The texture of soil response to the rate at which particles are distributed within it. Permeabilizing capacity of a soil and water retention are features that depend directly on the texture. If the different factions that are divided solid elements do not dominate each other on each other is said that the soil is balanced, the clay and silt particles are the fine fraction, the mean fraction sands and gravels and stones fraction thick.
Vertical ground structure comprises a series of layers or strata of unequal width called horizons. In turn, a set of horizons is called the soil profile. The horizons of the structure between the surface and bedrock compositions can have type A, B or C, the importance of the layer can be divided into further sublayers. Horizon “A” is the horizon called “wash” to be exposed to erosion and washing of the rain, is the most abundant surface soil where the roots. It is rich in organic matter by micro-organisms, plants and animals. The horizon is extremely interesting and easy to study, but its composition is complex and had to be subdivided in subhorizons, which are not recognizable to the naked eye.
The soil erosion is a natural product of the action of atmospheric agents, although this action is strengthened by human activities. Spain is an example of this process desert, with a quarter of the area under its effects, resulting in annual one million tons of topsoil loss, caused mostly by the physical characteristics of much of the territory, marked orography and large areas of clay soils, which are easily eroded by the action of the rains, supported by the Mediterranean climate which is heavily concentrated downpours and in no time.