EURASIAN JOURNAL OF SOIL SCIENCE

292 - 299

Authors: Teshome Yitbarek , Abdeta Jembere , Habtamu Kerebeh

The main purpose of this study was to characterize and classify soils of Wolkite University research sites, Gurage zone, Ethiopia. In each five research sites, Wabe (RS1), Geche (RS2), Yefereze (RS3), Kotergedra (RS4) and Keratemo (RS5), representative pedons were opened and described. Almost all the pedons were deep (>150 cm) with argillic B horizons and had clay textural class. The pH of the surface soils ranged from strongly acidic (4.5) to moderately acidic (5.6). The soils had medium (2.60%) to high (3.84%) organic carbon content and very low (1.46 mg kg-1) to low (10.34 mg kg-1) available phosphorus. The status of cation exchange capacity (CEC) and base saturation were ranged from medium (23.15) to very high (66.32 cmolc kg-1) and low (33%) to high (99%), respectively. According to WRB classification, pedon RS1 was classified as Haplic Vertisols (Hypereutric) with USD equivalent of Typic Haplusterts. Pedons RS2 and RS3 were classified as Vertic Alisols (Hyperdysric), which is correlated with Ultisols (Typic Haplustults) in USDA classification. Pedon RS4 and RS5 classified as Vertic Luvisols (Hypereutric), which is correlated with Alfisols (Vertic Haplustalfs) in USDA classification. Generally, the soils of the research sites were acidic with low status of available phosphorus, which need amelioration of soil acidity and nutrient management.

308 - 317

Authors: Henry Oppong Tuffour , Mensah Bonsu , Awudu Abubakari , Janvier Bigabwa Bashagaluke , Murphy Acheampong Opoku , Jimmy Clifford Oppong

The infiltration rates of variable soils were scaled using factors derived from the steady state infiltrability (Ko) and the saturated hydraulic conductivity (Ks) based on the similar media theory and dimensional analysis. Infiltration rates were successfully scaled when the characteristic scaling infiltration rate equations were formulated through combination of the similar media theory and dimensional analysis. This study disproved the earlier notion that to successfully scale variable infiltration measurements, both sorptivity and steady state infiltrability were required. Thus, the study revealed that using the saturated hydraulic conductivity as a substitute for the steady state infiltrability could predict and scale infiltration rates more accurately. The study further highlighted the importance of the scaling factor (α) in any characteristic equation supposedly to have been developed from the similar media theory. Invariably, the ability of any characteristic scaling equation containing no scaling factor to scale variable infiltration measurements successfully could be fortuitous and not evolved from the similar media theory.

326 - 336

Authors: Md. Abdul Mojid, A.B.M. Zahid Hossain , Guido C. L. Wyseure

Solute-transport parameters are needed to assess the pollution risks of soil and groundwater resources. A reliable estimate of these parameters from easily measurable soil properties is therefore important. So, the correlations of the transport parameters for one metalloid compound (NaAsO2), six heavy metal compounds (Cd(NO3)2, Pb(NO3)2, Ni(NO3)2, ZnCl2, CuSO4 and Co(NO3)2), two pesticides (cartap and carbendazim) and one inert salt (CaCl2) with some basic properties of eight agricultural soils of Bangladesh were investigated. The purpose of this study was to generate information for development of non-parametric pedo-transfer functions for reactive solute transport through soils. The transport experiments with the solutes were done in repacked soil columns under unsaturated steady-state water flow conditions. The major solute-transport parameters – velocity of transport (V), dispersion coefficient (D), dispersivity (l), retardation factor (R) and Peclet number (P) – were determined by analysing solute breakthrough curves (BTCs). The basic soil properties pertinent to solute transport: clay content, median grain diameter (D50), pore-size distribution index (n), bulk density (r), organic carbon content (C) and pH were determined. The associations of the solute-transport parameters with these soil properties were investigated and evaluated. Both the solute dispersivity and retardation factor increased significantly (p<0.05) (l linearly and R following power law) with the increase in soil clay content. Dispersivity significantly decreased with the increase in median grain diameter following power law. The V, D, l and P values were weakly and negatively correlated with the soil bulk density. Retardation factor, R, was moderately and positively correlated with the ratio of clay content to organic carbon content. Dispersivity decreased but P increased, both significantly, with increasing pore-size distribution index, n. V, D and P were positively correlated with soil pH, while R and l were negatively correlated with it. The correlation of the solute-transport parameters with soil properties being significant (p < 0.05), in most cases, provides strong possibility of predicting solute-transport parameters from the basic soil properties through the development of pedo-transfer functions.

346 - 354

Authors: Simon Djakba Basga , Jean Pierre Temga , Désiré Tsozué , Nicodème Danbé , Jean Pierre Nguetnkam

In the present study, two topomorphic vertisols profiles used for sorghum production were described and characterized. After macroscopic characterization, physicochemical, mineralogical and geochemical analyses were made. Physicochemical analyses were made by standard methods while mineralogy was determined on clay fraction (˂2µm) by X-ray diffraction coupled to Fourier transform infrared spectroscopy. Geochemical analysis was determined on 180µm fraction by inductively coupled plasma- Atomic Emission Spectroscopy (ICP-AES) and mass spectrometry (ICP-MS). Results revealed that studied vertisols were average deep, less differentiated with desiccations cracks and gilgai micro relief. The angular blocky structure and clayey texture were observed. They were alkaline (7.3 ≤ pHwater ≤ 8.4) and recorded a low to moderate organic matter and nitrogen contents. Cation exchange capacity was high reaching 52.24 meq 100g-1 and exchangeable cations were moderates with Ca2+ (3.69- 29.6 meq 100g-1) the most represented cation. Vertisols were made of smectites associated to kaolinite and a lesser content of quartz. Illites and calcite were also identified in some horizons. On the geochemical point of view, Si02 (55.87- 83.64%), Al2O3 (6.08-20.25%), Fe2O3 (2.09-6.39%) and K2O (1.43-2.24 %) were the dominant oxides. Traces elements were represented essentially by Ba (518-1202 mg kg-1), Zr (334-685 mg kg-1) and Sr (71-190 mg kg-1). The overall features are suitable to dry season sorghum production. The amount of smectites seemed to be an important factor affecting their water holding capacity on which dry season sorghum production depends. Improved cropping systems have to be developed to sustain productivity in vertisols with low smectites and where annual rainfall is lesser.

365 - 372

Authors: Mushtaha Ali , Abdalla Elhagwa , Jamal Elfaki

An artisanal gold mining region located in North of Atbara (Dar-Mali locality), River Nile State, Sudan (17.82289 to 17.82389N and 33.99974 to 34.02127E) has been studied with the aim to evaluate the soil contamination with mercury (Hg) using two parameters; (i) Comparison of the Hg concentration with the mean concentrations in world soils, (ii) Enrichment Factor (EF). The results revealed that, the concentrations of the Hg are varying in the studied area and the highest concentrations were obtained inside the mining basins used for gold extraction (2.62 mg kg-1 soil) it is around 29 times more than mean Hg concentration in world soils, while the lower concentrations are found at recent Nile River terrace (0.10 mg kg-1 soil). The results also indicated that the soil samples collected from inside mining basins had a highest E.F value (352.84) that means, this site must be closed and remediation process should be started immediately. While the E.F value of recent Nile River terrace site was 8.74, means, all studied sites have significant contamination with Hg. The mobility of Hg may have influenced by northeast wind, or water runoff from mining zone to nearest areas at same wind direction or water flow direction.