Browsing by Author "Majeme, Julius"

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    Influence of soil physico-chemical properties on the mobility and retention of fertilizers in soils of Buwali sub-county, Bududa district.
    (Busitema University, 2026) Majeme, Julius
    Efficient fertilizer use in smallholder agriculture requires a clear understanding of how soil physico-chemical properties govern nutrient mobility and retention. This study assessed soil pH and organic matter (OM) content from three sites in Buwali Sub-county, Bududa District, Uganda (Buwashi, Bunabumali, and Bukobero), and evaluated their influence on the horizontal and vertical mobility of nitrate (from CAN fertilizer) and phosphate (from NPK fertilizer) using controlled laboratory column and trough experiments. All three soils were slightly acidic (pH 6.12–6.65). Organic matter varied markedly: Buwashi 8.00% > Bunabumali 6.60% > Bukobero 4.60%. Nitrate was determined by the UV spectrophotometric method (corrected absorbance Acorr = A₂₂₀ − 2A₂₇₅) using a linear calibration curve with regression equation Acorr = 0.0467 × C − 0.0007 (R² = 0.9999), which provided excellent linearity across the full 0–25 mg/L range. Phosphate was determined by the Molybdenum Blue method at 880 nm (R² = 0.9948). Nitrate mobility was strongly controlled by OM content. Buwashi soils retained 85.8% of nitrate within 6 cm horizontally and 88.5% within 15 cm vertically, indicating excellent nitrogen retention. Bunabumali soils showed very poor retention (15.5% horizontal; 24.0% vertical), representing a significant nitrate leaching risk. Bukobero showed moderate to good attenuation (20.3% horizontal; 55.1% vertical). Phosphate was strongly immobile in all three soils (75–80% attenuation within 6 cm and 15 cm), controlled by mineral fixation chemistry rather than OM content. The study concludes that organic matter is the primary driver of site-specific nitrogen retention differences, while phosphate immobility is universal across all sites. Split CAN applications are strongly recommended for Bunabumali and Bukobero soils; NPK fertilizer should be band-incorporated at root depth at all site