Soil Carbon Sequestrations in Forest Soils in Relation to Parent Material and Soil Depth in South-Eastern Nigeria

There has been increased interest in soil organic carbon in recent times because of its role in carbon sequestration. Different parent materials affect soil properties and hence will influence how much carbon is sequestered by soil. The study was conducted in June 2019 to investigate soil carbon stock in forest soils with respect to their parent materials in three States in South-eastern Nigeria. Sampling was aided by the location map of the area and free soil survey method was used to locate sampling points. 0ne profile was dug in each location and described using the Food and Agricultural Organization guideline. A total of twelve soil samples were collected and analyzed for selected properties. Results showed that sand content was significantly higher in soils under coastal plain sands (851.96 g·kg−1) and was lowest in soils of Imo clay shale (605.60 g·kg−1). Clay content was higher in soils of Imo clay shale (277.34 g·kg−1) and was lowest in coastal plain sand (118.80 g·kg−1). Silt and clay had moderate variation in coastal plain sand (>15 ≤ 35%) and high variations in Asu River and Imo clay shale (CV > 35%). The soils studied were generally acidic with values ranging (3.52) in soils formed from coastal plain sand, followed by forest soils of Imo clay shale (3.64) and Asu river group (3.85). Soil organic carbon decreased with increase in soil depth in all soil parent materials studied. Mean values ranged from 6.14 g·kg−1 in soil underlain by coastal plain sand to 10.62 g·kg−1) in soils of Imo clay shale. Soil carbon sequestered under the three different parent materials ranged from 1575 - 4676.41 (g·cm−2). Also, soil depth had a notable impact on carbon sequestration with values ranging from 1529.42 - 4374.0541 (g·cm−2) and the thicker the horizon, the more carbon sequestered. Hence, the study concluded that more carbon is sequestered in the subsurface horizons of the soil pedons than in the epipedons.

Changes in Soil pH and Exchangeable Acidity of Selected Parent Materials as Influenced by Amendments in South East of Nigeria

Soil chemical degradation caused by acidity is a serious constraint to food production in most parts of the Tropics. It was in the bid to proffer solution to this that the present study was conceived. Anincubation study was conducted at the laboratory of Soil Science and Meteorology Department of Michael Okpara University of Agriculture Umudike. The aim was to ascertain the effect of amendments namely: Control (no amendment), Biochar, Ash, Lime, Biochar + Poultry Manure, Ash + Poultry Manure and Lime + Poultry Manure, on soil pH and exchangeable acidity of Sandstone, Shale and Alluvium. The rate of application was 1.43 g for the sole amendments and 0.72 g each for the combined amendments to give an equivalent of 2 t/ha. They were applied to 100 g of the soil and replicated three times in a Completely Randomized Design. The incubation study lasted for eighty-four days, the pH and exchangeable acidity were determined at fourteen days intervals. The result obtained revealed that all the treatments increased the soil pH and decreased the exchangeable acidity over the control. In all parent materials, applied Lime and Lime + Pm significantly (p < 0.05) gave the highest pH of 6.6, 6.9 and 7.2 for Shale, Sandstone and Alluvium respectively on the 28th day of incubation which, was the time, the maximum pH value was attained. Biochar and Biochar + Pm were considered the appropriate amendments because the pH values they gave were towards neutral, unlike that of Lime and Lime + Pm that were towards alkaline. It is recommended that field trial of this work is conducted.

Impacts of soil properties on phosphorus adsorption and fractions in purple soils

Information on phosphorus(P) adsorption and its impacts on the redistribution of the P fraction in soil profiles are important for environmental management under intensive agricultural practices.To clarify the dominant factors influencing soil phosphorus adsorption in an Entisol(locally known as purple soil), P adsorption experiments were conducted in Sichuan Basin of southwestern China for cropland and woodland soils with acidic, neutral and calcareous origins throughout their profile. After various doses of P were added during incubation experiments, soil P fractions were also analyzed. The results showed that there were no significant differences in Fe-oxides and P adsorption along the vertical gradients. Agricultural practices and lower p H conditions reduced the P adsorption capacity of purple soils throughout the soil profiles. For acidic and neutral purple soil profiles, the P adsorption capability was mainly influenced by Fe-oxides and soil texture. Ca-bound P and Fe-Al-bound P represented the majority of the total inorganic P of calcareous soils.There was a saturation of adsorption capacity by sesquioxide and a high risk of dissoluble reactive P(NH_4 Cl-P) being released out of the soil profile in acidic and neutral purple soils after the greatest P addition, indicated by the higher proportions of NH_4 Cl-P(over 40%) and decreasing Fe-Al-P fraction.P fractions migrated with greater difficulty in calcareous purple soil profiles as Ca-P fraction peaked over 65% when adding a P dose at or greater than 80 g P kg^(-1), indicating the high potential of P adsorption.The X-Ray Diffraction analysis also verified the formation of brushite. Adaptive management practices should be designed to alleviate P losses for acidic and neutral purple soils.

Implications of Non-Carbonate Dolomite Minerals in the Formation of Red Soils in a Paleokarstic Context in the Taoudeni Basin in Burkina Faso

Uncertainties remain as to the ability of certain carbonate rocks to form the red soils covering them. These doubts, which have been the subject of debate for several decades, become real when carbonate rocks are pure and low in insoluble residues. In the carbonate rocks of the Taoudeni basin in Burkina Faso, brown-red to red soils develop, at the top of hillsides and in karstic cavities. No study in the region has yet shown the existence in these carbonate rocks of sufficient insolubles to form soils after decalcification. The objective of this study was therefore to identify and quantify the minerals of carbonate rocks in order to identify the origin of red soils. Petrographic, chemical (XRF) and mineralogical (XRD) investigations on dominant carbonate rocks features in the study area show that the rocks studied are mainly magnesian dolomites (Dolomite > 50% of carbonate minerals and Ca/Mg ratio < 1.5). Non-carbonate residues from detrital and hydrothermal origin, negligible in certain pure dolomites (<2%), are on the other hand significant (>12%) in other dolomitic features. These insoluble silicates formed of quartz, potassium feldspar (orthoclase), clays (talc, phlogopite and kaolinite) and iron oxides constitute the main original material of reddened soils in karstic cavities.

Land Suitability Evaluation for Oil Palm (<i>Elaeis guineensis</i>Jacq.) in Coastal Plains of Southwest Cameroon

Declining yields in oil palm fresh fruit bunch (FFB) have been recorded over the past years in the coastal lowlands of southwest Cameroon and current actual yields are very low (<12 t FFB ha−1•yr−1) compared to the potential yields (25 t FFB ha−1•yr−1). One of the problems limiting optimum oil palm production is lack of detailed pedological information to guide plantation establishment and management. A land suitability evaluation was carried out for some major oil palm producing areas of southwest Cameroon to identify land qualities limiting optimal production. Thirteen sites (9 with sedimentary parent materials and 4 with volcanic parent material) were evaluated using a parametric method. Results indicate that climate was not a major limiting factor for oil palm production in coastal plains of southwest Cameroon. However, soil physical characteristics (mainly clayey texture and poor drainage) and soil fertility constitute limitations to oil palm production. Specifically, limitations in cation exchange capacity (CEC), base saturation (BS), organic carbon (OC) and pH were slight to moderate while K mole fraction was the most severe and the most limiting in all the sites. The fertility limitations were more pronounced in soils derived from sedimentary parent materials where 33% had limitations caused by soil pH and OC compared to none for volcanic soils. In addition, 77.8% of sedimentary soils had limitations caused by CEC compared to 25% for volcanic soils. Considering the overall suitability, soils derived from volcanic parent materials were potentially more suitable for oil palm cultivation ((S3)—50%, (S2)—50%) compared to sedimentary soils ((N)—11%, (S3)—78% and (S2)—11%). Based on the suitability classes of the different soils derived from dissimilar parent materials, appropriate site-specific soil management is needed to improve oil palm yields, especially with emphasis on K fertilization and improved soil water management. Plantation management in coastal plains of South West Cameroon therefore should factor in differences in soil parent material.