Cleansing soil contaminated with organic chemicals comprises: (a) composting plant material (PM) with C:N ratio of 10-30:1; (b) mixing with composted PM (CPM) contaminated soil, and (c) allowing to stand at ambient temp. The improvement of this method comprises: (i) making CPM at a site remote from the contaminated soil; (ii) inoculating PM with contaminated soil sample plus soil from an area immediately adjacent to the contaminated soil prior to composting, and (iii) adding iron sulphate, ammonium nitrate and manganese oxide. Also claimed is a process for cleansing contaminated soil as above comprising: (a') composting cotton gin trash (CGT) by wetting windows contg. CGT to a moisture content of 50-90% based on dry wt. of CGT with 50-1000 ppm aq. carbohydrate based on a dry wt. of plant material 50-500 ppm soluble iron; mixing windows and allowing to stand with periodic addn. of water and mixing until individual plant parts are no longer easily identified; (b') mixing 3 vol.pts. contaminated soil with 1 vol.pt. composted CGT; and (c') allowing the mixt. to stand at ambient temp., where the improvement is as above.     The plant source is cotton, legumes, alfalfa and/or tomatoes esp. cotton gin trash or alfalfa hay. The organic chemicals is a residue of DDT, dieldrin, toxaphene, 1,1,1-trichloroethane, 1,1-dichloroethane, trans-1,2-dichloroethene, trichloroethylene, CH2 Cl2and/or petroleum fuel hydrocarbons. The contaminated soil is mixed with CPM in a vol. ratio of 1:1-5.    USE -   The process is used to clean the soil of unwanted chemical substance such as petroleum hydrocarbons which have found their way into soils rendering them harmful to man, animals and plants. The biologically active absorbent generated from the compost and inoculant neutralises spills.    ADVANTAGE -   The process cleanses the soil of its unwanted contaminants in a time period of a few months depending on seasonal temps. and the concn. of unwanted entities. In prior art the contaminated soil would have had to be replaced by new soil.