REGOSOL: CHARACTERISTICS AND USES - ENVIRONMENT - 2025

Regosol is a group of reference soils in the classification of the World Reference Base for Soil Resources. In the classification of the Department of Agriculture of the United States (USDA soil taxonomy) they are known as Entisols.

These are soils whose formation is related to their topographic position, similar to what happens with Lithosols (leptosols), but they differ from these in that they have a depth greater than 25 cm.

Regosol. Source: U. Burkhardt / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Regosols are made up of fine, unconsolidated material because they grow on crumbly (melt) rocks.

Being composed of unconsolidated material, with very little organic matter, they retain little moisture. Furthermore, its superficial ochric horizon tends to form a crust in the dry season, making it difficult for both water infiltration and the emergence of seedlings.

They develop in mountain areas, as well as in river and marine sediments, in all types of climates and in all parts of the world. They are more abundant in hot and cold dry areas.

Given their physical properties and low fertility, they are not very productive from an agricultural point of view; however, with proper management, various vegetables can be grown there or fruit orchards established.

On the other hand, when they support natural grasslands, they can be used for grazing with a low stocking load. In any case, in steep conditions, given their predisposition to erosion, it is preferable to use them for the conservation of the original natural vegetation.

Characteristics of regosols

Regosols include all those young soils that do not fall into the rest of the established groups. Therefore, they are described more by characteristics that they do not have than by their own diagnostic characteristics.

In this sense they are soils similar to leptosols or lithosols, but with greater depth and on crumbly rock. Likewise, they show similarity to aridisols, but they are not very sandy and they show similarity to fluvisols (without showing their mottling due to oxidation and reduction processes).

In general, these are deep mineral soils, poorly developed, with a superficial ocric horizon on the original material not yet consolidated. The presence of this thick material in most of the profile gives it good drainage due to its high porosity.

Parenting material and training

They are poorly evolved mineral soils that are formed on various types of crumbly parent material, exposed to erosion due to their topographic position. The parent material can be river or marine sediments, as well as volcanic sediments, sandstones or clays.

These are unconsolidated fine-grained materials, due to low temperatures in the soil, extreme drought or permanent erosive processes. On the other hand, its scarce organic matter does not allow aggregates to form, so that under these conditions there is little soil development.

The crumbly rock melts under the action of weathering factors (water, wind, vegetation) and accumulates. Over time a first thin horizon forms, but the rest of the depth of the profile remains composed of the original waste material.

This group also includes soils in formation (young) from mining waste, sanitary landfills and other materials caused by human action.

Profile

Although they are deep soils, they do not present a definition of horizons, except for a superficial ochric horizon on the slightly altered original material. Ochric is a superficial diagnostic horizon (epipedon), characterized by having a very light color, with very little organic carbon and it hardens when it dries.

Profile of a regosol. Source: Jan Nyssen / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

In cold weather conditions the organic matter present in this horizon is poorly decomposed. Likewise, regosols from coastal marshes that have sulfidic materials (based on sulfur) form a histic epipedon.

On the other hand, depending on the parent material that gives rise to them and the environmental conditions of formation, different types of regosols are identified. Among them are calcareous regosols, characterized by high concentrations of calcium carbonate.

Likewise, dystric regosols with low content of bases and eutric regosols with abundant bases. Another type is glyic regosols, with typical gray and bluish-green hues, since being saturated with water part of the year they undergo reduction processes.

Environments and regions where they develop

Regosols predominate in arid zones and in mountainous areas where types of rocks that are crumbly or easily disintegrated are present. They are, together with leptosols, one of the most widespread soil groups on the planet, covering about 260 million hectares.

They are especially abundant in the North American Midwest, dry areas of Central and South America, North Africa, Australia and the Middle East. In Europe, regosols are more common in the south of the continent than in the north, especially in the Mediterranean area and the Balkans.

From the climatic point of view, they are found in tropical, temperate and cold climates all over the planet (azonal soils). Due to the material condition that makes them up, they are susceptible to the formation of gullies (large trenches or cracks undermined by runoff water, wind or ice).

Applications

Regosols due to their poor development, low moisture retention, susceptibility to erosion and compaction, are not very productive. However, with proper management, they can be used for agricultural production of certain crops and for grazing, without expectations of high productivity.

Limitations and handling

Due to the poorly consolidated condition of the material that makes up regosols, they are very susceptible to erosion. This especially when they are in conditions of high slope, which makes it difficult to use them for agriculture.

Regosol in Africa. Source: Jan Nyssen / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Due to their high porosity, they have a very low capacity to retain water, being sensitive to drought and the ochric surface horizon tends to crust when it dries. The latter makes water infiltration difficult, increasing surface runoff and forming a barrier for the emergence of seedlings.

Given these conditions, these soils require adequate management for agricultural production, understanding that they will not be very productive. Among other things they require abundant irrigation or techniques such as drip irrigation that maximize efficiency in the use of water.

While in mountainous areas with high slopes it is preferable not to intervene, leaving the natural vegetation. Where they achieve greater productivity is in conditions of cool and humid climate.

Crops

With proper management and in flat areas or with very low slopes, various vegetables can be grown, such as sugar beets. The establishment of fruit orchards on soils of this type is also possible.

Grasslands

The natural vegetation in these soils in many cases consists of grasslands, so they can be dedicated to extensive grazing. However, their low productivity and erosion problems warrant that the animal load is low, since excess trampling compacts them on the surface.

References

1. Duchaufour, P. (1984). Edaphology 1. Edaphogenesis and classification. Ed. Toray-Masson. Barcelona.
2. Driessen, P. (Edit). (2001). Lecture notes on the major soils of the world. FAO.
3. FAO-Unesco. The FAO-Unesco Soil Classification System. The World Reference Base for soil resources. (Seen on April 11, 2020). Taken from:
4. Jaramillo, DF (2002). Introduction to soil science. Faculty of Sciences, National University of Colombia.
5. Lal, R. (2001). Soil degradation by erosion. Land Degradation and Development.
6. USDA (1999). Soil Taxonomy A Basic System of Soil Classification for Making and Interpreting Soil Surveys. United States Department of Agriculture, Natural Resources Conservation Service. Second Edition.