Soil and Soil forming factors

Soils are earth materials modified over time by physical, chemical, and biological processes that support rooted plant life.  It can be defined as : “Soil is a collection of natural bodies occupying a portion of the Earth’s crust that support plant growth which have acquired properties due to the integrated action of climate and vegetation upon parent material as conditioned by relief over a period of time.”  

The four major components of soil are air (25%), water (25%), mineral matter (45% {sand, silt, and clay}), and organic matter (5%).

Soil forming factors

The type of a soil at a particular site depends on five factors such as

• Parent material (geological or organic precursors to the soil),
• Climate (primarily precipitation and temperature),
• Topography (relief) (slope, aspect, and landscape position),
• Biological activity (living organisms, especially native vegetation, microbes, soil animals, and human beings), and
• Time (the period of time since the parent materials became exposed to soil formation).

Soils are extremely important in many environmental considerations. As a result, the study of soils continues to be an important part of environmental sciences.

             Soil material  S = f(p+cl+r+v+t......)

Soil Fertility

Soil fertility refers to the capacity of a soil to supply the nutrients and physical properties necessary for plant growth. Ironically, agriculture depends heavily on soil quality, but agriculture can lead to a decline in that quality. A high-quality agricultural soil has all the chemical elements required for plant growth and a good physical structure that lets both air and water move freely through the soil, yet retains water well. Such a soil has high organic matter (Soil organic matter is the plant and animal residues, leaves, forest litter, etc. at various stages of decomposition, considered as the storehouse of nutrients) content. Organic matter in soil is rich in chemical nutrients and provides a physical structure conducive to plant growth.

Plowing (shattering of soil uniformly with partial to complete inversion) the soil and planting crops has been a way of life for several thousand years and continues today.                            

                       

                        Fig: Tillage operation in soil to receive the crop.