Land is the part of the world not covered by the oceans, while soil is a mixture of minerals, organic material, living organisms, air, and water. Soil is a thin covering over the land.
The five major components of soil are mineral, organic material, living organisms, air, and water.
Soil is formed by the physical fragmentation and chemical changes in the parent material through a process known as mechanical and chemical weathering.
Physical processes include freeze and thaw, glaciers, wind, and moving water. Chemical weathering includes oxidation, hydrolysis, and the chemicals released during growth of lichens and the decomposition of dead and decaying material.
Other characteristics that determine a soil's usefulness include the size of the particles, or texture, the way the soil clumps together, or structure, its moisture content, biotic content, and chemical composition.
Soil composed of various-sized particles has spaces for both air and water and allows excess water to drain out. Soil composed of uniformly small particles has less space for air and water will not drain out. Soil with only large particles has a tendency to lose
all of the water it receives. Since roots require air, water, and good drainage, the soil with the various-sized particles would be better able to support crops.
A soil profile is a series of horizontal layers of different chemical composition, particle size, and amount of organic material.
Erosion is the wearing away and transportation of soil by water or wind.
Soil conservation practices include contour farming, in which tilling is performed at right angles to the slope of the land; strip farming, in which strips of closely sown crops like wheat are alternated with strips of row crops like corn; and terracing, in which level areas are constructed at right angles to the slope to retain water.
Other uses of soil include grazing, wood production, wildlife production, and recreational purposes.
