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Book: Landscape Planning, Environmental Applications by William M. Marsh

Top Soils:

Composition (refers to the materials that make up the soils.)

It constitutes of four elements mineral particles, organic matter, water and air.

Mineral Constituents:

Mineral particles comprise 50 to 80 percent of the volume of most soils and form the all-important skeletal structure of the soil. This structure, built up of particles lodged against each other, enables the soil to support its own weight as well as that of internal matter such as water and the overlying landscape, including buildings.

Organic Matter:

The quantity of organic matter varies radically on soils, but it is extremely important for both negative and positive reasons. Organic particles usually provide weak skeletal structures with very poor bearing capacities. Organic matter tends to compress and settle differentially under roadbeds and foundations, and when dewatered, it suffers substantial volume losses as well as decomposition, wind erosion, other effects.

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Four elements constitute the composition of soil. Those are mineral particles, organic matter, water, and air. The majority of the top soils volume consists of 50 to 80 percent of these particles which form the skeletal structure of most soils. This composition allows the soil to sustain its own weight, and other internal matter such as water and overlying landscape. Organic matter, another important element, varies on quantity on different soils. This provokes positive and negative effects or reactions on the soil. The strength of soil structure decreases with the presence of organic matter, creating weak bearing capacities. Organic matter condenses and settles in different ways under certain conditions, such as roadbeds and foundations. The skeletal structure becomes affected once the soil is dewatered. The soil’s volume substantially decreases. It decomposes and suffers wind erosion.

Arch 361 - Ecological Factors in Design