The soil of Thiruvidaimaruthur near the east coast of Thanjauvr District have been investigated to study the seasonal changes in soil moisture, soil pH, organic carbon, available nitrogen and macronutrients during the period of one year (2015-2016) at four different seasons viz monsoon, post monsoon, summer and pre monsoon. Physico-chemical analyses were performed to study the soil characteristics related to fertility and chemical nature. It was noticed that the regular addition of fertilizers from agricultural runoff, sewage contaminated water out falls, rain water and other anthropogenic activities contribute major changes in soil physiochemical properties that in turn significantly manifest the microbial populations. Determination of microbial diversity by culture method showed the predominance of bacterial genera such as Micrococcus luteus, E.coli, Enterobacter spp, Pseudomonas aeroginosa, Rhizobium spp, Azospirillum spp, Azotobacter spp, Bacillus spp Staphylococcus spp, Streptococcus spp, Proteus spp, Neisseria spp, Rhizobium meliloti. The result showed the predominance of fungal genera in Thiruvidaimaruthur taluk such as Penicillum spp, Fusarium spp, Alternaria spp, Enterobacter spp, Aspergillus spp, Candida albicans, Rhizopus oryzae, Trichoderma spp, Verticilum spp, Gilocladium virens.
