Changes in soil nitrate, phosphate, and sulfate stocks as a function of forest litter type in a derived Savannah ecosystem of Abeokuta, southwest Nigeria

In order to adequately monitor the contributions of different tree species to soil nutrient stocks and soil properties, the impact of forest tree species on the above was investigated. Soil samples were collected in triplicate from the middle of tree clusters of Gmelina arborea, Bambusa vulgaris, Treculia africana, arable crop farm, fadama, and organic farm. They were analyzed for some soil properties and nutrient stocks at 0–20, 20–40, 40–60, and 60–80 cm using standard procedures. Results revealed that soil organic matter accumulated more at 0–40 cm under the different tree types compared with lower depths. It was also observed that soil pH, electrical conductivity, organic matter, hydraulic conductivity, and bulk density increased at 20–40 and 40–60-cm depths under some of the tree plantations. Soil sulfate (SO₄²⁻), phosphate (PO₄³⁻), and nitrates (NO₃⁻) were concentrated at depths 20–40 and 40–60 cm. There was the accumulation of 75.57 Mg PO₄³⁻ ha⁻¹, 56.19 Mg SO₄²⁻ ha⁻¹, and 37.57 Mg NO₃⁻ ha⁻¹ in the soil. Soils from arboreal plantations had higher nutrient stocks compared with the non-tree land use (arable crop farm, fadama, and organic farm). Soils under B. vulgaris had the highest accumulation of nutrients. There was an improvement in soil properties and nutrient stocks, particularly with T. africana and B. vulgaris.