3. Geochemical pattern of soils in Bobovdol valley, Bulgaria. Assessment of Cd and Co contents

The study of distribution of trace elements in soils of Bulgaria is still concentrated in areas affected by industrial activities, such as mining, and processing of mineral resources. Most of these studies are designed to assess soil contamination and include the surface 30-40 cm of soil profile . This approach is used in monitoring programs, but does not provide enough information for three-dimensional (3-D) geochemical characteristics of soils and the cycles of trace elements in pedosphere. Geochemical maps designed by the grid sampling procedure to reflect the spatial distribution of chemical elements in soils may be used for predicting the extension of soil degradation and its negative impact on the interacting environmental components. Detailed information on the natural variability of background concentrations of chemical elements in soils and the quantitative database allow imaging the geochemical diversity. In this regard, the elements cadmium and cobalt are of great interest in Bulgaria where there is a limited knowledge of their distribution and availability in the pedosphere. A large number of studies reveal the role of cadmium in geochemical processes. However, its geochemical fate in pedosphere and especially in soil surface layer is still not well understood. It is known that cadmium persists only in the +2 valence state in soils and goes readily into solution on weathering. The enrichment of soils with cadmium occurs primarily through the adsorption and/or complexation of cadmium onto organic matter followed by the accumulation of organic debris in the depositional environment. Cd mobility is affected mainly by the pH and oxidation potential. It is most mobile in acidic soils within the pH range 4.5 - 5.5 and is rather immobile in alkaline soils, wherein CdHCO3 prevails. Studies of cobalt geochemistry in terrestrial environments have also received a lot of attention. However the case studies of cobalt variability and accumulation in soils could contribute to the better knowledge of element global cycling. This article deals with the geochemical patterns of soils located in the vicinity of the "Bobov dol" Thermal power plant, Bulgaria, emphasizing on the amount and spatial distribution of Cd and Co in order to determine their geochemical behavior, associations and origin in soils.

4. Dynamic surface soil components of land and vegetation types in Kebbi State Nigeria

Soils vary on how long they can be used in agriculture without decline in quality and functional status before management may be needed. Assessments and classification of surface soil components, including land and vegetation are helpful in understanding the current status and condition of soil for proper and sustainable soil management in crop production. Unfortunately, scientific knowledge of surface soil components and in particular the aspect of assessment and classification of land and vegetation is very limited in Kebbi State, Nigeria. Consistently, the need for background information outlining the major components of surface soil environment in poor research areas is also essential. In the present study, the major components of the surface soil (land and vegetation types) according to the geo-physical context of the current status of the soil environment in Kebbi State are taken into consideration based on visual assessment. This assessment was regarded as a key element for obtaining soil data information, and especially when the methodology and procedure are developed under the general principles on which the assessment and classification of soils should be made in the field. This assessment is highly cost and time consuming, and needs to be carried out according to the purpose intended. Soil Survey Staff (1999) noted that visual assessment requires many assessments and classifications that can be related to the surface soil and that facilitate comparisons of both similarities and differences among the soil characteristics for a great variety of uses. In this study, visual assessment was intended to assess and classify the land and vegetation types from 2010 to 2011 in Kebbi State. Therefore, the objective of this study was assessment and classification of land and vegetation types in dryland and fadamasites of Kebbi State Nigeria. This is hoping to ensure better understanding of environmental soil function for sustainable crop production in the State.

II. PLANT PROTECTION