Browsing by Author "Oguntunde, Philip G."

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    Effects of charcoal production on maize yield, chemical properties and texture of soil
    (Biology and Fertility of soils (Springer-Verlag), 2004-03) Oguntunde, Philip G.; Fosu, Matthias; Ajayi, Ayodele E.; Van de Giesen, Nick
    The effects of charcoal production on soil textural and chemical properties were investigated in Ejura, Ghana. The aim was to study the effects of heating and charcoal residue on maize yield, soil texture and soil chemical properties. Composite samples were taken from the 0–10 cm layer of soil at charcoal-making sites and from adjacent fields (control). Twelve sites were randomly selected for the study across the range of the Kotokosu watershed. Maize was planted in four selected locations on charcoal site soils (CSS) and adjacent field soils (AFS) to assess the impact of charcoal production on crop yield. There was a significant increase in soil pH, base saturation, electrical conductivity, exchangeable Ca, Mg, K, Na and available P in the soil at the kiln sites as compared to the adjacent soils. A relative change of up to 329% was observed in K while organic C and total N decreased by 9.8% and 12.8%, respectively. Organic C and total N were highly correlated ( P <0.01) and both parameters significantly ( P <0.05) depended on clay minerals in the soils. Soil texture was also modified with a significantly higher sand content and lower clay fraction in the CSS. The grain and biomass yield of maize increased by 91% and 44%, respectively, on CSS as compared to AFS. Further research to ascertain the longterm effects of charcoal production on the soil environment and the fertility of tropical soils is needed. Keywords Charcoal production · Soil heating · Soil fertility · Maize yield · Ghana
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    Effects of charcoal production on soil physical properties in Ghana
    (WILEY‐VCH Verlag, 2008-08) Oguntunde, Philip G.; Abiodun, Babatunde J.; Ajayi, Ayodele E.; Van De Giesen, Nick
    Charcoal production, widespread in Ghana like in other W African countries, is a major driver of land-cover change. Effects of charcoal production on soil physical, including hydrological, properties, were studied in the forest–savannah transition zone of Ghana. Core and composite samples from 12 randomly selected sites across the width of Kotokosu watershed were taken from 0–10 cm layer at charcoal-site soils and adjacent field soils (control). These were used to determine saturated hydraulic conductivity (Ksat), bulk density, total porosity, soil texture, and color. Infiltration rates, surface albedo, and soil-surface temperature were also measured on both sites. The results showed that the saturated hydraulic conductivity of soils under charcoal kilns increased significantly (p < 0.01) from 6.1 ± 2.0 cm h–1 to 11.4 ± 5.0 cm h–1, resulting to a relative increase of 88%. Soil color became darkened under charcoal kilns with hue, value, and chroma decreasing by 8%, 20%, and 20%, respectively. Bulk density on charcoal-site soils reduced by 9% compared to adjacent field soils. Total porosity increased from 45.7% on adjacent field soils to 50.6% on earth kilns. Surface albedo reduced by 37% on charcoal-site soils while soil-surface temperature increased up to 4°C on average. Higher infiltration rates were measured on charcoal-site soils, which suggest a possible decrease in overland flow and less erosion on those kiln sites. Keywords: charcoal production / soil physical properties / Ksat / infiltration rates / reflection coefficient / watershed hydrology
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    Rainfall trends in Nigeria, 1901–2000
    (Elsevier (Journal of Hydrology), 2011-12-09) Oguntunde, Philip G.; Abiodun, Babatunde J.; Lischeid, Gunnar
    There is the need to evaluate changes in the spatial and temporal patterns of rainfall in order to improve water management strategies of a given region. In this study, standard tests are used to examine the existence of trend in annual and monthly rainfall of Nigeria over the last century. Rainfall variability index was estimated as standardized rainfall departure while autocorrelation spectral analysis is used to obtain the periodicities inherent therein. Rainfall spatial distribution was highly latitudinal dependent (r2 > 0.90) and had no clearly linear relations with the longitude. Rainfall variability index showed that 1950s was the wettest decade (+0.84) while 1980s was the driest (−1.19), with the two decades between 1970 and 1990 being drier than any other comparable period in the last century. Observed rainfall changes varied between −3.46 and +0.76 mm yr−2. About 90% of the entire landscape exhibited negative trends but only 22% showed significant changes at 5% level. There was a sharp difference between changes in rainfalls in 1931–1960 and 1961–1990 periods. Annual precipitation reduced by 7% between the two periods. While more than 90% of the landscape showed no significant rainfall change in the first period, about 57% of Nigeria showed a significant (P < 0.05) decrease in the second. The dominant peaks can be classified into four distinct rainfall cycles with periods 2–3, 5–7, 10–15 and 30 yr. These cycles may be associated with the stratospheric Quasi-Biennial Oscillation (QBO), the El-Nino Southern Oscillation (ENSO); the sunspot cycles and the Atlantic Multi-Decadal Oscillation (AMO) sea surface temperature, respectively.