Effects of soil management on aggregation and organic matter dynamics in sub-Saharan Africa

Maintenance of soil organic matter (SOM) is important for soil quality and agricultural productivity. However, little is known about the effects of management practices of different intensities on soil aggregation and SOM dynamics in tropical arable cropping systems of sub-Saharan Africa. We investigated the influence of land use practices and management intensity on soil aggregation and SOM dynamics across 12 long-term field experiments in eastern and western Africa. Aggregate size distribution and SOM were measured in arable systems under contrasting management intensities of high carbon, low carbon and a fallow. Aggregate stability indices and SOM were generally higher in the fallow compared to the arable systems. Fallowing and high carbon inputs in arable soils, significantly improved aggregate stability and carbon (C) and nitrogen (N) stabilization in whole soil, and in aggregate fractions. In contrast, no significant improvements in soil aggregation and C and N stabilization were found when organic inputs were either applied in low quantities or not applied at all, thus resulting in low carbon in soils. Our study showed that fallowing and long-term application of organic amendments alone or in combination with mineral fertilizers were the best among the practices tested in this study, for enhanced C and N stabilization in soils with the subsequent benefits of improving soil physical and chemical properties. These results emphasize the importance of management for sustaining soil quality. It is recommended that fallowing be an integral part of sustainable soil management strategies in these regions.Keywords: Soil aggregation, soil organic matter, carbon, nitrogen, managementintensit

Uptake of Polycyclic Aromatic Hydrocarbans by the Fingerlinks of Oreochromis Niloticus (Linneaus, 1757) From the Dispersed Phase of Bonny Light Crude Oil

In many crude oil spill sites, dispersants are widely applied during clean-up operations without adequate consideration of their environmental effects. This is despite the fact that the water accommodated fractions of these mixtures contain toxic components. This study investigated the uptake of polycyclic aromatic hydrocarbons (PAHs) from the water accommodated fractions (WAF) of a mixture of a dispersant, Goldcrew and Bonny Light crude oil using a tilapian fish, Oreochromis niloticus. The aim was to determine the critical body residue (CBR) of the PAHs in the fish exposed to the dispersed, dispersant and crude oil in water (DCOWAF-PAH) and undispersed, crude oil in water only (COWAF-PAH) regimes of the mixtures in the WAF. The control experiment had water only. The concentrations for both regimes of exposure were at sub-lethal levels of 0.2, 0.4, 0.8 and 1.6ml/L for fifty days using renewal static bioassay. The types and total concentrations of PAHs were analyzed for in the crude oil, fish feed administered, preexposed fish sample, dispersant and test water before exposure. The sixteen known carcinogenic PAHs were found in the crude oil (1916.4ppm), eleven in the fish feed (0.57ppm), three in the pre-exposed fish(0.007ppm), and none in the dispersant and test medium (water). The concentration of the PAHs in the fish from the DCOWAF-PAH ranged from 3.6128-7.9744ppm while that of the COWAF-PAH ranged from 3.4114-3.9693ppm. The concentrations of individual PAHs recovered in the fish showed that napthalene had the highest CRB level of 6.7780ppm and 3.2610ppm, anthracene was 0.6590ppm and not detected (N.D) while acenaphthene had the lowest CBR of 0.00001ppm and below the limit of quantification (FL>BaF>BaP>BaA>FLU>PHE in the COWAF-PAH irrespective of exposure concentration, while for the DCOWAF-PAH, it was NAP>FLU>BaF>BaP>B(ghi)P>BaA>BkF>PHE. The results demonstrated that the presence of the dispersant, Goldcrew increased the critical body residue of the PAHs irrespective of the concentration in the fish samples. This was especially so for the low molecular weight PAHs (<200). Thus, the application of dispersants for crude oil spills need to be done with utmost care particularly in fishing ground

The anatomy of pelvic corona mortis vessles in black Africans: A cadaveric study

Objective: To study prevalence and variant anatomy of the corona mortis vessels in a black African population in relation to side and gender.Methodology: Forty embalmed hemipelvices obtained from the Department of Human Anatomy at Moi University were used for this descriptive cross sectional study. The cadavers were dissected at the preperitoneal area of the abdominal wall from inside to look for corona mortis. Chi-Square test was used to compare the incidence of the corona mortis between males and females. The level of significant difference used was p &lt; 0.05. The unpaired t-test was used to compare mean of incidences of corona mortis in males and females.Results: Corona mortis was present in 38% (15 of 40). Of these, 47% were in men and 53% in women. The mean distance from the pubic symphysis to the point where the corona mortis traverses the pubic ramus was 53.2mm (arterial) and 54.3mm (venous). The mean distance from the pubic ramus to the point of anastomosis with the external iliac systems were 16.4mm and 11.5mm for the artery and vein respectively. Regarding the nature of connection, 2(13.4%) were purely arterial, 5(33.3%) were purely venous while 8(53.3%) had both. From the chi-square results it showed that there was no significant relationship between the gender and nature of connections or side of the pelvis; (χ2=0.134, df=2; p&gt;0.05).Conclusion: In pelvic and acetabular surgery, the corona mortis must be ligated or clipped to advance the dissection further along the pelvic brim and quadrilateral surface during the modified Stoppa approach which enables access to the anterior wall, anterior column, and associated anterior column and posterior hemitransverse fractures, as well as certain both-column, T-shaped, and transverse fracture

Guidelines for soil fertility management in Uganda.

bitstream/item/189022/1/Folder-Guidelines-for-soil-fertility-management-in-Uganda-2018.pd

Hydatid disease of the spine: Case report

A rare case of spinal hydatid disease presenting with paraparesis and sensory loss is reported. The patient was treated with albendazole resulting in significant improvement within eight weeks. Investigations and treatment modalities are discussed. (East African Medical Journal: 2002 79(3): 165-166

Medium-term impact of tillage and residue management on soil aggregate stability, soil carbon and crop productivity

Conservation agriculture is widely promoted for soil conservation and crop productivity increase, although rigorous empirical evidence from sub-Saharan Africa is still limited. This study aimed to quantify the medium-term impact of tillage (conventional and reduced) and crop residue management (retention and removal) on soil and crop performance in a maize–soybean rotation. A replicated field trial was started in sub-humid Western Kenya in 2003, and measurements were taken from 2005 to 2008. Conventional tillage negatively affected soil aggregate stability when compared to reduced tillage, as indicated by lower mean weight diameter values upon wet sieving at 0–15 cm (PT <0.001). This suggests increased susceptibility to slaking and soil erosion. Tillage and residue management alone did not affect soil C contents after 11 cropping seasons, but when residue was incorporated by tillage, soil C was higher at 15–30 cm (PT*R = 0.037). Lack of treatment effects on the C content of different aggregate fractions indicated that reduced tillage and/or residue retention did not increase physical C protection. The weak residue effect on aggregate stability and soil C may be attributed to insufficient residue retention. Soybean grain yields tended to be suppressed under reduced tillage without residue retention, especially in wet seasons (PT*R = 0.070). Consequently, future research should establish, for different climatic zones and soil types, the critical minimum residue retention levels for soil conservation and crop productivity