Evaluation of Soil Microbiological Properties Under Organic and Conventional Farming in Ogun State

This study evaluates and compares soil microbiological properties under organic and conventional farming systems in Ogun State, located in Nigeria's South West geopolitical zone. Soil microbial communities are the primary drivers of nutrient cycling, organic matter decomposition, and disease suppression in agricultural soils, and their abundance and diversity are sensitive indicators of soil biological health affected by management practices. Using a comparative field design, paired organic and conventional plots were identified on 20 farms in three local government areas. Surface soil samples were collected from each paired plot and analysed for total microbial biomass carbon using the chloroform fumigation-extraction method, soil respiration by alkali absorption, dehydrogenase enzyme activity, and cultureable bacterial and fungal counts. Findings revealed that soils from organic farming plots showed 38 percent higher microbial biomass carbon, significantly greater dehydrogenase enzyme activity, and higher fungal-to-bacterial ratios compared to conventionally managed plots. Soil respiration rates were significantly elevated in organic plots, reflecting greater biological activity. The application of compost, farmyard manure, and reduced synthetic pesticide use in organic systems was identified as the principal driver of biological quality differences. However, no significant difference in total crop yield was observed between management systems in the survey year. The study recommends the integration of organic amendments into conventional fertiliser programmes to sustain soil biological health in Ogun State farming systems without compromising productivity. Keywords: soil microbiology, organic farming, conventional farming, microbial biomass, Ogun State.