in the context of soil formation and geology. The common factor among Minnesota soils is that they were formed by the last glacier in the northern United States, 11,000 to 14,000 years ago. Minnesota is a land of geologically young soils with many different parent materials (Figure 1). Figure 1: Parent materials of Minnesota soils.
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