PHYSICAL PROPERTIES OF SOIL AND SOIL FORMATION

Written by Corry Capone, Lorenzo Bias, Shane Bernesser

There are over 2,000 types of soil in the U.S.

SoilEach with their own name given to it for where it was foundSurvey reports have the names and descriptions of the soils

Soil Forming Factors

Few soils weather directly from the underlying rocks. These “residual” soils have the samegeneral chemistry as the original rocks.

The Five soil forming factors include

Parent material. Few soils weather directly from the underlying rocks. Climate. Soils vary,

depending on the climate.

Topography. Slope and aspect affect the moisture and temperature of soil. Steep slopes facing the sun arewarmer, just like the south-facing side of a house. Steep soils may be eroded and lose their topsoil as theyform.

Biological factors. Plants, animals, micro-organisms, and humans affect soil formation. Animals and microorganismsmix soils and form burrows and pores.

Time. Time for all these factors to interact with the soil is also a factor. Over time, soils exhibit features thatreflect the other forming factors.

Understand the importance of soils and appreciate the relatively small amount of usable soil that exists on Earth.

Soil provides ecosystem services critical for life: soil acts as a water filter and a growing medium; provides habitat for billions of organisms, contributing to biodiversity; and supplies most of the antibiotics used to fight diseases. Humans use soil as a holding facility for solid waste, filter for wastewater, and foundation for our cities and towns. Finally, soil is the basis of our nation’s agro ecosystems which provide us with feed, fiber, food and fuel.

Understand the origin and types of soil parent materials. Soils are named and classified on

the basis of physical and chemical properties in their horizons (layers).The material in which soils form is called “parent material.”It also may be material

that has been deposited by wind, water, or ice.

Soils tend to show a strong geographical correlation with climate, especially when viewed globally.

Examination and Description of Soils A Soil Profile is exposed by a vertical cut through the soil. A Soil Horizon is a layer, approximately parallel to the surface of the soil. The Solum, of a soil consists of a set of horizon that are related through the same cycle of pedogenic processes. Solums and soils are not synonymous. Some soils include layers that are not affected by soil formation.

PedonsPedons representative of an extensive map able area are generally more useful than Pedrons that border of an area.

For a soil description to be of greatest value, the part of the land that the pedron represents and the vegetation should be described.