Soil is a mixture of mineral and organic matter. Plants are rooted in and draw nutrients from it. 

The decaying litter layer is responsible for a great deal of the carbon (organic matter) and plant nutrients that enter the soil.  Soils, depending upon their textures, also contain varying amounts of water and air. 

Heavy textured soils (clays) have smaller pore spaces through which air and water can pass. Lighter textured soils (sands) have larger pore spaces that can be occupied by water or air.

Soil formation results from the interaction of biotic (living) and abiotic (non-living) parts of the ecosystem. Climate, parent material from which the soil is derived, and living matter – plants and animals – interact to produce soils with specific characteristics. Soils that form under prairies (mollisols) differ from those that develop under forests (alfisols).
 
The major difference between forest and prairie soils is the thickness of the zone of organic accumulation (carbon from living organisms, like plants, as opposed to minerals). This zone starts at the soil surface. In forests the zone is very thin, consisting of leaf litter and the thin layer of developing soil beneath it. The leaf litter is acidic, and nutrients are leached through the organic zone. Clay is also leached into the deeper layers in forest soils. 

In prairies, the organic layer is thicker (deeper) because there is more litter. The clay content is higher in the surface layers and the nitrogen and carbon content is also higher than that of forest soils. Forest soils contain less nitrogen and carbon than prairie soils; and are therefore less fertile than prairie soils.