Soil Development and Fertility Characteristics of Inland Valleys in the Rain Forest Zone of Nigeria: Mineralogical Composition and Particle-Size Distribution

The particle-size distribution and mineralogical composition of the clay （〈 2 μm） and fine-sand （0.25-0.10 mm） fractions in soils of two inland valleys in Abakaliki and Bende, Southeast Nigeria, were investigated to provide basic information on soil-forming processes and agricultural potentials. These soils were silty or clayey, deriving from Cretaceous or Tertiary shale materials. The particle-size distribution and its computation on a clay-free basis revealed relatively remarkable lithologic breaks in a couple of pedons. The effect of lithologic discontinuities on soil mineralogical composition was not, however, conspicuous. Petrographic investigation revealed that quartz predominantly comprised the fine-sand fraction in the soils at both study sites. Nevertheless, the clay mineralogical composition of the soils was a mixture of kaolinite, irregularly interstratified smectite-illite intergrades （S/I）, hydroxyl-A1 interlayered 2：1 type clays （HICs）, vermiculite, smectite, halloysite and illite along with fine-sized quartz in Abakaliki. The soils of Bende predominantly contained smectite, which was partially interlayered with hydroxyl-A1 and kaolinite. It is suggested that seasonal floodwater has slowed the disintegration of weatherable clay minerals inherited from the shale, while quartz originating from the sandstone is predominant in the fine-sand fraction. Additionally, a possible soil-forming process observed at the both study sites was ferrolysis, which was indicated by a clear decreasing pattern of HICs downward in the soil profiles, The entry of S/I and vertical distribution patterns for a couple of clay minerals in the pedon suggested that the soils in Abakaliki have developed under the significant influence of aeolian dust delivered by the Harmattan. The findings might describe a site-specific deposition pattern of Harmattan dusts as well as hydromorphic soil-forming processes in the wetlands of the inland valleys.

Soil Attributes in Anthropized Hygrophilous Forest in Northern Minas Gerais State,Brazil

The soils of Brazilian Cerrado are characterized with high acidity and low fertility and productivity.However,these attributes are not homogeneously distributed through all phytophysiognomies of this biome,and wetland known as palm swamp or“veredas”are an exception.This study aimed to describe and compare the chemical and physical attributes of soil surface layers at six palm swamps areas under different anthropization processes in the northern region of Minas Gerais state,Brazil.Soil sampling of different hydromorphic soils were collected at 0-20 cm depth layer from 100 m2 plots in the studied areas.The variables were compared using the GLM procedure of ANOVA using Statistica 10 software.Soil chemical attributes and similarities between the six palm swamps areas were compared using the statistical software R.Soil chemical attributes were different and soil physical attributes were similar between the evaluated areas.The similarities among the attributes were classified into three groups according to the anthropic pressures,as well as with the origin of the soil material in the six palm swamps areas evaluated.It could be concluded that soil fertility can be reduced in palm swamps that suffered greater anthropic intervention.The three similarity groups might be associated not only to the anthropic pressures,but also to the raw material of soil at the six palm swamps areas evaluated.