TECHNOLOGY FOCUS - AGRICULTURE - Preferred Method: The method further involves mixing gypsum (5 - 15 vol.%) to break up and reduce adhesive characteristics of clay particles present in the spent water-based drilling mud; injecting an effective amount of air into the substantially homogenous mixture to enhance enzyme and microbial activity on hydrocarbons components present in the spent water-based drilling mud during conversion of the spent water-based drilling mud into fertile indigenous top soil; injecting an effective amount of air into the mixture to enhance enzyme and microbial activity on hydrocarbons components present in the spent water-based drilling mud; introducing an effective amount of water into the mixture to enhance formation of the substantially homogenous mixture and to enhance stirring of the mixture to provide the substantially homogenous mixture. The mixture is maintained at a pH of 7 - 9.5. The air is injected into the mixture in an amount and at a velocity sufficient to dry the mixture and thereby provide the fertile indigenous top soil. The air is injected into the mixture in an amount and at a velocity sufficient to dry the mixture and thereby as provide the fertile indigenous top soil. The temperature of the air supply is at least 60 (preferably 70 - 105)degreesF. WIDER DISCLOSURE - Apparatus for converting spent water-based drilling mud into fertile indigenous top soil at a well site or location, are also disclosed.    EXAMPLE - A spent water-based drilling mud was mixed with commercial compost (70 vol.%), cow manure (20 vol.%), sand (5 vol.%), gypsum (10 vol.%), and indigenous top soil (20 vol.%) to form a fertile indigenous top soil. Seeds of native grasses and small tomato plants were germinated and grown in the samples of the indigenous top soil produced from the water-based drilling mud. It was observed that the seeds of the native grasses and small tomato plants were planted in the indigenous top soil produced using the spent water-based drilling muds were grown and the tomato plants were produced beautiful and delicious tomatoes.