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Key definitions

What is soil ?

A farmer sowing carrot seeds in a vegetable plot irrigated by water from the Mpatheni Dam, Swaziland

Like many common words, the word soil has several meanings. In its traditional meaning, soil is the natural medium for the growth of plants. Soil has also been defined as a natural body consisting of layers (soil horizons) that are composed of weathered mineral materials, organic material, air and water. Soil is the end product of the combined influence of climate, topography, organisms (flora, fauna and human) on parent materials (original rocks and minerals) over time. As a result soil differs from its parent material in texture, structure, consistency, color, chemical, biological and physical characteristics.

Soil is an essential component of  “Land” and “Eco-systems” that both are broader concepts encompassing vegetation, water and climate in the case of land, and in addition to those three aspects, also social and economic considerations in the case  of ecosystems.

The word “soil” is also known as “dirt”, “waste” or  “earth” that are not discussed in these pages.

Soil survey

is a systematic study of the soil of an area including classification and mapping of the properties and the distribution of various soil units.

Soil Maps and Databases

are the main information products generated by soil surveys, in the early days of soil science they were  in paper format, but with rapidly developing technology they are now produced in advanced GIS environments.

Soil Assessment

in the context of land evaluation, soil assessment focuses on the matching of the specific soil requirements of the land use versus the properties of the soil. Most of soil assessments have been made for agricultural land uses and cropping systems, but the same principles could be applied for other applications.

Soil Management

The soil sustains most living organisms, being the ultimate source of their mineral nutrients. Good management of soils assures that mineral elements do not become deficient or toxic to plants, and that appropriate mineral elements enter the food chain.

Soil degradation

is defined as a change in the soil health status resulting in a diminished capacity of the ecosystem to provide goods and services for its  beneficiaries

Soil Improvement

concerns in the first place the appropriate management of problem soils. It also involves the improvement of degraded soils in terms of soil prevention, mitigation, and rehabilitation.

Soil Biodiversity

can be defined as the variation in soil life, from genes to communities, and the variation in soil habitats, from micro-aggregates to entire landscapes.

Soil Governance and Policy

concerns policies and strategies and the processes of decision-making by nation states and local governments on how the soil is utilised. Globally, governance of the soil has been focused on agriculture due to increased food insecurity in the most populated regions on earth.