Browsing by Author "Meliyo, Joel L."

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    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
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    Status and variability of soil micronutrients with landforms in the plague focus of Western Usambara Mountains, Tanzania
    (International Journal of Plant & Soil Science) 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
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    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.