Journal of Bioscience and Biotechnology Discovery

The challenge of managing burgeoning kitchen waste requires sustainable valorisation methods, with composting representing a solution for producing beneficial soil amendment. This study assessed the efficacy of locally-sourced compost against conventional chemical fertiliser and unamended soil based on its impact on soil characteristics and the subsequent growth response of lettuce (Lactuca sativa). The experiment involved three soil treatment groups: Compost-amended soil, chemically-fertilised soil, and non-compost control. A total of twenty-seven (27) soil samples which comprises of nine (9) soil samples each were collected from three different locations: Gusau Market, Bola Jeri and Gusau Hotel. Physicochemical analysis revealed that compost-amended soil maintained stable temperatures (26–28°C) and a slightly acidic to near-neutral pH (5.6–6.2), contrasting with the more alkaline profile of chemically fertilised (6.7–8.2) and non-compost soils (7.6–8.2). Furthermore, compost significantly enhanced moisture retention (23–28%), compared to chemically-fertilised (10–15%) and non-compost (5–10%) soils. Nutrient analysis showed that while phosphorus levels peaked in chemically fertilized soil (4.1%), compost-amended soil provided a competitive and stable nitrogen range (0.18–0.23%), consistently exceeding the control. The total bacterial load was highest in the compost soil (8.5 to 30.8×10^-6CFU/g), confirming it biological richness. The isolated species include Bacillus cereus (33.3%), Micrococcus luteus (33.3%), Pseudomonas fluorescens (22.2%), and B. megatherium (11.1%), all known for their roles in nutrient cycling and plant growth promotion. A bioassay using lettuce validated the non-toxic efficacy of the kitchen waste compost. All parameters, including germination rate, plant height, and leaf count, were within standard physiological ranges and significantly outperformed the control. Specifically, the kitchen waste treatment promoted superior seedling emergence and biomass compared to the control group, which was limited by low moisture (5–10%). These results confirm the potential of compost as an effective, sustainable soil amendment for improving soil health and promoting healthy lettuce growth.