Effects of Scattered Terminalia brownii Trees on Selected Soil Physico-Chemical Properties and Yield of Teff (Eragrostis teff) in Tembaro District, Southern Ethiopia

Parkland agroforestry systems integrate scattered trees with cereal crops to provide productive, protective, and socio-economic benefits to local communities. However, the effects of specific tree species on soil properties and crop yields vary depending on species and management practices. This study evaluated the effects of scattered Terminalia brownii trees on selected soil physico-chemical properties and teff ( Eragrostis teff ) yield in Tembaro District, southern Ethiopia. Five isolated trees with similar age, height, DBH, and crown radius were selected on farmlands with homogeneous site conditions. Soil samples were collected from three radial distances (1.5 m from trunk, crown edge, and 15 m open field) at two soil depths (0–15 cm and 15–30 cm) from four directions. Teff grain and biomass yields were estimated using 1 m² quadrats at each distance. Results showed that soil texture, bulk density, total nitrogen, organic carbon, organic matter, available phosphorus, exchangeable potassium, cation exchange capacity, and pH were significantly influenced (P < 0.05) by radial distance from tree trunk. Soil moisture content was significantly affected by depth but not by distance. Surface soils (0–15 cm) had significantly higher nutrient concentrations than subsurface soils (15–30 cm). Teff grain and biomass yields were significantly higher (P < 0.05) under tree canopies than in open fields, with the highest yields at the crown edge (1353.4 kg ha⁻¹ grain; 5145.2 kg ha⁻¹ biomass). These improvements are attributed to higher organic matter inputs through litter fall, root biomass, and nutrient cycling under tree canopies. We conclude that retaining Terminalia brownii trees on croplands enhances soil fertility and teff productivity, supporting sustainable agroforestry practices in the region.