Interest in bioremediation studies of deteriorated soils caused by over-exploitation and the indiscriminate agrochemical use is due to them altering microflora, the self-regulation system and long-term sustainability. An ultisol (soil having poor chemical properties and low fertility because of reduced aggregate size (< 2.0 mm)) was solarised to reduce the microbiological population; it was inoculated with the bacteria Basillus subtilis in 10 6 , 10 7 , 10 8 , 10 9 colony forming unit (cfu) concentrations. There was a significant increase in structural stability, average aggregate size, pH and available phosphorus during the 120 days; interchangeable