March 2016 essay - Soil (the pedosphere)

The pedosphere can be defined as “that shell or layer of the Earth in which soil forming processes occur” – Bates and Jackson, 1980.

The pedosphere, being the foundation of the Earth, develops by interacting between the hydrosphere - the  water cycle moves through the soil by infiltration and water may evaporate from the surface ; the atmosphere - the atmosphere may contain particulate matter that is deposited on the soils ; the biosphere - plants in the biosphere may extract nutrients from the soils and dead plants may end up forming part of the soil and the lithosphere – rocks in the lithosphere weather to form soils, and soils at depth and pressure. The pedosphere acts as a moderator of chemical and biochemical flux into and out of the previously mentioned systems.

The mineral portion of soil can be divided into three particles based on size, two of them being: sand and clay.  Sandy soils can be made out of rock fragments which contain many minerals e.g.: SiO2, there can be slightly brown, yellow or red, as a result of iron and aluminium oxides. Due its size, sand particles have a relatively low surface area thus have low water holding capacity. Soils with predominance of this fraction are considered to be non-cohesive - are more likely to be deficient in humidity in dry periods and so are low in nutrient storage capacity, primary production but high in air soil. On the other hand, clay soils have a large surface area therefore presenting a higher capacity of water/minerals absorption. This means that the particles are very united and tend to exhibit high plasticity. These are high in nutrient storage capacity, medium low in primary production but low in air space. Soil properties such as contraction and expansion, plasticity, water retention capacity, soil resistance and chemical adsorption elements are dependent on the type and amount of clay in the soil.

“The North American Prairies and commercial farming

Salinity, soil erosion and loss of soil fertility were recurrent problems. In order to stop these, farmers built snow fences or barriers which enabled snowdrifts to pile up which provide water that they then melt in – managing to reduce salinity. And to reduce erosion, contour ploughing and strip cropping was used.”


(could be continued)