Rio Grande do Sul has a wide variety of types of soil1 as consequence of the complexity of the geological formation and of the existing climatic action.
- Alisols are acidic soils with high aluminum content, low chemical fertility and high aluminum toxicity, besides low nutrient reserves for plants. They occur in several forms of relief, mainly in Central Depression, Campanha and in the region of the Southern Plateau Slope.
- Argissolos have a clayey subsurface horizon and are generally deep and well drained soils. They occur in smooth and undulating reliefs in the Central Depression, Campanha and the Slope of the Southern Plateau, and may present chemical limitations due to low natural fertility, strong acidity and high saturation by aluminum, being also highly susceptible to erosion and degradation. They can be used for annual crops and as native field, preferably with no-tillage and rotation of crops with protective and soil recuperating plants during winter.
- Cambisols vary from shallow to deep soils, in process of transformation, and generally occur in areas of high altitude with low temperatures. They present options for use as native pasture and silviculture, such as in Campos de Cima da Serra region. They have high acidity and low availability of nutrients, thus requiring intensive conservation practices and application of high levels of correctives and fertilizers.
- Chernossolos are dark soils in horizon A, due to the presence of organic material. They have high chemical fertility and may be shallow or deep. They may be used withhigh intensity depending on the relief to which they are associated. The floodplains of the rivers present greater potential for annual crops, especially with irrigated rice. They occur in the valley of Uruguay River and in the lower slope of the Southern Plateau.
- Gleysols are shallow soils, poorly drained, of grayish or black color and occur in depressions with low slope. They may be used for irrigated rice cultivation and, when drained, for annual crops such as corn, soybeans, beans and pastures.
- Latossolos are deep, well drained, acid and of low fertility, sometimes presenting aluminum toxicity to plants. However, soil depth associated with smooth relief makes them suitable for agriculture, since their chemical fertility be corrected. They may be used for winter and summer crops. They occur predominantly in the north of the State, in the Southern Plateau area.
- Luvisols are shallow with subsurface clay accumulation. Despite the lack of phosphorus, they present good natural fertility depending on the depth. They occur more frequently in Campanha region and between the municipalities of Uruguaiana and São Borja.
- Neossolos are poorly developed and normally shallow soils, of very recent formation, found in the most diverse conditions of relief and drainage. Their use is restricted by relief and low depth, requiring strong conservation practices. In general, areas the soft and undulating relief areas can be used for permanent pasture and in the regions of strong relief corrugated for reforestation and fruit growing. Very steep areas should be reserved for permanent preservation.
- Nitossolos are deep soils with similar appearance to latosols, differing from them because they present a B horizon with a more developed structure with a shiny coating (cerosity). They are acid with predominance of kaolinite and iron oxides in their composition. Depending on the depth, good drainage porosity, structure and relief conditions, they generally have good agricultural suitability. They may be used for winter and summer crops.
- Organossolos are formed by organic material in various degrees of decomposition, accumulated in poorly drained environments, in depressions and in the vicinity of lakes and lagoons. In general they have low agricultural use, since they are subject to significant changes in their characteristics, tending to disappear.
- Planosols are soils located in areas of smooth relief, wavy or flat, and poorly drained. They usually appear on the banks of rivers and lagoons as in the Central Depression and along the Coastal Plain. They are suitable soils for the cultivation of irrigated rice and, with efficient drainage systems, can also be cultivated with corn, soybean and pastures.
- Plinthosols are flat or slightly undulating soils, with imperfect drainage and, therefore, have limitations for perennial crops. In rainy periods there is elevation of the water table, saturating the soil and preventing its use with annual crops and cultivated pastures.
- Vertisols are soils of flat or slightly undulating areas, poorly drained and shallow. They occur in Campanha region and their use is facilitated with humidity, since they are very hard soils when dry. They have good fertility and and are suitable for natural grazing, and they may also be used for summer crops, provided that without use
¹ Based on the study Solos do Rio Grande do Sul (Streck et all. 2002) of the Departamento de Solos da UFRGS.