A glassy carbon electrode (GCE) was modified with a fullerene/Multiwalled Carbon Nanotubes (MWCNTs)/Nafion composite and applied to the determination of carbendazim, a fungicide. The voltammetric behavior of the analyte was investigated using Cyclic Voltammetry (CV), on the bare GCE and on the same electrode coated by a thin film of the composite material. The electrode response was more than fourfold important on the modified electrode, due to electrical conductivity of fullerene and MWCNT and to favorable electrostatic interaction between the negatively charged Nafion and the protonated fungicide. A sensitive electroanalytical procedure based on Square Wave Voltammetry (SWV) was then developed to detect the analyte. Under the optimum conditions, a linear relationship was obtained between the peak current and the concentration of carbendazim, in the range from 2.0 × 10−8 mol/L to 3.5 × 10−7 mol/L, leading to a detection limit of 1.7 × 10−8 mol/L and to a quantification limit of 5.57 × 10−8 mol/L. The developed procedure was successfully applied to detect carbendazim upon adsorption by some ferritic soils.

Soil organic carbon (SOC) dynamics after slash-burn agriculture are poorly understood in African tropical forest, though recent studies have revealed C4 grass invasion as a forest understory influences SOC dynamics after deforestation. This study aimed to quantify the relative SOC contribution of C4 and C3 plants separately through the sequential fallow periods of forest (cropland, or 4–7, 20–30, or >50 years of fallow forest) in the tropical forest of eastern Cameroon. We evaluated the SOC stock and natural 13 C abundance for each layer. The SOC stock was largest in 4–7 years fallow forest (136.6 ± 8.8 Mg C ha −1 ; 100 cm depth, and C4:C3 = 58:42), and decreased with increasing fallow period. SOC from C4 plants was larger in the 4–7 and 20–30 years fallow forests (57.2–60.4 ± 5.8 Mg C ha −1 ; 100 cm depth), while it clearly decreased in >50 years fallow forest (35.0 ± 4.1 Mg C ha −1 ; 100 cm depth), resulting in the smallest SOC in this mature forest (106.4 ± 12.9 Mg C ha −1 ; 100 cm depth). These findings indicate that C4 grass understories contributed to the SOC restoration during early fallow succession in the tropical forest of eastern Cameroon.

This study was designed to compare the phosphorous fixation capacity of three soils series named Tyele, Minkonmingon and Mekoto in the south region of Cameroon and to determine the soil properties that are the main predictors of the P activity of those soils. Five adsorption equations viz. Linear, Langmuir, Van Huay, Freundlich and Temkin were used to describe P adsorption processes. The results of the study showed that maximum adsorbed P of Minkonmingon, Tyele and Mekoto was 936.09, 311.15 and 823.37 mg kg-1 of soils respectively with the mean of 690.20 mg kg-1 of soils. By applying various models, P adsorption data revealed that for low concentration range, the Freundlich equation show a better fit followed by the Langmuir, Van Huay, Temkin and Linear equations. It can be thus concluded from the adsorption and Spearman correlation analysis that the soil of Minkonmingon has a greater capacity to fix P followed by those of Mekoto and Tyele respectively with silt, exchangeable acidity, free aluminum, potassium and soil organic carbon and pH KCl being the main predictors of P activity in these soils.

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