State of the art reporton global and regional soil information:

Abstract

Soil is a natural body consisting of layers (soil horizons) that are composed of weathered mineral materials, organic material, air and water (Bockheim et al., 2005). It is the end product of the combined influence of the climate, relief (slope), organisms (flora and fauna), parent materials (original minerals), and time. The most widely recognized function of soil is its support for food production. Farmers who use soil in crop production know very well that it is the foundation for agricultural production. This is because it is the medium in which growth of food-producing plants occurs. It supplies the plants with nutrients, water, and support for their roots. The plants, in turn, support human and animal life with food and energy. Soil also acts as a repository for seeds, germplasm, and genes for flora and fauna. In general, soil is the medium for preservation and advancement of life on earth (Brady, 1984; Foth and Ellis, 1997). Besides supplying water treatments to plants, soil also supports millions of organisms living in it. These organisms have proven useful in medicine, biodegradation and recycling of waste, as food, as well as being essential in the conversion of minerals and nutrients to readily useable formats for plants and in turn animal nutrition. In hydrology, soil interacts with the hydrosphere as a medium that absorbs, purifies, transports, and releases water. In the hydrological cycle, the water that passes through the soil accumulates temporarily in the form of rivers, lakes/oceans/dams, soil water, and groundwater. During the storage process, soil filters the water against pollutants including natural and synthetic compounds. It also acts as a buffer against natural phenomena such as floods and soil erosion. In hydrology, the interaction of soil with the atmosphere has numerous environmental benefits. It can absorb excess energy radiation from the sun and release it gradually. Soil’s gaseous exchanges with the atmosphere involve carbon dioxide, nitrogen oxides and methane and are of a magnitude that has been reported to have profound effects on the global climate. In fact, soil has been recognized as the largest terrestrial sink for carbon dioxide and consequently has great importance in mitigating the impacts of climate change (FAO, 2004).