Browsing by Author "Meliyo, Joel L."

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Insights into landforms and soils for explaining plague hosts-vectors interaction in Western Usambara Mountains, Tanzania
(Sokoine University of Agriculture, 2014) Meliyo, Joel L.
Western Usambara Mountains in Lushoto District, Tanzania, are highly populated owing to favourable climatic conditions for production of both cash and food crops such as coffee, tea, maize, beans, potatoes and assorted fruits and vegetables. Some areas in the district are also potential as tourist destinations. However, clusters of villages in the district are reported to be hot-spots of plague recurrence that has caused deaths of thousands of people. Plague outbreaks in some villages of Lushoto District show a high frequency (on average, more than 1 year out of three) while other villages, very nearby (<10 km) have low plague frequency (less than once in 10 years). In these areas, plague has persisted for over 20 years in some villages. It is not known why plague has persisted for years in some villages but is not observed in others in the neighbourhoods. Also the irregularity of the disease outbreaks (both in time and space) pose a serious risk to communities. Earlier studies show that this persistence and the foci of the disease could not be explained by differences in fauna composition or human domestic behaviour. Hence, it was thought that a critical analysis of landscape factors at farm scale could provide explanations for plague occurrence. This study attempted to establish a landscape ecological framework in which the importance of factors of landforms, soils and soil microclimate linked to rodents, fleas and rodent burrows can be analysed as proxy for plague risk prediction. Specifically the study was aimed to i) analyse landforms and associated soil properties in relation to occurrence of small mammals (rodents) and fleas, ii) investigate the status of soil micronutrients with respect to landforms and small mammals; abundance in the plague risk area, iii) investigate the influence of landform characteristics and surface attributes at farm scale on rodent burrows, and iv) examine the influence of soil physical properties and soil microclimatic attributes on rodent burrows’abundance, portals’ orientation and burrows’ use. The study employed standard field survey and mapping of landforms, surface attributes and soils using remote sensing and GIS techniques. Soil samples were analysed in the laboratory for physical and chemical properties following internationally accepted methods. Trapping of small mammals was conducted on purposely selected sites using traps of different types and sizes. The trapped small mammals were counted and recorded, and treated with ethanol for further analysis. Fleas were removed from the animals by brushing the fur using ethanol, counted, recorded and stored. In the field, rodent burrows were surveyed systematically in the mapped landforms at farm scale. Data were explored using correlation and descriptive statistical analysis while regression analysis was carried out by generalised linear models (GLM) and boosted regression trees (BRT) in the framework of R statistics and Geographic Information System (GIS). The results show that phosphorus, base saturation, elevation and slope aspect are soil and landform characteristics which favour diversity of rodents (p<0.001); with Shannon Diversity Index increasing with elevation with values of 1.58, 1.62 and 1.69 for Plain, Escarpment and Plateau respectively. Fleas abundance was discouraged by hill-shade and magnesium while it was favoured by available phosphorus and organic carbon (p<0.001). The studied DTPA extractable Fe, Mn, Cu and Zn were variable. Fe ranged from 2.13 to 399.4 mg/kg soil, with a mean of 65.3 mg Fe/kg soil across the geomorphic units. Mn ranged from 0.59 to 266.28 mg Mn/kg soil while Cu ranged from 0.25 to 8.19 mg/kg soil with a mean of 2.98 mg/kg soil. Results show that Zn ranged from 0.08 to 19.6 mg/kg soil. Higher concentrations of Mn and Zn occurred mostly in the topsoils which also contained relatively high organic matter. Iron and Cu showed more or less equal distribution with soil depth but generally micronutrients declined with soil depth. Iron was found to significantly (p<0.01 and p<0.05) influence abundance of plague hosts and vectors. It is concluded that micronutrient levels vary in function of soil types and geomorphic units. Whereas higher concentrations were found in the plateau and upper part of escarpment, lower levels were in the plain. Fe had positive influence on abundance of plague hosts and vectors. Landforms in the studied plague frequency landscapes vary significantly in terms of elevations and slopes (p<0.05). Abundance of rodent burrows varies significantly (p<0.05) with different landform characteristics in the studied plague frequency landscapes, with high abundance in the high plague frequency. Surface cover favoured rodent burrowing in high plague frequency areas. Elevation and slopes interactively provided a favourable environment for rodent burrowing. In the medium plague frequency landscape, slope length and slope aspect were the dominant landform characteristics favouring rodent burrows. Hence high elevations and vegetation cover favoured rodent burrowing; thus, these attributes should be considered in future plague research. It has been established in this study that topsoil depth, a natural Ap/Ah horizon was an important soil physical property (P<0.05) which influenced the abundance of rodent burrows with a relative influence of 39.5 percent. The results further showed that there was no statically significant influence of soil physical properties and soil microclimate attributes (P>0.05) on burrow port orientation. The results showed that both soil depth and temperature encouraged burrow use in the high plague frequency landscape (p<0.05). Soil depth, dry soil consistence and subsoil relative humidity (RH (%) within 30 cm depth) significantly (p<0.05) could explain the burrow abundance in the medium plague frequency landscape. The use of burrows depended on the resistance of burrow to collapse, a characteristics which is dependent on the compaction of topsoil. However, dry subsoil consistence discouraged burrowing. Subsoil dry consistence had a significant (p<0.05) negative influence on burrow portal orientation in the medium plague frequency area, something attributed to compaction of the soils. It is concluded that soil physical and soil microclimate in the high plague frequency landscape encourage burrowing, a phenomenon correlating with the reported human plague contact risks. The information obtained from this study could be applied for surveillance, monitoring and control of rodent populations.
Modeling the electrical conductivity relationship between saturated paste extract and 1:2.5 dilution in different soil textural classes
(Department of agricultural engineering, 2024-12) Omar, Moh’d M.; Shitindi, Mawazo J.; Massawe, Boniface H. J.; Pedersen, Ole; Meliyo, Joel L.; Fue, Kadeghe G.
Regression models were developed to estimate the electrical conductivity of saturated paste extract (ECe) from the electrical conductivity of soil-water ratio (EC1:2.5) for different soil textural classes. ECe is a crucial parameter used to indicate the presence, type, and distribution of salinity in soils. However, determining ECe is demanding, time-consuming, requires considerable skill to accurately identify the correct soil saturation point, and is not routinely performed by soil testing laboratories. Many laboratories, instead, commonly measure the electrical conductivity of soil-water extracts at various dilutions, such as EC1:1, EC1:2.5, or EC1:5. In this study, 706 soil samples were collected from depths of 0 - 30 cm across three rice irrigation schemes to determine EC1:2.5, with 50% analyzed for ECe. ECe values were grouped based on soil textural classes. The results showed a strong linear relationship between EC1:2.5 and ECe values, with a high coefﬁcient of determination (R² > 0.95). The Root Mean Square Error values were low (1.4 < RMSE), and the Mean Absolute Error values were similarly low (0.85 < MAE). Therefore, the regression models developed provide a practical means of estimating ECe for various soil textural classes, thereby enhancing soil salinity assessment and management strategies
Pedological investigation and characterization in Litembo village, Mbinga district, Tanzania
(Sokoine University of Agriculture, 1997) Meliyo, Joel L.
A pedological investigation was carried out in Litembo village, Mbinga district (Tanzania) to identify the various soil types and characterize them in terms of their physical, chemical and mineralogical properties. The soils were classified according to FAO-Unesco and USDA Soil Taxonomy systems. On the basis of soil and other ecological parameters the potentials and constraints of the land resources were assessed. Standard soil survey methods and laboratory procedures were utilised to generate both field and laboratory data. Results indicate that Litembo village has four major landforms i.e. plateaux, hills, piedmonts and valleys Most piedmont soils are deep to very deep having dark brown to dark reddish brown sandy clay topsoils and dark red to red clayey subsoils. The hills and plateaux have shallow sandy clay loam soils. All the studied soils are well drained to excessively well drained except those of the valley bottoms which are poorly drained. Topsoil bulk densities range from 0.99 to 1.2 Mg m'3 whereas subsoil values are slightly higher. Total porosity ranges from 56 to 72% in the topsoils and from 40 to 53% in the subsoils. Topsoils have lower penetrometer resistance (PR values 0.1 to 0.28 MPa) than subsoil (PR values 3.97 - 5.52 MPa). Available water capacity (AWC) of most topsoils ranges from 15 to 25% by volume and the values decrease slightly with depth. AWC per meter range from 125 to 177 mm which is medium to high. General soil fertility status is poor. Soil reaction is very strongly acid to strong acid with pH values between 4.4 and 5.4 in topsoils and 4.4 and 6.0 in subsoils. Total nitrogen ranges from very low to medium (< 0.03 - 0.3); phosphorus, bases, CEC and base saturation are low. OC ranges from low to very high in topsoils and very low in subsoils. The clay mineralogy is dominantly kaolinitic with accessory amounts of gibbsite and goethite. The piedmont soils classified as Ferric Acrisols, Haplic Acrisols and Humic Acrisols, plateau soils classified as Humic Acrisols; soils of the as Dystnc Leptosols and Haplic Acrisols and valley bottom soils as Umbric Fluvisols. From the results of this study it is concluded that Litembo soils developed under intensive leaching environment, facilitated by a mountainous/hilly topography. Fertility status is poor, and due to steep slopes and weak soil structure Litembo soils are prone to erosion. The traditional farming system (ngoro) seems to control soil erosion on steep slopes. It is recommended that steep slopes should be planted with trees that will protect soil from erosion. Use of the traditional farming system (ngoro) should be encouraged. Due to low soil fertility status, use of fertilizers both artificial and organic manures is recommended Non-acidifying fertilizers should be preferable because of the low soil pH values. The study area lacks climatic data. More research in this line is recommended. Research on different land use alternatives which can sustainably be applicable in the village should be carried out.
Status and variability of soil micronutrients with landforms in the plague focus of Western Usambara Mountains, Tanzania
(International Journal of Plant & Soil Science, 2014-11-13) Meliyo, Joel L.; Massawe, Boniface H. J.; Brabers, Leon; Msanya, B. M.; Kimaro, D. N.; Kihupi, N. I.; Deckers, Jozef A.; Gulinck, Hubert; Leirs, Herwig
A study was carried out in Western Usambara, Tanzania to assess the status of soil micronutrients across three geomorphic units viz., plain, escarpment and plateau in order to provide essential information for on-going studies on plague epidemiology. Nineteen soil profiles were opened, described and 54 samples collected for laboratory analysis. Standard methods were employed to analyse soil physical and chemical properties. Micronutrients Fe, Mn, Cu and Zn were extracted by DTPA and quantities estimated spectrophotometrically. Spatial distribution of micronutrients along the geomorphic units and within pedons was studied using descriptive statistics, correlation, ANOVA and means separation was done by Tukey’s test at 95 % confidence interval in Minitab 14 software. Relationships between small mammal and flea abundance and micronutrients were established by regression analysis using R-software. Results showed that DTPA extractable Fe, Mn, Cu and Zn were variable. Fe ranged from 2.13 to 399.4 mg/kg soil, with a mean of 65.3 mg Fe/kg soil across the geomorphic units. Mn ranged from 0.59 to 266.28 mg Mn/kg soil while Cu ranged from 0.25 to 8.19 mg/kg soil with a mean of 2.98 mg Cu/kg soil. Results show that Zn ranged from 0.08 to 19.6 mg Zn/kg soil, with a mean of 1.16 mg Zn/kg soil. Generally, micronutrients declined with soil depth. The micronutrient levels were high in the geomorphic units with the trend: plateau > escarpment > plain. Iron was found to significantly P<.01 and P<.05 influence plague hosts and vectors. The study concludes that micronutrients vary with soils and geomorphic units. Iron had positive influence on plague hosts and vectors. Further research on the relationships between micronutrients, and plague hosts and vectors in different plague foci in the country is recommended.