What is Soil?

Basically, soil is the outer portion of the earth's crust that provides a medium for plant growth. Soils physically support plants and act as reservoirs for the water and nutrients needed to sustain plant growth and development. This seemingly insignificant segment of the earth's crust is extremely important to the soil-plant-animal food chain. Without soil, there would be no plants; without plants, there would be no food; without food, animals could not survive. Mankind is clearly very dependent on the maintenance of the earth's thin layer of soil.
Soil forms the very basis of man's existence on earth. In fact, the earliest of the great civilizations were founded on pockets of naturally fertile soils. Today, the productive partnership between the farmer and his land forms the very essence of our complex social structure. Life on earth would be quite different if we spent all our time in gathering the food we require to feed ourselves and our families. Today, the efforts of one farmer can produce enough food to easily feed another 70 people.
Soils are extremely complex and some researchers can spend a lifetime attempting to provide a better understanding of one specific aspect of soil behaviour (e.g., characterizing the behaviour of one specific portion of the soil organic matter pool). However, the purpose of this lesson is not to deal with all of the complexities of soil and its behaviour. Rather, it is to provide the home gardener with sufficient background knowledge to gain a better understanding of the uniqueness of soil and its limitations, as well as methods that can be employed for improving soils so that they are made more productive and the efforts of the home gardener made more rewarding.

How Soils are Formed

Soil is a naturally occurring product of the environment. In many respects, the soil that forms in a given region is a distinctive fingerprint of the soil forming conditions that were active in that area. To the trained soils specialist, an examination of the soil reveals a great deal about the climate and the vegetation that was prevalent in the region .
The development of soils is a long-term process, starting with native mineral materials and involving both physical and chemical weathering, as well as biological activity. Key soil forming factors are:

Parent Material – the material from which the soils were formed.

Climate – temperature and water supply.

Vegetation – type of plants that normally grow in the region, as well as the associated chemical, physical, and microbial processes involved in the decomposition of the plant residues.

Topography – shape and position of land surfaces.

Time – period of time during which the parent materials have been subjected to the processes involved in soil formation.