International Journal of Academic Engineering Research (IJAER)   Year: 2021 | Volume: 5 | Issue: 2 | Page No.: 22-27 Combined Effects of Spent Mushroom Substrate (SMS) and NPK Fertilizer in the Remediation of Crude Oil Polluted Soil Raymond Alex Ekemube, Davidson Dimabo Davis, Bernard Beabu Dumkhana, Tamunokuro Oswald Amgbara Abstract: This study focused on biostimulation of crude oil polluted soil by means of activated nutrients through spent mushroom substrate (SMS), and NPK fertilizer on the degradation of hydrocarbon pollutant. Soil pH, temperature, nitrogen, organic carbon, moisture content, total petroleum hydrocarbon (TPH), and changes in total heterotrophic bacteria (THB) counts were monitored from the baseline to the 62 days. In this study, 1500g of crude oil contaminant were sprinkled on 4000g agricultural soil with different applications of SMS and NPK fertilizer during the study period. The concentration of TPH was 6323 mg/kg prior to treatment, after 31 days of enhanced crude oil contaminants with the biostimulating agents. On the averaged, there was 63% reduction of TPH concentration across treatment samples. The results showed microbial degradation of TPH loss across treatment cells from 81% to 84% monitored at the end of 62 days period. There was significant increase in THB counts of 3.30 x106, 4.52x106, and 5.35x106 across control cell P, with the highest increase of 5.42 x106 to 5.87 x106 recorded in 62 days across the treatment cell. It is concluded that the combination of SMS and NPK fertilizer 20:10:10 is an effective stimulant in the degradation of densely hydrocarbon polluted soil and its associated risk in the environment.