03.2 (29.16 ha Index 131)
This group corresponds to plains of medium altimetric level, and two different situations can be distinguished. On the one hand, there is the region of Villa Soriano, which is expressed associated with the Uruguay River in the Department of Soriano and part of the Isla del Vizcaino. The geological material corresponds to ancient, stratified alluvial sediments, with clayey and sandy silt granulometry. The sandy levels, when exposed on the surface, form elongated bands (sandy banks). They are slightly descending planes towards the Uruguay River, Rio Negro and Rio San Salvador. The dominant soils correspond to Haplic Melanic Gleysols, paracuic aeric (Gley humicos). Melanic, hydromorphic Heterotextural Fluvisols (Alluvial Soils) and Haplic, hydromorphic Vertisols (Grumosols). In general, they all have an upper horizon of black color, silty clay loam, with very high fertility and poor drainage. It is flooded slowly and for periods that depend on the flooding of the Uruguay River since this, in turn, dams the mouth of the Negro River and the San Salvador River, which is precisely where this unit appears. The use is pastoral and the vegetation is summer meadow, with gallery forest against the channels and park in the rest. On the other hand, it is worth distinguishing the middle plains associated with many drainage routes in the Departments. from Rio Negro and Paysandu, an example being the Plains of the Queguay River and Don Esteban Streams, Las Flores, etc. The geological material corresponds to silty sediments and clayey silt. The relief in general is flat, with meso-relief. The predominant soils are Haplic Melanic Gleysols (Gley humicos) of black to very dark gray color, silty clay, very high fertility and poor drainage and Melanic Isotextural Fluvisols (Alluvial Soils), black in color, silt loam to silty clay loam, very fertility. high and moderately well drained. Hydromorphic Haplic Vertisols (mounded Grumosols) may exist. The use is pastoral, with summer meadow vegetation and gallery forest associated with water courses. The area is floodable quickly and for short periods. This group is part of the Villa unit Soriano of the letter at a scale of 1:1.000.000 (DSF).
03.52 (0.84 ha Index 53)
This group corresponds to two situations: a) -the high alkaline plains located on the western coast, associated with the low plains of the Uruguay River, with significant extensions in the surroundings of San Javier (Department of Rio Negro), but which also exist in the Depts. of Paysandu y Soriano and some areas in the Department of Salto. They are exceptionally flood prone and have park vegetation with variable density of trees, espinillos, carob trees, etc. This group integrates, in this region, the Villa units Soriano and Banados de Farrapos on the chart scale 1:1.000.000 (DSF) b) - Another situation corresponds to the floodplains of streams, such as the one existing in the A. Canelon Chico, occurring in the Departments. of Canelones, San Jose y Colonia. These plains present park vegetation and river jungle associated with water courses. For reasons of scale, these areas do not appear on the 1:1.000.000 (DSF) scale chart. In both situations the dominant soils are Eutric Luvic Brunosols (Praderas Pardas maximas), dark brown in color, silty loam texture, high fertility and imperfect drainage, and Solonetz Ocricos, light grayish brown in color, silty loam texture, very low fertility and imperfect drainage. . The association is completed by soils affected by alkalinity, such as Brunosoles Eutricos Luvicos (Alkaline Brown Grasslands), sodium phase and Solods Ocricos. In the stream plains there are Heterotextural Fluvisols (Alluvial Soils) associated with water courses. In both cases the use is pastoral, limited by alkaline (whitish) areas.
