Compositions for and method of degrading organic chemicals in soil. The composition is a nutrient medium serving as a substrate for microorganisms in the soil, preferably containing a major proportion of a source of carbon skeleton and energy, a macronutrient component preferably including nitrogen and other macronutrients, and a micronutrient component, preferably also a complexing agent and a vitamin/co-factor component. This nutrient material is added to soil, e.g. soil contaminated by a pesticide, to cause proliferation of microorganisms which are effective, or which develop effectiveness to degrade the organic chemicals. Preferably the microorganisms are those naturally present in the soil but useful microorganisms may be added with the nutrient medium.