The use remote sensing in mapping and characterization of soils North East of Rufaa, Gezira State, Sudan

A soil survey was conducted in an area of about 19600 ha north east of Rufaa town. The collection of data and analyses for the present study had been achieved through three steps: the office work, the field work and laboratory analyses In the office work the study area has been found to be covered by two land satellite images; the first image at scale 1 :80,000, was obtained from Google earth image. The second was the landsat thematic mapper image. The land satellite images of the study area were treated by GIS applications system. Specifically the first image by Arc GIS 9.1 to give the digital soil map, while the second one by false colour composite, supervised classification and unsupervised classification (ERDAS imagine 8.5). In the field work the soil boundaries was delineated by free surveying supported by grid surveying in places where the contrast of the colour tone was not so clear. By the end of the field work three different soils type were identified and separately delineated. A total of three soil profiles were excavated, studied and sampled according to the genetic horizons. In addition, five auger sites in different locations in the study area were sampled (0-30 cm, 30-60 cm and 60-100 cm) for further verification of soils characterization. Soil samples were delivered to the laboratory for the full routine analysis. The results of the study revealed that remote sensing (RS) are good tools for the study of soil surveys and land evaluation because of their high efficiency in time and cost is saving. In addition the study showed that the false color composite, supervised classification and soil digital map have provided good facilities for the different soil types (soil units) recognition and land evaluation ,while the unsupervised classification was used as a pre-requisite step as it is a significant tool to be used with the supervised classification. The results of the study also revealed that the soils of the area belong to Vertisols and Aridisols. The results of physical and chemical routine analyses were interpreted with respect to sorghum cultivation. The results showed that clay soil belongs to class S2, moderately suitable land with vertisolic, gravel and low fertility limitations; subclass S2vgf; whereas sandy clay loam soil (Azzaza) belong to class N1, land currently unsuitable and has very severe limitations due to low water availability to plants and presence of surface gravels; subclass N1mg. Sandy clay soil belongs to class S3, marginally suitable land with physical, gravels and wind erosion limitations. It is recommended that soil with land suitability subclasses S2vgf may be put under sorghum cultivation with the specific management that may alleviate some of their limitations, whereas soils of land suitability subclass S3pge, may be put under sorghum cultivation and forestry and soils of land suitability subclass N1mg, may be put under settlement, natural grazing and forestry