DEPARTMENT OF SOIL SCIENCE AND LANDMANAGEMENT

Soil carbon storage is a key component of the global carbon cycle and plays a vital role in climate regulation, particularly within forest ecosystems. This study assessed soil organic carbon (SOC) and associated soil properties in a teak (Tectona grandis) plantation at the University of Benin, Edo State, Nigeria. A plot measuring 50 m × 50 m was marked out in the plantation and divided into three sections to represent replicates, with two plots each, resulting in six georeferenced sampling points which include USS1 - USS6 (Uniben Soil sample). Soil samples were collected from the top 0–15 cm layer, processed, and analyzed for physical and chemical properties, Standard laboratory procedures were followed, and results were subjected to statistical analysis using ANOVA. Results revealed significant differences (p ≤ 0.05) among plots and replicates in most soil properties. SOC and organic matter were highest in USS1 and USS4, indicating greater litter input and reduced decomposition, while USS3 recorded the lowest values alongside higher bulk density and exchangeable acidity. Total nitrogen and exchangeable cations followed SOC patterns, reflecting the close linkage between carbon and nutrient dynamics. USS2 and USS5 showed relatively higher total nitrogen and cation exchange capacity, suggesting better nutrient retention. Available phosphorus remained low across all sites, indicating potential nutrient limitation. Soil pH and electrical conductivity varied significantly among sampling points, highlighting micro-site differences influenced by litter accumulation, root activity, and localized decomposition. Soil texture showed no significant variation, confirming uniform parent material. Overall, the results demonstrate that teak plantations enhance soil organic carbon and nutrient status, contributing to carbon sequestration and sustainable land management, while localized conditions drive variations in soil fertility and nutrient distribution.

Acid rain significantly impacts soil chemistry, particularly the availability of essential basic cations such as calcium (Ca²⁺), magnesium (Mg²⁺), sodium (Na⁺), and potassium(K⁺). This study examines the effect of acid rain on soil basic cations within coastal plains and parent material at three locations in the University of Benin, Edo State, Nigeria. Soil samples were collected from two depths (0-30 cm and 30-60 cm) in three different locations and were analyzed for some soil physical and chemical properties using standard procedure, while rain water samples were collected from the same locations and were analyzed for pH. The results indicated a general decrease in soil pH with depth, with JSQ showing the highest mean pH (5.65), followed by Hall 2 (5.31) and AGR305(5.10). The lowest pH (4.77) was recorded at 30-60 cm in AGR 305, suggesting increased acidification and leaching effects. Exchangeable cation analysis revealed calcium as the dominant cation, with mean values of 0.73 cmol/kg at JSQ, 0.64 cmol/kgat Hall 2, and 0.57 cmol/kg at AGR 305. Magnesium levels ranged from0.14to0.32cmol/kg, with JSQ (0.26 cmol/kg) near the critical threshold (0.2 cmol/kg), while Hall 2(0.19 cmol/kg) and AGR 305 (0.18 cmol/kg) indicated possible deficiencies. Sodium and potassium levels remained close to the critical limits across all locations, with potassium at 0.23 cmol/kg in JSQ, 0.17 cmol/kg in Hall 2, and 0.16 cmol/kg in AGR305.