Soils in the valleys tend to be deeper, darker, and contain more horizons. This is due to increased material deposition from hillside erosion, material accumulation from downward leaching from the tops of hills, and the collection of greater quantities of water in the low lying areas. In what area across a landscape would you likely find relatively flat, dark soils that are rich in organic matter with the potential for a high water table?
In what area across a landscape would you likely find shallow soils with little soil development? On the top of a hill Incorrect: Soils developed in these areas tend to be relatively flat but well drained, thus the potential for a high water table is low.
On the slope of a hill Incorrect: Soils developed in these areas tend to be shallow due to erosion, and they tend to not be flat or contain a high water table. Seasonal and daily changes in temperature affect moisture effectiveness, biological activity, rates of chemical reactions, and kinds of vegetation. Topography - Slope and aspect affect the moisture and temperature of soil. Steep slopes facing the sun are warmer.
Steep soils may be eroded and lose their topsoil as they form. Thus, they may be thinner than the more nearly level soils that receive deposits from areas upslope. Deeper, darker colored soils may be expected on the bottom land. Biological factors - Plants, animals, microorganisms, and humans affect soil formation. Animals and microorganisms mix soils and form burrows and pores. Plant roots open channels in the soils.
Different types of roots have different effects on soils. Grass roots are fibrous near the soil surface and easily decompose, adding organic matter. Taproots open pathways through deeper layers. Microorganisms affect chemical exchanges between roots and soil.
Humans can mix the soil so extensively that the soil material is again considered parent material. The native vegetation depends on climate, topography, and biological factors, plus many soil factors such as soil density, depth, chemistry, temperature, and moisture. Leaves from plants fall to the surface and decompose on the soil. Organisms decompose these leaves and mix them with the upper part of the soil.
In many Minnesota soils, the C horizon is similar to the parent material. The number of horizons in a soil is indicative of its developmental age. Minnesota soils are young compared to the rest of the world—only 10, to 14, years old. Soils formed under forest vegetation in Minnesota tend to be more developed than soils developed under prairie. If the soils have been farmed, the E horizon may be destroyed, but the organic matter content will be lower.
Prairie soils generally have a thick, dark A horizon greater than 10 inches , as well as B and C horizons. These soils are found in the southern and western parts of Minnesota. A soil profile is a vertical exposure of the soil that reveals the combination and types of horizons.
The combination of master horizons, thickness of the horizons, and sequence in which they occur in the profile can cause different chemical, biological and physical properties in each soil. Soils with similar profile characteristics are grouped together into named soil series. Knowing the different soil series allows you to group or separate them for management purposes. The master horizons for the two soils in Figure 6 differ in thickness.
The soil on the left was formed in a footslope position of the landscape. It has a very thick A horizon, a thin B horizon and a water-saturated C horizon. The soil on the right has a thinner A horizon and a thicker B horizon than the soil on the left.
The water table is much deeper in the profile, indicating a better-drained soil on the right than on the left. Because these soils formed differently, you should manage them differently. An example of management differences could be that the soil on the left should be tile-drained for optimum crop production, while the soil on the right may not need tile drainage.
Anderson, J. Soil orders and suborders in Minnesota. Minnesota Department of Natural Resources. Field guide to the native plant communities of Minnesota: The eastern broadleaf forest province. John A. Lamb, emeritus Extension soil scientist and George W.
Rehm, emeritus Extension soil scientist. All rights reserved. The University of Minnesota is an equal opportunity educator and employer.
Home Crop production Soil and water Soil management and health Five factors of soil formation. The five factors. Open all Close all. Parent material. Biota organisms Biotic agents have greatly affected the soil formation process. Soil organisms Organisms in the soil can speed up or slow down soil formation. Topography Slope and aspect are two topography features that affect soil formation. Slope Slope refers to steepness in degrees or percent from horizontal, which affects how much soil material is deposited or eroded.
Aspect Aspect is the direction the slope faces relative to the sun compass direction , which affects the amount of water that moves through the soil. Time Time is the fifth factor in soil formation. Factors that slow soil formation include: High lime content in parent material. High quartz content in parent material.
High clay content in parent material. Hard rock parent material resistant to weathering. Low rainfall. Low humidity. Cold temperature. Steep slopes. High water table. Severe erosion. Constant deposition, accumulations and mixing by animals or man. Soil horizons and series These five soil-forming factors have different influences, causing different soil horizons to form. Soil master horizons Soil horizons are horizontal bands or layers in the soil profile.
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