Soil Quality Assessment of Urban Garden Soils in Port Harcourt, Rivers State

This study assesses the soil quality of urban gardens in Port Harcourt, Rivers State, located in Nigeria's South South geopolitical zone. Urban agriculture is an important food security and livelihood strategy in Port Harcourt, yet urban garden soils may be compromised by contamination from industrial activities, waste disposal, and petroleum-related pollution that characterises the city's industrial landscape. Using a descriptive survey design, surface soil samples (0 to 20 cm) were collected from 30 urban garden plots across three municipal districts in Port Harcourt. Samples were analysed for pH, organic carbon, total nitrogen, available phosphorus, cation exchange capacity, heavy metals (Pb, Zn, Cu, Cd, Ni, Fe), total petroleum hydrocarbons (TPH), and polycyclic aromatic hydrocarbons (PAH). A soil quality index was calculated by integrating physical, chemical, and contamination indicators. Findings revealed that while most gardens had adequate pH and moderate organic matter, 43 percent showed total petroleum hydrocarbon levels exceeding the Department of Petroleum Resources remediation target values. Lead concentrations exceeded Dutch reference values in 37 percent of sampled gardens. Soil quality index scores classified 30 percent of sampled gardens as degraded, primarily in districts adjacent to industrial and petroleum storage zones. Vegetable crop uptake risk assessment indicated elevated risk for leafy vegetables in contaminated gardens. The study recommends mandatory soil testing before urban garden certification, bioremediation of contaminated plots, and the establishment of buffer zones between industrial areas and food-producing urban gardens. Keywords: urban garden soils, soil quality, Port Harcourt, heavy metals, petroleum contamination.